Cyclotron design rules, level 3: commissioning and optimization

The mean radius of curvature of the path is 10 cm., and the pole pieces are about 4 cm. wide and are separated by a 1-cm. gap. The electromagnet used will produce a field of 18,000 gauss between these pole-pieces. A slit Y, 0.5 cm by 1 cm, serves to define the deflected beam and sort out a given kind of ion with a small range of energies.

Oliphant & Rutherford, Experiments on the Transmutation of Elements by Protons (1933) — p. 262

Editorial note, tabletop extrapolation: In a cyclotron the machine itself is the analyzer, but an external species check on a next machine's beamline follows the same method: compute the magnetic rigidity of each species at the beam energy, choose bend radius and field to separate them, and let a defining slit pass one - the source's geometry is a worked example at its stated beam, not proportions to copy.

Precise machining of the surfaces in contact is necessary to make pole faces accurately parallel. The required machine tolerance is about 1/50,000 of the pole diameter and calls for the best machine practice. The structure of a few heavy blocks with machined faces in contact is quite rigid and requires very few bolts; alignment can be maintained by dowel pins or keys.

Livingston & Blewett, Particle Accelerators (1962) — p. 193

Editorial note, tabletop extrapolation: For 8-in poles that is ~0.00016 in (~4 um) parallelism - a surface-grinder job; non-parallel poles show up as the sinusoidal azimuthal error in field maps.

with a magnitude of decrease out to this point of about 2 per cent of the central field. Although this field shape can be achieved by machining of the surfaces of the pole faces, it is usually obtained by inserting a flat pyramidal stack of thin iron shims in shimming gaps outside the pole-face plates. ... obtained by the use of such stacks in the two shimming gaps, each consisting of four disks of 0.020-in. soft iron sheet of 6, 14, 18, and 22 in. diam.

Livingston & Blewett, Particle Accelerators (1962) — p. 195

Editorial note, tabletop extrapolation: MIT's stack is historical calibration, not a recipe - shim response does not scale geometrically with pole size or gap. For the reference machine, set the droop target from the focusing requirement, then determine disk diameters and count by field mapping or magnetostatic modeling, iterating; the graded flat-pyramid form is the transferable part.

At MIT the optimum ring section was 3/4 by 1/4 in. ... Shims which are too large produce a minimum in the radial field plot which would cause defocusing. Also, a set of shims which are correct at high fields will be too strong and produce a defocusing minimum in the plot at lower fields.

Livingston & Blewett, Particle Accelerators (1962) — p. 196

Editorial note, tabletop extrapolation: An edge ring can extend the reference machine's usable radius, but size it empirically: start conservative, map the radial field at every operating current (the lower-field defocusing minimum is the trap), and trim iteratively - MIT's 3/4 x 1/4 in section is their optimum on 42-in poles, not a scaling template.

The figure of merit used to describe azimuthal uniformity is the maximum per cent variation around a circle of constant radius, and the most critical region is near the exit-slit location. ... Most operators agree that a variation of less than 0.1 to 0.2 per cent is desirable in large cyclotrons. ... After careful correction by use of sector-shaped and wedge-shaped shims, the errors were reduced to less than 0.1 per cent for all radii out to the exit slit.

Livingston & Blewett, Particle Accelerators (1962) — p. 196-197

Editorial note, tabletop extrapolation: At 5.9 kG this means holding azimuthal wobble to ~6-12 G; an azimuthal bump acts like a field error that pumps radial oscillation amplitude.

A special search coil can be used to observe the median plane in the radially decreasing field, using two opposed identical coils equally spaced about the center and with the axis precisely aligned normal to the pole surfaces. At MIT the uncorrected field showed a median plane displaced 1/2 in. below the central plane ... adequately corrected by reducing excitation in the upper magnet windings relative to the lower ones.

Livingston & Blewett, Particle Accelerators (1962) — p. 197

Editorial note, tabletop extrapolation: The beam follows the magnetic plane, not the machined one; with separate top/bottom coil circuits (or a properly rated shunt across one layer, as MIT used for a dished plane) the builder can steer it back to mid-gap - size any shunt for its current and dissipation first.

The experience at MIT is typical. After several years of empirical shimming, with continual difficulties in maintaining high-intensity operation, a careful program of measurement and correction was carried out as indicated in the illustrations above. When this program was completed, the cyclotron was reassembled and on the first operation gave the highest beam intensities ever obtained, with no further empirical shimming.

Livingston & Blewett, Particle Accelerators (1962) — p. 197

Editorial note, tabletop extrapolation: The single strongest process lesson for a next machine: map first, shim from data - a systematic field map costs far less time than open-ended beam-chasing, and measurement-based correction is what ended MIT's years of cut-and-try.

A local weak spot in the field (0.5 per cent low) was observed in the MIT magnet which was presumed to be due to a blowhole in the pole casting; it was corrected by a local spot shim.

Livingston & Blewett, Particle Accelerators (1962) — p. 197-284

Editorial note, tabletop extrapolation: Read azimuthal maps by their harmonic content, as a first diagnosis rather than a chart: a dominant first harmonic says check tilt and centering first (it can also be a genuine dipole asymmetry of iron, coil or yoke, or nearby hardware); higher harmonics point at localised defects, sector features, extraction hardware or the measurement itself. Confirm a suspected cause by re-mapping after the mechanical correction, then trial shims taped on before permanent installation. [Note revised 2026-08-23: earlier note presented the harmonic reading as one-to-one.]

A typical 'exploring' coil for a cyclotron magnet would have about 1000 turns of fine wire ... Total deflection should be zero after a full circle; this provides a check on the stability of the amplifier.

Livingston & Blewett, Particle Accelerators (1962) — p. 283-285

Editorial note, tabletop extrapolation: A pivoted-arm coil (or a modern Hall probe on the same fixture) sweeping circles at fixed radii is exactly the mapping jig an 8-in machine needs before shimming.

the magnetic field can be determined with high precision ... this resonance frequency represents an average value of the magnetic field from the center out to the exit radius ... an error of the order of 0.5 per cent is possible.

Livingston & Blewett, Particle Accelerators (1962) — p. 287-288

Editorial note, tabletop extrapolation: The reference machine's observed resonance peak vs magnet current is a magnetization-curve measurement of their own magnet - log it at every retune.

a common phenomenon ... is to find the median plane dished into a shallow saucer shape caused by asymmetries in the magnet iron or of the reinforcing iron in the foundations. A similar shape will result if the coils are not located symmetrically or if there is a shorted turn. ... At MIT such a 'dished' median plane was corrected by connecting an external resistor in parallel with one of the coil layers, which reduced the current in this layer and in this case had the effect of flattening the median plane.

Livingston & Blewett, Particle Accelerators (1962) — p. 288

Editorial note, tabletop extrapolation: Rebar in the floor or a nearby steel bench can dish an H-frame tabletop field; remove or symmetrize nearby steel first where practical, then trim electrically (a rated shunt across one accessible layer, as MIT did) rather than re-machining.

The magnet has tapered poles, the poles being tapered from 12-inch pole stems to 10-inch pole faces. There is a 0.7 inch thick shoulder at the pole face ... The tapered pole shape and peripherally placed steel shims contribute to the uniformity of the field.

McGuire, The Iowa State University 1.5 MeV Undergraduate Cyclotron (1961) — p. 6-7

Editorial note, tabletop extrapolation: A concrete, machinable geometry pattern for concentrating flux into an 8-10 inch pole face - but transfer the method, not the numbers: taper, shoulder and shim dimensions depend on gap, saturation and yoke geometry, so model (FEMM) or map the field and set them iteratively.

an instrument operating on the principle of nuclear magnetic resonance is used ... The instrument may be read easily to one gauss accuracy.

McGuire, The Iowa State University 1.5 MeV Undergraduate Cyclotron (1961) — p. 9-10

Editorial note, tabletop extrapolation: The division of labor transfers: an NMR reading in a homogeneous region calibrates the mapping probe; a good calibrated Hall probe can carry the absolute job too if its spec covers the need. Either way the last word is the beam - resonance depends on the orbit-averaged field, harmonic and phase history, so set f from the map and trim on beam rather than expecting any point reading to set it exactly. (A DIY NMR gaussmeter is a classic amateur build; qualify its actual accuracy before trusting it.)

The pole gap is twenty-two inches, and, for any given radius, the gap variation is less than 0.005 inch.

Ramler & Parker, The Argonne 60-Inch Cyclotron — ANL-5907 (1959) — p. 10

Editorial note, tabletop extrapolation: Derive the reference machine's own tolerance rather than copying the number: with dB/B ~ -dg/g for a gap-dominated circuit, the field error the orbit budget allows sets the gap tolerance - the source's fraction (0.005/22 ~ 0.02%) applied to a 2-in gap would mean ~0.0005 in, so pick the acceptable field error first and verify by mapping.

Magnetic shimming consists of internal Rose rings and external stepped shims. The internal rings are fastened to both the top and bottom lids and are radially located at 26 inches and extend outward to 30 inches. The rings are 1/4 inch thick and 2 inches wide. External top and bottom shimming consists of a pyramid of twelve discs, each 1/16 inch thick and of the following radii: 2 of 20 inches; 2 of 16 inches; 2 of 10 inches; 2 of 6 inches; 2 of 4 inches; and 2 of 3 inches. The largest disc is located in contact with the lid.

Ramler & Parker, The Argonne 60-Inch Cyclotron — ANL-5907 (1959) — p. 10-11

Editorial note, tabletop extrapolation: The classic two-knob shim architecture for extending the reference machine's flat-field region: perimeter ring for the edge, thin stacked discs for the interior gradient.

implement a .02'' convex taper from the center of the pole to the edge, to create sufficient bending of the magnetic field lines.

Heuer & Baumgartner, Design of a 2 MeV Cyclotron (2009) — p. 31

Editorial note, tabletop extrapolation: The taper's size does not transfer: the gradient it produces depends on gap, pole radius, saturation and yoke geometry. Choose a target field index n = -(r/B)dB/dr for the reference machine, get the contour from magnetostatic modeling (FEMM), and finalize by field mapping and shimming - the source's 0.02 in is one machine's value, not a starting spec.

When passive materials such as iron are operated close to or above saturation the approximation mu_p = infinity does not hold and the method of permeance estimation is not readily practicable.

Leupold & Potenziani, A Permanent Magnet Circuit Design Primer — ARL-TR-946 (1996) — p. 6

Editorial note, tabletop extrapolation: Same lesson as Tanabe from the PM side: every quick hand method assumes unsaturated iron. Rather than trusting a universal flux ceiling, check the chosen steel's B-H curve and verify peak local flux density (pole roots, corners) with a nonlinear FEA pass - an average yoke figure can hide saturated corners.

Average magnetic field distribution adjustment process is shown in figure 4 (last measurement is 5th step). Both cutting pole and shimming was applied to reach isochronous field. The resulting magnetic field strength is close to designed value and its shape is nearly isochronous

Antokhin et al., Magnet System for PET Cyclotron Based on Permanent Magnets (2006) — p. 2

Editorial note, tabletop extrapolation: Budget several map-machine-remap cycles for a next machine's pole profile; the source machine took five.

Note that radial oscillations for this conditions and measured field is large enough as about 3 cm, that may lead to increasing axial oscillations through the nonlinear resonance Qr-2⋅Qz. The reason for increased radial oscillations is big first harmonic of magnetic field, which caused by non-symmetric structure of central part of cyclotron magnet ... radial oscillations now does not exceed 3 mm and axial ones does not exceed 2 mm ... to make symmetric central magnet part by setup second hole on opposite side with respect to ion source hole.

Antokhin et al., Magnet System for PET Cyclotron Based on Permanent Magnets (2006) — p. 2-3

Editorial note, tabletop extrapolation: A ten-fold reduction in orbit wander at the source machine for the cost of a symmetry-restoring second hole. For the reference machine, treat any asymmetric central feature as a first-harmonic suspect - but measure the harmonic (field mapping or orbit calculation) and choose the compensating geometry from the data; a mirror feature is not guaranteed to cancel a given perturbation.

Cited in: Beam Dynamics: An Interactive Laboratory · Beam Quality: What It Is and What Degrades It

The 'shim' is a small, additional piece of ferro-magnetic material added on each side of the two poles... optimised to reduce the 6, 10, 14... pole error harmonics.

Marks, Conventional Magnets for Accelerators — CAS lecture (2004) — p. 29, 37

Editorial note, tabletop extrapolation: Edge shims are how a next machine can widen its flat-field fraction without bigger poles (see dg-022 for how far short a bare flat pole falls); expect the gain to be geometry- and saturation-dependent, and verify by field mapping.

typically +/- 1:104 within the 'good field region' of -12mm <= x <= +12 mm.

Marks, Conventional Magnets for Accelerators — CAS lecture (2004) — p. 41, 43

Editorial note, tabletop extrapolation: Sets the metric - not the number - by which the builder should present their own field maps: normalized deviation from the required field profile over the region the beam actually occupies. Derive the reference machine's tolerance from allowable RF phase slip and harmonic orbit displacement rather than adopting a generic figure; even a sub-MeV machine can be intolerant of a 1% error.

This reduction is accomplished by reducing the saturation by making the yoke and back leg of the septum magnet as thick as possible.

Tanabe, Iron Dominated Electromagnets, Lecture 10: Forces, Stored Energy, Fringe Fields, End Chamfering (2005) — p. 17-19

Editorial note, tabletop extrapolation: Supports generous H-frame cross-section on the next machine, but the return path is only one leakage source - model or map the stray field before siting ion gauges, turbo pumps and CRT-era instruments near the magnet.

the meshing package for POISSON is rather weak and often does not have the flexibility nor is robust enough to generate difficult detailed meshes easily. ... I find it easier to develop the geometry lattice using the Excel. ... =CONCATENATE(C$1,A5,C$2,B5,C$3)

Tanabe, Iron Dominated Electromagnets, Lecture 4: POISSON — A Two-Dimensional Magnetostatic Solver (2005) — p. 10, 19

Editorial note, tabletop extrapolation: Saves hours on shim-profile studies where dozens of geometry variants are compared; also justifies using FEMM instead for fiddly shim shapes.

nptc=31 means number of points on the circle, rint=20 means interpolation on 20 mm radius arc, rnorm=25 means multipole normalization at 25 mm ... nterm=14 means the maximum number of multipole terms.

Tanabe, Iron Dominated Electromagnets, Lecture 4: POISSON — A Two-Dimensional Magnetostatic Solver (2005) — p. 7

Editorial note, tabletop extrapolation: Turns a simulation into the same harmonic numbers you get from a measured field map, so simulation and Hall-probe map can be compared directly.

nbsup, nbslo, nbsrt and nbslf means the boundary condition at the upper, lower, right hand, and left hand boundaries. = 0 means Dirichlet (flux parallel) and =1 means Neumann (flux perpendicular) boundaries.

Tanabe, Iron Dominated Electromagnets, Lecture 4: POISSON — A Two-Dimensional Magnetostatic Solver (2005) — p. 8

Editorial note, tabletop extrapolation: For the symmetric H-frame cross-section, a median-plane symmetry boundary halves the modeled domain and mesh - runtime usually falls accordingly, though not by an exact factor; a quarter model needs a second valid symmetry plane (geometry AND excitation symmetric about both).

The iron yoke area uses mat=2, which uses the BH curve for a 'generic' iron whose magnetic properties approximate the behavior of 1010 steel.

Tanabe, Iron Dominated Electromagnets, Lecture 4: POISSON — A Two-Dimensional Magnetostatic Solver (2005) — p. 9

Editorial note, tabletop extrapolation: Home-built yokes are typically A36/1018 mild steel; the default curve is a reasonable first pass, but A36 properties vary - run sensitivity checks with plausible BH curves (or supplier/measured data) before trusting predictions near saturation.

Note that all regions must close, that is the first and last coordinates are equal ... Negative currents in the right hand coil gives positive flux on the horizontal centerline.

Tanabe, Iron Dominated Electromagnets, Lecture 4: POISSON — A Two-Dimensional Magnetostatic Solver (2005) — p. 9

Editorial note, tabletop extrapolation: The two mistakes that make a first POISSON run fail; also shows amp-turns (not turns and amps separately) are what the model needs.

It is necessary to add a small weld bead, electrically connecting all the laminations. The core can then be grounded to a single ground point.

Tanabe, Iron Dominated Electromagnets, Lecture 8: Core Fabrication, Assembly, Installation and Alignment (2005) — p. 23

Editorial note, tabletop extrapolation: Single-point grounding of the yoke also matters on a solid-core machine carrying RF and HV nearby - one deliberate ground, no accidental loops.

The electrical bussing connection creates a loop around the beam line, resulting in a small solenoidal field... the in and out conductors should be placed close to each other.

Tanabe, Iron Dominated Electromagnets, Lecture 8: Core Fabrication, Assembly, Installation and Alignment (2005) — p. 24-26

Editorial note, tabletop extrapolation: Cheap to get right on a next machine: dress the coil leads as a twisted/adjacent pair and keep supply cables from encircling the chamber.

Magnet alignment specifications for accelerators and beam transport lines typically call for < +250 u precision transversely and vertically and < +500 u longitudinally. Rotational tolerances are typically < +0.2 mrad in roll, pitch and yaw.

Tanabe, Iron Dominated Electromagnets, Lecture 8: Core Fabrication, Assembly, Installation and Alignment (2005) — p. PDF p.27 (slide 'Magnet Fiducialization') for the alignment numbers; PDF p.3 for the retrofit sentence

Editorial note, tabletop extrapolation: For a single-magnet cyclotron the numbers relax, but the lesson holds: machine reference flats and leveling features into the next machine's yoke before assembly.

A true kinematic support system must have at least and at most six linearly independent supports.

Tanabe, Iron Dominated Electromagnets, Lecture 8: Core Fabrication, Assembly, Installation and Alignment (2005) — p. 38-41

Editorial note, tabletop extrapolation: A next machine's stand with three adjustable feet plus lateral stops gives repeatable leveling of the median plane without fighting a warped frame.

IV > 150 V-Amperes or I > 30 Amps or V > 130 Volts or when the magnet stored energy is > 5 joules.

Tanabe, Iron Dominated Electromagnets, Lecture 9: Coil Fabrication, Testing and Electrical Safety (2005) — p. 12-13

Editorial note, tabletop extrapolation: The reference machine's magnet exceeds several of these thresholds, so the source's guarding rule applies: a sheet-metal or polycarbonate coil cover including the hot cooling fittings. Guarding is one layer only - protective earthing, overcurrent protection, and stored-energy discharge are separate requirements this rule does not cover.

Shimming of pole edges or shims based on equation: dB(r)/B(r) = gamma(r)^2 * df_p(r)/f_p(r)

Zaremba, Magnets for Cyclotrons (2005) — p. 10

Editorial note, tabletop extrapolation: For protons from ~150 keV to 1 MeV, gamma is about 1.00016-1.00107. Relate the reference machine's measured phase slip to a local orbital-frequency error first, then use the formula for the required field correction, and get shim thickness from simulation or measured shim sensitivity - relativistic effects are small at these energies but not automatically subdominant to mechanical field errors.

Achieving the following homogeneity values is reasonable but nevertheless challenging. Dipole: ΔB/B0 ≤ 0.01% ; Quadrupole: ΔB'/B'0 ≤ 0.1% ; Sextupole: ΔB''/B''0 ≤ 1%

Zickler, Basic Design and Engineering of Normal-Conducting, Iron-Dominated Electromagnets — arXiv:1103.1119 (2010) — p. PDF 10 (printed 74)

Editorial note, tabletop extrapolation: A useful upper bar from beamline practice. A weak-focusing cyclotron deliberately wants a controlled radial gradient, and its azimuthal tolerance is a different quantity: specify it as Fourier-harmonic limits (especially the first harmonic) derived from orbit-error analysis, using 0.01% only as a sense of what precision magnets achieve.

In normal operation, the magnet is always cycled to its maximum value, irrespective of the required field, to ensure that hysteresis effects are reproducible.

Zickler, Basic Design and Engineering of Normal-Conducting, Iron-Dominated Electromagnets — arXiv:1103.1119 (2010) — p. 26

Editorial note, tabletop extrapolation: Free operational fix for run-to-run field shifts in a home cyclotron: resonance is set by B, so reproducibility matters directly - how much field error the beam tolerates depends on RF voltage, turn count and acceptance, so measure it rather than assume. If true zero field is needed, degauss with diminishing alternating cycles instead of trusting zero current.

At high fields, the top of the pole can saturate. The right hand figure illustrates a tapered pole which is wider at the top... The right hand figure illustrates a wider coil with approximately the same area and a higher reluctance path and a lower transverse field due to both the wider coil slot and the tapered pole edge. ... a radius at the pole corner, reducing this magnetic flux stress concentration. ... The results of the listed improvements in the two dimensional design are magnets whose field remains uniform and whose excitation remains linear over a wider range of excitation.

Tanabe, Iron Dominated Electromagnets: Design, Fabrication, Assembly and Measurements — SLAC-R-754 (2005) — p. 251-252

Editorial note, tabletop extrapolation: Cheap insurance for the next machine's pole design: a root taper and corner radius cost one lathe operation and help keep the field shape constant over a wider excitation range.

the field quality can be improved by adding smooth bumps near the edge of the pole, causing the flow lines to squeeze through a narrower gap and causing them to transition earlier to horizontal lines. This increases the fraction of the aperture with uniform field distribution. The smooth bumps also reduce the crowding of the flow and flux lines near the pole corner, reducing the saturation of the iron in this region.

Tanabe, Iron Dominated Electromagnets: Design, Fabrication, Assembly and Measurements — SLAC-R-754 (2005) — p. 63-65

Editorial note, tabletop extrapolation: The classic Rose-shim trick: a machined or stacked-shim ring at the edge of the 8 inch poles buys field uniformity (and hence more usable radius) far more cheaply than a bigger magnet.

T304 stainless steel 5/16-8 double lead (2 start) thread with 0.25-inch pitch ... Astrosyn Type 23KM-K213-P7V stepper motors that advance 1.8 degrees per step. A ramp-up and ramp down of velocity prevents skipping. Since the load on the x-y stage is low, the stepper motors are only required to run at 25% their rated operating maximum current. The aggregate of lead screw pitch and motor resolution correlates to 800 steps per inch. To further minimize the potential for backlash, field measurements are only made while stages are moving in the 'forward' direction.

Koeth & Krutzler, Field Mapping in Cyclotron Magnets (2015) — p. 2

Editorial note, tabletop extrapolation: A stage resolving 1/800 inch (0.03 mm) is more than enough for an 8-12 inch pole and is buildable from surplus stepper/leadscrew parts; verify actual positioning repeatability (the source checked theirs with a dial indicator) and pick the map grid from the field structure, not from the step size.

There are field profile differences in excess of 1% between zero of half-second dwell times. However, there is no measureable difference between dwell times of 2.5 and 2.0 seconds.

Koeth & Krutzler, Field Mapping in Cyclotron Magnets (2015) — p. 3

Editorial note, tabletop extrapolation: Directly applicable method: any DIY gaussmeter-plus-stepper mapper should measure its OWN settling behavior - step the dwell in 0.5 s increments along the steepest gradient and adopt the first value where successive profiles agree within the stationary noise. Rutgers' 2-3 s is their apparatus's answer; an uncalibrated mapper risks a systematic error of unknown size, which is the reason to run the calibration, not a guaranteed 1%.

To calibrate the Hall probe's position against the magnet's mechanical center we have employed five field bumps that are formed by iron needles excited by small copper coils which are precisely located around the cyclotron magnet pole tips. ... it was necessary for our field-bump calibration to be performed with the primary cyclotron magnet de-energized. After a full 2-D scan was completed; peaks, corresponding to the needles' centers are found by fitting a Gaussian, figure 6, to the measured field bump. Four needles were used to scale both dimensions; the fifth needle was used to break the symmetry, removing orientation ambiguities. Use of the lower field (<100 Gauss) bumps necessitates two scans ... A post-measurement analysis of the two returned a distance of 2.500 inches while mechanical measurement found the distance to be 2.500.

Koeth & Krutzler, Field Mapping in Cyclotron Magnets (2015) — p. 3-4

Editorial note, tabletop extrapolation: Trivially cheap (iron nails plus a few turns of magnet wire) and it ties the field map to the magnet's mechanical center - extend that to chamber-center registration only by surveying the needle positions against the chamber geometry.

After 1600 travel manipulations were executed by 2.4 million motor steps, the probe carriage reproducibly returned back to the distal point within the digital dial indicator's resolution of 0.0000 inches

Koeth & Krutzler, Field Mapping in Cyclotron Magnets (2015) — p. 4

Editorial note, tabletop extrapolation: Cheap insurance: an afternoon of cycling the homemade stage qualifies its endpoint repeatability under those conditions - also spot-check intermediate positions, the other axis, and repeatability across the session before trusting the maps; the indicator's resolution bounds what the test can see, not the stage's true error.

the sequence of standard deviations was fit to a parabola from which the minimum standard deviation, i.e. the center locations, could be inferred ... the centers of each measurement circle were found to be coincident to 10-4.

Koeth & Krutzler, Field Mapping in Cyclotron Magnets (2015) — p. 5-6

Editorial note, tabletop extrapolation: Exactly the analysis the builder needs for a symmetric-pole next machine: it also tells you how far the magnetic center sits from the mechanical center of the chamber.

we choose a reference circle to have a radius half that of the maximum ion radius ... the reference circle is swept to maximize the 4th harmonic, while minimizing the second, third, and fifth.

Koeth & Krutzler, Field Mapping in Cyclotron Magnets (2015) — p. 6-7

Editorial note, tabletop extrapolation: Applies if a next machine moves to sectored pole tips; on a 12-inch machine the whole analysis is a spreadsheet/Octave job on the map you already took.

fx = (gamma mo vz/qBo)/tan beta = rgo/tan beta.

Humphries, Principles of Charged Particle Acceleration (1986) — p. 141

Editorial note, tabletop extrapolation: If a next machine ever extracts a beam, angling the magnet exit edge can focus the diverging beam without any extra magnet - check the sign convention for the actual bend geometry and verify the full extracted-beamline optics rather than trusting the thin-lens number.

a pole piece with a flat surface at the edge with a thickness sufficient for the screws and a kind of lump in the middle with a flat top

Chun, The Cyclotron Magnet and RF Oscillator (2003) — p. 8

Editorial note, tabletop extrapolation: Directly applicable fabrication pattern for contoured pole caps that still bolt on - and a geometric design check to run: verify the theoretical contour leaves enough thickness at the mounting screws before committing, since a steep profile can thin the screw land below usability.

1st successful operation was recorded by slowly sweeping B-field to locate resonance condition. September 16, 1999

Koeth et al., The Rutgers 12-Inch Cyclotron for Students (2010) — p. 8

Editorial note, tabletop extrapolation: A good commissioning move for a next machine when the RF stays matched at fixed frequency; whether B is the easy knob depends on the magnet - supply limits, inductance, hysteresis and settling time can make slow, repeatable B sweeps the hard part.

Shimming involves the insertion of thin iron sheets (typically 0.25 inches or less) between the pole faces and the vacuum chamber. ... the magnetic field changes too quickly near the edge of the shim. This is a result of making the shim too thick. ... In retrospect it appears that these shims were far too thick and created too dramatic of a change in magnetic field. While shims could still be used with the Houghton cyclotron, the thin shims these calculations suggest would be challenging to make

Morrow, Focusing in the Houghton College Cyclotron — Houghton College thesis (2015) — p. 25, 44, 46

Editorial note, tabletop extrapolation: Warns the builder off the obvious first shimming attempt; the useful shims are thinner than are convenient to fabricate and hold in place - model, or test progressively thinner shims against, the actual gap geometry.

the magnetic field actually increases in magnitude out to around r = 5 cm at which point it begins decreasing again. This is problematic because it yields a negative field index

Morrow, Focusing in the Houghton College Cyclotron — Houghton College thesis (2015) — p. 51-53

Editorial note, tabletop extrapolation: A concrete trap when adding iron or coils near the center of an 8-inch pole: check the sign of dB/dr over the whole usable orbit range, not just at the edge - the 5 cm crossover and the -0.1 index are that geometry's numbers, not general thresholds.

the difference in radius is minimal - about 0.2 cm - and comes at the steep cost of a ~20% reduction in maximum magnetic field from 1.27 T to 1.07 T. As such, this modification was considered insufficient.

Morrow, Focusing in the Houghton College Cyclotron — Houghton College thesis (2015) — p. 53-54

Editorial note, tabletop extrapolation: Saves a next machine's builder from spending months on one class of trim-coil fix inside a small gap (they also steal gap height) - but this is one modelled geometry: evaluate any other trim-coil design from its full B(r) map and orbit dynamics.

The maximum magnetic field of the unmodified design is B = 1.27 T and is B = 1.77 T for the lid design. ... B = 1.77 T corresponds to a Dee frequency of 27.0 MHz

Morrow, Focusing in the Houghton College Cyclotron — Houghton College thesis (2015) — p. PDF 54 (printed 49) and PDF 55 (printed 50)

Editorial note, tabletop extrapolation: Cheap in materials and potentially the highest-leverage change of this class, but the numbers are one thesis's model of one geometry: model your own lid as part of the magnetic circuit, verify the full B(r) and n(r), confirm the chosen stainless grade is actually ferromagnetic and vacuum/structurally suitable, and recompute energy from the usable orbit radius.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

much of the beam current is being lost by the time the beam reaches larger radii... This could be done by adding shims of ferromagnetic material between the chamber and pole faces.

Fuller, Exploring the Capabilities of the Houghton College Cyclotron — Houghton College thesis (2013) — p. 52-53

Editorial note, tabletop extrapolation: Predicts the current-vs-radius profile the builder should measure. If a next machine loses beam before full radius, diagnose first - map B(r) and n(r) and identify the loss mechanism - then shim, and re-verify field and transmitted current; a shim can worsen the index if misshaped.

the dBz/dr term was approximated by dBz/dr, where dr is the difference between two radii (1 cm)

Loucks, Initial Results from the Houghton College Cyclotron — Houghton College thesis (2007) — p. 36-38

Editorial note, tabletop extrapolation: A directly copyable measurement rig for a next machine's field map: rotating grooved aluminum disc plus angular scale gives B(r,theta) with hardware the builder already owns; average over theta before differencing, and tighten the spacing where the gradient changes fast.

The magnet's upper and lower coils are independently energized enabling an intentional axial field imbalance so as to vertically shift the accelerating plane.

Koeth, Undergraduate Education with the Rutgers 12-Inch Cyclotron (2015) — p. 2

Editorial note, tabletop extrapolation: Cheap beam-height trim for a next machine: two supplies, or a properly rated current-trim circuit on one coil, instead of re-machining anything - verify the result with a field or beam measurement, since unequal excitation perturbs the midplane symmetry it exploits.

Cited in: Beam Dynamics: An Interactive Laboratory

We have built a set of poletips designed to intentionally drive a destructive axial resonance; we refer to these as the 'bad' weak focusing poles tips. The n=0.2 location occurs near r=3.5 inches, well within the 5 inch DEE radius, so as to allow the ion displacement to grow. Since the n=0.2 is a difference resonance the axial peak-to-peak amplitude is bounded by the initial radial offset. A displacement of the chamber's center of about 3mm with respect to the magnet center was necessary to seed the resonant axial blow up

Koeth, Undergraduate Education with the Rutgers 12-Inch Cyclotron (2015) — p. 5

Editorial note, tabletop extrapolation: Shows how little margin there is between good and bad tapers on an 8-12 inch machine; motivates measuring n(r), not guessing it.

Cited in: Beam Dynamics: An Interactive Laboratory

A 30 AWG wire loop, with a circumference of 71 mm, was energized with a current of 2.5 amps and placed in the magnet gap. ... The energized wire loop simply needed to be tossed towards the gap and it would reproducibly snap to the nearest stable orbit.

Koeth, Undergraduate Education with the Rutgers 12-Inch Cyclotron (2015) — p. 7

Editorial note, tabletop extrapolation: A cheap field-quality diagnostic, but run it as an engineered experiment, not a party trick: current-limit and isolate the supply, insulate and restrain the leads, set up de-energized, check the wire's temperature rise at the chosen current, and mind magnetic forces and pinch points around a 0.5-1 T gap.

The iron shaping methods zoo: Change the ratio of hill/valley spanned angle with radius ... Prevent field decrease at large radii ... Decrease the gap along radius ... Lateral edges milling ... Iron inserts ... Change local saturation

Beeckman, Cyclotron Magnets — ECPM37 lecture, Groningen (2009) — p. 34-46

Editorial note, tabletop extrapolation: A menu of things the builder can machine on 8-inch pole tips, drawn from practice on real cyclotrons; movable flaps in particular give post-build adjustability. Unordered and geometry-dependent - model (FEMM) and map before machining any of them.

The 3D geometry is modelled with a 2D code in axisymmetry using pseudo-materials. The stacking factor is the proportion of the circle occupied by the real material. Each pseudo-material is defined by a modified B-H curve

Beeckman, Cyclotron Magnets — ECPM37 lecture, Groningen (2009) — p. 74

Editorial note, tabletop extrapolation: Lets a hobbyist study an AVF pole set's average field and yoke sizing in free 2-D codes (POISSON/FEMM) before committing to a 3-D solver; the azimuthal flutter and edge focusing that make an AVF machine work need the 3-D model or measurement.

YOU must be in control of the mesh, not the code. A limited amount of quadratic elements is much more effective to accuracy than many linear elements

Beeckman, Cyclotron Magnets — ECPM37 lecture, Groningen (2009) — p. 83

Editorial note, tabletop extrapolation: Explains noisy field-index curves out of a home simulation: n and nu_z are derivatives, so mesh quality matters far more than for B itself.

Is the rest of the universe far enough ? TEST IT! ... Codes are very good in the computation of small changes between 2 models but less good at absolute values.

Beeckman, Cyclotron Magnets — ECPM37 lecture, Groningen (2009) — p. 85-86

Editorial note, tabletop extrapolation: Practical simulation hygiene: use FEMM/POISSON to compare shim options (differences), and use the Hall probe for the absolute field.

The shims were machined from 2 1/4 in. steel plate on a vertical boring mill ... The magnetization curve taken at the center of the tank with the contour shims in place is also shown. ... It is possible then to make minor changes in the shims and to take a complete set of field measurements in a few hours. ... After the contour shims were installed, field measurements indicated that the flux in an area of 3 to 4 square feet was ... higher than in the rest of the tank at corresponding radii. Approximately 0.020 in. of material from each pole over the area opposite the high field region was removed in about two hours with a portable grinder.

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 35, 116

Editorial note, tabletop extrapolation: Directly applicable method: leave gap allowance for machined shim rings/plates so a next machine's field shaping is a measurement-and-remachining loop, not a magnet rebuild - and note ORNL fixed a residual local error by grinding the pole, so plan for both add and remove operations.

By means of auxiliary coils wound on the pole pieces it is possible to control the position of the beam with respect to the median plane of the tank. The coils consist of 65 turns of #6 wire wound on each pole piece. A dc power supply provides up to 75 amperes

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 35

Editorial note, tabletop extrapolation: Cheap and direct for a next machine: an auxiliary winding on the poles gives a vertical-centering knob instead of mechanical re-shimming - size its ampere-turns from the field asymmetry the orbit calculation asks for (the 86-inch used up to ~4900 A-turns; a small machine needs proportionately less, but compute it), with a reversible supply and thermal check.

Cited in: Beam Dynamics: An Interactive Laboratory

A position of suitably low field intensity, < 60 oersteds, was located by mapping the stray field about the magnet.

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 59

Editorial note, tabletop extrapolation: Map the reference machine's H-frame fringe field with a Hall probe and site the LDMOS amplifier, its magnetics and instrumentation by each component's OWN field tolerance - 60 G is the historical machine's siting outcome, not an immunity standard. Copper lining screens RF and electric fields, not the DC fringe; DC-sensitive items need distance or a high-permeability shield.

The error due to probe position varies depending on the field gradient ... techniques available to us at this time fall short of the desired 0.1% accuracy.

Livingston & Howard (eds.), The Oak Ridge Relativistic Isochronous Cyclotron — ORNL-2648, OSTI 4275955 (1958) — p. 31

Editorial note, tabletop extrapolation: Directly applicable to a next machine's shimming: regulate and MONITOR magnet current during a map (in a linear magnet, current error maps ~1:1 into field error, so the regulation must beat the field goal, not just approach it), index the probe mechanically, and write the error budget with its combination rule before trusting shim-sized differences.

The voltage breakdown strength of a resin-impregnated layer of glass cloth or cotton mesh is usually over 100 volts/mil ... necessary to utilize mica-sheet or mica-flake insulation to obtain the higher voltage-to-ground insulation.

Livingston & Blewett, Particle Accelerators (1962) — p. 278

Editorial note, tabletop extrapolation: Potting the reference machine's coils stops the slow insulation abrasion that coil hum causes. The >100 V/mil figure is the source's historical material datum, not an allowable design stress: size insulation from maximum turn-to-turn and coil-to-ground voltage with margin for voids, transients, creepage and temperature - the quote itself reserves voltage-to-ground duty for mica - and prove the finished coil with a hipot test rather than resting on the coupon number.

The conductivity is maintained at 10 micromhos or less, with a pH of about seven. Dee system water temperature stability of 1 F or better is required for steady operation.

Ramler & Parker, The Argonne 60-Inch Cyclotron — ANL-5907 (1959) — p. 6

Editorial note, tabletop extrapolation: Two portable METHODS, not specs: monitor conductivity and pH on any hollow-conductor DI loop, and stabilize dee-water temperature if a next machine water-cools the dee (the RF tune walks with dee temperature). Set the actual limits from conductor material, voltage to ground, and measured RF drift, not from ANL's numbers.

It is necessary for the secondary coil to be cooled with oil or deionized water... because even minute thermal expansion of the copper can change the inductor's value.

Heuer & Baumgartner, Design of a 2 MeV Cyclotron (2009) — p. 23

Editorial note, tabletop extrapolation: Explains RF drift during long runs at the reference machine's power levels; cooling the tank coil stabilizes tune.

Using this type of winding allows for a more uniform field than a simple spiral winding.

Heuer & Baumgartner, Design of a 2 MeV Cyclotron (2009) — p. 32-33

Editorial note, tabletop extrapolation: A rebuild of the reference machine's 538 turns as potted double-pancakes with a cooling manifold is an attractive concept - as a design study: pancake count, potting, parallel water paths and repairability are engineering choices needing their own magnetic, hydraulic and thermal analyses, not properties the source's uniformity comparison confers.

Our magnet can achieve a maximum temperature of 173 oF and will normally operate at no more than 142 oF.

Heuer & Baumgartner, Design of a 2 MeV Cyclotron (2009) — p. 33

Editorial note, tabletop extrapolation: Set a next machine's potted-coil design point from the resin system's rated thermal class and a modeled or measured hotspot with margin for cooling failure - not from another magnet's numbers. Note 61 C at ordinary ambient is already a 36-41 C rise, looser than Tanabe's ~30 C-rise guidance for long potted-coil life.

f = 64/Re for laminar flow Re < 2000. For turbulent flow (Re>4000), the friction factor is gotten by solving a transcendental equation.

Tanabe, Iron Dominated Electromagnets, Lecture 6: Excitation, Coil Design, System Design and Water Flow (2005) — p. 32-34

Editorial note, tabletop extrapolation: The straight-passage core of hydraulic sizing for any hollow-conductor or tubing-wound coil - add bends, fittings and manifold (minor) losses on top, and confirm with a flow test; the formula alone is the floor, not the whole recipe.

For water velocities > 15 fps, flow vibration will be present resulting in long term erosion of water cooling passage.

Tanabe, Iron Dominated Electromagnets, Lecture 6: Excitation, Coil Design, System Design and Water Flow (2005) — p. 42

Editorial note, tabletop extrapolation: The cited source's upper design guideline when sizing pump and passage diameter for a hollow-conductor coil; onset of vibration and erosion also depends on bend severity, passage geometry, material and water chemistry, so use a lower limit where conductor-manufacturer guidance or testing warrants.

Pressure drop can be decreased by a factor of eight if the number of water circuits are doubled.

Tanabe, Iron Dominated Electromagnets, Lecture 6: Excitation, Coil Design, System Design and Water Flow (2005) — p. 47

Editorial note, tabletop extrapolation: Argues for manifolded pancake sub-coils on a next machine instead of one long series water path through 538 turns.

If the design hole diameter is increased, the required pressure drop is decreased dramatically. If the fabricated hole diameter is too small... pressure drop can increase substantially.

Tanabe, Iron Dominated Electromagnets, Lecture 6: Excitation, Coil Design, System Design and Water Flow (2005) — p. 48

Editorial note, tabletop extrapolation: When choosing hollow conductor for a next machine, weigh bore against copper cross-section (a bigger hole raises electrical resistance) and flow-test each pancake before potting - the fabricated bore, not the drawing, sets the pressure drop.

This test can only be performed on a coil isolated from metallic surfaces and will not work once the coil is installed on the core. ... the iron permeability will mask the expected behavior of the electrical circuit.

Tanabe, Iron Dominated Electromagnets, Lecture 9: Coil Fabrication, Testing and Electrical Safety (2005) — p. PDF p.18 (slide deck, unnumbered); procedure on PDF p.17, hipot/QA context pp.19-20

Editorial note, tabletop extrapolation: A pulse source, capacitor and scope let the builder screen the next machine's coils before they are trapped under the yoke - run the impulse test during fabrication, before the coil goes on the core, and photograph the low- and high-voltage waveforms as the baseline. Both tests put hazardous voltage on the coil: use rated, current-limited test gear, discharge and ground between steps, and keep others clear.

Water flow calculations made for the preliminary design may be unreliable for a coil designed with many tight turns... due to the added flow impedance of tight radius turns.

Tanabe, Iron Dominated Electromagnets, Lecture 9: Coil Fabrication, Testing and Electrical Safety (2005) — p. 25

Editorial note, tabletop extrapolation: A bucket-and-stopwatch flow test at operating pressure is the real spec for the reference machine's 538-turn tubing coil (many turns; check its bend radii against the passage size). Record water temperature - viscosity matters most if any branch runs laminar - and measure each parallel branch separately, since a total-flow test hides an imbalance.

Water hoses should be at least one meter long and use nonconducting material to prevent current leakage from the magnet. The water “in” fittings should be smaller than the water “out” fittings ... If a flow interlock (orifice plate) is used, it should be attached to the return manifold.

Tanabe, Iron Dominated Electromagnets, Lecture 9: Coil Fabrication, Testing and Electrical Safety (2005) — p. 3

Editorial note, tabletop extrapolation: The reference machine's water-cooled copper-tubing coil sits at supply potential; a meter of non-conducting hose per lead limits leakage current, and an interlock on the return detects a blocked circuit - cheap practices worth copying at home scale. They reduce specific risks; they are not shock protection as a whole, which still rests on earthing and supply-side protective devices.

The normal set-point of Klixons is about 89 C. It will generally reset at about 70 C ... One thermal interlock is installed on each water circuit ... All the interlocks on one magnet are connected in series. ... The Klixon is preferably mounted on the water return lead of the coil ... always mounted on the current carrying portion of the conductor ... mounted to a block hard-soldered to the conductor.

Tanabe, Iron Dominated Electromagnets, Lecture 9: Coil Fabrication, Testing and Electrical Safety (2005) — p. 5-7

Editorial note, tabletop extrapolation: A thermal snap-switch soldered to the coil exit tube, wired in series with the supply enable, is cheap, high-value protection against cooking a winding on a lost-water event - alongside the flow interlock (dg-202), not instead of it. Set-point and switch rating are the designer's to verify against the winding's own insulation limit.

ordered blank or pre-impregnated with varnish (0.02 ≤ t ≤ 0.1 mm) or half-overlapped polyimide (Kapton®) tape (0.1 ≤ t ≤ 0.2 mm) ... a filling factor between 0.63 (round) to 0.8 (rectangular) can be obtained.

Zickler, Basic Design and Engineering of Normal-Conducting, Iron-Dominated Electromagnets — arXiv:1103.1119 (2010) — p. PDF 29 (printed 93) for the quoted sentence; PDF 28-29 (printed 92-93) for the varnish/Kapton/filling-factor figures

Editorial note, tabletop extrapolation: Sets expectations for how much winding window the insulation eats on a hand-wound 538-turn coil - then compute the actual packing factor from the chosen conductor's finished insulated dimensions and the real winding layout, since fill depends on shape, pattern and voids, not on insulation thickness alone.

For a bending radius of three times the conductor width we can expect a keystoning of 3.6% ... we can ignore the effect of keystoning by systematically choosing a bending radius four times larger than the conductor width.

Zickler, Basic Design and Engineering of Normal-Conducting, Iron-Dominated Electromagnets — arXiv:1103.1119 (2010) — p. 30

Editorial note, tabletop extrapolation: For bending round copper tubing on a homemade coil the analogous risks are ovalization and bore pinch: use tube-specific minimum-bend-radius and ovality limits (diameter, wall, temper and tooling all matter), inspect or flow-test the formed passage, and watch the insulation at the bends.

Water resistivity higher than 0.1x10^6 Ohm m; pH-value between 6 and 6.5; dissolved oxygen below 0.1 ppm

Zickler, Basic Design and Engineering of Normal-Conducting, Iron-Dominated Electromagnets — arXiv:1103.1119 (2010) — p. 34

Editorial note, tabletop extrapolation: If a next machine uses water-cooled coils at supply potential, ordinary tap water misses all three quoted limits. A deionizing cartridge loop is the standard way to hold resistivity, but the spec is three-dimensional - oxygen and pH need their own control - and the source pairs the water spec with filters near the magnet.

flat donuts of 1/16 in. copper sheet ... During operation cold water is run through this set of pipes; together with a large fan for general circulation, such coils should operate steadily at 1300 amps per sq. in.

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. PDF p.4 (printed -5-); comparative current-density framing on PDF p.3 (printed -4-)

Editorial note, tabletop extrapolation: A cheap construction to reach for when a next machine's pancake coils run hot: 1/16-inch copper donut plates with soldered edge tubing between pancakes. The 1300 A/in^2 is the historical design target for that geometry, not a number to adopt - recompute I^2R, water flow and temperature rise, the thermal path through the insulation, and solder and tube reliability, then measure winding temperature in operation. [Note revised 2026-08-23: earlier note called it a directly applicable upgrade that 'nearly doubles' allowable excitation.]

These windings saturate the iron (~20 KG) at somewhat less than ten amperes; at this current the temperature becomes excessive in less than an hour

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 4

Editorial note, tabletop extrapolation: Directly applicable cautionary datum: quote coil ratings as (current, time-to-overheat) pairs, not just maximum field.

The magnet coil circuit must never be broken at high currents, of course, unless adequate surge protection is provided.

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 5

Editorial note, tabletop extrapolation: Directly applicable: any magnet coil whose stored energy exceeds a few joules needs a dump path across the winding - freewheel diode, varistor, or resistor - rated for the coil's stored energy, peak current and clamp voltage. Without one, opening the circuit at current can arc the switchgear.

An alarm warns the operator when the coil temperature has reached a predetermined value, usually 70 to 80 C ... one to three hours are required for the temperature to reach equilibrium ... the maximum life of the magnet coil insulation, which the manufacturer estimates will vary with temperature as follows: [table: 79 C, 8-40 years; 87 C, 4-20 years; ... 130 C maximum allowable]

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 33

Editorial note, tabletop extrapolation: Directly applicable: put a thermocouple in the next machine's winding and log it; a coil that is fine at 30 minutes can still cook at 2 hours. The 130 C figure is this manufacturer's rating for this insulation - a next machine's ceiling is its own insulation's thermal class.

It is important for the coils should be in the air stream of one of the cooling fans (they will run hot if not).

Buckler, Solid-State, 2-Decade, 1.25 kW Linear Amplifier — Development Notebook (2015) — p. 28

Editorial note, tabletop extrapolation: Applies to the homemade dee-tank coil: assess its RF loss and temperature under the intended loaded-Q and coupling conditions (resonator circulating current depends on Q and coupling, not on the DC feed), and give it forced air if it runs hot.

This operated normally at 65 C but when an identical coil, which had been nickel plated, was substituted, the operating temperature rose to 350 C.

Fowler, Radio Frequency Performance of Electroplated Finishes — Proc. IREE Australia (1970) — p. 4

Editorial note, tabletop extrapolation: Reject nickel-plated hardware anywhere RF current flows in the resonator, coil, or ground-return path unless the overplate is verified thick and continuous - or validate by measuring loss and temperature.

typically have true Q values of up to about 800. Very few practical circuits require a Q above 900. Attempting to design a coil with a True Q much over 1,000 usually results in a coil with abnormal physical dimensions

Murphy, The Elusive Q of Single-Layer Air-Core Coils — CQ Magazine, May 1999 (1999) — p. 1

Editorial note, tabletop extrapolation: Do not budget the resonant step-up on textbook thousands: measure or model the loaded Q of the actual resonator under representative coupling (loaded Q sits well below the coil's unloaded Q), then size the amplifier for 5-13 kV dees from that measurement.

Q increases with coil diameter (see figs. 1-4). Q increases with coil length, rapidly when the L/d ratio is small ... Q increases with frequency

Murphy, The Elusive Q of Single-Layer Air-Core Coils — CQ Magazine, May 1999 (1999) — p. 1-2

Editorial note, tabletop extrapolation: At 9 MHz a 3-4 inch diameter tank coil in the charted geometries reads Q over 1000. At fixed frequency and capacitance the dee voltage scales as sqrt(P*Q) - doubling Q at the same drive buys about 40% more voltage, not double - so treat Q gains as helpful, and verify with the loaded Q actually measured.

The conductor diameter must be within the range of 0.45 and 0.70 times the center-to-center distance between adjacent turns (not all commercial stock coils meet this condition).

Murphy, The Elusive Q of Single-Layer Air-Core Coils — CQ Magazine, May 1999 (1999) — p. 2

Editorial note, tabletop extrapolation: For a 9 MHz matching/tank inductor, space the turns so the wire fills 45-70% of the pitch - close-winding bare tubing costs Q (proximity effect is the standard explanation, beyond this source's scope) - and check any stock coil against the ratio before trusting its rated Q.

Maximum Q occurs at a coil L/d ratio of between (depending on other coil design parameters) 0.35 and 0.45, decreasing rapidly below that ratio and more slowly above

Murphy, The Elusive Q of Single-Layer Air-Core Coils — CQ Magazine, May 1999 (1999) — p. 2-3

Editorial note, tabletop extrapolation: Make the resonator coil short and fat (length a bit under half its diameter), not the long skinny solenoid that fits most easily in a corner - and not a pancake either: below the optimum Q collapses quickly.

after a power level of 200 watts, the measured voltage of the P6015 probe departed from the trend and dropped below the expected value. It is as if an additional resistance is introduced. The behavior was similar to that of a high-resistance break-down ... while the P6015 probe's value deviated from the trend, the induced voltage on the chamber's capacitively coupled pickup continued to followed the trend which was consistent with the theoretical model ... the induced voltage on the capacitive pickup facing the DEE was calibrated against forward power at lower levels. Extrapolation allowed us to measure forward power levels up to 1300 watts

Koeth, Theoretical Calculations and Measurements of the DEE Voltage in the Rutgers 12 Inch Cyclotron (2005) — p. 3-4

Editorial note, tabletop extrapolation: The measurement chain for the LDMOS upgrade, rebuilt on the reference machine's own hardware: calibrate its pickup against an independently validated dee-voltage measurement over an overlapping safe range, confirm linearity and unchanged tuning, and never transfer the 3710 ratio or the power breakpoints between machines.

The connections to one of the coils are then interchanged and the equivalent inductance is measured again. The difference between the two measured inductances is then 4M.

Koeth, Theoretical Calculations and Measurements of the DEE Voltage in the Rutgers 12 Inch Cyclotron (2005) — p. 5-6

Editorial note, tabletop extrapolation: A bench L-C meter trick for characterizing the coupling loop: measure series-aiding and series-opposing, difference is 4M. The M a matched loop NEEDS follows from M = sqrt(R_tank*Z_source)/omega with the tank's measured series resistance and the source impedance at the operating frequency - compute it for the actual tank rather than expecting a stock tens-of-nH answer.

is exactly 1/2 of Qo when the primary is critically coupled corresponding to the value giving maximum response ... a simple reflected RF power meter will suffice to show a perfect match - indicating critical coupling.

Koeth, Theoretical Calculations and Measurements of the DEE Voltage in the Rutgers 12 Inch Cyclotron (2005) — p. 6-7

Editorial note, tabletop extrapolation: The builder can tune their coupling loop with just an SWR bridge: adjust loop position/taps until reflected power nulls, and check Qloaded = Q0/2 with a NanoVNA S21 sweep.

From Fig.12 we determine Qmeasured at a distance of 11mm to be 460. This implies a Qo of 920.

Koeth, Theoretical Calculations and Measurements of the DEE Voltage in the Rutgers 12 Inch Cyclotron (2005) — p. 6-8

Editorial note, tabletop extrapolation: A benchmark to scale, not a floor: for the reference machine's ~9 MHz tank, skin-effect scaling of the same coil suggests Q0 ~ sqrt(9/15)*920 ~ 700-class; a measured Q0 far below the scaled expectation is the excess-loss flag (bad joints, steel in the return path) worth hunting.

Empirically it was found for a given forward power into each of the (50+j0) Ohm points, the peak capacitor voltage was always the same.

Koeth, Theoretical Calculations and Measurements of the DEE Voltage in the Rutgers 12 Inch Cyclotron (2005) — p. 7

Editorial note, tabletop extrapolation: Good news for coupler design: don't agonize over loop position vs tap point - but on a new tank, after nulling reflected power, verify dee voltage and coupler temperature once per geometry before treating settings as equivalent; a nominal match can hide coupler or cable loss.

the original purpose of the shield was to prevent RF from coupling to the pickup ... We agreed a large series inductance (an RF Choke) should mitigate this concern.

Koeth, Rutgers 12 Inch Cyclotron Ion Source Studies: Part I (2006) — p. 1

Editorial note, tabletop extrapolation: For nA-level collection near a ~9 MHz dee, treat the choke as one element of a verified filter: choose it from measured impedance and self-resonant-frequency data at the RF frequency, keep whatever shielding the noise floor turns out to demand, and validate by running RF with no beam - displacement currents into an unshielded tip can dwarf the beam signal.

there will be a somewhat lower potential at the ends of the D faces nearest the lines ... measured in some cyclotrons to be as great as 5 per cent ... a displacement of the ion source of over 2 in. has been necessary.

Livingston & Blewett, Particle Accelerators (1962) — p. 164

Editorial note, tabletop extrapolation: Make the source mount adjustable in both directions and tune position for beam, not for geometric center. Size the travel from RF-field and orbit modelling for the actual dee geometry - the large machines needed over 2 inches; what a tabletop machine needs is its own calculation, and generous commissioning range is cheap.

Cited in: Beam Dynamics: An Interactive Laboratory

these tubes spaced as closely as 2 to 3 in. to prevent local heating and warping of the D's under power. Approximately 10 kw of heat is dissipated in each D and D line during operation.

Livingston & Blewett, Particle Accelerators (1962) — p. PDF p.175 (printed p.159)

Editorial note, tabletop extrapolation: At tens of RF watts the builder likely needs no water, but check rather than assume: what matters is local RF current density and the thermal path, not total power. Dee thermal drift detunes the resonator - keep dee structures stiff and thermally anchored, and watch tuning drift as power rises.

At MIT, with an internal D aperture of 1.6 in. the optimum length of ionization column was 5/8 in. For 4-in.-wide D's in the Carnegie Institution 60-in. machine it was 1 3/8-in.

Livingston & Blewett, Particle Accelerators (1962) — p. 178

Editorial note, tabletop extrapolation: Hood or collimate the reference machine's source with the exposed column ADJUSTABLE, starting near a third of the aperture height, and optimize against extracted beam and dee voltage together - the historical ratios locate the starting point; the machine's own optimum may sit elsewhere.

A technique frequently used to adjust or trim the relative resonant frequencies of the two D-line circuits is to use one or more trimmer capacitors which can be adjusted by remote control under full power operation. Such a variable capacitance can be provided by a movable plate on the side wall of the chamber facing one edge of the D. It must have excellent electrical contact to the walls for the radiofrequency currents and a range of motion sufficient to tune over about 1 per cent in frequency. The availability of such a tuning device makes it possible to adjust relative D voltage as desired for optimum operation.

Livingston & Blewett, Particle Accelerators (1962) — p. 188

Editorial note, tabletop extrapolation: A bellows-actuated plate near the dee gives the builder live resonance trim without opening the chamber - invaluable when thermal drift walks the dee frequency.

It is common experience, however, that no amount of smoothing or polishing will eliminate the necessity of some high-voltage conditioning under vacuum. Clean laboratory techniques in preparing a chamber for reassembly after opening are essential; dust should be controlled and all grease removed (even fingerprints), and under no circumstances should steel wool or coarse abrasives be used in cleaning. The oscillator circuit must be capable of driving the cyclotron through these varied conditions of sparking and discharge, without the necessity of tuning or of manual resetting of overload relays.

Livingston & Blewett, Particle Accelerators (1962) — p. 189

Editorial note, tabletop extrapolation: After every chamber opening, ramp dee voltage gradually with vacuum and arc-rate monitoring until sparking subsides before expecting stable beam; how long that takes is the machine's answer, not a fixed budget.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

about 50 per cent thicker than the depth of the groove to allow for compression ... 1/4-in. gaskets have proved adequate for even the largest seals ... Conductivity for rf currents through such a seal can be assured by half-covering the gasket with a thin copper-foil strip. ... Most natural or artificial rubbers have unacceptable vapor pressures and also deteriorate when used with lubricating greases. Neoprene is free of these faults and is widely used in cyclotrons.

Livingston & Blewett, Particle Accelerators (1962) — p. 199-201

Editorial note, tabletop extrapolation: The copper-foil RF bridge over elastomer joints prevents mysterious Q loss and local heating and transfers directly. For the gasket itself, a modern machine should size grooves from the O-ring manufacturer's vacuum-service squeeze and gland-fill tables - the historical 1.5x ratio is the era's flat-gasket practice, not an O-ring spec.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

It would only take a few cycles, on the order of 12, for most cyclotrons to have reached this velocity.

King, A Preliminary Design for a Small Permanent Magnet Cyclotron — Houghton College thesis (2002) — p. 20

Editorial note, tabletop extrapolation: Explains failed runs where beam dies at small radius, and quantifies how little phase budget a mistuned machine has - for the actual machine, integrate the slip turn by turn from the measured B(r) and dee voltage rather than using 12 turns as a threshold.

Dielectric strength / Thickness: 240 kV/mm at 0.025 mm; 70 kV/mm at 5 mm.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 523

Editorial note, tabletop extrapolation: When insulating the reference machine's extraction or dee leads, design from certified data for the actual material, thickness, frequency and environment - a bulk breakdown number is a test-condition figure, not a working rating. Grade the field at edges, design creepage and surface flashover paths separately, and qualify the finished assembly under vacuum with a conservative withstand test.

the SWR measured using this directional coupler is 1.08 and 1.03 for 28 dB and 35 dB of directivity, respectively

Blodgett, 3.5 to 30 MHz Automatic Antenna Impedance Matching System (2012) — p. 19-20

Editorial note, tabletop extrapolation: Do not chase - or trust - SWR readings within the bridge's directivity band: near-1.0 does not prove a good match any more than 1.08 proves a bad one. Characterize the actual homebrew bridge's directivity first; then readings inside its band are 'unresolved', not data.

Figure 42 - 30 W to 100 W Power Calibration Setup using Bird 43 Wattmeter

Blodgett, 3.5 to 30 MHz Automatic Antenna Impedance Matching System (2012) — p. 57-58

Editorial note, tabletop extrapolation: A Bird 43 (owned or borrowed) transfers power calibration to permanently installed cheap sensors - within the installed element's frequency range, power range and its own accuracy spec, so record which element was used. Take the AD8307's slope and intercept from its datasheet and the actual unit's measured response, not nominal folklore.

high precision is necessary for a coil or circuit with a high Q value ... The Q of this cyclotron was measured at 1600, under no loading.

Chun, The Cyclotron Magnet and RF Oscillator (2003) — p. 11-12

Editorial note, tabletop extrapolation: A benchmark, not an expectation: measure the reference machine's own unloaded AND loaded Q, compare against a loss model to decide whether joints are costing Q, and judge retuning needs from measured thermal drift against the loaded bandwidth - Q alone predicts neither the drift rate nor the need for active tuning.

For typical cases of interest, 'vacuum' pressure is lower than 10-5 torr, and 'gas' pressure higher than 10-4 torr.

Werner, Probing and Modeling Voltage Breakdown in Vacuum — Cornell dissertation (2004) — p. 23

Editorial note, tabletop extrapolation: A gas-fed cyclotron chamber often sits in exactly this transition decade, so the spark limit can move with operating pressure: measure holdoff with the actual gas flowing at operating pressure as well as at base vacuum, and interlock conservatively - which direction the limit moves depends on where the geometry sits relative to the Paschen minimum.

Cited in: The Vacuum Budget of a Cyclotron

The power and length of application should be gradually increased until the vacuum remains less than 10^-4 mm with r.f. on steadily at, perhaps 2 kv. ... it may mean the presence of organic matter in the tank

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. PDF p.10 (printed -11-)

Editorial note, tabletop extrapolation: Directly applicable startup ritual at the reference machine's 1.3 kV dee level - ramp in short bursts with current-limited RF, arc detection and pressure monitoring. The report reads failure to reach its endpoint as organic contamination (grease, oil, rubber) in the tank; leaks and ordinary outgassing can mimic it, so inspect or run an RGA before blaming contamination.

Cited in: The Vacuum Budget of a Cyclotron

All circuits connected to tank elements should have adequate choking and bypassing to prevent r.f. from reaching the meters and supply lines.

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 9

Editorial note, tabletop extrapolation: Directly applicable: the reference machine's beam-current, bias and gauge lines all deserve feedthrough RC/choke filtering at 9 MHz - with 'adequate' proven by measurement: an RF sniff at the meter terminals with the transmitter running.

Mammoflex M-1 HV cable has C of 56 pF per foot ... ~20 feet total ~0.4 Joules at 30 kV ... Removed excess cable. Run is now ~ 5 feet total

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 43-49

Editorial note, tabletop extrapolation: For any HV feed on a next machine (deflector, source bias): keep cable runs short. Stored cable energy is delivered into an arc in the first instant, faster than any supply limiter acts - it adds to what the supply and other capacitances feed the fault, it does not replace them. Series resistance at the load (dg-286) limits the follow-on current.

We've encased the resistor in a grounded shield, and the coax shields go through 68 Ohm, 2 watt resistors ... 150 Meg HV resistor ... 5 Meg HV resistor ... inside an acrylic tube covered with copper mesh.

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 49 (also 43, 45, 47, 48)

Editorial note, tabletop extrapolation: A staged-resistance pattern for electrostatic HV feeds (deflector, PIG source bias) whose load draws no standing current: series megohms limit arc current at the price of regulation under load, so it does not transfer to circuits that must deliver current. Even with this shielding the arcs stopped only after the cable-energy fix (dg-285) - resistors limit damage, they don't prevent flashover.

Calculation showing first ions squeak by at 165 Watts ... Beam current abruptly dropped to zero at 170 watts !

Koeth et al., The Rutgers 12-Inch Cyclotron for Students (2010) — p. 20

Editorial note, tabletop extrapolation: A free end-to-end CONSISTENCY check for the builder: the power at which beam vanishes ties the trajectory model, the dee-voltage estimate and the RF chain together at one point. It is a cross-check, not a probe-independent voltage measurement - source emission, phase, pressure and detector sensitivity all sit inside the observed threshold - so use it alongside a calibrated pickup, not instead of one.

the DEE, chamber, tank coil, etc. heat up and slightly change the resonant frequency ... A DC 'error signal' is derived from comparing the phase of the driving RF to the Phase of the DEE pickup.

Koeth et al., The Rutgers 12-Inch Cyclotron for Students (2010) — p. 21

Editorial note, tabletop extrapolation: At 100-500 W expect real warm-up drift and MEASURE it: the measured drift against the loaded bandwidth decides whether hand-touchup, a slow motor loop, or nothing is needed. The cyclotron constraint is the point - the RF must stay synchronous with qB/(2 pi m), so the resonator follows the beam frequency, not the other way round.

Beam Inferred DEE Voltage ... In the 1st half revolution E(r) = (qB^2/2m) r^2 = 1/2 Vp-p

Koeth et al., The Rutgers 12-Inch Cyclotron for Students (2010) — p. 33

Editorial note, tabletop extrapolation: The builder can cross-check a dee-voltage estimate by measuring where the first half-turn lands - the beam is the most honest voltmeter - provided the landing radius is converted to orbit radius using the actual source-to-probe geometry, and the ion is assumed to cross near peak phase (real phases read low).

A large increase in current occurs only as the local field approaches 10^10 V per meter... After several minutes of current flow at the constant voltage, a remeasurement of the threshold voltage shows that it has increased. This phenomenon is called conditioning.

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 111-113

Editorial note, tabletop extrapolation: Bring the reference machine's dee and extraction voltages up gradually on first pump-down, watching for micro-discharge pulses. Conditioning raised the measured threshold in the source's account; the gain is not permanent capital - re-condition after venting rather than assuming the old ceiling still holds.

The optimum ratio as r_i/r_o = 1/e. This optimum ratio minimizes the stresses within the coaxial electrode arrangement, independent of the material of the dielectric used. ... In order to keep stress at Z below that at X in Fig. 4.15, the radius of curvature at Z should not be less than the radius of the inner cylinder.

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 117, 122-124

Editorial note, tabletop extrapolation: Preliminary ideal-coax sizing for the reference machine's HV stalk: a grounded 25-mm-bore port gives a ~9.2-mm center conductor at the 1/e optimum - then check the complete feedthrough (ends, dielectric interfaces, triple junctions) electrostatically, and never leave a sharp-edged washer or nut on the HV end.

This phenomenon causes the cathode grid material from the IEC device to be deposited on the high-voltage (HV) stalk. That can in time cause premature breakdown at the stalk. ... The electrode is surrounded by a coaxial aluminum tube, which in turn is shadowed by a coaxial large diameter, aluminum tube. ... The stalk is a conical-shaped insulator facing toward the cathode grid that is expected to block the ions passing through the cathode grid. ... The corrugated surface is intended to lengthen surface current path lengths, preventing premature surface breakdown.

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 87, 105, 109

Editorial note, tabletop extrapolation: In the reference machine's small chamber everything sees the source; a washer-stack or skirt shielding the feedthrough ceramic from the chimney slit is the same shadow-shield idea and should lengthen time between cleanings - validate on the actual geometry, since much of the sputtered flux travels as neutral atoms and simple line-of-sight shielding is the right first-order defense.

the location of current spikes at a given field strength always occur at or very near the theoretical resonances... at B/3, B/5, and so on.

Fuller, Exploring the Capabilities of the Houghton College Cyclotron — Houghton College thesis (2013) — p. 46-47

Editorial note, tabletop extrapolation: Essential for interpreting the reference machine's magnet scans: a peak at one-third field is likely a subharmonic, not a mystery species. H2+ vs H+ assignments need more than one matching peak - or an independent species diagnostic - since different q/m patterns can overlap.

the RF generator was adjusted in steps of 0.5 MHz ... adjusted in steps of 0.1 MHz near the maximum voltage ... a third sweep was performed using steps of 0.01 MHz ... The data points represent the voltage gain between the RF amplifier and the dee. The voltage gain will be a maximum at the resonant frequency. For this plot, f0=3.55MHz.

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 63-64

Editorial note, tabletop extrapolation: A simple, scope-only resonance-finding recipe after any mechanical change to a next machine's dee or stem: coarse-to-fine, with the fine step sized to the resonance linewidth rather than copied - and use a rated or noncontact voltage pickup on the dee side.

the resonant frequency occurred at f0=3.55 MHz ... Its results were f0=3.63 MHz at a SWR of 1.4:1 ... when the CT2591 HV probe was placed near the dee, the overall capacitance changed slightly. This would, of course, change the value of the resonant frequency.

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 64-65

Editorial note, tabletop extrapolation: When cross-checking NanoVNA SWR sweeps against powered probe measurements, probe loading is the first hypothesis for a small frequency disagreement - confirm it (adding the probe should lower the frequency, repeatably) before ruling out coupling, calibration-plane or mechanical causes; Houghton's 2 percent is their number, not a generic tolerance.

By comparing the CT2591 HV probe with the pickup probe, a scaling factor can be determined ... It was determined that the real voltage was roughly 11,300 times the pickup voltage. The frequency of the RF system will affect the values recorded by the pickup probe. For this reason, the probe had to be recalibrated every time the frequency was adjusted. The results given here were for a frequency of 3.55 MHz. ... A linear fit was performed and indicated that the real voltage was roughly 11,300 times the pickup voltage at an RF frequency of 3.55 MHz.

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 65-66

Editorial note, tabletop extrapolation: The pickup scale factor is frequency-dependent - the builder must recalibrate their pickup whenever they retune, not assume one constant.

First, the RF system was tuned to a resonant frequency of 3.55 MHz while the filament was set to 2.0 A and floated at -100 V relative to the chamber. At these settings, a SWR of 1:1 and forward power of 15.43 W were measured. ... there is a resonance peak with a magnitude of 1.5 pA at around 0.23 T. ... Collection took place at a radius of roughly 5.95 cm corresponding to proton energies of 9.2 keV.

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 69

Editorial note, tabletop extrapolation: Reassurance for commissioning a next machine: hunt for first beam at tens of watts with a clean match before scaling power - on the cited machine, detection sensitivity rather than RF power was the limiting factor at first beam.

momentary beam meter readings exceeded two milliamperes but operation at this level was very unsteady due to sparking; further increases were not attempted

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 24

Editorial note, tabletop extrapolation: Test discipline for a next machine's dee-voltage conditioning: rate the machine at the level it holds quietly under a defined acceptance protocol (duty cycle, thermal soak, vacuum stability, RF interlocks), not at the level it touches momentarily.

two 12 in. split silver-plated, water-cooled copper rings which can be clamped securely around the stems; the dee stems are also silver plated over the adjustment range

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 53

Editorial note, tabletop extrapolation: Scaled down: any sliding or bolted joint in the reference machine's dee-stem/coil path should be a broad, clean, firmly clamped contact - poor joints are a common and avoidable Q killer in small resonators; whether plating or water cooling is warranted follows from contact loss and temperature, not from the 86-inch's spec.

Since the dees are insulated to operate at a dc bias, ... two-inch rubber hose about seven feet long are used to insulate the dees and to connect to the inlet and outlet headers at the extension wall. ... The ceramic 'Lapp' coils originally used for introducing cooling water to the tube and the plate line failed whenever the oscillator voltage was increased to give 200 kv. They have since been replaced with choke coils wound from copper tubing.

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 55, 59

Editorial note, tabletop extrapolation: The principle - a conductive-liquid line into an RF-hot electrode must itself be an insulator or a choke - applies whenever a next machine adds cooling or bias plumbing to the dee. A hose is not automatically insulation: the water column conducts, so check coolant conductivity and path length for leakage current, the choke's impedance and self-resonance at the RF frequency, and creepage and pressure rating.

many amplifiers use a push-pull topology that tends to attenuate the second harmonic. For those amplifiers, it is often the third harmonic that has the highest amplitude ... The classic way is with a spectrum analyzer ... you would want to have about 40 dB of attenuation between the amplifier and the measuring device. ... The real issue was the third harmonic, though; in general, it was only down 10 dB down and on some bands only 8 dB down.

Buckler, Solid-State, 2-Decade, 1.25 kW Linear Amplifier — Development Notebook (2015) — p. 19

Editorial note, tabletop extrapolation: A cyclotron dee tank is narrowband, but the rule holds: measure what the PA actually emits before designing filtering or worrying about interference from a garage machine. Take the sample through a power-rated coupler or sampler and compute the pad from actual PA power against the analyzer's rated input - at 1.4 kW (61.5 dBm) a bare 40 dB still leaves +21.5 dBm, too hot for most analyzers.

reflecting all that energy back into the output of the FETs risked driving the oscillations I had worried about in the detailed design of the power deck... I chose the diplexer

Buckler, Solid-State, 2-Decade, 1.25 kW Linear Amplifier — Development Notebook (2015) — p. 19-20

Editorial note, tabletop extrapolation: Relevant if the builder drives the dee with a broadband solid-state PA instead of a tube - but a harmonic diplexer does not protect the FETs from the dee's reactive load at the fundamental. That protection is matching, reflected-power shutdown and, where needed, an isolator; the diplexer only tames the harmonic terminations.

a fundamental flaw in my design settings had been that all the crossover and cutoff frequencies were too low, causing too much insertion loss and high VSWR in the passband.

Buckler, Solid-State, 2-Decade, 1.25 kW Linear Amplifier — Development Notebook (2015) — p. 20

Editorial note, tabletop extrapolation: Schedule measurement-and-adjustment time for any homemade filter bank, dee tank or matching network as a first-class line item; which DIRECTION values move is what the measurements tell you - this author's all-upward shift was his design's particular error, not a law.

the maximum output power I've measured ... is about 1.4 kW. After going through T/R switches, filters and couplers, you can expect about 1.3 kW at saturation

Buckler, Solid-State, 2-Decade, 1.25 kW Linear Amplifier — Development Notebook (2015) — p. 4

Editorial note, tabletop extrapolation: Size the RF chain from a component-by-component loss budget (relays, filters, couplers, feedline, matching, resonator) measured or taken from datasheets - the cited 7% is one chain's number; a cyclotron drive's tax depends on what sits in its line, so derive the PA headroom rather than assigning a stock percentage.

a plating having about half the conductivity of the copper base will cause the greatest increase in overall resistance ... the conductivity of much of the commercial silver plating is about half of that of pure copper

Fowler, Radio Frequency Performance of Electroplated Finishes — Proc. IREE Australia (1970) — p. 1

Editorial note, tabletop extrapolation: Before specifying silver on the dee or coil, get the plating process's conductivity data and compare thickness to skin depth at 9 MHz; an uncharacterized jobbing-shop bright-silver finish risks raising resonator loss, while a verified high-conductivity deposit can lower it.

a layer of high conductivity copper plating at least two skin depths in thickness, at the operating frequency, then protecting this against corrosion by a very thin layer of low conductivity plating or a layer of low-loss lacquer

Fowler, Radio Frequency Performance of Electroplated Finishes — Proc. IREE Australia (1970) — p. 10

Editorial note, tabletop extrapolation: For dees, stems, and tank coils at 9 MHz: copper at least ~45 um thick plus a thin low-loss protective finish beats unspecified decorative plating; properly specified high-conductivity silver can do better still, and nickel remains excluded on permeability grounds (dg-222).

Several reasons have been given for the decrease in conductivity below the bulk values, including: (a) the Beilby layer ... (c) the hill and dale effect ... This last problem has been investigated fully by Benson who recommends chemical or electrolytic polishing to produce a smooth surface and lower losses.

Fowler, Radio Frequency Performance of Electroplated Finishes — Proc. IREE Australia (1970) — p. 8

Editorial note, tabletop extrapolation: Polishing dee edges and stems lowers RF resistance. Smooth, clean, well-conditioned electrodes may also reduce field emission, but the breakdown voltage must be established by field analysis and testing - do not book the second benefit in advance.

safety monitoring of temperature, load failure, and diplexer HPF outputs, and ALC feedback for driver

Buckler, A Solid State 1.25 kW Linear Amplifier — QST, January 2015 (2015) — p. 1

Editorial note, tabletop extrapolation: A directional coupler with fast drive-cut on high reflected power is a strong defense when the cyclotron dee arcs or drifts off resonance mid-run - one protection among the source's set (thermal, load-failure), not a complete answer on its own.

the design underwent several changes along the way, including the addition of degenerative feedback after a 'smoke in the cockpit' incident after about 350 contacts had been made.

Buckler, A Solid State 1.25 kW Linear Amplifier — QST, January 2015 (2015) — p. 2-3

Editorial note, tabletop extrapolation: A dee resonator is a narrowband, sometimes-detuned load: design feedback in from day one with a stability analysis over the expected load range, and pair it with real mismatch protection - drain-current limiting and reflected-power foldback - since feedback alone is not a detuned-load defense.

But the real issue was the third harmonic, which was only 10 dB down generally and on some bands only 8 dB down!

Buckler, A Solid State 1.25 kW Linear Amplifier — QST, January 2015 (2015) — p. 3

Editorial note, tabletop extrapolation: At 9 MHz the 27 MHz third harmonic can couple into a spurious dee-resonator mode if one lies nearby; filter between amp and matching network, sized from the measured spectrum.

favored the diplexer design for solid state amps in the HF range, because reflecting all that energy back into the output of the field effect transistors (FETs) risked driving the oscillations

Buckler, A Solid State 1.25 kW Linear Amplifier — QST, January 2015 (2015) — p. 3

Editorial note, tabletop extrapolation: The dee's off-resonance reflection is a fundamental-frequency problem the diplexer does not solve: give the LDMOS reflected-power foldback or shutdown and, if needed, an isolator, and characterize the dee's impedance across its detuning range. The diplexer buys clean harmonic terminations - that is all.

A peak DEE voltage of 10kV was chosen. First the ion source was not included as to see the distortion in the field lines due to the DEE-Dummy DEE asymmetry. The distortion is satisfactorily low with a dummy DEE of 3/8-inch thickness.

Koeth, Rutgers 12 Inch Cyclotron Ion Source Studies: Part I (2006) — p. 2

Editorial note, tabletop extrapolation: Supports the single-dee/dummy-dee topology at the reference machine's scale: a ~10 mm grounded bar is a proven starting geometry that frees chamber space - re-run the electrostatic model for a new machine's own dee, gap and pole geometry.

Graphite is coming into wide use for cones, arc bodies, and also for D feelers or accelerating electrodes; it operates at high temperatures with a minimum of sputtering or evaporation. ... Extensions on the D faces opposite the source, called 'feelers' or 'auspullers,' have been used to improve beam intensity; they decrease the physical spacings and increase the electric field at the source. They also change the dimensions and focal properties of this first electric lens.

Livingston & Blewett, Particle Accelerators (1962) — p. 166-178

Editorial note, tabletop extrapolation: Graphite source parts run hot without spraying metal; a feeler on the dee edge is a cheap first-turn-capture upgrade with historical standing - though even the source notes quantitative evidence on its focusing effect was thin, so tune it empirically.

most uncontaminated cathode sites did not break down at 95MV/m (figure 4.8). Excluding the two sites for which tests were halted prematurely (as explained in the caption of figure 4.8), 40 of 52 contaminated sites broke down, while only 1 of 16 uncontaminated sites broke down at or below the maximum field

Werner, Probing and Modeling Voltage Breakdown in Vacuum — Cornell dissertation (2004) — p. 78

Editorial note, tabletop extrapolation: A big lever on the reference machine's dee-voltage ceiling: gloves, solvent cleaning, and dust-free assembly of dee and stem are cheap holdoff - one major control among several, not a guarantee.

In the 'early processing' regime, breakdown is overwhelmingly likely to increase the breakdown field of a cathode site.

Werner, Probing and Modeling Voltage Breakdown in Vacuum — Cornell dissertation (2004) — p. 91-92

Editorial note, tabletop extrapolation: Ramp the next machine's dee voltage slowly and accept the limited, current-limited micro-discharges that come with first processing - that conditioning is what raises the ceiling. Deliberately provoking arcs as 'cleaning' is a different matter: arcs can damage electrodes and insulators, and current limiting does not control the stored-energy delivery into the fault (dg-285). Let conditioning happen; do not manufacture it.

slipping a 1/4 in. pyrex tube completely over the 3/16 in. copper dee support rod from the dee edge to at least 2 inches beyond the seal

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 7

Editorial note, tabletop extrapolation: The cited machine's construction: a continuous Pyrex sleeve over the dee support rod, extending well past the seal for creepage. For a new machine, design stem insulation from peak RF voltage, surface-flashover behavior and the sleeve-to-stem annulus (sealed or vented?) rather than copying the geometry - and note glass sleeves bring their own charging and thermal-stress habits under RF.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Aluminum=290 kV/inch ... We settled on a minimum radius of R=.1875 inches ... Emax=170 kV/inch

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 8

Editorial note, tabletop extrapolation: The method transfers to 5-13 kV dees: radius all dee and stem edges and check the enhanced field with the formula. The 290 kV/in is one team's design number, not a material constant - vacuum holdoff moves with gap, finish, contamination and conditioning - so copy their margin practice (peak field well under the adopted figure), not their number.

a discharge from the dee to the chamber wall damaged the glass insulation and 'dee' electrode ... Four machinable ceramic strips, each roughly 2.53 cm long, 0.77 cm wide and 0.18 cm thick, hold the two dees together at the appropriate separation gap of 0.635 cm.

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 2, 52

Editorial note, tabletop extrapolation: Machinable ceramic (Macor-class) spacers are the pattern to copy for the reference machine's dee-to-dummy-dee gap; ceramics still flash over and track, so verify surface-field and creepage margins for the actual gap and voltage rather than treating the material as spark-proof.

To vent the screw holes, a small hole was drilled in the side of each screw hole using a No. 55 drill bit. The screw holes need to be vented so that they do not trap air or water and slowly outgas when the dee is placed in the vacuum chamber.

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 52

Editorial note, tabletop extrapolation: Directly applicable to any screwed-together dee: unvented blind holes are virtual leaks that slow pumpdown and add residual gas load - size and place vents for conductance and cleaning access.

Cited in: The Vacuum Budget of a Cyclotron

the RF voltage on the dee is typically between 1 and 2 kV, far greater than the 1-3 V DC placed across the filament. Thus, the filament and wires must be adequately insulated from the dee ... Insulation was supplied by a 2.33 cm by 2.71 cm machinable ceramic rectangle approximately 0.18 cm thick. ... Two barrel connectors, each 1.28 cm long and 0.32 cm in diameter, were glued to the ceramic insulator using Hysol Loctite 1C vacuum epoxy

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 54

Editorial note, tabletop extrapolation: Matches the reference machine's ~1.3 kV operating point today. At the planned 5-13 kV, do not just scale the creepage proportionally: reassess peak field and vacuum surface flashover for the actual geometry and check the feedthrough's rating.

The peripheral walls of the dees are perforated to permit high pumping speed. Graphite plates are attached to the inside of the dees ... to protect the copper from the stray proton beam.

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 50, 7

Editorial note, tabletop extrapolation: Perforation transfers directly - pressure inside an unvented dee can sit far above gauge pressure (the dee interior is a conductance-choked volume). Graphite armor earns its place wherever stray beam dwells, at ANY energy: heating, sputtering and erosion first (dg-426's material lesson), with activation reduction joining the list at higher energies.

Cited in: The Vacuum Budget of a Cyclotron

the maximum current is produced from a discharge running at about 20,000 volts... the current collected by the Faraday cylinder F into which it can penetrate is of the order of 1 milliampere with 20 milliamperes in the discharge.

Oliphant & Rutherford, Experiments on the Transmutation of Elements by Protons (1933) — p. 260-261

Editorial note, tabletop extrapolation: Sets the historical scale: percent-class collected current from tens of mA of glow discharge - a budgeting anchor, not a conversion efficiency; aperture acceptance, extraction and species mix all live inside that 5%, so measure your own ratio before sizing the discharge supply.

The space between the two steel tubes is too small for a discharge to build up there and it concentrates naturally on the hole in the cathode. ... The anode is a second steel tube A, supported axially inside the cathode and separated from it by about 4 mm ... the cathode C and the steel tubes can run red-hot

Oliphant & Rutherford, Experiments on the Transmutation of Elements by Protons (1933) — p. 260-261

Editorial note, tabletop extrapolation: The 'gap smaller than the discharge can live in' principle is how a builder forces the source discharge to localize at the extraction aperture rather than wander - pick the clearance for the actual gas, pressure and voltage and verify it empirically; the 4 mm is the source's worked point.

At first this beam consists very largely of molecular ions, but after running for some time it changes over and becomes nearly all protons ... The H2+ ion may be thought of as a pair of protons travelling together with an electron. The binding energy between them is negligible compared with the kinetic energy, which for either proton is one-half the energy of the particle. Hence a given current of molecular ions represents a current of protons of twice the magnitude, but with half the energy. We would therefore expect to begin to detect disintegration particles at about twice the energy found for the protons, and that the curve would rise twice as steeply.

Oliphant & Rutherford, Experiments on the Transmutation of Elements by Protons (1933) — p. 261-262, 269

Editorial note, tabletop extrapolation: For p-B11 the point survives translation with care: a proton-tuned cyclotron does not even hold H2+ in resonance (half the cyclotron frequency), but any acceleration mode that does deliver molecular ions yields constituent protons at a half (fixed voltage) or a quarter (fixed rigidity) of the expected energy - and p-11B is exothermic with no kinematic threshold, so what collapses is the cross-section-weighted yield, not an on/off threshold.

This is continued at as high a current density as possible for about half an hour and on pumping out the hydrogen it is usually found that the tube is quite hard and stable up to 200,000 volts.

Oliphant & Rutherford, Experiments on the Transmutation of Elements by Protons (1933) — p. 7 (printed page 265; offset = printed minus 258)

Editorial note, tabletop extrapolation: A historical conditioning observation for electrode structures that must hold voltage - adapt, don't copy: ramp with current and stored-energy limits, remote operation, interlocks, and a measured breakdown-rate criterion, and remember DC column conditioning does not transfer one-to-one to RF dees.

one should be suspicious of the ion source if the measured beam current is very low in the region close to the ion source, i.e. the regime of large turn spacing

Koeth, Rutgers 12 Inch Cyclotron Ion Source Studies: Part I (2006) — p. 1

Editorial note, tabletop extrapolation: A triage order for the reference machine's low-current debugging: measure current at small radius first; if it's already low there, put ion production and extraction at the top of the checklist - while still verifying RF capture, focusing, alignment and the probe itself, since the clue is suggestive, not exclusive.

The heating power is either dc or high-frequency ac (~100 kc) to avoid damage from vibration in the magnetic field at low frequencies. Cathode life is ... materially shortened by traces of oxygen. Lifetimes in service of 100 to 200 hr have been reported. The limit is due to erosion of a small area the size of the exit hole on the cathode surface, which represents the effective emitting surface.

Livingston & Blewett, Particle Accelerators (1962) — p. 177-178

Editorial note, tabletop extrapolation: A mains-frequency-heated filament in a 0.59 T field risks vibrating itself to death; DC heating and clean hydrogen are cheap reliability.

The filament is heated to incandescence by a high-frequency a-c power supply. The high-frequency is used to minimize self-destructive magnetic effects in the spiral filament.

McGuire, The Iowa State University 1.5 MeV Undergraduate Cyclotron (1961) — p. 7

Editorial note, tabletop extrapolation: A real failure mode for hairpin/spiral filaments in a strong main field. DC removes the alternating force entirely (at the cost of a static deflection), so the practical choice is high-frequency AC or DC depending on filament geometry - mains-frequency AC is the option to avoid; filament life is a chronic tabletop complaint either way.

Molybdenum can be used up to 2000 C... there is a special alloy, TZM... Tantalum... up to 2600 C... W-Re alloy is an easily shaped filament material... graphite... can be used to high temperatures (3500 C)... showing a long memory effect.

Wolf (ed.), Handbook of Ion Sources (1995) — p. PDF p.355 (printed p.344), section 2.1 High-Temperature Metals

Editorial note, tabletop extrapolation: The trap in a source chimney is any hot joint touching stainless: the source's warning is that stainless alloys with BOTH tantalum and molybdenum above 900 C, so an intermediate piece helps only if the stainless contact itself stays below the reaction range - move the joint to a demonstrably cooler region or add thermal length. And check pairs, not just single-metal limits: graphite on hot tantalum can form carbides.

Macor or glass ceramic can be easily machined, but is very brittle. It has good vacuum behavior and can be used up to about 1000 C. ... Boron nitride is an excellent material for most applications for temperatures up to 1200 C. It can be used up to 1500 C but starts to decompose and releases large quantities of nitrogen. It outgasses badly and tends to absorb water, which can destroy the parts when heated too fast.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 356

Editorial note, tabletop extrapolation: BN filament insulators in a home source must be pre-baked and brought up to arc power slowly the first time after air exposure, or they crack and gas up the chamber.

For the cylindrically symmetric case the maximum current can be estimated from References 11 and 12 and the assumption of a certain aspect ratio (aperture radius to electrode separation). A good aspect ratio is on the order of S = 0.5.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 379

Editorial note, tabletop extrapolation: For the puller gap in a next machine, carry over the shape of the rule - aperture dimension about half the extraction gap, beam parallelism tuned by matching plasma density - but the cited numbers are for round apertures: model the actual chimney slit electrostatically or by simulation rather than substituting the slit half-width, and expect to adjust both arc density and geometry.

The increase of temperature for higher electron output is limited by the increasing evaporation of cathode material, which decreases the cathode lifetime. Tables 1.2 and 1.3 give the respective data for W and Ta.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 41-42

Editorial note, tabletop extrapolation: For a next machine, a fatter filament run cooler at ~0.1-1 A/cm^2 buys far more run time - but the tables are evaporation-limited upper estimates: in a real arc source, ion bombardment, sputtering and contamination can dominate, so measure actual filament life rather than banking on the table.

The arc current is 1 to 3 A and the arc voltage just 40 to 70 V. A quite massive cathode rod, usually 2 mm in diameter and made of tantalum or tungsten, is heated with about 130 A and a few volts to the right temperature. ... The erosion of the filament is not uniform, but stronger at the positive end due to electron movement and higher plasma density. Changing the polarity of the filament after some time of operation improves cathode lifetime. Heating by ac has the same effect but increases plasma instabilities and the energy spread of the extracted ions. ... The lifetime of the source is given by the lifetime of the filament, which is between 10 and 100 h

Wolf (ed.), Handbook of Ion Sources (1995) — p. 73

Editorial note, tabletop extrapolation: For a next machine: a thick rod cathode instead of thin wire is the cheap lifetime upgrade, plus an arc-hours log. Polarity reversal on a ~130 A heater that may float at source potential is not a toggle-switch job - reverse only de-energized and discharged, through buswork or contactors rated for the heater current and the source-to-ground voltage.

The extraction slit is usually about 2 mm wide and about 40 mm long. Larger slits are possible, such as 90 mm, but there are some disadvantages because the current density is not uniform along the long slit due to the bigger voltage drop along the cathode. By careful design of the anode and the magnetic field, however, it was possible to overcome this problem. ... The extraction slit is usually 40 x 2 mm but designs up to 100 x 5 mm have been realized.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 74, 76

Editorial note, tabletop extrapolation: For a cyclotron chimney, the ~2 mm slit width is the historical arc-source value to start from; the slit's length and total area still matter for gas load, arc stability and beam interception, so optimise chimney length and aperture for the actual puller and dee geometry against measured beam. [Note revised 2026-08-23: earlier note said only the few millimetres facing the dee gap matter.]

The ion current to the anode has about the same value as to the cathodes, which means that the ion current density at the cathodes is five to ten times the density at the anode surface, and, consequently, the extracted current densities show the same relation. The total extracted current of a PIG ion source is proportional to the arc current, and for extraction through the anode, about 10 to 100 (mA/cm2)/A.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 82

Editorial note, tabletop extrapolation: With a ~1 mm^2 chimney slit, a 1-A arc offers ~0.1-1 mA of ideal aperture current - orders of magnitude above the reference machine's nA accelerated beams. That margin lives at the slit: capture, centering and transmission still take their share, so treat it as headroom, not proof the source can never be the bottleneck.

The arc power for cold cathode operation is limited to about 1 kW per cathode, because of the start of thermal electron emission, and depends on the cathode material and the ion source design. ... Titanium has been selected as the best compromise. If the cathodes are allowed to run hot, tantalum has been shown to be a good choice. ... The cold and hot cathodes are worn out when the erosion crater's depth reaches around the anode bore radius. The discharge becomes unstable under these conditions.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 84-85

Editorial note, tabletop extrapolation: Gives a concrete inspection criterion: measure the cathode pit depth against the ANODE BORE radius (about half the bore diameter) each time the source is pulled, and machine spare cathode buttons in advance.

Electrons emitted from a filament and accelerated to about 1 kV heat the cathode from the rear side... The lifetime of the heated cathode exceeds that of cold or hot cathodes.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 86, 101

Editorial note, tabletop extrapolation: A next machine's source can hide a small filament behind a Ta-class block cathode, out of the hydrogen plasma - the filament stops being the consumable, and what erodes instead is the thick block face under PLASMA-ion sputtering (slow, by mass). The burn-down behavior, block material and electrical ratings are design choices to verify, not inherited guarantees.

hydrogen may be admitted to the tank, "opening" the valve until the tank pressure rises by another 10^-4 mm, meanwhile watching the arc current ... a needle valve ... a loose fitting thread ... a palladium metal valve

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. PDF p.10 (printed -11-) for the admission step; PDF p.7 (printed -8-) for the valve-type list - NOT PDF p.6

Editorial note, tabletop extrapolation: Transfer the method, not the number: admit gas gradually while watching pressure and arc behavior, and find the reference machine's own setpoint with its calibrated gauge and pumping stack (its parker metering valve fills the needle-valve role). The 1e-4 mm rise is the source machine's figure - gauge species, gauge location and pumping speed make it non-portable.

3.55 MHz 1700 Vpp (26 W) H2 1.5 10-5 torr Total 4.0 10-5 torr -100 V filament ... 6.04 MHz 1700V (26 W) H2 2.2 10-6 torr Total 1.3 10-5 torr -6 V filament ... Higher frequency, lower H2 and base pressure, lower filament voltage

Yuly et al., Modifications on the Houghton College Cyclotron (2010) — p. 17-18

Editorial note, tabletop extrapolation: For the reference machine's current-hunting: before adding RF watts, cut chamber pressure and re-optimize filament bias - Houghton's gain cost zero watts - but change one variable at a time so you learn which knob actually paid.

A power supply cannot differentiate between an ion reaching the cathode grid and an electron leaving it (they both appear as positive current on the ammeter).

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 135, 144

Editorial note, tabletop extrapolation: When metering beam current near a hot cathode, part of the reading can be electrons. High work function helps only against thermionic emission; a Faraday cup's secondary-electron escape needs its own fix - a suppressor electrode or magnetic suppression, validated on the actual geometry.

Assuming that sagging occurs at ~1,500 K and equating the black body radiation rate to the input power ... ~76 cm2 for a 10-cm grid made of 0.08 cm diameter with 5 latitudes and 12 longitudes ... the emissivity of the material (~0.15 for stainless) ... This gives 9.5 mA of ion current at 200 kV, whereas the power supply can produce 75 mA at 200 kV.

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 145

Editorial note, tabletop extrapolation: The same balance sizes any wire electrode, probe or beam stop in the reference machine's chamber - with its assumptions on the table: uniform temperature and radiation-only cooling. Compute A*eps*sigma*(T^4 - T_amb^4) against actual intercepted beam power, and check local hot spots and conduction separately.

The ion mean free path at 2 mTorr is ~7 cm, while at 20 mTorr it is around 0.7 cm... The striking voltage increases with decreasing pressure.

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 92, 94

Editorial note, tabletop extrapolation: For any glow-driven ion supply in the p-B11 experiment, pressure is the ignition control: strike at higher pressure, then throttle the MFC to the running point - a device-specific procedure to commission, with the actual striking curve measured (Paschen-type behavior depends on pd, gas, geometry and surfaces, not the ion mfp alone).

Cited in: The Vacuum Budget of a Cyclotron

it might be necessary to include a filament or other source of electrons to ionize the deuterium at low pressures. This filament should be placed just outside of the outer grid system and biased slightly positive (~200 volts)

Hull, The Farnsworth/Hirsch Fusor — The Bell Jar, Vol. 6 No. 3/4 (1997) — p. 7

Editorial note, tabletop extrapolation: Matches the reference machine's hydrogen filament philosophy: a modest bias on an emitter sustains ionization where a self-sustained discharge dies. Wire the POTENTIAL TOPOLOGY deliberately - what accelerates the electrons is the difference between emitter and the collecting electrode, so state the reference (the source does not say 'to ground') and set the electron energy against the ionization physics, not against the chamber wall by default.

Care must be exercised to electrically shield (insulate) the inner grid metallic support structure so that ions will not bombard that portion of the apparatus.

Hull, The Farnsworth/Hirsch Fusor — The Bell Jar, Vol. 6 No. 3/4 (1997) — p. 7

Editorial note, tabletop extrapolation: Same rule protects the reference machine's Faraday cup stalk and source supports: unshielded biased metal collects spurious current and sputters - and bare insulation over it charges up and distorts fields, so shield with guarded conductor, then insulate behind it.

It appears that filament bias has no effect on the beam current.

Fuller, Exploring the Capabilities of the Houghton College Cyclotron — Houghton College thesis (2013) — p. 48-49

Editorial note, tabletop extrapolation: Tuning-order advice, not physics: hold filament bias fixed during initial tuning and spend the effort on dee voltage and pressure - but scan bias if ionization or emission looks current-limiting, since other geometries and regimes do respond to it.

If there is too little gas, less ionization will occur... Too high a pressure and the ionized particles will likely interact with gas inside the dee and fall out of resonance.

Fuller, Exploring the Capabilities of the Houghton College Cyclotron — Houghton College thesis (2013) — p. 51-52

Editorial note, tabletop extrapolation: Map current vs pressure on your own machine, recording resonance width and source stability along with current - expect an apparatus-dependent optimum and a non-monotonic curve, and use Houghton's window as calibration context, not a target.

Cited in: The Vacuum Budget of a Cyclotron

To make room for a filament and to avoid another electrical discharge from the filament to the lid, a 0.3 cm deep circular depression was milled out of the bottom of the upper lid.

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 50

Editorial note, tabletop extrapolation: In the reference machine's tight pole-gap geometry, check every HV-to-ground clearance near the median plane; milling relief pockets is cheaper than chasing sparks later.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The pressure in the chamber has a large effect on the beam current obtained, and typically needs to be in the range from 1e-6 to 1e-4 Torr for the cyclotron to operate. ... [higher pressures] reduce the mean free path of the ions, and cause the resonance peaks to become broad and shift. The largest beam current recorded, shown in Figure 6, was about 0.1 uA

Yuly, The Houghton College Cyclotron: a Tool for Educating Undergraduates — Cyclotrons 2013, WE1PB01 (2013) — p. 5

Editorial note, tabletop extrapolation: Directly sets the gas-handling operating window for the reference machine and explains a common 'no beam' failure at too-good vacuum - throttle up before concluding the source is dead.

Cited in: The Vacuum Budget of a Cyclotron

The ion source anode is powered by a 6 kV 200 mA Hipotronics dc power supply and a 100 kOhm, 100 W resistor is connected in-line with the power supply to current limit the discharge. ... Because the 100 kOhm current-limiting resistor develops a voltage drop during source operation, the ion source voltage (anode-to-cathode voltage) is reported instead of the power supply voltage.

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 2

Editorial note, tabletop extrapolation: Directly applicable to the reference machine's DISCHARGE/ARC supply metering (the ballast correction belongs to the electrode circuit, not the filament heater): logging supply volts instead of electrode volts corrupts any operating-point map. Check ballast power, working-voltage and transient ratings for the actual supply.

the pressure internal to the ion source is only approximately a factor of 2 larger than the chamber pressure... source operation has also been achieved by simply backfilling the chamber.

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 2

Editorial note, tabletop extrapolation: Worth testing on the reference machine: in a small chamber the injection-vs-backfill distinction may shrink - but the source-to-chamber pressure ratio is set by aperture conductance, flow and pump placement, so measure it (or model the conductances) rather than assuming 2x transfers.

Cited in: The Vacuum Budget of a Cyclotron

the plasma discharge ignites easily at 1 kV or less for all cases and produces a continuous positively charged ion beam. ... For the 1 mTorr case, at 580 V, the discharge current and target current are 0.3 mA and 20.8 uA, respectively. As the ion source voltage increases to 5.4 kV, the discharge current and target current increase to 6.0 and 1.5 mA, respectively.

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 2-3

Editorial note, tabletop extrapolation: Tens of microamps of positive hydrogen ions at under 1 kV anode drive is ample raw current next to the reference machine's nA-scale accelerated beams - but it is aggregate H+/H2+/H3+ at the target: species fraction and RF capture are separate measurements before any of it is credited as proton beam.

the source has a current utilization efficiency (ratio of target to discharge current) of 25% and requires 32.4 W of power.

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 3

Editorial note, tabletop extrapolation: A test-stand collection ratio, not a cyclotron benchmark: the reference machine's beam-to-arc ratio folds RF capture, centering and transmission on top of extraction, so a much lower ratio there does not by itself convict the extraction geometry. Use 25% as the source-side sanity scale only.

The electrode closest to the source was the suppressor and was located 2.5 cm from the cathode faceplate. A target electrode was placed 7.6 cm from the suppressor. During high-voltage operation, the suppressor and target were biased negative with respect to the ion source cathode (i.e., ground). ... at a pressure of 0.4 mTorr and 10.5 W PIG source power, a continuous 1 mA positive hydrogen ion beam has been focused onto the target and accelerator voltages up to -30 kV have been investigated.

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 3

Editorial note, tabletop extrapolation: Template for a bench extraction test stand to characterize the next machine's source before it goes into the magnet.

The boron-nitride insulator, which is a tight fit, separates the high vacuum region behind the insulator (on the order of 10-5 Torr), from the lower vacuum region in the chimney and between the anodes and cathodes. ... The best vacuum achieved in the ion source test stand (with source gas supply turned off) was 8 x 10-7 Torr. With a gas flow rate of 2.5 cc/min of hydrogen, the pressure in the main vacuum chamber is around 4e-5 Torr.

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 17-29

Editorial note, tabletop extrapolation: A single calibration point (about 1.6e-5 Torr per cc/min at that stand's pumping speed), not a slope: characterize the reference machine's own MFC-vs-chamber-pressure curve with its calibrated flow and gauges before reading deviations as leaks or conductance faults.

Cited in: The Vacuum Budget of a Cyclotron

Their cathode was a U-shaped tantalum filament, heated with about 400 amps ... the arc current (the total current measured between the anode and cathode of the ion source) was between 2 and 6 amps. As seen in figure 1.2 a 0.2 in2 (129 mm2) area vertical slit provided the path for ions to exit the source. With this source Livingston and Jones were able to extract 150 mA using a puller voltage of 12kV and a source-puller gap of about 0.13 (3.3 mm).

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 3-4

Editorial note, tabletop extrapolation: Brackets the design space above the reference machine's filament source as an existence proof, not a scaling law: determine the arc a nA beam actually needs by measuring extracted and captured current against arc current on the real geometry.

an approximately flat plasma boundary provides the best match to the experimental beams emerging from the 'slit' style chimneys... while a concave plasma boundary... for the 'hole' style chimney ... The size of the hole in the chimney is 0.047 (1.19 mm) with a sixty degree chamfer. At 50 mA of arc current, the normalized luminosity of the beam which made it to the wire probe was 129 A/(mm2-sr), about half of that for the slit chimney with the same arc current (264 A/(mm2-sr)).

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 73-76, 91-107

Editorial note, tabletop extrapolation: Decides a next machine's chimney aperture style within the tested regime: cut a tall narrow slit rather than drilling a hole if beam brightness and predictable optics matter - and re-verify on the actual source, since the ranking comes from these apertures and operating points.

hydrogen gas flow rates greater than 2.0 cc/min) no H2+ ions were observed. We were able to observe H2+ ions by lowering the gas supply to 0.5 cc/min.

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 79-80

Editorial note, tabletop extrapolation: Directly actionable on the reference machine's MFC: starving the source of gas silently changes beam species, so locate the actual arc-mode transition for the machine and keep the setpoint above it - and remember 'no H2+ detected' is not 'pure protons': H3+ and below-detection species need their own check.

Vernier knob for repeatable flow settings ... Flow Coefficient (Cv): 0.029 (Series 20) ... Stem Taper: 3 deg ... Turns to Open: 9 (+/-1)

Parker Hannifin, Series 20 & 30 Metering Valves (datasheet) — p. 1-2

Editorial note, tabletop extrapolation: The 3-degree taper spread over 9 turns gives the fine, repeatable hydrogen admission an ion source needs. Log turns-open as the VALVE-POSITION setpoint - repeatable flow additionally needs regulated upstream pressure and a calibration of flow (or chamber pressure) against turns under operating conditions; the vernier repeats position, not sccm.

Not recommended for positive shut-off. If bubble-tight shut-off required, the use of a Series HR Metering Valve is suggested.

Parker Hannifin, Series 20 & 30 Metering Valves (datasheet) — p. 2

Editorial note, tabletop extrapolation: Practical form for the gas panel: give the metering valve an isolation valve between it and the bottle - or specify a metering valve designed for shut-off duty, the HR-class option the sheet names. Forcing a plain tapered stem closed to seal ruins the calibrated taper and still leaks into the vacuum system.

Arc voltage and arc current can each be varied independently ... This regulates the filament temperature and thus the arc current, which is then held constant regardless of arc voltage.

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 66

Editorial note, tabletop extrapolation: A control philosophy readily implemented with two small feedback supplies; a constant-current arc removes one major drift term from shot-to-shot beam current - stable gas flow and extraction conditions are still needed for real reproducibility.

201 through 284 / 1/8 / .139 +/-.004 / .101 to .107 / .028 to .042 / 20 to 30 / .177 to .187 / .158 to .164 / .010 to .025

Parker Hannifin, O-Ring Handbook — Design Chart 4-3: O-Ring Face Seal Glands — p. 1

Editorial note, tabletop extrapolation: Hands the mill the numbers for the chamber's lids and ports - per ring size and per geometry: these are STATIC AXIAL FACE seals; a port using a different cross-section or seal configuration gets its own chart row or chart. Note the vacuum groove width column is narrower than liquid service.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Surface finish X: 32 for liquids, 16 for vacuum and gases. Finishes are RMS values.

Parker Hannifin, O-Ring Handbook — Design Chart 4-3: O-Ring Face Seal Glands — p. 1

Editorial note, tabletop extrapolation: Specify and check the chamber lid seat to 16 RMS (fly-cut or turned); a rough or cross-scratched sealing face can contribute to leakage and belongs on the leak-diagnosis checklist - as one suspect among several, not a signature of any particular pressure plateau.

Cited in: Cyclotron Vacuum Chamber Design and Sealing · The Vacuum Budget of a Cyclotron

For Internal Pressure (outward pressure direction) dimension the groove by its outside diameter (HO) and width: (HO) = Mean O.D. of O-ring ... Tolerance = Minus 1% of Mean O.D., but not more than -.060 ... For External Pressure (inward pressure direction) dimension the groove by its inside diameter (Hi) and width: (H)i = Mean I.D. of O-ring ... Tolerance = Plus 1% of Mean I.D., but not more than +.060

Parker Hannifin, O-Ring Handbook — Design Chart 4-3: O-Ring Face Seal Glands — p. 1

Editorial note, tabletop extrapolation: For an evacuated chamber atmospheric pressure pushes the ring inward, so the groove ID (not OD) is the controlled dimension when laying out the lid groove.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

One butyl compound has been tested in face-type O-ring seals, using grooves that provide 15%, 30%, and 50% squeeze. It will be seen from the results plotted in Figure I that increasing the squeeze reduced the leak rate dramatically... at 50% squeeze the beneficial effect of the grease was not detectable. ... It is therefore recommended that dovetail or face type O-ring grooves be used whenever possible for static vacuum seals, employing a suitable vacuum grease as a sealing lubricant and surface coating in addition to a heavy squeeze on the O-ring.

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. 3-4

Editorial note, tabletop extrapolation: Cut a next machine's grooves toward the heavy end per the source's recommendation, but set the nominal from the ring manufacturer's static-vacuum gland tables under worst-case tolerances - 50% was a test point, not a design target; gland fill, compression set and assembly damage cap real designs. Grease is a crutch for light squeeze.

Cited in: Cyclotron Vacuum Chamber Design and Sealing · The Vacuum Budget of a Cyclotron

care being taken to insure that there are no machine or tool marks perpendicular to the seal... The ideal surface finish for any vacuum seal flange has a circular lay

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. 5

Editorial note, tabletop extrapolation: Face the lid seat on a lathe (concentric lay) rather than fly-cutting or hand-sanding radially; never sand a groove crosswise to remove a blemish.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Vacuum Level: Approximately 1 x 10-6 torr ... Butyl .18 ... Nitrile 1.06 ... Nitrile 3.45 ... Fluorocarbon .07

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. 6

Editorial note, tabletop extrapolation: At exactly the reference machine's operating pressure, nitrile's high weight loss marks it a potential outgassing concern near feedthrough insulators, optics and RF surfaces - where the lost mass actually lands was not measured, so treat the ranking as a screening result and prefer the low-loss compounds (Viton's 0.1%-class loss is the cheap insurance) rather than claiming proven film deposition.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Butyl 6.5 @ 77F ... Fluorocarbon 12.7 @ 77F ... Silicone 238.0 @ 77F

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. 7

Editorial note, tabletop extrapolation: Viton's placement plus its other properties is why it is the default; silicone's high permeability matters most when helium leak checking (He walks through silicone and fluorosilicone seals, confusing the sniffer) and in permeation-limited systems - compute the actual permeation gas load for the seal geometry before ruling a compound in or out, since at 1e-6 Torr with decent pumping the load is often ignorable either way.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Alpha resolution measurements should be made with a detector source spacing equal to 1.5 to 2 times the detector diameter and under good vacuum (< 100 microns HG or 10 Pa).

Canberra, PIPS Detector Instruction Sheet (2012) — p. 1

Editorial note, tabletop extrapolation: For his ~8 mm active-diameter PIPS, that is 12-16 mm standoff; closer spacing degrades resolution through wide-angle entrance-window losses.

Cited in: Experiments by Energy Band

O-rings are typically compressed 15-20% of their diameter... the general criterion for high vacuum sealing to be a minimum initial contact pressure of 13 kg/cm2

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 337-338

Editorial note, tabletop extrapolation: The 2.7 kg/cm figure sizes the lid bolting: a 10-inch-circumference seal (25.4 cm) needs about 69 kg of clamping just for the ring - a 10-inch-diameter ring (79.8 cm around) needs about 216 kg - before atmospheric load helps. Size bolts and flange stiffness from the complete load and allowable-stress calculation.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

An unbaked Viton O-ring will have an initial outgassing rate of 10-3 Pa-m/s... After a 4-h bake at 150C and 12 h of pumping, this value is reduced to 4x10-7 Pa-m/s.

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 340

Editorial note, tabletop extrapolation: Argues for baking the assembled system under vacuum where the components allow it. An ex-situ pre-bake in a small vacuum oven helps only to the extent air exposure before assembly is minimized, and the payoff in chamber pressure depends on whether the rings dominate the gas load - budget the gas loads before promising an order of magnitude.

Cited in: Cyclotron Vacuum Chamber Design and Sealing · The Vacuum Budget of a Cyclotron

Grease is not needed to make a static seal between an elastomer and a metal surface. It will cause pressure bursts as trapped gas pockets are released.

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 340

Editorial note, tabletop extrapolation: Counters the amateur habit of greasing everything: on a clean, undamaged seat with proper squeeze, a dry Viton ring seals without grease's gas burden. A scratched flange is a repair item first; grease is the temporary expedient, not the standard practice.

Cited in: Cyclotron Vacuum Chamber Design and Sealing · The Vacuum Budget of a Cyclotron

one should not rough a chamber with an oil-sealed mechanical pump below a pressure of circa 10-15 Pa (100-150 mTorr), otherwise oil backstreaming would contaminate the chamber... the '100-mTorr rule' is valid [for small systems]

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 379-381

Editorial note, tabletop extrapolation: For the reference machine: valve over to the SI100 around 100 mTorr rather than letting the rotary pump grind into the 1e-2 Torr range - after checking the SI100's own maximum inlet/crossover and foreline specs, which are the binding numbers for the diffusion-pump side.

Cited in: The Vacuum Budget of a Cyclotron

the mechanical pump should be disconnected and connected to a blank flange containing only a thermocouple gauge. ... If the pump is operating properly, sections of the foreline and roughing line can be pumped sequentially and systematically until the leaky section is isolated. ... External leak checking with helium should begin at the top of the chamber; only a small helium flow rate is necessary. ... Alcohol freezes in a small leak and allows adjacent areas to be checked without confusion. The alcohol can be removed with a heat gun. ... Welds and seals are the most common leak sites

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 467-470

Editorial note, tabletop extrapolation: Helium rises and migrates: working top-down with small flow keeps the migrated-helium background from swamping localization on a chamber with many ports (the source suggests nitrogen-flushed plastic wrap where sites crowd together). Alcohol near energized equipment is a flammability point - sensible precautions.

A molecular leak causes a linear increase in pressure with time. Outgassing causes the pressure to rise to a steady-state value that is determined by the vapor pressures of the desorbing species.

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 468-469

Editorial note, tabletop extrapolation: First diagnostic whenever a next machine won't reach base pressure - existing gauge plus stopwatch. A constant slope points toward the helium bottle, a rolling-over curve toward bakeout - as the leading hypothesis, not a verdict: virtual leaks also roll over, water outgassing can mimic a leak on an RGA, and a real leak departs from linearity once the pressure rises far enough.

Cited in: The Vacuum Budget of a Cyclotron

This pressure rise is due to helium permeation. The permeation time is about 20 min for a typical Viton O-ring. ... First, do not attempt to leak check the system during baking. Second, helium background from a loaded O-ring will not decrease until it has been pumped from the gaskets. A coffee break may be required before proceeding.

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 469-470

Editorial note, tabletop extrapolation: On an all-Viton chamber, spray briefly and wait: a slowly rising, broad He signal minutes after spraying is CONSISTENT WITH gasket permeation rather than a leak at the last joint - confirm by letting the baseline recover and re-testing for a prompt, reproducible local response before moving on.

Cited in: Cyclotron Vacuum Chamber Design and Sealing · The Vacuum Budget of a Cyclotron

Air leaks are discerned by the presence of oxygen at m/z = 32... Outgassing and water line leaks each can produce a large peak at m/z = 18, but they can be distinguished by the rate of rise.

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 471

Editorial note, tabletop extrapolation: A used RGA head is arguably the single best diagnostic upgrade for a next machine - one spectrum plus a short rate-of-rise watch replaces a day of guessing.

Room temperature outgassing data for most gases sorbed on metals, including water vapor, show the outgassing rate to vary inversely with time, at least for the first 10 h

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 80-81

Editorial note, tabletop extrapolation: Explains why the chamber keeps improving overnight without any leak being fixed, and why comparing pump-down curves is only fair at equal elapsed times.

Rule of thumb - one monolayer consists of ~1e15 molecules (atoms) per cm2

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 42-43

Editorial note, tabletop extrapolation: Explains why pump-down history and surface cleanliness dominate at high vacuum: the wall inventory dwarfs the volume inventory for ordinary chamber geometries - by a factor you compute from the actual area, volume and outgassing rate, which is also what sets whether the walls take hours or days to give up their load.

Real Leaks: external, constant flow, constant pressure rise. Virtual Leaks: internal, decreasing flow, decreasing pressure rise.

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 429-433

Editorial note, tabletop extrapolation: The decreasing-vs-constant slope distinction also flags virtual leaks from unvented hardware, which a helium sprayer can never find from outside.

Avoid phrases like; leak tight, vacuum tight, good to 10-8 Torr, good for ultrahigh vacuum, etc.

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 456-464

Editorial note, tabletop extrapolation: When farming out welds or buying used hardware, write the acceptance spec as a number DERIVED from the machine's gas-load budget: Q_leak,max = S_eff x (allowable pressure contribution), split between total and single-leak allocations, with tracer gas, test pressure and calibrated detection limit stated - detector sensitivity is what the instrument can see, never itself the acceptance criterion.

Stainless Steel (unpolished) 266 [1 hr] 20 [4 hrs]... Mild Steel, slightly rusty 58,520 199 (mBar-l/sec-cm2 x 10-10)

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 49

Editorial note, tabletop extrapolation: The ~200x one-hour penalty (dropping to ~10x by four hours) for rusty mild steel is the argument for keeping exposed in-chamber pole faces from corroding at all - and for qualifying any specific remedy (plating, vacuum-rated coating, stainless cladding) on its own outgassing, adhesion and magnetic-gap costs rather than prescribing one.

Cited in: The Vacuum Budget of a Cyclotron

Mechanical Cleaning; Degreasing or Solvent Cleaning; Detergent Cleaning; Chemical Etch; Electrolytic Polishing; High Pressure Spray; Bake-out ... Remove all tape, ink, & other residues with Acetone & a clean cotton rag ... DI rinse (2 x 10^6 Ohm min. resist. @ 65oC) Air dry or dry with filtered compressed nitrogen ... Protect with lint free paper, foil, or plastic bags ... Acid pickle (50% by vol. HNO3 ... @ 25oC) 10 minutes if removing mill scale, 30 seconds to remove trace alkaline ... A 200oC bakeout is still required after glow discharge cleaning.

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 497-513

Editorial note, tabletop extrapolation: Scaled down: acetone wipe, hot detergent wash, DI rinse, N2 or oven dry, gloves-only handling afterward gets most of the professional benefit for chamber internals. The acid pickle stays professional - HF work needs formal controls and alloy-specific procedure, and is not part of the amateur-safe subset.

the frequency with which starbursts appeared at particle sites, I have concluded that particles cause breakdown

Werner, Probing and Modeling Voltage Breakdown in Vacuum — Cornell dissertation (2004) — p. 46, 78

Editorial note, tabletop extrapolation: When a next machine sparks, a loupe inspection for starbursts and craters gives the builder candidate locations for the field problem instead of guessing from outside the chamber - corroborate with particle, geometry and field checks before machining anything.

if there are contaminant particles, then they, and not the substrate material, determine the breakdown voltage. ... The Cu and Au films were about 1000 A thick; the oxide films were hundreds of angstroms thick. ... there seems to be no significant difference in breakdown voltages on niobium and copper cathodes.

Werner, Probing and Modeling Voltage Breakdown in Vacuum — Cornell dissertation (2004) — p. 84

Editorial note, tabletop extrapolation: The builder can reasonably keep aluminum dees and spend the effort on cleaning and conditioning instead of exotic electrodes - with the caveat that the tests covered Nb, Cu, Au and their oxides, not aluminum's native oxide; let the machine's own conditioning behavior confirm it.

Both sites reached 95 MV/m at 100 C with no evidence of field emission ... At room temperature (22 C), field emission began near 40 MV/m, and breakdown occurred around 90 MV/m

Werner, Probing and Modeling Voltage Breakdown in Vacuum — Cornell dissertation (2004) — p. 96

Editorial note, tabletop extrapolation: Motivates a controlled experiment on the reference machine, not a guaranteed fix: try a gentle bake of the dee assembly before HV runs and measure field-emission onset and holdoff after cooldown - the cited data compare performance AT temperature and don't establish that the improvement survives cooling, or the mechanism.

preliminary washing of the parts in CCl4 is recommended to remove organic matter

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 9

Editorial note, tabletop extrapolation: Degrease everything on a next machine that sees vacuum - machining oil, fingerprints, rubber residues - with a solvent chosen per material (elastomers, coatings and trapped volumes need their own compatible process); CCl4 itself is excluded on toxicity grounds.

Steel supporting rods allow thin top and bottom plates to minimize thickness

Baumgartner & Heuer, The Cyclotron Kids 14-Inch Accelerator (2010) — p. 6-7

Editorial note, tabletop extrapolation: Every millimeter of lid steel is a millimeter of magnet gap - but posts are not free: ferromagnetic posts in or near the gap distort or shunt the field, so place them outside the useful-field region (or use nonmagnetic posts) and verify by model or map; and do the plate-stress and buckling arithmetic for full atmospheric load before trusting a thin lid.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

You can hasten the process by running the fusor to degas the inner surfaces. This sends the pressure upward, but after a few minutes it starts to drop ... Turning the fusor power down or off after a few minutes of on time will have the pressure plunge to new lower levels.

Hull, The Farnsworth/Hirsch Fusor — The Bell Jar, Vol. 6 No. 3/4 (1997) — p. 5-6

Editorial note, tabletop extrapolation: The same logic applies to the reference machine's chimney and dee surfaces - but translate it as controlled RF or discharge conditioning with pressure and arc interlocks, not an open-ended beam-on bake-in: beam operation adds sputtering, beam loss, and (at higher energies) activation questions a conditioning plan should assess first.

To fully clean the system of residual gases, an initial base pressure of around 1e-6 Torr is necessary. A leak valve is then used to backfill the chamber with deuterium to a pressure in the range of 1 to 10 microns.

Hull, The Farnsworth/Hirsch Fusor — The Bell Jar, Vol. 6 No. 3/4 (1997) — p. 6

Editorial note, tabletop extrapolation: The base-pressure-then-backfill discipline is exactly the reference machine's MFC workflow; at the quoted fusor numbers the operating-to-base ratio is 1,000-10,000:1, which is what keeps the feed gas dominant - but composition is earned by measurement (RGA or gas-load accounting), not by a pressure ratio alone.

continuous square rubber gaskets located in grooves in the faceplates of sufficient cross section to accommodate the entire gasket under pressure. The resulting metal-to-metal contact ... has proved very satisfactory.

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 41

Editorial note, tabletop extrapolation: A strong pattern for a next machine's chamber lids: the metal stop limits further squeeze after closure and makes reassembly repeatable - still check gland fill and squeeze for the actual compound (groove depth sets the squeeze; a too-shallow groove over-crushes even with a metal stop), including tolerance, swell and thermal growth.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

a steady stream of dry air injected into the outlet side of the pump cylinder could eliminate the need for a refrigerated vapor trap ... dry air is used in the tank in order to minimize the amount of moisture

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 44

Editorial note, tabletop extrapolation: Two separable methods: vent the next machine's chamber with dry nitrogen or desiccated air rather than room air (admitted water vapor drops and pumpdown shortens), and treat exhaust-side purging as pump-specific - follow the pump manual, keep any inlet trap the pump needs for vapor handling or oil backstreaming, and mind oxygen deficiency when nitrogen-venting in a small space.

Cited in: The Vacuum Budget of a Cyclotron

the ion gauge is not turned on until the tank pressure is less than 0.5 microns ... In this position the conductance from the diffusion pumps around the gate valves to the ion gauge has been estimated to be approximately the same as the conductance from the diffusion pumps to the tank proper. ... the wall of the manifold provides the tube filament with some protection from the magnetic field

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 45

Editorial note, tabletop extrapolation: Directly applicable gauge practice near a stray-field-rich H-frame magnet: place the gauge to read the pressure you care about (conductance gradients bias a badly placed gauge under gas flow), and verify the shielding by comparing readings with the field on and off.

Cited in: The Vacuum Budget of a Cyclotron

far more rugged than the triode ion gauge and sensitive to small changes in pressure; but it is probably not as accurate in reading absolute pressure.

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 46

Editorial note, tabletop extrapolation: A cheap Penning head earns its keep as a trend and gas-flow indicator, with the ion gauge kept for absolute readings. For protection interlocks use fail-safe, manufacturer-approved instrumentation - Penning cells can ignite late and drift with contamination - and commercial heads carry their own magnet: mount and shield per the head's specification rather than borrowing the cyclotron's field.

Rate of rise on tank assembly 0.00015 microns/sec

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 46

Editorial note, tabletop extrapolation: Measure rate-of-rise after every re-seal as the standard leak-health metric, and state the benchmark as a gas load, not a pressure rate: the ORNL figure corresponds to Q = V*dP/dt ~ 1.2e-3 torr-L/s. A ~30 L chamber would rise at ~4e-5 torr/s only if it carried that same total load - rate-of-rise includes real leaks, virtual leaks and outgassing, so 'equally tight' means equal Q, not equal construction scaled by volume. [Note revised 2026-08-23: earlier note scaled the expectation by volume alone.]

For vacuum seals, O-rings must be comprised of elastomeric materials featuring low gas permeability, low weight loss under vacuum, and good compression set characteristics. ... With outstanding low permeability to gases, Butyl is especially effective in vacuum sealing applications. ... Employing a seal squeeze of up to 40% inhibits media flow through the seal... because of the decreased groove depth, increased groove width is essential.

Apple Rubber Products, Seal Design Guide — p. 84

Editorial note, tabletop extrapolation: Endorses heavier-than-usual squeeze on critical static vacuum joints when the groove is widened to take the displaced volume - within the compound's own application limits. A pre-bake ('post cure' in vendor language) to drive off volatiles before service is cheap insurance on silicone and fluorocarbon compounds.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

As we tighten the rest of the bolts the joint is further compressed, and the previously tightened bolts tend to relax and lose some of their preload. In some cases, this can virtually eliminate our bolt tension.

Fastenal, Technical Reference Guide, Rev. 9 (2005) — p. 26

Editorial note, tabletop extrapolation: On the next machine's lid, single-pass tightening leaves the first-torqued sector under-clamped - a plausible contributor to O-ring leaks that seem to move with each reassembly; the multi-pass cross-pattern with recheck is the fix either way.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

This stretch should be between 1%-5% with 2% as the ideal in most applications. A stretch greater than 5% is not recommended. The resulting stress on the O-ring will cause accelerated aging and cross section reduction.

Apple Rubber Products, Seal Design Guide — p. 11

Editorial note, tabletop extrapolation: When picking the AS-568 size for a non-standard groove (dee-stem feedthrough, viewport), size so the ring sits at ~2% stretch rather than swimming or straining.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The maximum volume of the O-ring should never surpass the minimum volume of the gland... For a static crush seal application, it is recommended that the O-ring volume does not exceed 95% of the gland void.

Apple Rubber Products, Seal Design Guide — p. 14-16

Editorial note, tabletop extrapolation: Check fill arithmetic including worst-case ring tolerance before machining. Viton heated by RF or magnet proximity needs that free volume: elastomer linear expansion is around 1.6e-4/C, so use the volumetric coefficient (roughly three times the linear value) in the fill calculation.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Surface finishes as rough as 64 to 128 micro-inches RMS can be tolerated. However, a finish of 32 micro-inches RMS is preferred ... Static Gland Detail Surface finish: 32 for liquids, 16 for vacuum and gases ... Static seal cross sections are generally compressed from 10% to 40%, whereas dynamic seals are from 10% to only 30%.

Apple Rubber Products, Seal Design Guide — p. 19, 61

Editorial note, tabletop extrapolation: For a rotating or sliding shaft feedthrough (target manipulator), back off to <=30% squeeze and finish the shaft to the guide's dynamic-service figures (16 RMS; 10-20 micro-inches called most desirable for dynamic seals) - a rough shaft raises friction, wear and leakage quickly.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Do not use a lubricant composed of the same material as the O-ring because 'like' will dissolve 'like.' For example, a silicone lubricant should not be used with a silicone O-ring.

Apple Rubber Products, Seal Design Guide — p. 20, 109

Editorial note, tabletop extrapolation: Check the actual lubricant and elastomer grades against a manufacturer compatibility chart. Silicone grease on Viton is commonly compatible but must still clear vacuum-outgassing requirements; petroleum grease on Buna-N is usually acceptable (NBR is built for mineral oils) though additives vary - the firm rule is the quoted one: never lubricate a ring with its own chemistry.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

H2+/9 H+/7 H+/5 H+/3 H+ H2+

Yuly et al., Modifications on the Houghton College Cyclotron (2010) — p. 15-18

Editorial note, tabletop extrapolation: Prevents misidentifying beam in the reference machine's B-field sweeps: a peak at one-third the expected field is a CANDIDATE for the same ion on the 3rd harmonic - confirm by species diagnostics or scaling tests, since another species/harmonic combination can land at the same field.

If many ions in the beam fall out of phase before reaching maximum Dee radius, the beam current will drop suddenly to near zero beyond whatever radius the ions tend to reach

Morrow, Focusing in the Houghton College Cyclotron — Houghton College thesis (2015) — p. 28, 57

Editorial note, tabletop extrapolation: Diagnostic direction, not verdict: a sharp cutoff in the radial current profile is CONSISTENT with phase slip - and also with aperture interception, wall collisions or vertical-envelope loss - so discriminate by what moves it: RF frequency and dee-voltage changes shift a phase-slip radius, mechanical interception does not, and field trim tells its own story.

for a fixed frequency f, resonances will occur for lower magnetic fields, e.g. B/3 and B/5, corresponding to an odd multiple of a lower frequency

Yuly, The Houghton College Cyclotron: a Tool for Educating Undergraduates — Cyclotrons 2013, WE1PB01 (2013) — p. 4-5

Editorial note, tabletop extrapolation: Practical commissioning technique: a magnet-current sweep plus an electrometer assigns candidate species/harmonic pairs to each peak. Confirming that a peak is really protons (and clean) still needs field calibration and, where purity matters, an independent species check.

The stray magnetic field over T effectively prevents the escape of secondary electrons, so that the current measured is the true ion current.

Oliphant & Rutherford, Experiments on the Transmutation of Elements by Protons (1933) — p. 262

Editorial note, tabletop extrapolation: The reference machine's internal Faraday cup may get partial secondary suppression free from the fringe field - VERIFY it: sweep a suppressor bias and look for a current plateau, or compare with/without a suppressor electrode; outside the field an explicit suppressor is mandatory. Insulation isolates the signal but does not suppress emission.

a mica window W, 1 cm in diameter and supported on a grid which subtends the smallest possible area... The solid angle obtained in this way is approximately 0.7.

Oliphant & Rutherford, Experiments on the Transmutation of Elements by Protons (1933) — p. 262-265

Editorial note, tabletop extrapolation: The close-geometry, calibrate-with-a-known-alpha-source method is how the builder should commission the PIPS geometry before hunting p-B11 alphas - an analogous procedure, with a traceable sealed source, the PIPS dead layer in the accounting, and the solid angle computed for the actual geometry.

Cited in: Experiments by Energy Band

One technique has been to measure the width of the region of induced radioactivity on the leading edge of probes inserted to different radial locations.

Livingston & Blewett, Particle Accelerators (1962) — p. 174-167

Editorial note, tabletop extrapolation: A radial probe (the reference machine's shielded Faraday cup on a linear feedthrough) is the workhorse diagnostic: falling collected current at some radius localizes WHERE the beam is lost - field shape, phase slip, focusing, apertures and probe interception then get tested separately as causes. At sub-activation energies, beam marks or a phosphor coat replace the activation-width trick.

The frequency for resonance can be measured and reduced to magnetic field through the relation B = (234.82 +/- 0.13)f where B is in gauss and f is in megacycles per second.

Livingston & Blewett, Particle Accelerators (1962) — p. 286-287

Editorial note, tabletop extrapolation: 5.9 kG sits at 25.1 MHz proton NMR - an accessible DIY measurement. Modern calibrated Hall systems can do far better than the era's 1%, so use each instrument's actual spec; and the machine's own resonant frequency gives an orbit-averaged field cross-check whose accuracy is set by how well f, harmonic and species are pinned - budget it, don't assume half a percent.

Pulser line width should be about 5 keV (FWHM) narrower than Alpha Resolution ... the noise level which is approximately 3 times the pulser line width (FWHM).

Canberra, PIPS Detector Instruction Sheet (2012) — p. 1-3

Editorial note, tabletop extrapolation: A pulser check exercises the whole electronic chain and baseline - including grounding, 9 MHz RF pickup, and detector leakage/capacitance contributions while connected - without risking source contamination; isolating charge-collection or detector-response degradation still needs a real particle peak for comparison.

Cited in: Experiments by Energy Band

A retarding grid attached to the front of the Faraday cup will eliminate loss of secondary electrons... The grid will be at some negative potential.

King, A Preliminary Design for a Small Permanent Magnet Cyclotron — Houghton College thesis (2002) — p. 24

Editorial note, tabletop extrapolation: The better-engineered cousin of the simple cup bias (cf. dg-523's cited 9 V machine result): make the grid voltage adjustable and find the suppression plateau experimentally - the plateau, not any particular voltage, is the evidence - while checking what the grid itself intercepts.

either one rocked back and forth until a current peak is indicated on the target probe. The probe may be pushed in closer to the center to facilitate locating this resonance.

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 11

Editorial note, tabletop extrapolation: Directly applicable commissioning move; starting the search at small radius makes the resonance easier to find. Once a peak is found, walking the probe outward while re-optimizing source and RF settings is the natural continuation - standard practice, though beyond this quote.

the authenticity of the beam should be checked by the sharpness of resonance as a function of r.f. tuning and magnet current, as well as by its sensitivity to hydrogen gas pressure

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 11

Editorial note, tabletop extrapolation: Directly applicable: a 'beam' that stays constant while you detune B or RF is background until proven otherwise - candidates include ion leakage to the probe, RF pickup, dark current and secondary-electron paths - so diagnose it rather than count it.

The target probe must show a high resistance to ground; of course, a sensitive galvanometer (protected by r.f. chokes and bypasses) may be used initially for detecting the beam current ... The six-inch cyclotron has indicated a 7 microampere beam

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. PDF p.11 (printed -12-)

Editorial note, tabletop extrapolation: The choke-protected, well-insulated probe is the right pickup design. Treat the 7 uA as one historical machine's result, not an expectation: beam current rides on source, vacuum, RF voltage and capture, and tabletop machines have commissioned at picoamps.

a convenient target substance would be LiF which, when bombarded with protons, will emit gammas from Li ... The target may be prepared by simply fusing a small amount of LiF onto a small stainless steel block

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 11

Editorial note, tabletop extrapolation: Partially applicable: 7Li(p,gamma)8Be is exothermic - there is no threshold - but its prominent resonance near Ep = 441 keV is what makes the signal jump, so at the reference machine's ~150 keV the yield is far down the tail. A next machine near 0.5 MeV could use exactly this check; estimate thick-target yield and detector response first, and remember LiF adds fluorine channels (19F(p,alpha-gamma) with its own strong resonances).

Cited in: Experiments by Energy Band

The relative solid angles for each detector were measured using low energy Rutherford scattering on gold as well as a known 241Am source.

Spraker et al., The 11B(p,α)8Be → α+α and the 11B(α,α)11B Reactions at Energies Below 5.4 MeV (2012) — p. 360

Editorial note, tabletop extrapolation: The builder already owns the pieces: an Am-241 check source exercises the PIPS geometry and energy scale in practice, and the Faraday cup/Keithley 617 integrates charge for yield normalization - noting that ABSOLUTE calibration needs certified source activity, controlled geometry and live-time accounting, and a single alpha line is a one-point energy check.

Cited in: Experiments by Energy Band

Predicted dT=25.46 kV ... (Approx half beam spot) ... energy at far left: T=.5087 MeV ... energy at far right: T=.4954 MeV ... dT=13.3 keV ... Theory: dT/2=12.73 keV

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 35-40

Editorial note, tabletop extrapolation: A phosphor screen plus this formula gave a student-machine energy-spread estimate without a spectrometer - as an apparatus-specific check: spot width also carries emittance, coherent radial motion and screen resolution, so deconvolve or bound those before quoting a spread from a screen.

The location of the ammeter in the circuit keeps it essentially at ground potential... CAUTION! This supply is lethal. Allow at least 2 minutes after shutdown before touching any connections. Make sure that the voltmeter reads zero. Do not omit the 10 meg bleeder resistor.

Hull, The Farnsworth/Hirsch Fusor — The Bell Jar, Vol. 6 No. 3/4 (1997) — p. 8

Editorial note, tabletop extrapolation: The ground-leg metering trick lets the builder log arc and extraction currents on the next machine without floating instruments at kilovolts - the meter still needs protection (shunt, series resistance, clamping) against fault transients. On shutdown, the source's voltmeter-zero check is the load-bearing step: the 2-minute wait is a floor that depends on the actual RC of supply and bleeder, and zero on the meter - then a shorting stick - is what proves it.

When ions collide with the current collector, they can cause electrons to be ejected. This results in an additional current to that caused by the ion beam itself. ... The beam current measured was lower with the addition of the voltage bias... the bias reduces the emission of secondary electrons, resulting in a more accurate measurement.

Fuller, Exploring the Capabilities of the Houghton College Cyclotron — Houghton College thesis (2013) — p. 55-56

Editorial note, tabletop extrapolation: A one-component fix for honest current numbers on any Faraday-cup measurement the builder makes: apply the bias and sweep its magnitude until the reading plateaus - the plateau, not any particular voltage, is the evidence that suppression is complete.

A +9 V bias can be applied to the target using a battery to reduce the effect of secondary electrons on beam current measurements ... secondary electrons are created in significant numbers on the target.

Yuly, The Houghton College Cyclotron: a Tool for Educating Undergraduates — Cyclotrons 2013, WE1PB01 (2013) — p. 4-5

Editorial note, tabletop extrapolation: One battery attacks the main systematic in the builder's main diagnostic, and the biased/unbiased comparison sizes the secondary contribution - verify the suppression is sufficient by stepping the bias and looking for a current plateau; energetic secondaries and backscatter can survive +9 V.

Cited in: Experiments by Energy Band

it is a good idea to evacuate the chamber for 10 to 15 minutes before applying bias. This will remove excess surface moisture ... It is recommended to wait 30 seconds to stabilise the detector.

Canberra, PIPS Detector Instruction Sheet (2012) — p. 1

Editorial note, tabletop extrapolation: Build the pump-first-then-bias order into the beam-diagnostics routine as a TIMED permissive (vacuum reached plus 10-15 min), not a bare pressure interlock, and keep the 30 s post-bias stabilization; moisture raises initial leakage current, which is reason enough for the discipline.

Cited in: Experiments by Energy Band

Remember that leakage current doubles for about 5 C rise in temperature and take this into account when you compare your measurement to that of the factory.

Canberra, PIPS Detector Instruction Sheet (2012) — p. 1-3

Editorial note, tabletop extrapolation: A detector near warm cyclotron hardware can legitimately read several times its certificate value. Before blaming radiation damage or contamination, walk the checklist: temperature, bias setting, light leaks, humidity, cabling and connectors, microdischarge - the doubling rule is an approximation, not a diagnosis.

(10 ... 300 um thick): 100ps-30ns. Thick (~cm) Si or Ge detector: 1-10us

Spieler, Semiconductor Detectors Part 2 — SLUO Lectures on Detector Techniques, Lecture 7 (1998) — p. 2

Editorial note, tabletop extrapolation: The reference machine's ~500 um PIPS sits above the quoted 10-300 um range - its collection time should still be tens of ns (verify from the datasheet or a rise-time measurement) - and shaping time is then chosen for noise TOGETHER WITH count rate, pile-up and pulse-height stability, not noise alone.

a 1 MeV neutron transfers about 60 to 70 keV to the Si recoil atom, which in turn displaces roughly 1000 additional atoms in a region of about 0.1 um size.

Spieler, Semiconductor Detectors Part 2 — SLUO Lectures on Detector Techniques, Lecture 7 (1998) — p. 49

Editorial note, tabletop extrapolation: The reference machine's PIPS detectors tolerate its X-ray background as far as displacement damage goes (ionizing/surface effects are a separate, slower concern), but shield or retract them during any neutron-producing run - deuterium work above all - and budget by estimated neutron fluence at the detector, not just by whether the reaction label says neutrons.

Cooling to 0 C typically reduces the reverse bias current to 1/6 of its value at room temperature.

Spieler, Semiconductor Detectors Part 2 — SLUO Lectures on Detector Techniques, Lecture 7 (1998) — p. 52

Editorial note, tabletop extrapolation: A Peltier or cold-finger on the PIPS mount is a cheap resolution upgrade WHEN leakage-current shot noise dominates the noise budget - verify that first, control condensation and temperature stability, and remember cooling does not repair irradiation-induced charge-trapping losses.

the common mode of disintegration is into two [alpha] particles which proceed at angles of 150 to 180 relatively to one another, the third particle receiving very little energy

Spraker et al., The 11B(p,α)8Be → α+α and the 11B(α,α)11B Reactions at Energies Below 5.4 MeV (2012) — p. 357-358

Editorial note, tabletop extrapolation: Two PIPS detectors in near-back-to-back coincidence would give the builder a background-crushing p-B11 signature even at very low count rates.

Cited in: Experiments by Energy Band

Fast neutron bubble detector acts as backup to electronic detection

Hull, Fusor: An Easy to Construct Fusion Reactor Based on Inertial Electrostatic Confinement (2009) — p. 43

Editorial note, tabletop extrapolation: Same philosophy for p-B11: pair the PIPS/electronics chain with a passive detector (e.g., CR-39 track plastic) immune to the cyclotron's RF pickup.

Cited in: Experiments by Energy Band

in severe cases, galling can completely weld the nut and bolt together and prevent removal of the fastener ... Thread lubrication is one of the most effective measures to lessen the potential for galling... Heat contributes significantly to thread galling. Installing a fastener generates heat and high-speed installation generates significantly more heat. ... Avoid prevailing torque locknuts. ... Mating parts of the same alloy have a greater tendency to gall than parts of dissimilar alloys having different degrees of hardness.

Fastenal, Technical Reference Guide, Rev. 9 (2005) — p. 8

Editorial note, tabletop extrapolation: Every stainless-on-stainless bolt into the chamber flange gets anti-seize OUTSIDE the vacuum boundary; inside, any coating or lubricant must be separately qualified for vacuum service (silver plating is a common accelerator practice, but qualify it - Fastenal doesn't cover vacuum). One galled lid bolt can strand the whole chamber.

Pitting primarily in the outline of the electrode - not directly underneath or on top.

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 45-47

Editorial note, tabletop extrapolation: When the builder opens the chamber after sparking, pit geography is the first CLUE: perimeter concentration is consistent with edge-field enhancement (fix radii - dg-353), scattered pits with contamination or particulates (clean and re-condition). A lead to follow, confirmed by whether the fix actually moves the breakdown voltage.

We coated the HV electrode with Aerodag G dry lubricant, which is also conductive and has low secondary electron emission coefficient. The RU shop machined away the top and bottom plates to gain more of a gap.

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 50 (cited 53 is off by 3)

Editorial note, tabletop extrapolation: A cheap surface treatment to try if a deflector or dee edge hits breakdown limits near the top of its range - one element of the Rutgers fixes, and their own account credits the cable-energy fix (dg-285) and staged resistance (dg-286) with the decisive difference, so treat the coating as a contributor, not a cure.

With conventional steel nut and bolt materials, a length of engagement of about one nominal diameter of the bolt is typical. A longer thread length engagement will be needed when dealing with tapped holes in soft material.

Fastenal, Technical Reference Guide, Rev. 9 (2005) — p. 14

Editorial note, tabletop extrapolation: Tapped holes in aluminum lids or pole pieces need substantially more engagement than steel - size them against thread-shear stripping for the actual alloy, or use inserts; a stripped hole in the finished chamber is far costlier than a longer bolt.

Torque = K x d x F... F = 75% of bolt material proofload for standard bolts... even perfect input torque can give a variation of preload by as much as 25 - 30 %. ... K Factors: Bolt Condition - Non-plated, black finish: K 0.20 - 0.30; Zinc-plated: 0.17 - 0.22; Lubricated: 0.12 - 0.16; Cadmium-plated: 0.11 - 0.15

Fastenal, Technical Reference Guide, Rev. 9 (2005) — p. 25-26

Editorial note, tabletop extrapolation: Gives defensible torque numbers for lid and magnet-clamp bolts once F is set from the joint design (gasket stress, flange stiffness, thread strength). The lubrication trap is the K ratio: a bolt lubricated to K~0.14 but torqued to a dry-table value assuming K~0.25 sees ~1.8x the intended preload - enough to yield or snap small fasteners.

we used an installation torque of 70 ft-lbs to obtain a clamp load of 9000 lbs... By the fourth installation, we required 145 ft-lbs to reach a clamp load of 9000 lbs.

Fastenal, Technical Reference Guide, Rev. 9 (2005) — p. 30

Editorial note, tabletop extrapolation: Lid bolts cycled dozens of times a year walk away from any torque table - in either direction, since reuse changes the friction coefficient unpredictably. For repeatable magnet-gap or flange clamping: set inspection/replacement criteria for the hardware, and validate preload by a joint-specific method (measured load, bolt elongation, or a calibrated procedure proven on THAT joint - turn-of-nut included only once shown repeatable on its compliance).

The voltage divider allowed use of a low voltage meter by tapping the divider string at a 10,000 part fraction of the total voltage drop.

Kovalchick, Deuterium Fusion Using Inertial Electrostatic Confinement (2012) — p. 18-19

Editorial note, tabletop extrapolation: Reusable for the reference machine's DC monitoring - extraction or supply voltage - with a divider rated for the voltage and power, in a fail-safe enclosure, and calibrated. NOT for the dee: a high-resistance DC divider on an RF resonator capacitively loads and detunes it, reads wrongly, can overheat, and can put RF onto the meter. Measure dee voltage with a calibrated capacitive pickup or an RF-rated probe. [Note revised 2026-08-23: earlier note offered the DC divider for 'dee/extraction HV monitoring' without distinguishing the two.]

One might choose a 12 kV, 60 mA neon sign transformer and use 2 - 12 kV microwave oven diodes... Never apply full voltage immediately to the fusor!

Hull, The Farnsworth/Hirsch Fusor — The Bell Jar, Vol. 6 No. 3/4 (1997) — p. 5-8

Editorial note, tabletop extrapolation: A scrounger-grade current-limited architecture for source-conditioning and glow-cleaning supplies. Current limiting makes faults survivable for the hardware, not the operator - 12 kV at 60 mA is far beyond lethal, so the full HV practice set applies (grounded case, bleeder, voltmeter-zero, shorting stick; dg-522). Check diode ratings against the topology: in a center-tapped full-wave circuit each diode blocks about twice the half-winding peak - around 17 kV here - so single 12 kV parts are marginal; stack diodes in series per leg.

At voltages greater than 20 kV, the resulting x-rays can be hazardous. ... Radiation surveys of the chamber showed the presence of x-ray radiation at voltages exceeding 18 kV.

Kovalchick, Deuterium Fusion Using Inertial Electrostatic Confinement (2012) — p. 14, 25, 45

Editorial note, tabletop extrapolation: The reference machine's dee/extraction voltages sit below this line today, but HV conditioning or a higher-voltage upgrade crosses it. Monitor with an instrument that actually responds at 15-25 keV - a thin-window GM or scintillation survey meter; a standard thick-walled GM tube under-reads soft X-rays - and remember the viewport is one weak point among several (feedthroughs and thin walls count too).

Cited in: Choosing Your Machine · Shielding a Small Cyclotron

currently produces in excess of 600,000 neutrons per second which allows some low level neutron activation work of short lived isotopes. Both light neutron and x-ray shielding are needed beyond this level and the planned fusor V will incorporate these upgrades.

Hull, Fusor: An Easy to Construct Fusion Reactor Based on Inertial Electrostatic Confinement (2009) — p. 39

Editorial note, tabletop extrapolation: One experienced builder's numeric line for when a home device graduates from monitored to shielded - specific to his output, geometry and occupancy, not a universal threshold: dose scales with distance, time and moderation, so a measured survey decides the actual case. p-B11 alpha work produces no comparable neutron source term.

Cited in: Shielding a Small Cyclotron

if the field is formed such that the deviation from the isochronous one for all operating radii is no more than 5 G, then this corresponds to a deviation of the RF phase... by no more than 5 degrees

Smirnov, The Cyclotron and Its Modeling — Phys. Part. Nuclei 52 (2021) — p. 50

Editorial note, tabletop extrapolation: The 5 G <-> 5 deg pairing is that machine's arithmetic, not a portable spec: phase slip accumulates with turn number, harmonic and energy gain per turn, so integrate it turn by turn from the measured B(r) and RF parameters, and set the reference machine's shimming tolerance from the resulting phase-acceptance budget.

the so-called calibration coefficients are introduced to the level of the field created by the windings, which, as a rule, are not large and amount to ~1-2% of the current value

Smirnov, The Cyclotron and Its Modeling — Phys. Part. Nuclei 52 (2021) — p. 50

Editorial note, tabletop extrapolation: For the reference machine's FEMM-vs-Hall-probe comparison: compare field SHAPE versus radius and current first - a residual that is genuinely a scale error can be absorbed in a per-coil factor (checked for current-independence, since saturation makes such factors drift), while a shape mismatch means geometry, B-H data or probe calibration, and no scale factor should paper over it. The cited 1-2% is that machine's correction, not a normal-mismatch budget.

Then the RF phase shifts to the values at which the particles cross the accelerating gaps with the optimal phase. Thus, conditions are created for the additional focusing of particles in the axial direction at the first revolutions by a high-frequency electric field. Depending on the configuration of the central region of the cyclotron, the level of the magnetic field in the center is raised to an amount of a few tens to a few hundred gauss

Smirnov, The Cyclotron and Its Modeling — Phys. Part. Nuclei 52 (2021) — p. 50-51

Editorial note, tabletop extrapolation: Usable on a next machine: shim a small central cone so B falls gently from center outward, and set the central-region phase so the electric focusing helps rather than hurts - then verify the resulting field index and phase history by model; RF electric focusing means n~0 first turns are not wholly unfocused even before the bump.

Its second purpose is to ensure the stability of operation of electrical components of the accelerator... by increasing the breakdown voltage. In modern cyclotron facilities, a pressure of ~1e-7 Torr is practically possible.

Smirnov, The Cyclotron and Its Modeling — Phys. Part. Nuclei 52 (2021) — p. 14

Editorial note, tabletop extrapolation: The dual criterion is the transferable part: if the dee sparks before the beam is lost to gas, vacuum improvement should be judged on breakdown margin, not just stripping loss. What pressure the reference machine actually needs comes from its own gas-loss arithmetic and holdoff behavior - not from this figure in either direction.

Cited in: The Vacuum Budget of a Cyclotron

The number of lost particles dN at each time step dt can be estimated by the formula dN = sigma nN v dt

Smirnov, The Cyclotron and Its Modeling — Phys. Part. Nuclei 52 (2021) — p. 70

Editorial note, tabletop extrapolation: Lets the builder tool convert a gauge reading and total path length (hundreds of turns) into a survival fraction - with the composition stated, the gauge's gas-sensitivity factor applied, and the cross sections taken at the right energies. An assumed oxygen-like composition is a labeled assumption, not a guaranteed worst case: water and hydrocarbons can exceed it for the processes that matter.

Cited in: The Vacuum Budget of a Cyclotron

The slit is most functional if it is installed in the place of the largest radial size of the beam... The closer to the center the device is installed, the more efficient it is, and the less radiation losses thereon. ... If there are several slits, then it is advisable to place them at different revolutions and azimuthally with a difference of half the period of the system, e.g., in a hill and a valley. ... Elements should be installed away from accelerating gaps, e.g., along the center lines of the space between the dees

Smirnov, The Cyclotron and Its Modeling — Phys. Part. Nuclei 52 (2021) — p. 56

Editorial note, tabletop extrapolation: Practical placement rules if the builder adds a beam-defining post or slit to clean up phase spread and improve turn separation at extraction radius.

Accelerating the beam far into the fringe field often means passing the vr = 2 vz coupling resonance. Energy can be exchanged from the radial to the vertical motion, blowing up the beam vertically and leading to beam loss. If the radial oscillation amplitude is not too large, and if the resonance is passed in only a few revolutions, vertical amplitude increase is avoided. In practice, a coherent radial oscillation amplitude of the same size as the incoherent amplitude, is a good criterion for efficient extraction. Another reason for requiring not too large radial oscillation is avoiding strong non linear effects.

Botman & Hagedoorn, Extraction from Cyclotrons — CAS, CERN 96-02 (1996) — p. 7

Editorial note, tabletop extrapolation: If a next machine's radial beam half-width is ~2-3 mm, start near a ~2-3 mm coherent amplitude and set the acceptable ceiling by tracking through the extraction field - the equality criterion is the source's practical starting point, not a hard limit.

one has to limit the radial amplitude, induced from the v = 1 resonance, to a few mm.

Heikkinen, Injection and Extraction for Cyclotrons — CAS, CERN 94-01 (1994) — p. 18

Editorial note, tabletop extrapolation: In a weak-focusing field the last turns sweep the field index upward toward these resonances: compute the actual tune curves from the measured field map, and keep energy gain per turn high through any crossing so that tracking predicts acceptable vertical growth - speed of crossing, not a fixed turn count, is the criterion.

Cited in: Beam Dynamics: An Interactive Laboratory

For a typical conventional cyclotron (Bo ~ 1.7 T) a bump of 0.1 mT (1 G) introduces a radial gain of about 0.2 mm. To get a desired turn separation bigger bumps are needed (brute force). ... Since, for a given energy, the magnetic rigidity BR is constant, the radial gain per turn increases with a factor of R favouring larger machines.

Heikkinen, Injection and Extraction for Cyclotrons — CAS, CERN 94-01 (1994) — p. 14

Editorial note, tabletop extrapolation: Scaled to 0.6-0.9 T and r ~ 0.1 m the per-turn gain from 1 G is only ~0.04 mm, so mm-scale separation would take tens of gauss of first harmonic - precession is far cheaper than brute force.

n_eff is the effective duration of the resonance (typically around ten revolutions). ... Typically the extraction takes place near v = 0.8.

Heikkinen, Injection and Extraction for Cyclotrons — CAS, CERN 94-01 (1994) — p. 14

Editorial note, tabletop extrapolation: A smooth azimuthally symmetric weak-focusing machine approaches nu_r=1 from below and never crosses it, so create the amplitude by ion-source off-centering instead (a different mechanism than resonant buildup - verify what it delivers by tracking) and use the fringe region where nu_r has fallen toward the source's typical ~0.8 for precession, with the actual tune taken from the measured field map.

Mammoflex M-1 HV cable has C of 56 pF per foot ... ~0.1 Joules at 30 kV ... ~0.4 Joules at 30 kV ... The bottom plate and deflector electrode - no pitting on the electrode noticed.

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 43 (stored energy; repeated 45, 49) and 44 (pitting)

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: Rutgers' slide sequence recounts arcing a feedthrough run above its class and rebuilding with the feedthrough inside vacuum plus a corona adapter. The specific numbers, page-image verified 2026-09-06: cable stored energies ~0.1 J (5 ft) and ~0.4 J (20 ft) at 30 kV via 56 pF/ft Mammoflex M-1, and a feedthrough 'rated for 30 kV (we want to run it at 35)' - the overrun plan is the cautionary half of the lesson. Choose feedthrough rating from the manufacturer's figure, the vacuum-side geometry and test history, and never run a feedthrough above its rating. [Note revised 2026-08-23: 'rate 2-3x over operating voltage' was an invented margin.]

the spreading of orbit centres for different HF phases due to HF mixing, is small for an originally well centreed beam, as in general the number of turns from the vr = 1 resonance till extraction is not so large.

Botman & Hagedoorn, Extraction from Cyclotrons — CAS, CERN 96-02 (1996) — p. 9

Editorial note, tabletop extrapolation: If a next machine uses source off-centering (amplitude created at turn 1, necessarily - it cannot be placed late), evaluate the phase-mixing integral from tracked particles in the actual field map before assuming the coherent centroid survives: individual amplitudes persist while the ensemble centroid can smear. A trim bump near the extraction region, where late placement IS possible, is the cleaner tool.

Figure 11 shows a differential probe measurement for this cyclotron in the extraction region. The separation between the probe fingers is 2 mm. The figure reveals the radial oscillation near extraction.

Botman & Hagedoorn, Extraction from Cyclotrons — CAS, CERN 96-02 (1996) — p. 11-12

Editorial note, tabletop extrapolation: Adding a two-finger (or shadow-bar) differential head turns the reference machine's existing radial probe into the diagnostic that informs septum placement - choose the finger spacing from the PREDICTED turn separation and beam width (2 mm was that machine's), and combine the measured pattern with orbit tracking and clearance requirements rather than reading placement off the probe alone.

The arc plasma is a few volts negative in respect to the anode potential and nearly the full arc voltage drops along the narrow cathode sheath ... One electron can produce about eight ions or charges on average.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 82

Editorial note, tabletop extrapolation: Ion energy at the cathodes is ~ the full arc voltage (times charge state) before collisional losses - evaluate sputtering from species/material yield data at that energy, not a linear-in-voltage assumption. Grounding the chimney (anode) to the chamber with cathodes negative is ONE workable topology if the source body is meant to sit at chamber potential - check it against the machine's RF/HV design, heater isolation and filtering before wiring it.

the arc voltage increases with decreasing gas flow or particle density in the discharge chamber until the discharge becomes unstable

Wolf (ed.), Handbook of Ion Sources (1995) — p. 83

Editorial note, tabletop extrapolation: Run current-regulated and watch arc voltage as a flow/health indicator: creeping arc voltage at fixed current is evidence of falling gas density and approaching instability - cross-check against gas supply and cathode condition before acting, since a worn cathode and other drifts move arc voltage too.

Cited in: The Vacuum Budget of a Cyclotron

The cold and hot cathodes are worn out when the erosion crater's depth reaches around the anode bore radius. The discharge becomes unstable under these conditions ... Titanium has been selected as the best compromise ... If the cathodes are allowed to run hot, tantalum has been shown to be a good choice.

Wolf (ed.), Handbook of Ion Sources (1995) — p. 84-85

Editorial note, tabletop extrapolation: Cathode buttons are the main consumable: with a ~3 mm diameter anode bore, end-of-life comes near ~1.5 mm of crater depth (the criterion is the bore RADIUS). Stock spare buttons and log arc-hours. Material follows regime, not convenience: titanium for demonstrated cold operation, tantalum where the cathodes verifiably run hot.

Gas is fed to the discharge usually through the anode close to the cathode(s) to ease ignition of the arc and to keep the neutral gas flow through the extraction slit in the anode low

Wolf (ed.), Handbook of Ion Sources (1995) — p. 81

Editorial note, tabletop extrapolation: Plumb the MFC line to feed near the cathode end of the chimney where the geometry allows (AMIT feeds through the cathode cavity - a variant of, not identical to, the quoted through-anode arrangement): it eases ignition and keeps neutral flow out the slit low. Chamber backfill still works (dg-409) - the injection win is lower chamber pressure for the same source density, to be verified by measurement on the actual machine.

A disadvantage is the need for cathode replacement and anode cleaning at intervals of a few hours to a day.

Clark, Ion Sources for Cyclotrons — Cyclotrons '81, Caen (1981) — p. 3

Editorial note, tabletop extrapolation: Lower arc power and lighter gas both cut sputter erosion, so a small hydrogen source should do far better than the cited heavy-ion interval - but how much better is a measurement, not a scaling law: run the source and log the wear before promising a lifetime.

The cathode body is a 5.1-cm-diameter iron rod that has been machined to the dimensions and geometry shown in Fig. 1. ... samarium cobalt (Sm2Co17) permanent magnet ... surface flux density of approximately 3 kG ... the cathode faceplate is fabricated using the same iron rod as the cathode body. A 3.2-mm-thick, 5.1-cm-diameter disk is cut from the iron rod and machined with a 6.4-mm-diameter hole on centerline. ... a 100 kOhm, 100 W resistor is connected in-line with the power supply to current limit the discharge. ... generate a plasma discharge that yields a continuous 1 mA beam of positively charged hydrogen ions at 1 mTorr of pressure. This operating condition requires 5.4 kV and 32.4 W of power.

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 1-3

Editorial note, tabletop extrapolation: Existence proof that mA-class hydrogen PIG output needs only tens of watts and modest fabrication (machined rod, spot-welded sheet anode). The axial-extraction geometry differs from a cyclotron chimney, so the discharge economics transfer as encouragement - the chimney's own extraction still needs its own validation, and the 1 mA is aggregate hydrogen ions, not mass-analyzed H+.

the plasma discharge ignites easily at 1 kV or less for all cases ... a current utilization efficiency (ratio of target to discharge current) of 25%

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 2-3

Editorial note, tabletop extrapolation: Use the right utilization figure for the right geometry when predicting a next machine's beam: Rovey's ~25% is axial extraction; Forringer's radial-slit configurations measured I_beam/I_arc of about 0.0005 to 0.0046 - nearly two orders lower, because the slit samples a small part of the plasma - and neither number transfers to a new source without measurement.

Under normal ion source opperating conditions ... no H2+ ions were observed. We were able to observe H2+ ions by lowering the gas supply to 0.5 cc/min.

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 89

Editorial note, tabletop extrapolation: Treat gas flow and arc regime as a species TUNING HYPOTHESIS for the reference machine, not as a purity guarantee: 'below detection' in one analyzer does not exclude H2+ at a lower level, says nothing about H3+, and the cc/min thresholds depend on that source's geometry and pumping. Species misidentification propagates into energy, range, resonance interpretation and any radiation assumption, so verify H+/H2+/H3+ in the actual machine - analyzing magnet, time-of-flight, the f = qB/2*pi*m resonance check, or a reaction diagnostic - before claiming a proton beam. Transfer only the method: scan flow and arc regime while directly measuring species; do not assume the direction or the thresholds reproduce in another source.

We observe that an approximately flat plasma boundary provides the best match to the experimental beams emerging from the 'slit' style chimneys in our study, while a concave plasma boundary (curving toward the source axis) provides a better match for the beam that emerges from the 'hole' style chimney. In all cases, the plasma temperature that provides the best match for experimental beams is approximately 35,000 K (resulting in a central starting energy of 4.5 eV). Using the methods presented in this dissertation, the orbit tracking code Z3CYCLONE is able to predict the beam produced by a cold cathode PIG ion source with adequate accuracy such that construction of actual cyclotrons can proceed with reasonably prudent confidence that the cyclotron will perform as predicted.

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 3

Editorial note, tabletop extrapolation: Drop-in starting condition for the reference machine's central-region orbit models: start protons from a flat sheet across the slit with the source's 4.5 eV central energy, not from rest at a point - and sweep the parameters against measured beams per dg-423.

Arc Current 0.27 A / Arc Voltage 550 V / Arc Power 150 W / H2 Gas Flow 5.5 sccm / Beam-on-Post (Extraction Current) 800 uA (Table 1)

Potkins et al., Improvements to Siemens Eclipse PET Cyclotron Penning Ion Source (2017) — p. 2-3

Editorial note, tabletop extrapolation: The single most relevant commercial datapoint - 0.7 T (nearly the reference machine's field), 150 W arc, sub-amp arc current, hundreds of uA extracted, 120+ hour consumable life. It makes H-: useful as discharge and lifetime context, but it does not quantitatively predict a positive-ion version's H+ output - species fractions, meniscus and extraction all change with polarity, so measure H+ directly.

Post-to-foil transmission increased dramatically (from 19% to 30%) but the total target current decreased from 120 uA to 40 uA

Potkins et al., Improvements to Siemens Eclipse PET Cyclotron Penning Ion Source (2017) — p. 3-4

Editorial note, tabletop extrapolation: For a machine starved of axial acceptance a hole source may waste less injected beam, while total current favored the tall slit in the Eclipse test. The reference machine's 1.42 in physical gap suggests but does not establish generous DYNAMIC acceptance - pick slit vs hole from central-region tracking or a measured acceptance/delivered-current comparison, not the gap dimension.

For arc currents below 250 mA the electrons are mainly furnished by secondary emission and the impedance is high. When the current increases, the cathodes heat up and begin to supply electrons by thermionic emission

Obradors et al., Characterization of the AMIT Internal Ion Source with a Devoted DC Extraction Test Bench — IPAC 2017 (2017) — p. 3

Editorial note, tabletop extrapolation: Staying below the transition keeps the discharge in its high-impedance regime, which is the friendlier load - but 'stable with a simple regulated supply' is a property of the measured V-I curve plus the ballast, not of a current number: measure the tabletop source's own V-I and dynamic behavior over gas flow, and choose ballast and compensation from the measured differential resistance, ignition included.

the anode with 7 mm in inner diameter is demonstrated to be capable of producing the highest density of electrons while the 8 mm inner diameter anode gives the highest beam current density in KIRAMS-13 ... when the anode with inner diameters higher than 9 mm, the number of electron production will decrease ... The cylinder shape anode with 20 mm in length having different internal diameters of 6.16 mm to 10.1 mm, were used in simulation.

Mu et al., Simulation of Electron Behavior in PIG Ion Source for 9 MeV Cyclotron (2015) — p. 3, 5

Editorial note, tabletop extrapolation: A starting range, not a spec: at 0.59 T the electron column is fatter than at KIRAMS's 2 T, so begin near the top of the 7-8 mm range or make the chimney bore an interchangeable insert and find the optimum at the actual field, pressure and arc voltage.

with 20,000 gauss at the center, produced a field of 96.7 percent of this value at 96.5 percent of the total radius (corresponding to the magnetic index n = .2), with an approximately linear decrease in field from center to edge.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 9-10

Editorial note, tabletop extrapolation: The transferable practice is the method: measure H(r), compute n(r) from its local slope, and place the working radius where n stays in the focusing band - do not set a shim target from endpoint percentages, and do not adopt n = 0.2 as a goal without orbit, phase-slip and extraction analysis.

Cited in: Beam Dynamics: An Interactive Laboratory

A method of measuring the relative field in the gap at points along a radius to .1 percent was developed and used on later detailed shim studies on this magnet.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 9

Editorial note, tabletop extrapolation: A 0.1% relative radial map (differential Hall probe or flip coil) was that team's entry ticket; derive the next machine's actual requirement from its field and orbit tolerances, and qualify the probe's calibration, positioning, thermal drift and repeatability as part of building the capability.

The deflection of the poles under the magnetic load was found to average .002 to .004 inches for the model.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 9

Editorial note, tabletop extrapolation: Historical calibration context, not a prediction: estimate the next machine's load from magnetic pressure B^2/(2 mu0) over the pole area and its structure's stiffness, distinguish per-pole motion from total gap closure, and always shim and map at operating excitation, not cold.

The machining of the pole tip was held to +/- .0025 inches on almost all dimensions.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 11

Editorial note, tabletop extrapolation: A few-mil pole tolerance is achievable in a good hobby/job shop - derive the next machine's actual requirement from gap sensitivity and the field-uniformity budget, and remember final mapping and shimming absorb what machining leaves.

Numerous holes are drilled in them to facilitate vacuum pumping.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 19

Editorial note, tabletop extrapolation: Virtual leaks behind liners and skins are a classic small-chamber trap: vent every otherwise-trapped volume on the next machine with holes or slots sized for pumping conductance - checked against RF current paths, structure and field quality - and deburr and clean the openings.

Cited in: Cyclotron Vacuum Chamber Design and Sealing · The Vacuum Budget of a Cyclotron

Each assembly was leak-tested with a helium mass spectrograph after manufacture.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 20

Editorial note, tabletop extrapolation: Bench-test each next-machine spool, duct, and feedthrough before it disappears into the stack - vacuum-mode helium mass-spectrometer testing is the acceptance method the source used. Rate-of-rise and sniffing are preliminary screens only; keep soap solutions off vacuum-wetted surfaces, and pressurize a vacuum-only part for testing only if it has a documented pressure rating.

Cited in: The Vacuum Budget of a Cyclotron

Only two leaks were detected, and these were in the gasket seals. They were believed to be due to non-uniform thickness of gasket material.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 24

Editorial note, tabletop extrapolation: A useful prior for a next machine's leak hunt: check O-ring/gasket joints first - while still testing welds and feedthroughs, since one chamber's tally doesn't make welds innocent; compression, gland condition and damage are additional gasket failure modes beyond thickness.

Cited in: Cyclotron Vacuum Chamber Design and Sealing · The Vacuum Budget of a Cyclotron

The vacuum reached was 3 x 10-6 mm of mercury. Starting with cool pumps and the system at atmospheric pressure, the pump-down times were as follows: 1 hour, 45 minutes to reach 10-5 mm mercury; 2 hours, 30 minutes, to reach 3 x 10-6 mm mercury.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 24

Editorial note, tabletop extrapolation: Transferable practice - a recorded reference pump-down curve for the next machine's chamber is the cheapest early-warning leak/contamination diagnostic.

Cited in: The Vacuum Budget of a Cyclotron

Parasitic modes at higher frequencies than desired for proton acceleration were successfully eliminated with light-bulb loads inductively coupled to the tube lines, and the lower mode ... was avoided by means of a series resonant circuit from dee to vacuum chamber.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 30

Editorial note, tabletop extrapolation: The general methods transfer - coupled lossy loads to damp unwanted modes, and a tuned series trap for a specific mode - but not component values or topology: identify the actual unwanted modes of the LDMOS-driven resonator first, then design the damper/trap for the measured mode, checking its dissipation and its effect on the operating mode.

results now indicate that four 880's will suffice, while the data from the three-fourths scale model had indicated that six would be necessary.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 29

Editorial note, tabletop extrapolation: Transferable caution - stray capacitance, proportions and device parameters do not scale cleanly; validate a next machine's dee voltage vs drive on the actual resonator, using models as guides.

requires the addition of an inhibitor to reduce attack on the aluminum and steel provoked by the presence of minute quantities of copper in the water.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 53

Editorial note, tabletop extrapolation: Directly applicable chemistry for any next machine's water loop touching Cu plus Al: pick a modern inhibitor for the actual alloy set, water chemistry and temperature - the transferable fact is that trace copper is the aggressor, so the loop needs treatment even when each metal alone would be fine.

All the adapters on the coil terminals are water cooled and supplied with thermal switches to protect the coil terminals from overheating.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 56

Editorial note, tabletop extrapolation: Directly applicable - thermal cutouts on a next machine's coil terminals/lugs (and dee stem cooling) are cheap insurance against a loose-joint meltdown.

The valves are automatically operated by compressed air cylinders and are controlled by vacuum gauges so that they will close when a leak occurs which the pump is not able to handle.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 58

Editorial note, tabletop extrapolation: Directly applicable: an interlocked isolation valve (even a spring-loaded solenoid gate) protects a next machine's diff or turbo pump from a chamber let-up - with closure speed and actuation chosen for the pump being protected.

good contact is established by the use of strips of thin soft copper sheet backed by foam rubber pads.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 10

Editorial note, tabletop extrapolation: The cheap 1948 equivalent of RF finger stock for external, low-temperature joints - removable housing panels and line covers. For vacuum-facing or high-current joints (dee-stem clamps), use vacuum-compatible spring contacts or engineered clamps with verified pressure and RF heating: ordinary foam rubber outgasses and relaxes.

Initially the model condenser blades were bare steel. As had been expected, the Q dropped by a factor of two at the lowest frequency, so all surfaces were copper-plated.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. PDF 10 (printed -7-) for the quote; PDF 15 (printed -12-) for the halved-Q figure

Editorial note, tabletop extrapolation: On a next machine keep steel (chamber walls, bolts, pole faces) out of RF current paths or plate/line it with copper - Q and dee voltage per watt are at stake; how much a given steel surface costs is a measurement or model result for that geometry.

Over 50 kilovolts rf could be developed across the insulator at 13 mc by a 5 kilowatt oscillator. Under the most severe test conditions, air blast cooling of the insulators was found necessary.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 13

Editorial note, tabletop extrapolation: A bench resonator lets the builder soak-test dee-stem insulators at full 5-13 kV RF from modest drive - how modest depends on the fixture's measured loaded Q (constant-Q scaling of the cited point suggests tens of watts at 5 kV but hundreds at 13 kV), so measure Q and compute the drive rather than assuming it.

The water circuit is completed to ground potential by means of sets of flexible polyethylene tubing, each several feet long. Treated water of low conductivity is used.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 13

Editorial note, tabletop extrapolation: Applicable if the next machine's dee or stem is water-cooled while biased - but hose length plus DI water is the historical arrangement, not a sufficiency proof: calculate the water-column resistance at worst-case conductivity (DI water degrades in service - monitor it), include RF capacitive current through the column, and ground/interlock accordingly.

There is sufficient magnetic field at the rotary condenser to allow a Philips gauge discharge when positive bias is applied; a negative bias is therefore imperative.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 23

Editorial note, tabletop extrapolation: The next machine's dee sits in 0.59 T, so if a DC bias is used to kill discharges, start negative on the strength of this precedent - then verify empirically: whether a Penning discharge ignites depends on the E/B geometry and pressure, not the field alone.

the upper two insulators are under pure compression, the lower two under pure tension. ... The rf insulators have given no trouble whatever since installation one year ago, though at the time of assembly, their fragility was evidenced insofar as shear forces were concerned. The care taken in insuring that only pure tension and compression forces would be applied was thus well justified.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 24

Editorial note, tabletop extrapolation: Directly applicable to a next machine's dee-stem standoffs and feedthroughs: arrange the support geometry (threaded rods, spherical seats) so ceramics never see bending or shear - prefer compression where practicable, avoid point loading, and respect the manufacturer's tensile rating, which is far below the compressive one.

the inner face, or back, is made of 1/2 in steel ... this house serves as a magnetic shield for the oscillator tube. A crude replica (1/16 size) was tested by the magnetic measurements group ... using the 1/16-scale 184-inch model magnet, and this shielding was found sufficiently effective, the field being cut from 140 Gauss to less than 20 Gauss. This is further reduced at the 9C21 elements by means of a 1/2 in steel sleeve slipped over the cooling jacket. The magnetic force on the oscillator box amounts however to 450 lbs.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 20

Editorial note, tabletop extrapolation: LDMOS amplifiers, fans and ferrite-cored parts near a 0.59 T magnet want a steel housing - and the source's method is the transferable part: they verified the shielding on a scale model before committing, and budgeted the large attractive force on the box. Measure the fringe field at the amplifier location and check the housing's effect; do not assume a thickness.

The horizontal joints are also rubber backed, but no particular care is necessary to insure contact as the current flow is parallel to the joint.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 6

Editorial note, tabletop extrapolation: Plan a next machine's panel seams along the RF current direction and spend the contact-strip effort on the seams that cross current - remembering fringing and return currents can cross nominally parallel seams, so verify with a current map or by checking seam temperatures at power.

It was tried this way at 20 megacycles, but it soon became necessary to copper plate most of the surfaces.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 6

Editorial note, tabletop extrapolation: At 9 MHz bare steel may survive, but plating (or copper construction) is cheap insurance for Q and hot spots - decide from an Rs estimate and verify temperatures at full power rather than reading 10-vs-20 Mc as a safe cutoff.

Such oscillations will usually not occur if the time constant of the resonant system is more than ten times the time constant of the grid leak grid condenser network.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 8

Editorial note, tabletop extrapolation: The bias-network-vs-resonator time-constant race is the transferable idea for any self-excited driver on a next machine's dee - for transistor circuits the mechanisms are topology-dependent, so do a small-signal/transient stability analysis rather than relying on this RC ratio.

The loops are therefore made of large diameter tubing and the length of tubing which is not serving as mutual inductance in the dee stem circuit is kept at a minimum. ... the total shift between plate and filament voltages is 21 [deg]. The correction is made in the filament circuit by inserting a capacitor of 140 uuf (c, in Figure 3) in series with the loop. ... The capacity (c, Figure 3) used in the actual installation is around 220 uuf, part of which serves to neutralize the inductance of the filament chokes. It was made adjustable over a small range and varied until minimum plate current was obtained.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 9

Editorial note, tabletop extrapolation: Minimum-DC-input trimming is a meterable, practical phasing procedure for a feedback-coupled driver - hold the required RF output/dee voltage while trimming, or the 'minimum' you find is just reduced drive; other topologies need their own phase-margin analysis.

the frequency of the plate loop could not be made higher than 38 megacycles. At one point this will coincide with the first harmonic. ... It has been predicted theoretically and demonstrated experimentally that most of the ions can be lost by such a variation if the ions reach their final radius at 19 megacycles. ... It was therefore necessary to add about 15 uuf to this circuit, which lowered its frequency to 34 megacycles.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 10

Editorial note, tabletop extrapolation: Even at fixed frequency, sweep the next machine's system for modes near 2x and 3x of 9 MHz; a found mode matters only if it is coupled and excited - measure its effect on dee voltage before detuning it, since an added capacitor perturbs the mode structure too.

Provision was made for arbitrary amplitude modulation by inserting an 893 triode in series with the power supply lead. As yet it has not been used for this purpose, but as it has a 20 kw plate dissipation, it has been used as an emission limiting device to protect the oscillator tubes when discharges occur in the tank and condenser.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 12

Editorial note, tabletop extrapolation: The principle transfers: fast current limiting or foldback in the LDMOS drain supply, plus a VSWR trip, is the modern form. It reduces fault energy; it is not immunity - reflected-power overvoltage and drain transients are separate failure paths needing their own protection (dg-338).

Since the tickler oscillator does not derive its excitation from the load, it can drive the main oscillator over the critical voltage.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 12

Editorial note, tabletop extrapolation: With an externally driven LDMOS chain the analogue is a controlled fast RF ramp through the low-voltage (multipactor-prone) band - with vacuum, arc and reflected-power monitoring, since driving through a discharge can reflect hard; there is no self-excited handover in a driven architecture.

For reasons which are not clearly understood this bias usually increases the size of the beam by a factor of two or more.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 12

Editorial note, tabletop extrapolation: Conditionally applicable - and 'try both polarities' is a controlled test, not a knob: use an RF-rated bias network with proper isolation and discharge paths, current and arc monitoring, and vacuum interlocks, and assess Penning-discharge conditions (crossed E and B regions) before applying either polarity. The dee's RF stored energy does not care about the bias supply's current limit.

The measurements were made with G-R Impedance Bridge, Type 650-A Serial #1977, and are +/- 2 uuf. Lead capacity of 29 uuf has already been deducted.

Anderson, 184″ Cyclotron: Oscillator Capacitance Measurements — MDDC-964 (1947) — p. 3

Editorial note, tabletop extrapolation: A modern LCR meter with lead-nulling does the same job on the reference machine's dee stem. C-to-ground alone doesn't predict the ~9 MHz resonance - combine it with the stem inductance (or a distributed model), then confirm the assembled resonance with a low-power VNA; a kHz-range LCR reading can differ from the effective RF capacitance.

a high intensity point (21 mr/hr) on the top outside edge of the copper foil holder, another high intensity point (18.5 mr/hr) on the foil just above the median plane

Reyenga, 184″ Cyclotron: Radiation Measurement of Breech Load Probe Head — MDDC-982 (1947) — p. 3

Editorial note, tabletop extrapolation: At nA currents and sub-MeV energies on ordinary holder metals, residual activation of the hardware is small where it occurs at all (thresholdless capture and deuteron operation excepted - the standard scoping). The lesson transfers regardless: check holder edges and apertures for beam strike with film, phosphor, or discoloration, because a large fraction of the beam can miss the target.

Cited in: Shielding a Small Cyclotron

The autographs indicate a rapid spreading vertically of the beam at about 81 1/2 inches. This agrees quite closely with the point at which n = 0.2 from magnetic measurements.

Vale, 184-inch Cyclotron Vertical Beam Oscillations in the Region of 82-inch Radius — MDDC-984 (1947) — p. 3

Editorial note, tabletop extrapolation: Fully applicable as a diagnostic: map B(r) on the bench, compute n(r) and the tunes, and if the reference machine's beam stalls early, the n = 0.2 crossing is suspect number one - but confirm with tracking and check field-error resonances and aperture before moving the target radius.

bombarded with a large deuteron beam for about 1 to 3 minutes, removed from the tank and radioautographs were taken to determine where the beam was hitting.

Vale, 184-inch Cyclotron Vertical Beam Oscillations in the Region of 82-inch Radius — MDDC-984 (1947) — p. 3

Editorial note, tabletop extrapolation: Copy the slotted C-target geometry but read it with a vacuum-compatible phosphor/scintillator viewed through a window (validate its spatial response) instead of activation film; a set of slotted witness targets at different radii still gives the whole vertical envelope in a few runs.

The usual beam pattern of two to three pips was obtained at several probe radii; namely, 22", 28 1/2" and 35". ... the regular probe radius was 28 1/2".

Yeater, 184″ Cyclotron: Synchroscope Beam Pictures on Two Probes — MDDC-987 (1947) — p. 3 (printed "- 1 -")

Editorial note, tabletop extrapolation: The two-azimuth comparison transfers to any machine: it is a test, not a verdict - accept the precession reading when the measured inter-probe phase agrees with an orbit model and controls exclude RF pickup and coherent source modulation (which can also arrive with a fixed offset).

An auxiliary copper probe, shielded for RF pickup, was introduced into the main vacuum tank through a Wilson seal on the port near the ion source ... made adjustable as to its radial depth

Yeater, 184″ Cyclotron: Synchroscope Beam Pictures on Two Probes — MDDC-987 (1947) — p. 3

Editorial note, tabletop extrapolation: Exactly the right probe pattern for the reference machine's chamber: an O-ring/Wilson-sealed sliding shaft with grounded coaxial shield tube and a defined exposed collector. Near a 9 MHz dee an unshielded probe's reading is dominated by RF pickup superposed on any beam signal - shield, then verify with beam-off RF-only background runs and filtering before crediting the remainder as beam.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The best detection of the beam deflection was made by mounting X-ray film on the probe and exposing it to both the undeflected and deflected beam.

Sewell, 184″ Cyclotron: Vertical D.C. Electrostatic Deflector — MDDC-1051 (1947) — p. 2

Editorial note, tabletop extrapolation: Start extraction commissioning with on/off comparison images - film or a scintillator-plus-camera at the channel exit - alongside a shielded Faraday collector: integrating detectors trade time for sensitivity and ignore RF pickup, while a well-guarded electrometer is also capable of picoamps when the noise is managed. Use both; agreement is the commissioning signal.

Cited in: Experiments by Energy Band

There was considerable sparking between the HV electrode and the .002 inch copper foil. The copper foil was warped badly ... The 0.002 inch copper foil supported in this manner is not suitable for this job.

Sewell, 184″ Cyclotron: Vertical D.C. Electrostatic Deflector — MDDC-1051 (1947) — p. 2

Editorial note, tabletop extrapolation: A next machine's septum should be sized against the deflector's stored spark energy and thermal impulse, then tensioned or heat-sunk accordingly - conditioning sparks are part of deflector life, and the septum edge is where they concentrate. Thickness follows from that calculation, not from a fixed minimum.

a sharp peak of radioactivity was found on the dee lip at the 82-inch radius, which gave additional evidence that the beam was spreading vertically in this region.

Sewell, Henrich & Vale, Some Operating Phenomena Associated with the 184-inch Cyclotron — MDDC-1092 (1947) — p. 3

Editorial note, tabletop extrapolation: At tabletop energies activation of ordinary structural metals (copper, steel, aluminium) is small and short-lived where it occurs at all - thresholdless (p,gamma) capture and any deuteron operation are the exceptions - so a survey of the dee lip may well find nothing; a cheap wipe survey costs little and settles it. The localization logic transfers regardless: line the dee aperture with removable witness strips (paper, phosphor, anodized Al) and read burn or discoloration marks to find the loss radius. A bombarded target is a separate question and is surveyed on its own terms (dg-1041). [Corrected 2026-08-22: previously 'No activation at tabletop energies', an absolute the site's own safety pages contradict.]

Cited in: Shielding a Small Cyclotron

The frequency of the minor pulses in each beam pulse agrees quite well with the calculated frequency of precession of the center of rotation of the ions about the magnetic center of the system

Sewell, Henrich & Vale, Some Operating Phenomena Associated with the 184-inch Cyclotron — MDDC-1092 (1947) — p. 4

Editorial note, tabletop extrapolation: Transfers with caveats: on a CW fixed-frequency machine you need a pulsed source or fast probe electronics to see the structure, but a pulsed-arc run makes precession directly visible on a scope - treat the inverted n as an approximate effective-tune diagnostic, cross-checked against the field map.

Cited in: Beam Dynamics: An Interactive Laboratory

Beam defining slits used on 1, 2, and 3rd revolutions to define center of beam rotation; 3rd turn slit is 1/2 mm wide. 100% extraction efficiency with low beams, requires better than 1/2 % stabilization of dee volts.

Howard, Cyclotrons and High-Energy Accelerators, 1958 — ORNL-2644 (1958) — p. 27

Editorial note, tabletop extrapolation: A historically successful, mechanically simple extraction aid: slits in the center region plus tight dee-amplitude regulation. Evaluate it for a next machine by comparing its interception losses and centering benefit against the calculated turn separation and deflector tolerances - slits select phase space by throwing beam away, so they complement, not replace, deflector design.

Electric focusing with carbon grids on the dees successful on first four revolutions

Howard, Cyclotrons and High-Energy Accelerators, 1958 — ORNL-2644 (1958) — p. 27

Editorial note, tabletop extrapolation: First-turn loss at low dee voltage is a classic tabletop failure mode, and the ANU carbon-grid result makes grid focusing worth testing - model the electric fields first, note a slit plate is not the same as a transparent grid, and check interception, RF loading, heating and outgassing at low current before adopting it.

As a result of these circuits improper tuning cannot damage the power tubes.

Osterlund & Smythe, A Cyclotron Power-Amplifier RF System Using a 4CW50,000C/8350 Tetrode — COO-535-543 (1963) — p. 5-6

Editorial note, tabletop extrapolation: For the LDMOS upgrade, take the architecture (limiters that seize the control loop) but not the sufficiency claim: LDMOS dies fail on single-cycle peak Vds, mismatch load-line excursions and oscillation faster than an averaged ALC responds - so add device-specific SOA protection, fast reflected-power shutdown, thermal sensing and a stability check, with polarities and response times defined and fault-tested.

The dee voltage is depressed about 1% for each 10 uA of injected current, and because a balance is maintained at the input of the amplifier, the recovery time is limited only by the bandwidth

Osterlund & Smythe, A Cyclotron Power-Amplifier RF System Using a 4CW50,000C/8350 Tetrode — COO-535-543 (1963) — p. 6

Editorial note, tabletop extrapolation: A tabletop ALC loop gets dee-voltage modulation for free by injecting an offset into the amplitude setpoint - but that is voltage modulation, not proven beam gating: measure the transfer to extracted current, energy and extinction ratio (and where the un-extracted beam goes) before using it for activation or timing work; true beam-off needs a validated source-side chopper. The 1%/10 uA constant is their circuit's, not a scaling law.

below a dee voltage of 15 kV, the flip-flop will remain in one state and only if the dee circuit happens to be tuned to the low frequency side of resonance will the servo run in the proper direction

Osterlund & Smythe, A Cyclotron Power-Amplifier RF System Using a 4CW50,000C/8350 Tetrode — COO-535-543 (1963) — p. 7

Editorial note, tabletop extrapolation: Any auto-tune loop (phase comparison of PA drive vs dee pickup) needs a validity gate: characterize the detector's own signal-threshold, enable the servo only above it, bound the tuner's travel and rate so a confused loop cannot run away, and provide a manual jog mode to walk into range - the low-signal failure mode recurs across detector technologies even though its details differ.

adjusting Cn for coincidence of maximum dee voltage and minimum plate current as the dee was tuned through resonance

Osterlund & Smythe, A Cyclotron Power-Amplifier RF System Using a 4CW50,000C/8350 Tetrode — COO-535-543 (1963) — p. 4

Editorial note, tabletop extrapolation: Neutralization is a triode/tetrode matter, and the coincidence test belongs to a neutralized tuned-plate PA: on that class of amplifier the dee-voltage peak and plate-current dip should line up through resonance, and a skew flags feedback. On a solid-state or matched-line chain there need be no input-current dip at resonance at all - verify resonance and match there with dee voltage, reflected power and the device's rated currents instead. [Note revised 2026-08-23: the earlier note generalised the test to 'any amplifier-dee chain' and changed the observable to PA input current.]

It was decided to use Eimac grid collet (which is .020" thick in contrast to their regular line of finger stock which is .010" thick) mounted on water cooled copper blocks ... dee stem surface was silver-plated copper which was also water cooled. The shorting plane as originally installed has been in service for nearly three years and has performed flawlessly. There is no discoloration or other indication of heating of the contacts, despite routine operation to 110 A/in and occasional operation to higher current densities

Osterlund & Smythe, A Cyclotron Power-Amplifier RF System Using a 4CW50,000C/8350 Tetrode — COO-535-543 (1963) — p. 8

Editorial note, tabletop extrapolation: The recipe transfers - thick fingers, positive clamping, plated surfaces, cooling on both sides of the joint - the number does not: calculate the proposed tuner's actual contact current, then verify temperature rise and contact resistance under representative duty; a demonstrated operating point in one cooled geometry is not a ceiling for another.

Tuning drifts are always experienced in cyclotron operation. Since a tuning drift would change the relative amplitudes and phases of the first and third harmonics, such a drift would alter the wave form. A visual means of monitoring the wave form and a remote tuning or an automatic servomechanism for tuning should be provided.

Goodman, A Square-Wave Cyclotron Oscillator — ORNL-2403 (1958) — p. 25

Editorial note, tabletop extrapolation: Even a plain sine system drifts (thermal detuning is logged on the reference machine); a calibrated capacitive pickup on a scope is the minimum instrument, and it is a prerequisite for any auto-tune servo on a next machine.

one degree of phase error will apply full power to the servo motor... the trimmer will shift the resonant frequency of the dee 1% in one minute... the dee trimmer should have sufficient range to shift the resonant frequency 2%.

Smith, A Three-Phase Radiofrequency System for Cloverleaf Cyclotrons — UCRL-3153 (1955) — p. PDF p.7 (printed -4-)

Editorial note, tabletop extrapolation: Good starting criteria for a stepper-driven trimmer on a next machine's resonator - then derive the actual range and slew from measured cavity drift (thermal and mechanical) and actuator dynamics, and verify loop stability margins; the field tolerance and the tuning range are separate constraints.

the amplitude of the intermediate frequency is exactly equal to the magnitude of the local oscillator signal and entirely independent of the magnitude of the phase signals

Smith, A Three-Phase Radiofrequency System for Cloverleaf Cyclotrons — UCRL-3153 (1955) — p. 12-13

Editorial note, tabletop extrapolation: The principle transfers: servo dynamics should not change with dee-voltage level over the operating range, and the ion arc is a noise source the phase detector must tolerate. Modern equivalents are limiting amplifiers or digital phase detection - but every implementation has a floor: specify and test input dynamic range, limiter behavior, phase noise and loss-of-signal handling, because no detector stays accurate as the signal approaches its noise floor.

Once the three dees are isolated electrically by adjusting the neutralizing loops the machine behaves like three separate single-phase systems.

Smith, A Three-Phase Radiofrequency System for Cloverleaf Cyclotrons — UCRL-3153 (1955) — p. 18

Editorial note, tabletop extrapolation: The architectural moral - decouple where practical, then control each loop as SISO - applies to a next machine's interacting adjustments (tuner vs coupling vs amplitude); measure the residual interaction after decoupling, and where it stays significant use coordinated control rather than fighting coupled loops one at a time. The programme burned months servoing the coupled system first (ucrl-3187 p.5-6, 11).

A major improvement was effected when an off-center source was installed which injected azimuthally into one of the dees.

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 12

Editorial note, tabletop extrapolation: For the reference machine's filament source, radial position and slot azimuth are cheap, high-leverage experiment variables (directly relevant to the planned source-species test) - scan them, normalized to the first-orbit geometry. Expect improvement mechanisms to be entangled as they were historically; measure, don't assume a factor of two.

the calorimetric method gave 90% of the probe method, while in the 6- to 8-ma range this ratio dropped to 75%. The probe method was believed to be the more reliable.

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 14

Editorial note, tabletop extrapolation: At the reference machine's nA scale the transferable doctrine is: never trust one beam-current method - independent checks can reveal method-dependent bias, as the mA-scale probe/calorimetry comparison did. Establish the actual uncertainty from calibrated measurements, blank runs and charge integration; the electrometer-background subtraction is a control within one method, not an independent second method. OCR note - the 75% figure was verified on the page image.

at this radius was unaffected by 450-v positive bias on the probe. However, inside 6 inches the probe current rose steeply with decreasing radius and was decreased by positive bias voltage.

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 12

Editorial note, tabletop extrapolation: Directly usable on the reference machine's probe: sweep the bias until the reading plateaus, and back it with controls (RF on/no beam, source off) - bias-flatness alone can miss RF pickup, leakage and photon-induced currents. Set the bias magnitude from collector geometry and secondary-particle energies, not from the beam current.

The beam load would cause a two- to threefold increase in the amplifier plate currents compared to the source-off condition.

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 14

Editorial note, tabletop extrapolation: The 2-3x signature does NOT transfer to nA beams (P_beam = I*E/q puts a nA beam far below amplifier-meter resolution - compute it for your parameters); what does transfer is the habit of plotting beam current against dee voltage empirically as a run-log staple, WITHOUT imposing linearity - capture and transmission bend that curve, and V_dee itself goes as sqrt(P) at fixed impedance.

protected by an interlocked air-cooling system, spark gaps at both ends of the half-wave transmission lines leading to the dee stems, and by an rf-dc fault circuit

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 11

Editorial note, tabletop extrapolation: The rf-dc comparison is the tube-era ancestor of modern output-detect foldback and ports to the LDMOS upgrade: DC applied but no RF developing means something is wrong - an arc, a detune, or a failed stage - so kill drive and investigate. Spark gaps at the feedthroughs remain cheap insurance.

during this time the servos received spurious signals and tended to creep away

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 12

Editorial note, tabletop extrapolation: A control-system rule that transfers verbatim to any next machine's auto-tune or ALC firmware - hold integrators and actuator positions during spark recovery/restart, and make both the recycle delay and the servo-hold adjustable; same lesson as coo-535-543's amplitude gate, learned independently.

thermal effects detuned the machine sufficiently so that ion lock prevented the rf from being restored ... It was then necessary to retune the machine by exciting each of the dee-stem tanks with a grid dip oscillator and adjusting the tuning capacitances for resonance.

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 12

Editorial note, tabletop extrapolation: The transferable practice is a permanent low-level resonance-check capability - a VNA or dip meter on a pickup loop, with RF-rated isolation or interlocking so it can never see drive power - so resonance can be found cold, plus logging tune position vs temperature. The reference machine already shows warm-up drift.

peak efficiency did not correspond to 120 phase difference between the dees

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 11

Editorial note, tabletop extrapolation: Measure the quantity you care about at the electrode (same moral in ucrl-3153 p.7): derive a next machine's tuning/phase feedback from the dee pickup, and before trusting LDMOS drain current or forward power as a tuning indicator, verify at the electrode that its optimum coincides with the dee-voltage optimum - the historical machine's did not.

stainless steel, inconel, molybdenum, K-monel, titanium, and nickel seem to be comparable and were the best materials. Copper, tantalum, and aluminum were intermediate. Silver showed the most severe spark damage. Carbon appeared to resist spark damage well, but would not remain baked out. Heard and Chupp claim that after baking out carbon electrodes and turning the voltage off for even a few minutes, the whole bake-in process had to start over again. The spark dust of K-monel and nickel was found to be magnetic. That from stainless steel and the other materials tested was not.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 8

Editorial note, tabletop extrapolation: 316 stainless is the economical best-tier candidate for the next machine's deflector electrode (cheap, machinable, tested) - validate under the intended field, finish, gap and stored energy; copper and aluminum ranked intermediate in this test, which argues against them for HV surfaces where a best-tier metal is just as easy to use.

There seemed to be a critical magnetic field for each material beyond which the spark damage was severe and below which the spark damage was negligible. The critical fields ranged from 4 to 15 kG.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 7

Editorial note, tabletop extrapolation: The reference machine's ~6 kG is above the 4 kG end of the tested range, so no advantage can be assumed without knowing the chosen electrode material's own threshold. Conditioning at reduced magnet current is a hypothesis worth testing - it cannot prevent severe damage from later sparks at full field if the material's threshold sits below the operating point, so validate at full field before trusting it.

when a 0.0125-uF capacitor was added across the gap, the electrodes baked-in to 60 kV, a six-fold increase. Adding a 0.5-uF capacitor across the gap reduced the breakdown voltage to 5 kV.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 8

Editorial note, tabletop extrapolation: For the deflector supply, the transferable idea is that conditioning behavior depends on the discharge circuit, not just the gap: compute the total fault energy (all capacitance plus supply feed-through), current-limit and interrupt faults quickly, and establish any deliberate conditioning-energy setting by controlled test - not by defeating arc extinction.

all of them baked in in a similar fashion except 316 stainless steel, which required about ten times as many sparks to reach the ultimate breakdown voltage. It takes about 30 sparks per cm2 to bake in high-voltage-electrode surfaces. Since it takes about a second for the vacuum to recover following a spark, the bake-in time of an electrode is about 30 sec/cm2.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 13

Editorial note, tabletop extrapolation: Applying the source's scaling to a palm-sized ~100 cm^2 electrode gives about 50 minutes of spark time - or roughly 8.3 hours for 316 stainless - excluding setup, failed ramps and downtime. Write conditioning into the next machine's ops checklist as a scheduled activity, not a nuisance.

the high-voltage electrode should have the minimum possible surface area. This minimizes the amount of sparking required to bake out the cathode spots and reduces the amount of electrode contamination.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 16

Editorial note, tabletop extrapolation: Measure or track the next machine's actual beam envelope at extraction radius - vertical oscillations, alignment and median-plane shift included - set the field window from that worst case plus explicit margin, and keep the HV bar as small and short as the trajectory allows; the 88-inch's 2x is their outcome, not a sizing law.

The minimum radius of curvature of the high-voltage electrode should be large enough to prevent appreciable field-gradient magnification. In practice, the minimum radius should be no less than about half a gap.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 17

Editorial note, tabletop extrapolation: Direct machining rule - for a next machine's 3-mm deflector gap, radius every HV edge to at least 1.5 mm and polish.

At the smaller gaps the electrode vibrated like a tuning fork in a tuning-fork oscillator. ... The forces driving the electrode were electrostatic; the device that provided the pulsating force was the dark current. ... Simplifying this circuit by the techniques of network analysis the system reduces to that of a Colpitts oscillator. ... The period is 50 msec corresponding to a vibrational frequency of 20 cps. ... Curve 1 was taken before insulators were installed and electromechanical oscillation occurred, resulting in VE = 1.23 x 10^4 (kV)^2/cm; curve 2 was obtained with insulator supports which prevented electromechanical oscillation, crowbar was set at 0.4 A, resulting in VE = 1.47 x 10^4 (kV)^2/cm

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 17

Editorial note, tabletop extrapolation: Very much in reach of amateur trouble - a small cantilevered electrode has low mass and compliance. Support a next machine's deflector bar on insulators at both ends and check the deflector voltage on a scope for slow oscillation buildup.

With the tungsten anodes, the VE number increased to 2.25 X 10^4 (kV)^2/cm, an increase of 17% in VE number. In addition, we found that the tungsten anodes resisted spark damage better.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 24

Editorial note, tabletop extrapolation: A cheap, historically demonstrated upgrade candidate: line the grounded surfaces opposite the next machine's HV bar with thin tungsten sheet, edges overlapped so only tungsten is exposed - then verify in the actual geometry, since breakdown gains depend on geometry, finish, stored energy and conditioning; molybdenum is a plausible substitute only on its best-tier spark-damage ranking (dg-744), not on this VE test.

A 500-µA beam of 32-MeV deuterons did not destroy the carbon septum. It did thoroughly contaminate the high-voltage electrode and insulators though. ... unless a solution appears to the carbon contamination problem, metal septums will be required for the high-energy beams.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. PDF p. 28 (printed -24-)

Editorial note, tabletop extrapolation: A next machine's beam power is watts, not kilowatts, so a carbon septum's activation advantage may yet win at sub-MeV - but the mechanism is temperature-driven and thin-foil hot spots concentrate it, so default to a tungsten or molybdenum septum and revisit carbon only with septum-temperature estimates in hand.

Hydrogen is let into the vacuum tank until the pressure becomes 200 to 300 u. ... A discharge current of about 100 mA is maintained for about an hour.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 32

Editorial note, tabletop extrapolation: The reference machine and a next machine use oil diffusion pumping, so the dirty-system dark-current regime is the thing to MEASURE, not assume. The hydrogen ion-scrub is a historical conditioning procedure to adapt, not a weekend recipe: it needs an isolated, current-limited supply (a variac is not isolation and 480 V is lethal), controlled H2 admission with pressure regulation, a safe purge/exhaust path, and interlocks - reviewed against the actual apparatus before first use.

a deflector is limited by sparking phenomena and not from an extraneous cause can be tested simply by a log-log plot of the voltage versus gap to see that it follows a VE line.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 27

Editorial note, tabletop extrapolation: Free instrumentation for a next machine: run the V(d) test during commissioning with several repeated gap settings (conditioning history scatters single points). The report's practice of insulating each ground electrode and metering intercepted current as an alignment monitor is worth copying too - reported practice, scan re-read queued for the exact passage.

Each circuit board consists of 100 Unitrode, Type UT71, silicon diodes connected in series. Each diode is shunted by a 250-pF, 500-V, ceramic capacitor to divide the inverse voltages equally.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 10

Editorial note, tabletop extrapolation: Today this is a standard multiplier stack; keep the two features that matter - per-diode grading capacitors (transient sharing; add static resistors or integrated HV rectifiers for dc sharing) and high drive frequency, which buys regulation into a varying load. What frequency does NOT buy is low stored energy: 0.5*C*V^2 is set by the capacitors, so compute the stack's accessible spark energy and add local limiting before pointing it at a sparking deflector.

typically, it takes a few microseconds ... The recycling time is 1 sec. ... the power supply can be turned off before a spark becomes visible.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. PDF 28 carries the quoted sentence; the two performance figures are on PDF 19

Editorial note, tabletop extrapolation: The feature to replicate in a modern build: fast drive-kill on spark detection with an operator-adjustable threshold, used deliberately during bake-in (UCRL-10654's practice). A solid-state inverter's gate shutdown gives the fast drive-kill - but killing drive is not a crowbar: energy already stored in the output stack and cable still feeds the spark (dg-285), so pair gate-kill with a dump path or series resistance rated for that stored energy.

The spacing between boards is about 2 in. and provides a nominal maximum design gradient of 10 kV per in.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 10

Editorial note, tabletop extrapolation: For an amateur HV column, run the real layout numbers: air clearance and surface creepage separately, field stress at conductor curvatures, contamination and altitude derating, and a controlled HV test - matching the historical 10 kV/in exactly (6 in at 60 kV) leaves zero headroom by construction.

We can attenuate this ripple by using an RC filter consisting of a series resistance connecting the Cockcroft-Walton to the deflector, and a capacitance which is the deflector capacitance.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 30

Editorial note, tabletop extrapolation: Pick R from the measured deflector capacitance, ripple frequency, allowable voltage drop and the discharge-energy model - and note what the resistor cannot do: the 0.5*C*V^2 already ON the deflector side discharges into the arc regardless. Size the part honestly (dc dissipation I^2*R, pulse rating, voltage grading) - at the report's own 5 mA, 100 kOhm burns 2.5 kW only if run continuously at that current, so check the real duty before calling any resistor cheap.

the deflector oscillators are located close to the magnet yoke of the cyclotron in a field of about 150 G, magnetic shields had to be put over the 4CW2000 oscillator tube and the 3D22.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 19

Editorial note, tabletop extrapolation: Map the field where equipment will sit and shield or relocate per COMPONENT tolerance: transformers, inductors, Hall sensors, relays and fans all care about DC field to different degrees, PMTs need residual fields far below 150 G (high-permeability or multilayer shields), and a mild-steel can's attenuation depends on geometry, seams and saturation - the cited caps are proof the approach works, not a universal thickness spec.

the effective rise time is about 0.15 us, 50 percent more than that desired. ... it is felt that increasing the peak voltage compensates for the longer rise time of the pulse.

Kerns et al., High Voltage Pulser for 184-inch Cyclotron Electric Deflector — UCRL-95 (1948) — p. 16

Editorial note, tabletop extrapolation: A commissioning lesson in trade-offs: extraction elements have one strong knob (voltage/field) that can sometimes buy back deficiencies in the others - design in voltage headroom, but check what the slower edge costs in turn selectivity and what the higher voltage costs in breakdown and switch margin before leaning on it.

The synchronous radius suitable for deflection in the cyclotron is just inside the radius at which normal beam destruction occurs.

Stubbins, Extraction of Synchrocyclotron Beams Near the Maximum Energy — UCRL-3476 (1956) — p. 7

Editorial note, tabletop extrapolation: The siting logic transfers, the threshold does not: put a next machine's septum or regenerator equivalent just inside where its OWN analysis says the beam dies - measured field map, tune calculation and tracking, not a universal n = 0.2 wall (linear radial stability formally extends to n = 1, and real loss radii are set by resonances, apertures and field errors). And every mm inward is extracted energy given away.

f_z = f - f_0, where f_z equals (sqrt n) f_0 ... and n is the conventional cyclotron magnetic field parameter. The relation f = f_0 ((sqrt n) + 1) is one required condition for this process to occur

Stubbins, Radiofrequency System for Extracting Particles from a Cyclotron — UCRL-8578 (1958) — p. PDF p.5 = printed p.-3- (UCRL-8578, Sec. I Introduction)

Editorial note, tabletop extrapolation: A real design caution at any scale: an E_z gradient of the right symmetry near a nu_z resonance can dump the beam. Note dee misalignment gives mostly a dipole-like midplane E_z, not the z-proportional gradient this parametric resonance needs - but asymmetric liners and gap geometry can supply the gradient term, so keep the dee/dummy-dee vertically symmetric and check nu_z against strong rf harmonics at operating field.

A dee voltage of 75 kv dee-to-dee was reached after some routine difficulties were overcome. The cyclotron now maintains this voltage for long periods of time without showing any tendencies to failure.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 15

Editorial note, tabletop extrapolation: The transferable practice is endurance-above-operating-point as the acceptance test for the LDMOS upgrade - with the margin chosen from the new system's own component deratings (capacitors, feedthroughs, transistor SOA), stored energy and interlocks, and with arc and X-ray monitoring during the test. A margin that survives only seconds is not margin; a margin that exceeds a component rating is not a test, it is a failure in progress.

The location of the germanium crystals was such that neutron bombardment from the cyclotron affected the resistivity calibration. With the present system, the vacuum tube rectifiers are unchanged by neutron bombardment and, unless the probe-to-dee distance is changed, the calibration remains constant.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 10

Editorial note, tabletop extrapolation: Two transferable halves, properly scoped: (1) semiconductor sensors near the chamber are a calibration-drift RISK once neutrons appear - characterize candidate devices at the expected fluence rather than banning them; (2) a capacitive dee-voltage pickup is calibrated GEOMETRY - fix and document the complete pickup geometry and signal chain, or every calibration is void. Bears directly on retiring the reference machine's uncalibrated ~1.3 kV dee-voltage number.

It is now possible for the operator to obtain in a few minutes a complete calibration of the probe water temperature differential up to a maximum power of 27 kw.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 9

Editorial note, tabletop extrapolation: The trick transfers if the calibration heat matches the beam's thermal path: a nA-to-uA tabletop calorimeter (thermistor on an isolated cup) can be calibrated with a surface-mount resistor dissipating known milliwatts - verify the heater and beam deposit heat comparably, calibrate over the working range, and budget for backscatter, escaping radiation and conduction losses before calling the result absolute.

The measured beam power is determined from the measured temperature rise in the target cooling water. The calculated power and measured power readings agree within 5%.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 8

Editorial note, tabletop extrapolation: The redundancy principle transfers even at nA: Faraday-cup current times computed kinetic energy should match any independent measurement. Set your own acceptance band from the actual uncertainties (current, energy, calorimetry or activation), and treat activation as a separately calibrated fluence check - it needs cross sections, target data and timing, and works only above the chosen reaction's useful yield range.

The increase in proton energy resulted from relocation of the ion source 1 1/2" upward; the source is now effectively only one inch below the magnetic center.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 8

Editorial note, tabletop extrapolation: On the reference machine, treat filament/chimney height relative to the MAGNETIC median plane (find it by measurement - it need not match the mechanical midplane) as a tuned parameter worth systematic scans. What the height buys is centering, vertical transmission and usable radius; at a fixed field and radius the energy is p = qBr regardless, so measure where the gain actually comes from rather than expecting a fixed percentage.

the beam striking the periphery of the south dee. This condition resulted from the center of rotation of the beam being offset to the south by a distance of approximately three inches. ... The dees were moved 1/2 in south, measured at the horizontal center line of the dees.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 7

Editorial note, tabletop extrapolation: Witness marks on the reference machine's dee edges are a free orbit-centering CLUE - corroborate with radial probe scans and the field map before moving anything, since phase, axial focusing and apertures make similar marks; then correct at the source or dees once the cause is identified.

To insure proper positioning and grounding of the lower end of the ion source, a bracket has been attached to the west side of the liner which places the ion source one inch below the center of the magnetic field. This arrangement insures that the position will be the same from run to run and also reduces heating of the tube due to rf pickup.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 10

Editorial note, tabletop extrapolation: Cheap and directly imitable — once the optimum source position is found by scanning, capture it in a hard registration feature so it survives every source rebuild; grounding the support also kills a stray RF-heating path.

most of the loss of protons to the dees occurs during early revolutions. Only a small percentage of the beam is lost beyond one-half of maximum radius, Figure 5. ... [Figure 5:] Z-WISE BEAM DISTRIBUTION on Each of Five Segments

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 16

Editorial note, tabletop extrapolation: Both the finding and the instrument transfer as guidance: stack 3-5 insulated foils as a segmented z-probe on the reference machine to see where the beam sits vertically, and expect the early turns to deserve the tuning effort - on that machine, beam surviving to half radius mostly escaped further DEE loss; extraction, phase and radial channels are separate ledgers.

At low arc current the ratio of H3+ ions to H1+ ions is high. The total number of H1+ ions and the ratio of H1+ ions to H3+ ions may be increased by increasing the arc current.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 16

Editorial note, tabletop extrapolation: The prior art for a source-species test on the reference machine: a field sweep at fixed frequency is a species analyzer needing only the existing probe, and source arc power is the species-ratio control - expect molecular ions to be strong at weak arc, and raise the arc within the source's thermal and electrical limits when protons are wanted. (Fig. 6, PDF p.18, shows the resolved peaks.)

the ion source arc slit was shortened from 2 1/2" to 1/2". Thereafter the ratio of accelerated beam power to ion loading power was increased, as predicted.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 16

Editorial note, tabletop extrapolation: On a tabletop machine where every watt of RF matters: try slit length as an EXPERIMENT, watching accepted beam per unit dee loading rather than raw source output. The over-emission mechanism is the natural reading of the ORNL result, but slit changes also move plasma and extraction optics, so let the measurement decide.

the pressure was reduced to 10^-5 mm Hg. A rate of rise of 0.00025 microns/sec indicates that the system is vacuum tight.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 12

Editorial note, tabletop extrapolation: Log an isolated rate-of-rise after every reassembly as a regression test against the machine's OWN baseline - the number folds together leaks, outgassing and permeation scaled by volume, so it does not transfer between chambers in either direction; where true leak-tightness must be established, helium leak testing is the tool.

Cited in: The Vacuum Budget of a Cyclotron

It was found that distortion of the magnetic field when the tank is evacuated is negligible. Latest measurements of the magnetic field reveal a first harmonic inhomogeneity of approximately 0.03%.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 15

Editorial note, tabletop extrapolation: Two transfers: verify a next machine's field map with the chamber assembled and pumped (pole deflection under vacuum load is a real worry that proved negligible for them - measure once to confirm); and read 0.03% as what a carefully shimmed classical machine ACHIEVED - the new machine's allowable first harmonic comes from its own orbit-centering budget, and note 0.03% of a 0.5-1 T tabletop field is 1.5-3 G, so gauss-level targets and fractional targets must be kept straight.

The bombardments are tabulated below: Beam profile 10, Isotope production 8, Experimental 16, Energy 5, Physics 7, Radiation damage 4.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 8

Editorial note, tabletop extrapolation: A quarterly cadence in miniature for the reference machine: after any change (RF upgrade, source rebuild), the run log should show dedicated profile and energy runs alongside the physics runs - the ORNL table records the proportion by count; durations and ordering it does not give, so import the habit, not a timeline.

Energy measurements by foil stack, by calorimetry, and by production yields indicate the average energy of the beam is now approximately 23 Mev at 30.5 inches. This value is well established, since many runs have been made at this radius.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 6

Editorial note, tabletop extrapolation: Directly actionable for the '~150 keV-class computed' number on the reference machine: convert computed to measured with independent checks where feasible - foil range/transmission steps (which at 150 keV means micron-class calibrated foils) and, at higher current after the RF upgrade, cup calorimetry with E = q*P/I and its backscatter/thermal corrections. A single method is weaker than agreeing methods.

With the cyclotron operating steadily at 0.5 ma and at 22.5 Mev, the beam was increased progressively until the metered beam current approached 2 ma. At each level the power dissipated on the target was measured calorimeterically. The maximum beam power measured in this manner was over 41 kw, corresponding to an average beam current of 1.85 ma.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 7

Editorial note, tabletop extrapolation: The stepped-ladder protocol transfers to any record attempt on the reference machine — each step cross-checks meter vs thermal response and catches secondary-emission or leakage error before it contaminates the headline number; a record with only one point behind it is fragile.

the net ion-loading efficiency was 40%, that is, 40% of the power expended in acceleration of ions was to the target. There was a two-fold increase in electrical efficiency as the beam was increased.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 7

Editorial note, tabletop extrapolation: On the reference machine at nA the beam power is invisible next to fixed RF losses - the transferable lesson is the metric, not the number: log P_beam/P_RF per run, and chase resonator Q and coupling rather than amplifier watts for efficiency on any small machine.

grazing-incidence type aluminum targets were used because of the high beam intensities they withstand.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 6

Editorial note, tabletop extrapolation: The geometry trick matters twice on a small machine: thermally on any upgrade path (do the target thermal model with actual beam energy, spot size and interception - even mW into an isolated foil or microscopic spot can damage it, so 'nA cannot melt anything' is not a law), and for beam viewing, where a tilted phosphor or foil presents more area to the spiral - a detector-specific claim to verify by eye, not assume.

Since the singly-ionized nitrogen ions at this radius have an energy of only 2 1/2 Mev, it may be concluded that the burst of radiation observed was indeed due to triply-charged nitrogen ions.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 9

Editorial note, tabletop extrapolation: The evidentiary pattern transfers - an observed nuclear signature whose energetics disfavor the alternative species is strong evidence - but treat it as evidence, not proof: identify the radiation, use modern Q-values and cross-sections, run detector controls, and exclude electron-induced X-rays, contaminants and other q/m candidates (and remember radiative capture has no threshold, only Coulomb suppression). The reference machine's 5.6x-background best-beam sits in this tradition as supporting evidence for acceleration, with species claims needing their own case.

Current measurements beyond 18.5" were unreliable; the current at the maximum radius, 25.5", is estimated to be of the order of one microampere.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 10

Editorial note, tabletop extrapolation: Calibrates expectations qualitatively, not in absolute scale: an untuned machine can lose orders of magnitude between small radius and full radius, so log the whole I(r) curve - its shape (where the loss happens) is the tuning roadmap. This is one machine's commissioning history, not a norm to be satisfied with.

When nitrogen was bombarded in the form of TaN, 2-minute, 10-minute, 112-minute, and 15-hour activities were observed ... it is difficult to assign any but the 10-minute activity as unequivocally due to N 13

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. PDF 10 (printed 10) and PDF 11 (printed 11)

Editorial note, tabletop extrapolation: Not a casual check, and not closed to the reference machine by any blanket "threshold": which reactions are open depends on the beam SPECIES and the target ISOTOPES - D-D is exothermic with no threshold, so 150 keV deuterons make neutrons and tritium, and neutrons can then activate surrounding materials by capture, with no charged-particle threshold at all (dg-1041, dg-1047). Before using activation as an energy bound: pick candidate reactions from modern Q-values, thresholds and cross-sections for the actual beam and target; treat a half-life alone as preliminary (ambiguous assignments, tiny near-threshold yields, contaminants that dominate) until backed by an absorber or spectrum check; and accept that deliberately activating a target means prompt radiation, a survey, dosimetry and handling the residual activity. [Corrected 2026-08-23: earlier wording said "below nuclear thresholds the 150-keV reference machine cannot use this" and called the method "only a GM counter and a stopwatch" - the same absolute already corrected at dg-1041, dg-685 and dg-695.]

Carbon lips of a new design were installed on the edges of the dees to reduce sparking at the increased dee-to-dee voltage, 400-500 kv, required for operation at the high energy level.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 7

Editorial note, tabletop extrapolation: The 400-500 kV is MW-era and does not transfer; the material practice is a candidate to test - if the reference machine's 5-13 kV upgrade sparks at the dee gap, carbon edge pieces are the period remedy and trivially machinable. Verify grade choice and watch for carbon dust on insulators; and note ucrl-10654's caveat that carbon loses its bake-in minutes after voltage-off (dg-744).

It was never possible to make a dc test without high drain to the accelerating electrode. This is a definite clue to the lower output obtained in the rf tests.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 24

Editorial note, tabletop extrapolation: Current bookkeeping is cheap diagnosis: meter the puller and chimney drains separately from the Faraday cup. A weak beam with a hot puller points first at geometry near the source exit - then confirm by varying extraction voltage, alignment and arc conditions, since plasma meniscus, secondaries and leakage also move those meters, and arc power can reshape the optics as well as the density.

no evidence of the mass transfer type of corrosion due solely to a thermal gradient is found. The enhanced corrosion observed in Figure 2a seems to be quite definitely associated with the proton irradiation.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 19

Editorial note, tabletop extrapolation: The discipline transfers whole to any 'the beam did X' claim: run a sham control reproducing the specimen's full temperature-time history and every non-beam condition - identical-setup-minus-beam is only adequate when beam heating is negligible or separately reproduced. Log uncertainties honestly in the lab book while at it.

The isochronous fields are obtained with trim coil settings computed by a linear program, and their greatest deviation from isochronism is less than 15 gauss in all cases.

Jungerman, Kibbe & Peek, Central Region Studies for Incorporating an Axial Ion Source in the Davis 76-in. Cyclotron — UCD-CNL-49 (1966) — p. 6

Editorial note, tabletop extrapolation: Calibration, not criterion: what any machine tolerates is the accumulated RF phase slip - the signed integral of the frequency error over ITS acceleration history - so run the phase-slip integral in the tracker for the actual field map, turn count and dee voltage, and let that set the gauss tolerance; a few-tens-of-turns classical machine and a hundreds-of-turns AVF machine land in different places by exactly that arithmetic.

The starting conditions for all cases were estimated by starting the ions on an equilibrium orbit of 12 inch radius and de-accelerating them to the center.

Jungerman, Kibbe & Peek, Central Region Studies for Incorporating an Axial Ion Source in the Davis 76-in. Cyclotron — UCD-CNL-49 (1966) — p. 6

Editorial note, tabletop extrapolation: Directly implementable in the Python orbit tracker: find the equilibrium orbit at modest radius (well-conditioned), integrate backwards keeping the RF phase time-consistent, and read off CANDIDATE source-slit and puller coordinates - then validate with a full central-region field model and forward tracking; the backward pass suggests the geometry, it doesn't determine it.

the beam measured at extraction is augmented by possibly 10% by using 22 amps in trim coil number 1 rather than -145 amps. The former produces the central radial bump.

Jungerman, Kibbe & Peek, Central Region Studies for Incorporating an Axial Ion Source in the Davis 76-in. Cyclotron — UCD-CNL-49 (1966) — p. 6

Editorial note, tabletop extrapolation: Consistent with the classical-cyclotron instinct - a small central bump (field falling with radius from turn one) focuses the early turns where the ORNL 22-inch z-studies located most dee loss - as a HYPOTHESIS the correlation supports, not a demonstrated mechanism. Empirically checkable on the reference machine with shim washers at the pole center: calculate the phase-slip cost first, map the shimmed field, and measure both transmission and where the losses move.

The particles pass through the 3/3 resonance at a radius of 6-7 inches. The computer calculations show that the radial oscillation build-up at resonance is not excessive and soon damps to 0.3 inch.

Jungerman, Kibbe & Peek, Central Region Studies for Incorporating an Axial Ion Source in the Davis 76-in. Cyclotron — UCD-CNL-49 (1966) — p. 6

Editorial note, tabletop extrapolation: Method for the CYCLOPS-lite tracker: don't just plot nu_r(r) and forbid resonance lines - integrate through them with realistic errors and acceleration rate, and report maximum excursion in millimeters against the aperture. A fast-crossed resonance can be acceptable if the complete envelope keeps clearance; 'damps' in the historical usage reflects detuning and adiabatic effects, not dissipation.

We have not attempted to obtain particle beams for the cases discussed here as we do not plan to accelerate protons until the shielding vault is completed.

Jungerman, Kibbe & Peek, Central Region Studies for Incorporating an Axial Ion Source in the Davis 76-in. Cyclotron — UCD-CNL-49 (1966) — p. 7

Editorial note, tabletop extrapolation: Directly relevant to the plan's shielding gate: species choice is a radiological control. Commissioning on H2+ at the same B*rho halves the total kinetic energy and quarters the per-nucleon energy versus protons - same tuning fields, gentler consequences - and the proton program waits until the vault or survey case is ready. Davis's sequencing is the model; the record itself says only that they deferred protons until shielding was complete.

Cited in: Shielding a Small Cyclotron

An effort to obtain a value of the pole-tip efficiency, E, which could be used as a goal for experimental magnet design gave E = 0.64.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 25

Editorial note, tabletop extrapolation: Gives the next machine's FEMM loop a quantitative habit: compute gap-flux/pole-base-flux utilization for each candidate tip and compare candidates against each other and against the report's 0.64 goal - treat the absolute expected range for a small pole as something the FEMM runs themselves establish.

It is shown that this can be increased to about 96 per cent by cutting a groove into the pole face just inside of the raised edge. This result may be obtained in several ways and is unquestionably correct.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 25

Editorial note, tabletop extrapolation: On 8-in poles the 92->96% difference is ~9% in energy at fixed field - cheap to try in FEMM and on the real shims; the tapered-pole-superiority claim and the NYO-780 comparison need their own citations before leaning on them.

The contour of the shim when the steel surface is not an equipotential is best determined experimentally. An approximate shim can be put on a pole which otherwise has its final form.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 8

Editorial note, tabletop extrapolation: The next machine's shim program: FEMM (finite permeability, saturation modelled) resolves much of what 1952 needed bench passes for - validate the final contour against a probe map where the nonlinearity is significant, as NYO-780 (p.7) did with its bolt-together model magnets.

The costs which are affected are the combined costs of steel, copper, and energy.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 30-32

Editorial note, tabletop extrapolation: This collection's only explicit dollar-optimization of magnet proportions: redo the sweep with 2026 unit costs (scrap steel, surplus copper, $/kWh over expected machine life and duty cycle) - after re-reading the source for the variable definitions, since a cost formula reused without its unit system is a trap. NYO-780 p.8 did the equivalent sweep by model.

For operating convenience, the coils should be made smaller than is indicated because the total cost is a slowly varying function of the coil outside diameter near the minimum of cost.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 30

Editorial note, tabletop extrapolation: Licence to trade cost-optimality for access, cooling clearance, or stock material sizes - the optimum is a plateau, not a peak. How much plateau: evaluate the cost function at the smaller diameter and report the actual penalty rather than assuming it is a few percent. Same flat-minimum finding as NYO-780 p.8 (coil height); cite both.

It appears that the unit costs can only be determined after the cyclotron has been in operation for several years, so estimates must be employed.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 30

Editorial note, tabletop extrapolation: A 1952 statement of the plan's own doctrine, applied with modern tools: use estimated lifecycle costs with a sensitivity check on the uncertain inputs, update from quotations and commissioning actuals as they arrive, and avoid polishing the spreadsheet past its input accuracy.

It is quite clear from either equation that this factor, optimum x, depends on scale factor. The assumptions made cause the value of x given by the equation to be too large.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 31

Editorial note, tabletop extrapolation: Two cautions in one: treat big-machine coil proportions (including TID-454's own x~1.4) as non-transferable to an 8-12 in machine, and rather than mechanically shaving the computed value, redo the optimization at the actual scale with a geometry-dependent field/cost model.

One square centimeter of metallic contact distributed over the joint will carry 10,000 amps with negligible resistance and temperature rise.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 32

Editorial note, tabletop extrapolation: Bolted bus laps at amateur coil currents have huge nominal margin by this figure - but nominal lap area is not metallic contact area: oxide, pressure, fastener relaxation and thermal cycling decide the real contact. Prepare surfaces, clamp hard, lock against loosening, then verify with a four-wire millivolt-drop measurement and a full-current temperature check. A joint that passes those two tests is electrically invisible; one that hasn't been tested is a fire waiting for a loose bolt.

In most cases, the ratio is not so sensitive to the current used to excite the magnet as the corresponding absolute value and the required accuracy of current control is reduced.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 38-40

Editorial note, tabletop extrapolation: The principle survives the instruments: when Hall-mapping a next machine's shims, log B(r)/B(0) with an always-live reference probe at center. Simultaneous ratioing cancels the common-mode excitation drift - saturation-driven profile changes, probe drift and cross-calibration error remain, so keep decent regulation and repeat-check a few points.

This additional pumping speed then can be considered as being in parallel with that through the opening at the mouth of the dee.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 129

Editorial note, tabletop extrapolation: Dees are pumping dead-ends by construction, and the ion source dumps its gas inside one: added holes in the dee back or stem shrouds are valuable conductance exactly there - size and place each pattern with an RF-current and field review, a structural check, and a molecular-flow conductance estimate; below-RF-significant hole size is the starting constraint, not the whole analysis.

Cited in: The Vacuum Budget of a Cyclotron

The fact that the conductances are considerably greater for hydrogen, therefore will have very little effect toward increasing the net speed in this region.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 138-139

Editorial note, tabletop extrapolation: Kills a tempting error for hydrogen-fed machines: do not credit the 3.8x conductance factor to the whole system. Check which element (duct or pump) limits for H2 specifically, using the selected pump's own hydrogen speed and compression data - pumps differ.

Cited in: The Vacuum Budget of a Cyclotron

Neglecting outgassing and assuming a perfectly tight system, the pump-down times are as follow.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 139

Editorial note, tabletop extrapolation: The calculation pattern transfers to any chamber: compute t = (V/S)*ln(P1/P2) per stage with the pressure-appropriate effective speed (roughing pumps slow markedly with falling pressure, and series conductance caps S). When the observed pump-down runs many times the ideal, treat the excess as a prompt to check - outgassing, leaks, conductance restrictions, pump condition, gauge error - rather than as proof of any one of them.

Cited in: The Vacuum Budget of a Cyclotron

opened automatically when the mechanical pump is shut down so as to break the vacuum in the line and prevent the pump oil from backing up the line.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 140

Editorial note, tabletop extrapolation: Transfers directly to a garage system: an automatic vent interlocked with the roughing pump - or a vacuum-rated anti-suckback valve, which is not the same thing as a generic check valve - prevents the classic oil-suckback chamber contamination. The source's practice of putting flexible connections in vertical runs (so oil cannot pool in them) is worth copying too - reported practice, scan re-read queued.

Cited in: The Vacuum Budget of a Cyclotron

They permit, however, the backing of all three diffusion pumps by a combination of any two of the booster pumps, should any one of the booster or mechanical backing pumps become inoperative.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 140-142

Editorial note, tabletop extrapolation: Scales down to one gauge and two relays: a foreline-pressure interlock that kills the diff-pump heater and an over-temperature switch on its casing are the two automatics that protect an unattended amateur system's pump and oil - necessary automatics, not a complete unattended-operation case. Setpoints come from the pump's own tolerable forepressure, not the source's 50/160 microns.

Cited in: The Vacuum Budget of a Cyclotron

welding neck flanges with double O-ring gasket grooves machined in a standard flat face flange and provided with a pump-out connection between the two gaskets.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 141

Editorial note, tabletop extrapolation: The double-O-ring-with-interspace-pumpout trick is worth stealing for any large troublesome amateur flange (chamber lids especially): sniff the interspace for leak location, or hold it at rough vacuum to intercept most of the atmospheric load across the inner ring - it reduces, not nulls, permeation, since the elastomer still outgasses and a gradient to the chamber remains.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Unfortunately it is theoretically impossible to filter a transient without introducing time delay. The time delay thus introduced was kept to a minimum.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 170-171

Editorial note, tabletop extrapolation: General fast-timing wisdom for beam-pulse and kick timing chains: every smoothing stage costs latency. Measure the chain's end-to-end latency and compensate the FIXED part in the trigger schedule or delay setting; threshold bias (the historical method) only advances the crossing for a given waveform - it walks with amplitude and slew rate, so calibrate it over the expected pulses.

the bias adjustment is made with reference to the actual critical firing voltage.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 172

Editorial note, tabletop extrapolation: A self-calibration idiom worth copying into any comparator/discriminator in the DAQ: trim to the observed threshold at session start (their multivibrator = today's comparator with drifting offset). That removes the threshold error present AT calibration - within-session drift, and aging that changes delay or hysteresis rather than threshold, still need periodic re-trim or monitoring.

That alternative was abandoned in view of the susceptibility of high-frequency switching circuits to unforeseen difficulties.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 172

Editorial note, tabletop extrapolation: A complexity-avoidance pattern with 2026 force - blanking a known-bad time window (one line of firmware now) - valid when no wanted events occur in the window and the gate acts early enough that the front end isn't overloaded by the artifact; otherwise the analog filtering earns its complexity.

the field obtained is proportional to the inside radius of the coil and a high field can be obtained by increasing the scale ... the power p and the volume of conductor v increase with the cube of the inside radius.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 116

Editorial note, tabletop extrapolation: SCALE-SCOPED (megagauss-era context), and useful for estimating specific coils: it explains why small-bore air-core inserts and compact analyzing magnets are economically comfortable while large air-core fields carry punishing power bills - run the numbers for the actual coil rather than treating the scaling as a feasibility verdict.

equipped with a small coupling loop ... used to load the unwanted mode, which on the three-fourths scale model was about 50 megacycles, in which the oscillator stub forms a capacity-loaded half-wavelength line.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 162

Editorial note, tabletop extrapolation: Both steps are amateur-accessible: find candidate modes cheaply (a scale model or a bench sweep of the real resonator), then load the parasite selectively into a lossy element that leaves the wanted mode alone. Scaling shifts parasitic frequencies, and the final amplifier's loading shifts them again - so verify and re-suppress on the fully assembled system; that matters the moment the LDMOS upgrade raises the reference machine's gap voltages.

foils of aluminum, copper, iron, and stainless steel were affixed at various positions on the walls of the cyclotron vault and on the cyclotron vacuum tank.

Boom, Toth & Zucker, Residual Radiation of the LRL 184-inch Cyclotron — ORNL-3158 (1961) — p. 15

Editorial note, tabletop extrapolation: The one activation rule that applies at any energy, because it is a measurement, not a prediction: a witness-foil pack plus the next machine's NaI/PIPS counters is a near-zero-cost check. Read a null correctly - it bounds what those foils, positions, counting and cooling times could detect; strong practical evidence, not proof that nothing anywhere activated. Useful for licensing conversations and for catching surprises if beam or species ever changes.

Cited in: Shielding a Small Cyclotron

To reduce the radiation by an order of magnitude one needs only 2 cm of lead - an amount that can readily be made into a portable shield. Shadow shields of 6 cm of lead would reduce even the 100 r/hr radiation field to a quite tolerable 100 mr/hr. The same radiation has a half-thickness of 4 cm for concrete.

Boom, Toth & Zucker, Residual Radiation of the LRL 184-inch Cyclotron — ORNL-3158 (1961) — p. 18

Editorial note, tabletop extrapolation: ENERGY SCOPE: a sub-MeV machine on ordinary structural materials produces no comparable residual gamma fields (light-element targets, thresholdless capture and deuteron operation are the exceptions - see the safety pages). The transferable part is the sizing discipline: identify the actual photon energy first, then buy attenuation in half-thickness units - the same arithmetic sizes the lead around a NaI detector against room background. Note the report's own arithmetic: even 6 cm of lead leaves 100 mr/hr from a 100 r/hr field - reduced is not zero.

Cited in: Shielding a Small Cyclotron

the important source of radiation in the cyclotron comes from the gap and the structures in it, rather than from neutron-induced activities in the magnet yoke.

Boom, Toth & Zucker, Residual Radiation of the LRL 184-inch Cyclotron — ORNL-3158 (1961) — p. 12

Editorial note, tabletop extrapolation: An energy-APPROPRIATE technique: a lead collimator with a removable plug around a next machine's NaI turns it into a pointing instrument for X-ray leak hunting (RF multipactor sites, dee-liner discharge bremsstrahlung) on a running machine. Choose wall thickness for the photon energies in play - soft dee X-rays need little lead; harder sources need more, plus attention to fluorescence and off-axis penetration. The aimed-vs-plugged comparison is the transferable discipline.

Cited in: Shielding a Small Cyclotron

use of a reliable radiation meter in the cyclotron near the targets ... takes much of the guesswork out of the question "How long should the target cool?"

McWalters et al., Radiation Exposures of Personnel at the 60-inch Cyclotron — UCRL-8276 (1958) — p. 16

Editorial note, tabletop extrapolation: ENERGY SCOPE: Crocker's 10-24 MeV/nucleon beams at tens of uA made 100-500 r/hr targets; a sub-MeV proton machine on ordinary targets produces no comparable residual source term (light-element targets and deuteron operation are the exceptions). The instrument discipline transfers exactly: a logged dose-rate channel at the machine - an instrument whose response covers soft X-rays (dg-559) - gives prompt X-ray dose during RF conditioning and a defensible record alongside the beam-current log.

The average time required for setting up a target is usually about 3 minutes ... removing the target assembly from the cyclotron is about 1 minute. The assembly is then dismantled, which takes less than a minute.

McWalters et al., Radiation Exposures of Personnel at the 60-inch Cyclotron — UCRL-8276 (1958) — p. task-time and shield figures on PDF p. 7 (report's opening page); exposure figures on PDF p. 16 as cited

Editorial note, tabletop extrapolation: The practice - rehearse any hands-on task near a radiation hazard until it is quick and sure, and put a bench shield where hot items are worked - is the cheapest safety hardware there is, because dose = rate x time. Do not transfer speed to electrical work: HV and RF tasks are controlled by de-energizing, verifying zero and lockout (dg-522), where hurrying adds risk rather than removing it.

Cited in: Shielding a Small Cyclotron

Measurements of the internal beam of the ORNL 86-inch cyclotron very early indicated that the energy of the proton beam might vary as much as +/-10% from H-rho calculations. ... The energy of maximum intensity was found to vary by as much as several hundred kilovolts with minor adjustments of the ion source position, dee voltage, magnetic field tuning, and oscillator frequency.

Cohen, Measurement of Beam Energy and Energy Distribution on an Internal Cyclotron Target — ORNL-1347 (1952) — p. 5

Editorial note, tabletop extrapolation: The direct historical support for this collection's energy-convention discipline: the reference machine's '150 keV-class computed' is a convention, not a measurement, and its own discrepancy must be measured, not assigned ORNL's +/-10%. For a next machine's B11(p,alpha) work, where yield vs energy is steep, measure energy AT the target (absorber stack in front of the PIPS, or foil methods) every time tuning changes.

A photographic film is covered with a stepped absorber (made by folding an aluminum foil), wrapped in aluminum foil, and exposed directly in the cyclotron beam.

Cohen, Measurement of Beam Energy and Energy Distribution on an Internal Cyclotron Target — ORNL-1347 (1952) — p. 6

Editorial note, tabletop extrapolation: At 150-170 keV the material budget dominates everything: compute proton range and straggling with PSTAR/SRIM through the CUMULATIVE areal density - wrapping foil, absorber steps, emulsion overcoat, detector dead layer - before trusting any variant, since micron-scale layers can stop such protons outright. The architecture transfers (stepped degrader + position-resolved readout + reference channel), but an ordinary PIPS is a single channel: use per-step exposures, a scanned detector, or a segmented one, and establish low-current operation for the actual ion source rather than assuming the arc-off trick.

These factors limit the accuracy of determination of the most probable energy to a few hundred kilovolts. The high energy portion of the energy distribution can be determined with almost equivalent accuracy

Cohen, Measurement of Beam Energy and Energy Distribution on an Internal Cyclotron Target — ORNL-1347 (1952) — p. 5

Editorial note, tabletop extrapolation: The asymmetry - high-energy side of an absorber spectrum better determined than the low-energy tail - is the shape to remember, but the historical few-hundred-keV floor belongs to that apparatus: for a PIPS-plus-degrader setup, build the detector-and-degrader response matrix and quote separate uncertainties for mode, upper edge and tail rather than scaling ORNL's numbers.

the cyclotron operating conditions are so different from those used in normal operation that it may well be that the energy distribution is not the same.

Cohen, Measurement of Beam Energy and Energy Distribution on an Internal Cyclotron Target — ORNL-1347 (1952) — p. 9

Editorial note, tabletop extrapolation: Methodological honesty that transfers directly: IF detector protection forces attenuated or otherwise-configured beams for a measurement, log the machine state (dee voltage, field, frequency, source position, attenuation method) alongside every energy measurement so diagnostic-mode and run-mode data are never silently mixed - attenuation need not mean detuning, so record what actually changed.

each carbon foil was broken into 1/2-inch sections, along previously made scorings, and counted in a Geiger counter.

Cohen, Spatial Distribution of Current on an Internal Cyclotron Target — ORNL-1348 (1952) — p. 5

Editorial note, tabletop extrapolation: ENERGY SCOPE: C12(p,pn) needs ~20 MeV, so the activation readout is closed at tabletop energies. Keep the geometry, swap the readout - a probe-tip mosaic of insulated segments read as Faraday collectors gives a one-shot 2-D map IF built properly (guarded insulation, secondary-electron suppression, RF isolation, calibrated electrometers); a witness material (film, phosphor) needs calibrating at the actual energy, spot size and vacuum before its image is trusted. Either way the map decides where the B11 target goes and how big its hot spot runs.

From (5) the measurement of dr is essentially a determination of the phase.

Cohen, Spatial Distribution of Current on an Internal Cyclotron Target — ORNL-1348 (1952) — p. 9

Editorial note, tabletop extrapolation: Energy-independent physics: a differential probe (shadowed double tip) or the sectioned-target map gives dr, and with the dee voltage - stated in ONE convention, peak dee-to-dee or dee-to-ground, never mixed - that is a direct measurement of ion RF phase, the quantity a next machine's field-tolerance budget protects. A rare experimental handle on phase for machines with no beam-position monitors.

leaving the ion source ungrounded has a very substantial effect, since it then floats nearer the potential of the accelerating slit which is attached to the dees. This reduces the effect of the latter and the radial width approaches the theoretical predictions for a cyclotron without an accelerating slit.

Cohen, Spatial Distribution of Current on an Internal Cyclotron Target — ORNL-1348 (1952) — p. 9

Editorial note, tabletop extrapolation: Direct lesson for the reference machine's central-region debugging: the source body's electrical state - DC connection AND RF return impedance, since a floating body near driven dees picks up RF capacitively - is a real optics knob (or a real gremlin). Verify and log the filament/chimney ground path; an intermittent source ground would masquerade as day-to-day beam irreproducibility of exactly the kind ORNL-1347 warns about.

the ions which were the chief contributors to the current at resonance are lost by defocusing and ions of more positive phases are now the chief contributors.

Cohen, Spatial Distribution of Current on an Internal Cyclotron Target — ORNL-1348 (1952) — p. 9

Editorial note, tabletop extrapolation: Explains an observation class on the reference machine: probe current can look tolerant of field/frequency error while the surviving phase distribution, turn spacing, transmission and attained radius shift underneath - reinforcing ORNL-1347's rule that current on target is not evidence the energy is what B-rho says (at a FIXED radius the momentum is still ~qBr; what moves is which ions get there and how). Whether self-selection broadens your tuning curves is testable with phase- or energy-sensitive measurements - treat the width cautiously either way.

The threshold is practically independent of radius ... the threshold seems to be limited by conditions at the center, phase-slip or otherwise, rather than by field errors throughout the machine.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 285

Editorial note, tabletop extrapolation: Usable on the reference machine now with its existing probe: a dee-voltage threshold scan at several probe radii - holding source output, frequency, field and geometry fixed - helps distinguish central-region limits from accumulated field errors; it is an indicator to combine with other diagnostics, since source drift, detection threshold and interception can each move the measured threshold.

this drop is primarily a result of electron scattering from the probe tip. It is now believed that the actual beam loss, if any, is very small.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 278

Editorial note, tabletop extrapolation: Direct transfer to the reference machine's probe work: an apparent current fall-off with radius can be instrumentation, not physics - test by swapping probe material and geometry and by biasing, and think about where particle range in the probe sits relative to the beam dimensions, before redesigning the machine around an artifact.

Certain features of the performance of the Analogue are much improved by the injection of the highly defined beam. It is now possible to accelerate the beam through the difference-coupling resonance vr - vz = 1 without attenuation

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. PDF p.285 (printed p.271)

Editorial note, tabletop extrapolation: Central-region collimation and source definition are high-leverage (relevant to the planned source-species test): a better-defined beam gives resonances and apertures less to eat. That is margin against loss mechanisms that scale with beam quality - not against gas scattering, RF faults, or extraction geometry, which have their own fixes.

References to maze design for high energy accelerator shields are almost completely absent from the literature. We have based our design on the methods used for nuclear reactor shielding.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 199

Editorial note, tabletop extrapolation: Scale-free research method as practiced there: when the accelerator literature lacked the subproblem, they adapted reactor-shielding methods and said so. The pointer stands with its age showing: reactor duct/labyrinth texts remain a usable starting point for amateur questions this corpus lacks - checked against modern references (NCRP 144-class) wherever safety rides on the answer.

Cited in: Shielding a Small Cyclotron

the attenuation at a bend is approximately 1/3 csc(theta) ... An additional factor of 3 attenuation at bends may be gained by extending the entering leg beyond the bend

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 200-204

Editorial note, tabletop extrapolation: The product-of-elements method transfers to a next machine's cable penetrations and entry labyrinth; the factors do not transfer blind - they are low-energy-neutron empirics from that facility's geometry, and spectrum, wall material, duct size and coupled legs move them. Use the method with factors from a current reference (NCRP 144-class data), never sight a source down a straight leg, and verify the result by survey.

Cited in: Shielding a Small Cyclotron

Should the maze design shown prove inadequate ... the attenuation can be greatly improved by the addition of plugs at the bends. The extension of the leg beyond the corner offers a convenient location for a plug door

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 204

Editorial note, tabletop extrapolation: Scale-free insurance: reserving a plug location costs little at design time - some space and a formed recess - and buys a recovery path if the survey finds the maze wanting. Initial shielding estimates often need adjustment, which is why the survey decides (dg-914's bookkeeping); this is the cheap way to be wrong.

Cited in: Shielding a Small Cyclotron

The steps provided at the top and sides minimize the dimensional accuracy required. With 12 in. steps, 1/2 in. wide cracks between the plug and the wall are easily tolerable. ... Inevitably the effective thickness of the shielding is reduced somewhat by the space for the wheels.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 206

Editorial note, tabletop extrapolation: The stepped-joint principle scales to block-wall doorways and removable concrete/poly plugs around a benchtop target station - but the tolerable crack size was specific to their 12-in steps and their radiation field, so a scaled-down plug's steps and gaps are checked against its own field (survey), not copied. Where a mechanism eats thickness, make it up locally - added length, or denser material in that spot.

Cited in: Shielding a Small Cyclotron

solid concrete walls can be placed for about 2/3 the cost of walls cored with compacted rock fill.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 242

Editorial note, tabletop extrapolation: Their specific answer is 1963 Oak Ridge civil engineering; the transferable habit is costing shielding alternatives (block vs poured vs water vs borated poly) per unit attenuation before building any enclosure for a next machine.

Cited in: Shielding a Small Cyclotron

Because the major novelties and complexities of the project lie in the area of the machine and the beam handling, these areas were programmed. The building and shielding portions of the project were not programmed

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 252

Editorial note, tabletop extrapolation: Scale-free effort allocation: plan the risky subsystems (source, RF, field mapping) at fine grain; conventional logistics still get milestone-and-dependency tracking - procurement lead times, lifting, electrical and shielding milestones - just not fine-grained networks.

All activities on the critical path were then re-evaluated ... It was decided that the cyclotron vault and cyclotron building could be completed first, to allow the magnet assembly to begin at an earlier date.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 258

Editorial note, tabletop extrapolation: Scale-free: iterate the schedule, overlapping long-lead assembly with remaining construction. Note what sat on their critical path per the report's activity lists - field plotting, re-plot analysis, iron alignment rechecks - field mapping is schedule, not an afterthought, at any scale.

The data show individual orbital positions from the first orbit up to the twelfth, the upper limit being determined by the potential on the dees.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 December 1951 — ORNL-1269 (1952) — p. 40

Editorial note, tabletop extrapolation: A candidate measurement for the reference machine - measured turn spacing plus the field map gives effective energy gain per turn, which would anchor its uncalibrated ~1.3 kV dee voltage (via gap count, synchronous phase and transit-time factors, not directly). First check feasibility: at ~1.3 kV the inner-turn spacing may be smaller than the existing probe wire - compute dr against probe width before promising resolution. Fig. 12 (PDF p.41) shows the 22-inch doing this at 9.2-12 kV dee-to-dee.

There is a slight increase in probe current with increasing radius because of increased thermal emission of electrons from the probe as it was bombarded by protons of higher energy.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 December 1951 — ORNL-1269 (1952) — p. 40

Editorial note, tabletop extrapolation: Same artifact family as the reference machine's Faraday-cup offsets - with the mechanisms kept straight: at nA and sub-MeV, deposited power is ~mW and an ordinary wire will not reach thermionic temperatures (do the conduction arithmetic before invoking it); SECONDARY emission and electronic offsets are the live suspects at that scale, so bias or shield the probe and log the baseline against beam-off checks.

The alignment of the electrodes with the magnetic field is critical. High energy electrons are obtained when no gas is fed to the chamber, but when gas is introduced the average electron energy is greatly reduced

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 December 1951 — ORNL-1269 (1952) — p. 49

Editorial note, tabletop extrapolation: For the reference machine's filament source and the planned source-species test: align the source to B before blaming the arc supply, and treat arc electron energy as gas-pressure-COUPLED - which direction and how strongly, for the actual source, is a pressure-scan-plus-mass-analysis measurement, not an inherited monotonic law about H+/H2+ balance.

The output of the ion source was found to be approximately proportional to the effective length

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 September 1952 — ORNL-1383 (1953) — p. 21

Editorial note, tabletop extrapolation: The chimney-slit length is a free knob - to first order, more length is more current at constant width, arc and extraction - but pair any lengthening with the z-distribution probe check (the same machine's earlier quarter tied arc-slit length to z-wise beam loss), and verify the gain survives to TRANSMITTED beam, not just source output.

Since the current measured at 1.5" continues to increase with accelerating potential while the beam measured at 10.5" is optimized at 3 kv or less, changes in ion focus are indicated

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 September 1952 — ORNL-1383 (1953) — p. 22

Editorial note, tabletop extrapolation: The central tuning trap: a source tweak that fattens the inner-radius signal can starve the Faraday cup at full radius - so score source changes at the radius that matters (extraction or target), with the near probe as the diagnostic companion rather than the scoreboard.

the position of unstable equilibrium at the median plane can be found The current-carrying loop also tends to center itself with respect to the magnetic center of the field

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 September 1952 — ORNL-1383 (1953) — p. 22

Editorial note, tabletop extrapolation: A near-zero-cost magnet diagnostic - but engineer the five minutes it runs: compute the wire's I^2R heating and use a current-limited supply with short energizations, restrain the loop and add travel stops (a free conductor in a tesla-scale field moves hard when energized), and keep hands clear at switch-on. Use it as the coarse locator of median plane and center, then confirm with the Hall-probe map.

the median plane of the 22-inch cyclotron, at 6", 11", and 22" diameter, coincides with the geometric median plane within +/- 0.125" and that the magnetic center coincides within +/- 0.25"

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 September 1952 — ORNL-1383 (1953) — p. 22

Editorial note, tabletop extrapolation: The measure-both discipline transfers; the inch values do not - they are one machine's observed alignments, not acceptance limits. Derive the reference machine's own tolerances from its pole radius, gap, harmonic budget and central-region sensitivity, then survey against those.

The dee voltage will undoubtedly be limited, though, by the spacing between the dee stems outside the vacuum tank, which is only 1.5" at one point

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 September 1952 — ORNL-1383 (1953) — p. 23

Editorial note, tabletop extrapolation: For the LDMOS upgrade toward 5-13 kV dees, walk the whole RF path on BOTH sides of the wall - feedthroughs, stem gaps in air, coupling hardware, creepage across insulator surfaces, and the vacuum-side gaps and multipactor windows - and let field analysis, ratings and conditioning tests say which limit binds first; the cited machine's air-side cap is one historical outcome, not a law.

Direct-current accelerating electrodes of several geometries have been tested, but none were found to accelerate the proton beam to maximum radius as well as the standard type of r-f accelerating electrode.

Howard (ed.), Electromagnetic Research Division Semiannual, period ending 20 March 1953 — ORNL-1531 (1953) — p. 20

Editorial note, tabletop extrapolation: A caution for any puller-electrode or biased-extraction scheme on the reference machine: after four quarters of ORNL trials, dc injection still lost to the ordinary rf gap on that machine. Simulate candidate geometries (fields calculate fine; the plasma boundary is the uncertain part), validate experimentally, and keep an unmodified configuration as the control in every source A/B test.

One of these coils consists of an insulated conductor wrapped half-way around the magnet pole piece and attached so that the pole piece completes the circuit.

Howard (ed.), Electromagnetic Research Division Semiannual, period ending 20 March 1953 — ORNL-1531 (1953) — p. 18

Editorial note, tabletop extrapolation: A field-trim knob that steers orbits without touching iron - as a modeling hypothesis for a next machine: specify ampere-turns and the return-current path, run the magnetostatic and orbit analyses (FEMM models it directly), check contact heating and forces, and only then test; variable-energy operation is a beam measurement away, not a feature to advertise from the wiring diagram.

Beam radius, in. 11 / 20; Proton energy, Mev 1.5 / 4.9; Magnetic field, oersteds 6400; Magnet gap, in. 13.5; Maximum dee-to-dee potential, kv 100; Frequency, megacycles/sec 9.7 (spec table, condensed)

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 September 1953 — ORNL-1663 (1954) — p. 18

Editorial note, tabletop extrapolation: The nearest professional sibling to a next machine in this collection - same ~0.64 T field class and ~9.7 MHz as the reference machine's 0.59 T / 9 MHz. Use it to sanity-check B-f consistency; note the 100 kV (vs ~1.3 kV) buys energy per turn and fewer turns - less phase slip and interception - while the energy-radius relation stays set by the field.

the magnet pole faces (tank walls) are being ground with a portable grinder to provide a very uniform magnetic field, as near +/- 0.01% as possible. This will then provide a standard base for the various magnetic shim designs

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 March 1954 — ORNL-1670 (1954) — p. 20

Editorial note, tabletop extrapolation: For a next machine's shim development: establish and map the unshimmed field to the best flatness attainable FIRST, so every FEMM-predicted shim is measured against a known zero rather than an uncharacterized pole error. Set the flatness target from a phase budget, not a fixed gauss figure: accumulated slip is roughly 360 deg x N_turns x dB/B for a uniform mismatch, so a many-turn low-voltage machine needs proportionally tighter field than a few-turn one. (Also proof that hand tooling on installed poles was acceptable ORNL practice - no magnet disassembly required.)

This spacer moves the dees back from the center of the magnetic field so that the machine can be operated at approximately 1.5 Mev for test operation at very high proton currents.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 March 1954 — ORNL-1670 (1954) — p. 20

Editorial note, tabletop extrapolation: Mirrors staged-gate logic - plan a low-energy high-current commissioning configuration as a mechanical state, not an improvisation, so beam-physics problems are separated from full-energy behavior. Reduced energy closes many reaction channels but not all: thresholdless capture (12C(p,gamma), 14N(p,gamma)) and light-element targets remain live, and very high current makes small cross sections and thermal loads consequential - so each commissioning state still gets its own reaction check, survey and beam-loss budget.

several leaks in very inaccessible locations have delayed final assembly. In order to repair the leaks in the internal water-cooling tubes it was necessary to cut windows through the sides of the dees. The windows were then closed by Heliarc welding.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 September 1954 — ORNL-1795 (1954) — p. 19

Editorial note, tabletop extrapolation: If a next machine's dees carry water: treat internal cooling leakage as a credible failure and route tubing so joints and runs can be reached (or provide removable covers) where RF and vacuum allow; pressure-test the dee as a unit BEFORE it meets the liner; and note the historical recovery mode - cut a window, fix, reweld - is documented practice worth keeping in the back pocket.

Grinding and shimming of the tank walls to produce a flat magnetic field was continued. The magnetic field is now uniform to within 0.05%.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 September 1954 — ORNL-1795 (1954) — p. 19

Editorial note, tabletop extrapolation: Calibrates expectations, not a budget line: sustained professional effort on the 44-inch bought 5e-4 base-field uniformity against a 1e-4 aspiration - so plan for the ground pole to fall short of its target and for shims to close the remaining gap, with the actual allowable derived from the machine's own phase-budget arithmetic and verified by mapping. How the 0.05% split between grinding and shimming the report does not say.

The one-quarter-scale model magnet is of the closed-yoke type. ... Its total weight will be 14.4 tons; 12.7 tons will be iron and 1.7 tons will be copper. The magnet gap will be in a vertical plane to provide the greatest access for making field measurements. The pole tips are removable so that shims of any shape can be inserted readily.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 September 1954 — ORNL-1795 (1954) — p. 19

Editorial note, tabletop extrapolation: For any next-machine shim-test rig (or a scaled FEMM-validation magnet), design for the measurement campaign: open sightlines for the Hall probe, pole tips that unbolt, gap oriented for jig access - the orientation serving the probe rather than mimicking the final machine is the editorial reading of ORNL's choice.

at an r-f load of 100 amp per lineal inch, the temperature rise could be held to less than 10 C by a water flow of only 0.5 gpm.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 September 1954 — ORNL-1795 (1954) — p. 23

Editorial note, tabletop extrapolation: For a next machine's shorting planes and tuning bars, compute the actual RF surface current at the contact, then validate the joint thermally at that current and duty - the cited numbers say such joints are buildable, not that 100 A/in is free. The material lesson (plate stainless with copper; bare SS is an RF resistor) is sound skin-effect physics at any scale.

The whole dee system is supported by a cantilever mounting at the outer end of the dee stems. This mounting is supported on insulators in order to permit the application of a bias potential to the dees.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 March 1955 — ORNL-1884 (1955) — p. 19

Editorial note, tabletop extrapolation: An attractive pattern for a next machine: one stiff cantilevered dee-stem mount outside the field region, isolated for DC bias, is mechanically simpler than distributed insulated supports. Design the RF side separately - insulating the mount enables bias but does not by itself define the RF return path, so engineer the ground plane, bypassing and bias feed network explicitly, and check insulator loading and flashover.

the effective 'point' source in the vertical plane does not coincide with that in the horizontal plane and is such that the vertical-plane object distance V is greater. ... The second is simply that the common image be real and beyond the magnets themselves. ... Since it is known that the angular spread is greater in the horizontal than in the vertical plane, we make the first lens convergent in the horizontal plane.

Bromley & Bruner, The Design of a Focusing and Analyzing System for the 27-inch Cyclotron Beam — NYO-3823 (1954) — p. 14

Editorial note, tabletop extrapolation: DIRECT design input for next-machine transport modeling: fit separate horizontal/vertical source points and divergences from measured beam profiles (or a quadrupole scan) rather than assuming a stigmatic waist at the extraction channel - then let the measured two-plane phase space, not the historical ordering, choose the first quad's polarity.

The effect of the fringe field is to shift the effective pole boundary outward, and this is taken into account empirically by adding to the right-hand side of III-20(b) a term 0.4 G

Bromley & Bruner, The Design of a Focusing and Analyzing System for the 27-inch Cyclotron Beam — NYO-3823 (1954) — p. 43

Editorial note, tabletop extrapolation: For a next machine's analyzer designed in FEMM, the sanity check is the concept, not the constant: compute the effective field boundary from the longitudinal field integral of the simulated fringe and compare against the steel edge - an offset of very roughly half a gap is the expected order. Do not equate the 0.4G term with a tracking code's FINT parameter (FINT conventions carry fringe focusing integrals, a different quantity).

The operation of the wedge analyzer has been checked using the standard current carrying wire technique.

Bromley & Bruner, The Design of a Focusing and Analyzing System for the 27-inch Cyclotron Beam — NYO-3823 (1954) — p. 52

Editorial note, tabletop extrapolation: The wire method is a superb zero-beam measurement of magnet optics for a teaching lab or a first analyzer - state tension, sag and field-orientation assumptions when using B-rho = T/I. Budget alignment and tuning provisions into any multi-element line as a design habit; the cited line's transmission and energy-spread figures await the re-read before serving as benchmarks.

the location and magnitude of these non-uniformities were the same at both 6.8 and 14 kilogauss, and it was not expected that these variations would have any significant effect

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 11

Editorial note, tabletop extrapolation: Two ideas worth writing into a mapping procedure, each with its limit: (1) an error that scales rigidly with excitation CAN be absorbed by end-to-end calibration for a relative instrument - after a trajectory or resolution check shows it does not bend the optics; reproducible is necessary, not sufficient. (2) Degrading NMR signal above some field is a prompt to investigate - saturation inhomogeneity is one suspect among probe tuning, gradients and positioning; confirm with B-vs-I behavior before concluding.

The tips formed the top and bottom of the vacuum chamber of the magnet, while the side walls of the chamber were strips of non-magnetic stainless steel welded to the tips.

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 9

Editorial note, tabletop extrapolation: The poles-as-chamber pattern eliminates the gap-wasting separate tank (the alternative Bromley rejected on machining/gasketing grounds, nyo-3823 p.6) - carry the METHOD and derive the gap tolerance from the analyzer's own field-error and resolution budget, minding weld distortion across the span.

One of the other ports is located opposite the entrance slit to facilitate alignment of the magnet and the fourth one houses the nuclear magnetic resonance probe.

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 9

Editorial note, tabletop extrapolation: Cheap at design time and expensive to retrofit: a straight-through optical path (laser today) opposite the entrance slit plus a permanent probe port turn alignment and field checks from teardown jobs into routine ones - each port still buys its window, its leak path and its magnetic clearance, so put both on the port list and budget them honestly.

The track has been rendered flat and horizontal to within 0.01" by a grinding machine rotated about the vertical post.

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 10

Editorial note, tabletop extrapolation: Two machine-design lessons to EVALUATE at any scale: generate precision in place with the tool swung about the final axis (kin to Wilson's lapped dees), and consider kinematic three-point support so the instrument neither rocks nor needs a precision floor - choosing the actual bearing layout from load, stiffness, overturning-moment and angular-accuracy analysis rather than copying the 5-ton architecture at 1/50 size.

Since all exposures were for equal times, the measured intensity of each group provided a measurement of relative solid angle as a function of focal position.

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 12

Editorial note, tabletop extrapolation: Teaching-lab gold with its conditions stated: one sealed alpha source calibrates the focal-plane acceptance function that theory only estimates - under controlled equal-exposure conditions (stable source output, fixed geometry, detector response and processing held constant, no saturation). What it cannot test: proton-specific detector response and beamline effects, which need their own checks. Validate the peak-position convention against the actual detector's lineshape.

the information of Figs. 5 and 6 can be combined into a nomograph ... corresponding values of proton energy, lithium resonance frequency and image position on the focal surface

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 13

Editorial note, tabletop extrapolation: DIRECT for the teaching program: the 2026 equivalent is a small lookup app with nu*rho-vs-energy curves per probe nucleus and kinematics tables for the expected reactions (natural extensions of the sourced three-variable nomograph); run-time decisions need precomputed inverse tables, and students can build the nomograph itself as an exercise.

The output pulses are made about 10 volts high. Their rise time is of the order of 5 ns or less. ... When the cyclotron is operating at about 10 mc the shortest rise time available is about 3 ns, according to sampling oscilloscope observations.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. PDF 8 (printed 4) for the antenna and harmonic-mixture sentences; PDF 9 (printed 5) for the 10 V / 5 ns / 3 ns figures; PDF 10 (printed 6) for the retune time

Editorial note, tabletop extrapolation: Buildable on the reference machine: loose capacitive pickup plus stub-phased harmonic mixing sharpens the oscillator's waveform into a fast edge with zero active electronics at the pickup - noting a passive stub network can only re-phase and weight harmonics ALREADY in the picked-up signal (an oscillator's tank waveform has them; a purified sine does not). Check the pulse shape after every retune, and measure the actual 10-90% rise rather than assuming the vintage figure.

stop trigger pulses emerge only after an event occurs in the neutron detector.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 8

Editorial note, tabletop extrapolation: The reversed (common-stop) architecture inverts the time axis and slashes unnecessary converter starts and their dead time (pileup in the detector chain is its own problem). With a modern TDC or digitizer you can instead timestamp both the detector and RF streams continuously and form differences offline - the gated arrangement remains the right shape for TAC-style hardware.

The problem was to set the continuously variable slow discriminator dial so that the level of discrimination would correspond to a certain standard light signal from the scintillator. A Cs137 source was used as a standard. The discriminator level was set to correspond to the peak in the observed y-ray pulse height spectrum.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 13

Editorial note, tabletop extrapolation: Two transfers: keep the background-rejection threshold out of the timing path (the source's chains fought when combined), and standardize the threshold against a reproducible spectral feature - in an organic scintillator a Cs-137 source gives a Compton distribution, so define the set-point on its observed peak or edge, exactly as the source did with its own spectrum. A check source is cheap in effort; acquiring one follows the applicable sealed-source rules.

One channel is equivalent to about one millimicrosecond. ... The full width of the lines at half maximum is about 2 ns in this favorable case. Generally the widths have ranged from approximately this to about 3.5 ns, although it is easily possible to do worse by using incorrect stop signal pulses, or too low photomultiplier voltage, etc. ... the thickness of the [scintillon] neutron detector used in these measurements was 1 in, which made the counting efficiency high, but contributed appreciably to widening the peaks. The flight time of a 5 Mev neutron through the detector is about 0.8 ns, for example.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 11

Editorial note, tabletop extrapolation: DIRECT budgeting template: list every term (source bunch width, detector transit, electronics jitter, reference-edge slope) and know which one you bought deliberately. A next machine's TOF or coincidence lab should have students build exactly this budget before blaming the electronics.

Most experiments have been made with flight paths less than 1.2 meters long in order to avoid difficulty with neutrons scattered from the solid concrete floor

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 12

Editorial note, tabletop extrapolation: DIRECT pair of lessons: (1) geometry (short path, floor clearance, timing window) is often cheaper background suppression than shielding mass; (2) never bolt on a detector shield whose effect on efficiency you haven't calibrated - it converts a known instrument into an unknown one. Both transfer to any next-machine counting station.

Cited in: Shielding a Small Cyclotron

Calibration curves were obtained by use of the D(d,n) reaction, the cross sections for which are known to 4% accuracy. ... the yield of annihilation radiation from the N13 decay positrons was compared with the known flux of annihilation radiation from a sodium 22 source calibrated at the Bureau of Standards. A coincidence counter setup was used for these measurements. Results obtained in this way agreed to within 10% with expectations from the absolute calibration of the neutron detector

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 12

Editorial note, tabletop extrapolation: Metrology doctrine that transfers whole: one calibration path is an assumption, two are a measurement. For a next machine's yield claims, require a primary calibration plus an activation- or source-based cross-check, use CURRENT evaluated cross sections at the actual energy and angle (the 4% was the authors' 1950s assessment), and treat the disagreement as a diagnostic to explain - folding it into the systematic only once understood.

In order to simplify tuning procedures the scaler system was designed with a minimum of tuned circuits; there is only one, the tank circuit associated with the beam deflection plates.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 17

Editorial note, tabletop extrapolation: Every tuned circuit is a knob someone must retune at every frequency change - minimize them by design. On timing: the cited system took its precision edge directly from the oscillator, a sound default; a modern divider or PLL can carry timing when its phase error and jitter are characterized against the experiment's budget - the rule is budget-the-jitter, not never-divide.

Only the radio frequency circuit was simulated in the model, the vacuum system and purely mechanical equipment was not included. Insulation required for the application of bias voltage to the dee and condenser rotor was not included as it had no radio frequency function.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 7

Editorial note, tabletop extrapolation: License to mock up the next machine's RF cavity in bare copper/aluminum on a bench plate - no chamber, no pumps - provided every electromagnetic boundary that shapes the mode is reproduced: RF-current surfaces (liner included), coupling structures, and any dielectric near high fields. A bare-metal model validates resonance and field geometry; Q, loss and breakdown under vacuum still need the real thing.

For 30 kv on the full scale system the above power input figures become 146 kw at 9.25 mc, 132 kw at 12 mc, 146 kw at 15 mc, and 98 kw at 23 mc for continuous operation.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 15

Editorial note, tabletop extrapolation: The V^2 term is the live part for power budgeting: measured drive power at a safe low dee voltage extrapolates as (V_target/V_test)^2 on the SAME matched, linear, unloaded cavity - so a 1500-V measurement anchors the 5-13 kV LDMOS requirement, with beam/plasma loading, thermal drift of losses and amplifier efficiency budgeted on top, and the extrapolation ending where multipactor or breakdown begins.

the insertion of the dummy dee had dropped the upper frequency limit from 48.8 to 44.5 mc, and the lower limit from 19.9 to 18.8 mc

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 9

Editorial note, tabletop extrapolation: Final RF tuning of a next machine's cavity must be done with dummy dee, source structure, and probes installed - the model's single grounded dummy dee moved the band edges ~9%, and each added structure perturbs by its own amount: measure or simulate the shift for the actual geometry rather than budgeting any particular percentage in advance.

a shorted stub - a section of transmission line less than a quarter wave length at 50 mc - was connected to each side of the dee.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 9

Editorial note, tabletop extrapolation: The recovery plan if a next machine's fixed-frequency cavity misses its target after assembly. Both fixes tax drive power, and the directions dictate the design bias: aim the design HIGH in frequency if you want to trim with the cheaper capacitive side (which only moves frequency down), or low if you accept stub-trimming up. The cited shift/power figures are that cavity's calibration, not guaranteed ranges.

This region is a current maximum point at the highest frequency and most sensitive to volume or inductance.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 10

Editorial note, tabletop extrapolation: On a small machine the dee-stem-to-chamber-wall clearance is the candidate critical region - it plausibly sets both the resonant frequency and where I^2R heating concentrates. Confirm with an eigenmode/surface-current calculation (or low-power RF measurement with a thermal camera) for the actual cavity, then machine that region to drawing rather than shimming by eye.

The dee voltage must be at least twice the d.c. plate voltage. 2. The oscillator must be stable enough to sustain an arc drawn from the dee face (simulating discharges in that region). ... 4. The phasing capacity, as calculated in MacKenzie's report ..., should be as near [the calculated value] as possible.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 12

Editorial note, tabletop extrapolation: The requirement transfers as a criterion, not a procedure: the planned LDMOS amplifier must demonstrably survive dee-side arcs before it is trusted in vacuum, where conditioning sparks are guaranteed. For solid-state that means proving the protection chain - VSWR trip, drain clamping, fast drive-cut (dg-338, dg-679) - against controlled fault tests, not drawing an open arc onto an unprotected amplifier the way the 1947 tube crews could.

A deviation of an inch or two one way or the other will cause this response to rise or fall at either end of the range.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 13

Editorial note, tabletop extrapolation: Even a fixed-frequency amateur system inherits this through the amp-to-dee coax and its stray resonances: sweep the ASSEMBLED feed system, not just the cavity, and choose line lengths from the measured input impedance and matching bandwidth at the operating frequency. The cited inch-scale sensitivity belongs to that swept resonant feedline - your system's sensitivity scale comes out of your sweep.

the original ones used were resonant at 18 mc, which may account for a sharp drop observed in the dee voltage ... The coils were rewound and made resonant at 60 mc after which the voltage drop was no longer noticed.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. PDF p.13 (printed p.-10-)

Editorial note, tabletop extrapolation: Filament, bias, meter, and interlock leads entering the tank all need chokes whose behavior is MEASURED across the operating band - impedance or insertion loss over the whole band, not just the self-resonant frequency - because a choke resonant near the operating frequency silently loads the dee.

Ratio Max-capacity/Min-capacity = 1370/50 = 27.6

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 14

Editorial note, tabletop extrapolation: Same differential technique as Koeth's Rutgers dee-capacitance note in this collection: an LCR meter plus one disassembly step estimates the selected lumped capacitances in a tank model - subject to fixture and stray-capacitance errors, which set how many elements one subtraction chain can honestly resolve.

the errors in readings should be assumed to be +/- 5 to 10 percent. ... For power measurements, a Leeds and Northrup optical pyrometer, Cat. #8622-C, was used to observe plate dissipation in the triodes. ... In using the optical pyrometer, one spot on one plate of a triode was selected as the comparison point. The excitation was removed by connecting the plate line to the oscillator housing so that no r.f. currents would flow and all the power input would appear in the plates of the triodes.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 8

Editorial note, tabletop extrapolation: The thermal-reference trick survives translation with a defined reference plane: calorimetry on the LDMOS heatsink (or dee cooling loop) calibrated at DC gives THE HEAT INTO THAT PATH - write the full power balance (P_RF_out = P_DC - P_device - other paths) with matched thermal boundary conditions and steady state before quoting an output power; and publish instrument error bars the way Anderson did.

the inductance inherent in the 304-TL triodes is large compared with that in the 9C21 triodes to be used in the final oscillator. ... The power measurements at this stage in the experiments were found to be very inaccurate due to differences in plate capacity on the two 304-TL triodes and the consequent difference in distribution of r.f. currents.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 12

Editorial note, tabletop extrapolation: When bench-testing a next machine's RF with a stand-in amplifier or without the real chamber wall, write the fidelity caveats into the test log - the model predicts the cavity, not the parts that were substituted. (The filament-line impedance discontinuity previously listed here is dropped pending re-read - the scan discusses filament-line length effects but not that specific claim.)

the acceleration can be considered to good approximation as being a simple impulsive change in the energy of the particle at the azimuth of the accelerating gap

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 4

Editorial note, tabletop extrapolation: The core architecture for CYCLOPS-lite - thin-gap kicks alternating with magnetic coasting maps - with phase carried as a dynamical variable from the first line of code; MSUCP-12's analytic gap field upgrades the kick to a distributed one when transit time matters, and a comparison against distributed-gap tracking on the actual geometry is the validation step, not the 1961 result alone.

The Fixed Point Code locates closed orbits by means of a highly effective linear transfer matrix procedure, the General Orbit Code tracks arbitrary orbits as desired either with or without acceleration effects. For both routines the magnetic field is described by tables of Fourier coefficients as functions of radius; each uses equations of motion which are exact in the median plane.

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 5

Editorial note, tabletop extrapolation: This is the CYCLOPS architecture in embryo (the lineage the planned "CYCLOPS-lite" copies); a next machine's tracker should likewise separate the equilibrium-orbit /tune solver from the general tracker, sharing one Fourier-vs-radius field representation fed by FEMM.

the small axial beam space in a cyclotron constrains the particles to move in a region where the z dependence of the field is quite linear.

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 3

Editorial note, tabletop extrapolation: Build the next machine's first tracker around (r, pr, E, phase) PLUS linearized (z, pz) from the outset - the aperture does not hold particles near the median plane, it deletes the ones that leave, so vertical tune, resonance crossings and the physical aperture decide transmission. Full-3D spot checks then benchmark the linear model over representative launches; a handful of them is the check on the linearization, not a license to omit z.

modifications to <B> to yield isochronism out to the 29th entry in the radial table and with the flutter field modified by a small amount to smooth out effects of measurement errors. In addition, Fourier components of argument greater than 99 have been dropped since these components are sufficiently small to have a negligible effect on the particle motion. The radial spacing of the table entrys is interpreted as increased by the factor 64/8.75 corresponding to the ratio of pole diameters ... In the Fourier analysis the measured field has been assumed to have perfect 120 [deg] symmetry.

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 6

Editorial note, tabletop extrapolation: The historical analog of the CadQuery->FEMM->field-map pipeline, plus the habit worth copying exactly as MSU practiced it: document every cleanup applied to the field the tracker ate. For an as-built machine, keep the RAW map too - symmetrizing and smoothing erase the very error harmonics that drive resonances - and use the cleaned copy only for idealized nominal studies; check magnetic similarity (saturation behavior) before radially scaling any model field.

The powerful effect of a cos 0 field component in a cyclotron ... is clearly evidenced by the large changes in the phase plot which result when the small 1% bump is added.

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 22

Editorial note, tabletop extrapolation: Cuts both ways near nu_r = 1: the demonstration is why first-harmonic errors get 'great respect' - so Fourier-analyze the candidate field map and track the measured B1(r) through the local tune to learn what YOUR machine's shim asymmetries cost; and a deliberate bump coil is a powerful orbit-steering experiment once its ampere-turns are sized from that same analysis, not assumed few-turn-cheap.

introduction of the field bump has caused a discontinuous jump in the location of the central stable orbit in the phase diagram

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 24

Editorial note, tabletop extrapolation: The conceptual mechanism to have in hand before a regenerative extraction attempt on a next machine: it needs nu_r to pass unity with a controlled first harmonic, both of which a FEMM-fed tracker can compute for a candidate pole design. It is one extraction method - electrostatic deflection, stripping, or simply large natural turn separation do not require crossing nu_r = 1. [Note revised 2026-08-23: earlier wording read as if this were prerequisite to any extraction.]

stretching and rotation are fine but not twisting, filamentation, etc.

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 24

Editorial note, tabletop extrapolation: The right figure of merit for any next machine's beamline or extraction simulation - track a grid of particles and judge the deformed shape, not just the centroid. Five to two dozen particles sufficed in 1961 for the smooth cases; check convergence by refining the grid where the map is nonlinear, since a sparse grid can miss filamentation entirely.

The sinusoidal voltage, it is seen, shifts the final position of the beam spot but has almost no effect on the distortion.

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 40

Editorial note, tabletop extrapolation: A permission slip for CYCLOPS-lite staging — start with constant energy gain per gap to get the radial dynamics right, then add cos(phi) gain and phase slip as a second-stage refinement, checking that conclusions survive.

the result is seen to fairly accurately predict the actual amplitude and 0 of this point of the grid

Blosser & Gordon, Computational Study of a Resonant Extraction System for a 3-Sector Cyclotron — MSUCP-9 (1961) — p. 44

Editorial note, tabletop extrapolation: Two lessons - build point analytic cross-checks into a next machine's tracker test suite (transfer-matrix estimates against tracked orbits), and note that in the idealised 180-degree-symmetric two-dee case this particular excitation cancels to first order; check the real machine with its measured field, RF balance and gap geometry rather than assuming it. [Note revised 2026-08-23: earlier note called the physics 'benign' for a symmetric tabletop field.]

Table 1, k/h = 0.1: V/V0 = 0.73760 at x/h = 1.0, 0.94468 at 2.0 [verified against page image]

Beal, Computation of Electric Field and Potential of an Idealized Dee Geometry — MSUCP-12 (1961) — p. 11

Editorial note, tabletop extrapolation: Transit-time factors and gap-crossing phase errors must be computed on this extended profile - and whether a delta-kick model is adequate is the transit parameter's call: evaluate omega*L_eff/v for the actual first-turn velocities and the ~2h-long field region, and let that number, not a blanket assumption, decide when the distributed kick is needed.

This radiation is soft and the shielding problem small. It is however important to be remindful of its existance and importance even at low energies of the incident particle. Instruments must be able to detect and measure this soft radiation.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 30

Editorial note, tabletop extrapolation: The reference machine's survey problem in one sentence: a ~10 kV dee makes sub-10-keV photons that ordinary GM/ion-chamber walls partly block — pancake/thin-window instruments are required to even see the hazard (pairs with the Ch. VI 150-keV response rule).

The % of the electron energy that is converted to X-rays upon complete stopping of the electrons ... 0.5 ... 0.265 ... 0.59 ... 1.34 ... 4.77 ... 6.21

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 23

Editorial note, tabletop extrapolation: Sets the scaling logic - conversion efficiency rises with Z and with energy - even though the table starts at 0.5 MeV. At dee-voltage energies the Z-trend persists in direction, but the table's factors do not extrapolate cleanly (characteristic lines and backscatter enter), so the design instinct is what transfers: land stray electrons on LOW-Z surfaces (aluminum, graphite) rather than tungsten or steel, and let the survey measure the actual benefit.

At very low electron energy (few keV), the intrinsic angular distribution is the same as from a radio-antenna, i.e., the intensity is greatest perpendicular to the direction of the electron beam.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 23

Editorial note, tabletop extrapolation: For dee-gap electrons, the INTRINSIC few-keV emission peaks sideways to the electron path - a reason to survey all around the chamber midplane and its windows rather than along any assumed axis. What actually leaks where folds in scattering, multiple electron directions, self-absorption and wall attenuation - so the survey pattern, not the dipole formula, is the finding.

The dose rate D in rads per hour is obtained by multiplying the values in the Table by W/R2, where W is the electron beam power in kwatt and R is the distance in m to the detector from the X-ray target.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 26

Editorial note, tabletop extrapolation: Scope honestly: this is the collection's only full X-ray shielding workflow, and its tables start at 5.5 MeV. For the 5-13 kV dee upgrade none of it applies numerically - take source terms and barriers from X-ray-tube shielding data (NCRP-49-class R/mA-min at 1 m vs kVp), keep the chapter for its structure (source term, then barrier, then verify), and treat the 0.2*I stray-electron assumption as a lesson, not an input (dg-1036).

about 6.5 x 10^10 neutrons per second are produced for each microampere of proton current ... the shield must reduce the fast neutron flux by six orders of magnitude. Therefore e-Sigma_r X = 10-6. For barytes concrete (i.e., Sigma_r = 0.0945 cm-1 ...): X = 146 cm

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. PDF 60 (printed 51) — the whole worked example, yield line included, is on the cited page

Editorial note, tabletop extrapolation: The template to copy for any neutron-capable scenario: source yield -> flux at the shield (1/4pi r^2) -> required attenuation from the dose criterion -> x = ln(A)/Sigma_r. Also the scale anchor for why amateur neutron machines are enclosure-limited: the chapter's 20-MeV, mA-class case needs five feet of concrete.

In the slowing down process ... an insignificant amount of induced activity is produced as compared with the activity produced by thermal neutrons. Therefore the thermal cross section should be used for purposes of calculating the activity produced.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 78

Editorial note, tabletop extrapolation: The correct FIRST bookkeeping if a neutron-capable operation is ever run: inventory surrounding materials against thermal flux (Cu 3.9 b, W 34 b, Au 96 b thermal, per Table IV-2). Capture is the floor of the inventory, not its ceiling - epithermal resonances and fast threshold reactions ((n,p), (n,alpha), (n,2n)) can dominate for some materials and spectra. On today's neutron-free machines there is nothing to activate either way.

The effective dose called the "Dose Equivalent" in units of rem is given by DE=D*QF*DF.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 110

Editorial note, tabletop extrapolation: The structure survives (modern practice uses operational quantities and wR), applied only where the instrument actually reads absorbed dose: a calibrated rem/Sv survey meter already reports a weighted operational quantity, and re-weighting it double-counts. Log what each instrument reports, record WHICH quantity that is, and weight only raw rad/gray readings before comparison to limits.

X-rays, gamma rays, electrons or positrons 1 ... Neutrons, Energy < 10 KeV 3 ... Neutrons, Energy > 10 KeV 10 ... Protons 1 - 10 ... Alpha particles 1 - 20

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 111

Editorial note, tabletop extrapolation: HISTORICAL VALUES - cite for provenance, apply ICRP-103 wR in analysis (photons 1, neutrons 2.5-20 by energy, alphas 20). Where endpoints agree (photon 1, alpha 20) the numerical conclusions survive - re-derive under modern operational quantities all the same (dg-1052's instrument-quantity discipline).

2.5 x 10-8 (thermal) 2 680 ... 5 x 10-1 11 27 ... 1 11 19

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 112

Editorial note, tabletop extrapolation: The conversion pattern for any future neutron survey, used with its conditions: a reading converts only when the energy is known or the instrument already folds the spectrum in (a rem-meter does), and these are 1972 occupational numbers - modern public limits sit far lower. The design fact survives: fast neutrons near 0.5-1 MeV are the most restrictive per unit flux, which is why a D-D contamination field matters at even a few n/cm2-s.

When the whole body is exposed to relatively non-penetrating radiation it may be assumed that the skin is the "critical organ" ... When the whole body is exposed to penetrating radiation the blood-forming tissue is assumed to be the critical organ ... background radiation varies considerably over the earth (approximately 50-175 mrad/year with isolated areas over 1000 mrad/year)

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. PDF 116 (printed 107) for the skin / blood-forming-tissue pairing; PDF 115 (printed 106) for the natural-background range

Editorial note, tabletop extrapolation: Directly relevant to sub-10-keV dee bremsstrahlung, which deposits mostly in shallow tissue: the shallow/skin dose is usually the governing quantity for the machine's leakage fields - established by measurement, not assumption, since photons near 10 keV do reach past the epidermis - which is why survey instruments must be thin-window (Ch. VI) and why whole-body numbers alone can understate the field.

An approximation to the dose equivalent in a mixed neutron and gamma ray field can then be given by DE = Gamma + 1ON ... 10 = a conservative value for the quality factor

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 127

Editorial note, tabletop extrapolation: The cheapest credible mixed-field method for an amateur program - two chambers and a subtraction - and the fallback if a rem-ball is out of budget for future neutron-capable tests. Two updates travel with it: modern wR for D-D neutrons is ~16-20, so the manual's 10 is no longer conservative - plan with 20; and the subtraction is only as good as each chamber's known gamma and neutron response, so calibration is part of the method, not an extra.

The ICRU has recommended a quality factor of 2 for neutrons between thermal and 10 KeV. This then rises to a peak of about 11 near 500 KeV before falling back to about 6 between 10 and 20 MeV.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 131

Editorial note, tabletop extrapolation: Amateur-scale neutron concerns CENTER on the worst band: D-D neutrons are born at 2.45 MeV and moderate down through the keV-MeV weighting peak, so never average a survey away with a thermal-flux conversion. Modern wR moves the peak to ~20 near 1 MeV - the reasoning got MORE conservative, not less - while fully moderated thermal populations still get their own, lower weight.

At energies below about 150 KeV the principal interaction mechanism is the photoelectric effect. ... In a cavity ionization chamber the relative response falls off at low energies because of the effect of the thickness of the walls. Just above this energy the relative response can rise above unity because the effective atomic number of the walls exceeds that of air.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. PDF 130 (printed 121)

Editorial note, tabletop extrapolation: The measurement-side half of the reference machine's X-ray problem: the machine's photon spectrum ends at the dee voltage - tens of keV at most - squarely inside the misbehavior region, so an uncalibrated chamber reading of dee bremsstrahlung can err in either direction. Use thin-window instruments with a low-energy calibration point (dg-559, dg-1035).

Commercial mu metal shields, if properly used, will normally provide sufficient shielding against magnetic fields. To eliminate the effects of RF fields, aluminum foil or screening can be used.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 128

Editorial note, tabletop extrapolation: Written for exactly such a bench: a scintillator PMT near a 0.6 T magnet's fringe field and a 9 MHz (soon LDMOS) transmitter. 'Properly used' is load-bearing - mu-metal saturates in strong fields and PMT gain moves at millitesla - so position the PMT where the fringe field is already small, shield, and verify gain with a check source in place; confirm RF quieting with the transmitter actually running. The Keithley 617 grounding lore in the reference machine's as-builts is this rule independently rediscovered.

Moyer estimated that for a 90 deg scattering of X-rays it is conservative to assume that 0.05 of the incident energy would be scattered into one steradian in the new direction.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 146

Editorial note, tabletop extrapolation: The same hand calculation sizes a cable or vacuum-line dogleg or an instrument-port baffle in a product-machine enclosure - where a straight-through hole would dominate the leakage - with the estimate verified by survey once built (dg-917's discipline).

only heavy duty industrial type limit switches should be employed, avoiding light duty switches to insure durability and reliability.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 149

Editorial note, tabletop extrapolation: BOM-level guidance for product machines — safety-rated (positive-opening) limit switches on lids/doors, not PCB microswitches, plus an interlock-test line item in the ops checklist (Cyclotron_procedures2 already has the pattern for vacuum; extend to safety chain).

This system uses a dual input which prevents the single key from disabling an interlock which affects personnel safety without the additional input provided by the Radiation Safety Officer's key.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 153

Editorial note, tabletop extrapolation: What the two keys buy is INDEPENDENT CUSTODY of the bypass itself: no single person can disable a personnel-safety interlock alone. Restoration is a separate control - the written restore-verification the manual calls for. A school machine can reproduce both (instructor key distinct from the operator credential; signed restore checklist before the next class). A one-person home lab cannot reproduce the independence: a logged bypass record preserves the paper trail, not the custody - which is the argument for designing so bypasses are rarely needed at all.

After completion of the lockup procedure the person who has performed the survey should have seen every position capable of hiding a man.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 153

Editorial note, tabletop extrapolation: Trivially satisfied on a benchtop machine, but a REAL checklist line for any walk-in enclosure a customer institution builds (dg-1065's accident mechanism is the reason); it belongs in the product installation manual's commissioning procedure.

Colors of lights should represent constant situations. ... Confusion with meanings of various audible alarms can be avoided by routine test alarms at programmed times. Too frequent tests, however, may do more harm than good (cry wolf).

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 154

Editorial note, tabletop extrapolation: The product HMI spec seed — a "machine on" beacon distinct from "RF enabled", consistent across every unit shipped, with an alarm-test entry in the curriculum's first lab.

The recorded cases in which potentially lethal doses of radiation have been received have all involved highly experienced personnel. This accents the need for continuous education programs.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 17

Editorial note, tabletop extrapolation: Aimed straight at a two-person family lab and at teacher-operators: familiarity is the documented risk factor, and the visitor/helper (the "maintenance worker") is the documented victim class — brief every guest, and rehearse the rules even after years of clean operation.

noted an approximate "half-life" for the ozone in their measurements at Rensselaer and Yale of 35 minutes.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 178

Editorial note, tabletop extrapolation: Practical basement rule of thumb: after an RF/HV session with ozone smell, a ventilated half-hour is one measured half-life - which only halves an unknown starting concentration. The checklist entry is therefore 'ventilate, wait, then confirm by fresh-nose absence of odor at re-entry' - surfaces, humidity and any continued production move the real decay rate, in either direction.

The capacitor housings have separate vacuum systems using turbomolecular pumps. RF feed through insulators separate them from the main cyclotron vacuum system.

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 10

Editorial note, tabletop extrapolation: Scales down as a case-by-case method: a sealed partition (like Nevis's insulator barrier) actually isolates the gas load; an OPEN differentially pumped appendage - the reference machine's diff-pumped source region - only reduces transfer through its conductance. Pick per mechanism from a conductance and gas-load estimate, and remember debris control is geometry, not pumping.

stopping the beam at r < 10 in. radius in graphite targets. This avoids neutron production and induced cyclotron radioactivity

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 5

Editorial note, tabletop extrapolation: The staging discipline transfers to every machine even where activation does not: low-duty, small-radius-first commissioning also protects septa, collectors, and instruments. Stage one's activation-safety is species- and energy-specific, not automatic - deuterons on carbon make neutrons above ~0.33 MeV via 12C(d,n), and D-on-D in any deuterium-loaded surface is thresholdless - so re-establish the claim whenever species or energy changes.

The value of mu used was found experimentally by measuring the field from a precisely known configuration of conductors

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 13

Editorial note, tabletop extrapolation: A model-calibration pattern for the FEMM pipeline: one known-geometry measurement (a wire loop, a known coil) in the actual gap BENCHMARKS the model at that operating point - repeat at several magnet currents and locations before trusting the saturation model across the map; one point pins one point, not the whole BH curve.

each wire will have its own thermocouple to sense any rise in the cooling water temperature which will shut off the current in the channel

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 13

Editorial note, tabletop extrapolation: Per-element thermal interlocks scale down perfectly - the RF amplifier dummy load, water-cooled dee stubs, any powered septum - and match the fail-safe doctrine (dg-1110). A coolant-temperature sensor only responds after heat reaches the water: pair it with a flow interlock (dg-202's return-orifice practice) so loss of flow trips the supply without waiting for temperature to say so.

techniques of dealing with problems such as relay races, sneak grounds and power-supply crossties

Ohnesorge & Butler, Recent Trends in Particle Accelerator Radiation Safety — CONF-741040-6, Oak Ridge National Laboratory (1974) — p. 2

Editorial note, tabletop extrapolation: Fully transferable and cheap: a deliberate review pass asking 'what unintended path can energize the HV or open the shutter' on the interlock schematic - a shared ground defeating an enable line is exactly the class it hunts. One pass finds sneak paths on paper; it does not validate the built system, so it complements, never replaces, fail-safe design and periodic function tests (dg-1110, dg-1065).

A - Slab under test. Dimensions 3' x 3' x thickness. C - Concrete "Igloo". D - Detector, in cubical cavity 1-1/2" edge. M - Beam moniter [sic]

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 3

Editorial note, tabletop extrapolation: A shielding survey needs no separate neutron source — run the machine at a reference beam current and take detector-to-monitor ratios; the monitor normalization is what makes readings taken hours apart comparable.

The monitor and detector employed were aluminum-walled ionization chambers, with DC Amplification, indicating on microammeters placed outside the magnetic field of the cyclotron.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 2

Editorial note, tabletop extrapolation: Analog meter movements and photomultipliers misread in modest stray fields (PMTs at well under a millitesla); GM tubes themselves are largely field-insensitive, though their electronics may not be. The transferable practice is the source's separation: passive sensing volume at the measurement point, readout where the field is negligible - verified by moving the readout and watching for a change.

The transition effects occur as the neutron beam approaches equilibrium with the secondary and scattered particles produced in the absorbing medium.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 3

Editorial note, tabletop extrapolation: A dosimeter just behind the first inches of shielding can be measuring the buildup region rather than the attenuation slope, so thin-shield tests can misestimate a thick shield in either direction. How pronounced the transition is depends on the field and geometry; the transferable part is the fitting discipline - use the asymptotic slope.

Paraffin yields a transition increase of 60% following Fe, and of 100% following Pb with similar geometry.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 3

Editorial note, tabletop extrapolation: When adding polyethylene or paraffin outside a metal chamber wall, a survey reading between the layers or behind too thin a hydrogenous layer can exceed the bare-wall reading - recoil protons from the hydrogen. Make the hydrogenous layer thick enough to absorb the recoils it creates, and take the dose reading OUTSIDE the complete stack: interlayer readings are diagnostics, not the answer.

Cited in: Shielding a Small Cyclotron

Because of the geometry employed, these measurements are neither a true determination of pure scattering nor pure absorption.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 5

Editorial note, tabletop extrapolation: Handbook removal cross-sections assume corrected geometry; a home measurement's bias depends on the arrangement - a narrow-beam, small-acceptance setup excludes scatter and reads MORE attenuating than a broad shield really performs, while a detector bathed close behind a slab collects scatter and reads pessimistic. State the geometry with the number, as the rule says, and compare only like with like.

Measurements with a BF3 proportional counter have indicated diffusion of slow neutrons through various access openings from the enclosure.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 2

Editorial note, tabletop extrapolation: Cable ways, viewport lines-of-sight and door gaps are where slow-neutron leakage concentrates ONCE the bulk shield is adequate - penetrations dominate when the walls no longer do, which is the regime a designed enclosure should be in. Thermal-neutron instruments answer a different question than fast-neutron ones; both belong in a survey.

With an ionization reading of 24 r/hr in the center of the neutron beam cone 1 foot outside the tank wall (9 3/4 feet from the probe), the ionization just outside the shielding in the center of the beam is 10 mr/hr, while the general building areas are 0.5 to 1.5 mr/hr. These quoted measurements are made with Al-walled ionization chambers, and correspond to a deuteron beam of about 0.2 x 10-6 amp.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 2

Editorial note, tabletop extrapolation: A survey number without the simultaneous beam current is unusable later: log dose rate, location, instrument, and Faraday-cup current as one record so the map rescales when beam current grows - and re-survey when anything besides current changes (energy, species, tune, loss pattern), because those break the linear rescale.

The Q of the model will be 0.7 times the Q of the actual installation and so will require 1.4 times as much power for a given dee voltage.

MacKenzie, Preliminary Report on the “Three Quarter Wave” R.F. System for Frequency Modulated Cyclotrons — AECD-1850, University of California (1947) — p. 6

Editorial note, tabletop extrapolation: Bench-model a dee-stem or resonator geometry at reduced size before cutting full-size copper, applying the sqrt(scale) Q correction to power comparisons - and determine coupling separately, from impedance or measured external Q: the power ratio says nothing directly about what a tap or loop must pick up.

excited by a separate oscillator ... It was suppressed with 2 wavetraps slightly staggered in tuning to cover a small frequency band ... A total of 6 wavetraps sufficed to suppress all unwanted modes throughout the proton range. The parasitic modes were not completely eliminated, however, when the dee was shorted, as would occur in a discharge.

MacKenzie, Preliminary Report on the “Three Quarter Wave” R.F. System for Frequency Modulated Cyclotrons — AECD-1850, University of California (1947) — p. 7

Editorial note, tabletop extrapolation: Sweep the assembled dee/stem/liner system with a signal generator and probe before first power-up; every resonance within the amplifier's gain bandwidth is a candidate parasitic. Repeat the survey for fault-like boundary conditions - a dee spark momentarily retunes the system into modes the clean census missed, exactly the source's shorted-dee exception.

It was found that the parallel mode was discouraged by grounding the supports ... two of them require that large currents flow in the rotor supports, which can be made fairly high resistance. These modes are therefore not excited in favor of the much higher Q correct mode.

MacKenzie, Preliminary Report on the “Three Quarter Wave” R.F. System for Frequency Modulated Cyclotrons — AECD-1850, University of California (1947) — p. 7

Editorial note, tabletop extrapolation: Mode-selective damping - resistance placed at a current maximum of the unwanted mode and a current null of the wanted one - is a powerful alternative to tuning the parasite out of band. Verify with a current map that the wanted mode's null is real (an imperfect null costs Q), and check the resistive element's dissipation and temperature at power.

the insulators will be subjected to about 3 times the rotor voltage to ground. This is because the long metal supports act as open transmission lines

MacKenzie, Preliminary Report on the “Three Quarter Wave” R.F. System for Frequency Modulated Cyclotrons — AECD-1850, University of California (1947) — p. 8

Editorial note, tabletop extrapolation: Check the electrical length of every support, cooling line, and instrument stalk inside the RF volume against its actual return path and termination (loaded lines behave differently from open ones): a mechanically convenient standoff can sit at a voltage antinode and flash over at dee voltages its rating should easily hold. The 3x is MacKenzie's installation, not a universal factor - model or measure your own.

The oscillating circuit actually is a long folded transmission line consisting of the two rows of meshed teeth.

MacKenzie, Preliminary Report on the “Three Quarter Wave” R.F. System for Frequency Modulated Cyclotrons — AECD-1850, University of California (1947) — p. 16

Editorial note, tabletop extrapolation: The diagnostic transfers as a leading suspect, not a verdict: a sharp frequency-specific dead spot MAY be a resonant conductor assembly (screen, liner seam, feedthrough array) - confirm with low-power sweeps, probing or damping tests before modifying the structure, since matching faults, mode coupling and measurement artifacts produce nulls too. When confirmed, fix by shortening or breaking up the structure, not by driving harder.

if the frequency of the transverse mode is still higher than the fundamental when the teeth are fully meshed, then the transverse frequency will always lie above the fundamental for any partially meshed position.