Cyclotron beam measurement design rules

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.

The magnet field must be accurately regulated to maintain a steady beam ... A constant-current regulator is needed, capable of reducing fluctuations to better than 1/1000.

Livingston & Blewett, Particle Accelerators (1962) — p. 194

Editorial note, tabletop extrapolation: A modern current-regulated supply can meet this - verify ripple AND thermal drift on the actual unit: 0.1% of 5.9 kG is 6 G, a shift of the same order as deliberate shim corrections, so supply drift competes with the shim budget (and with RF detuning) for the resonance.

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 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.

This regulation system is capable of holding the 17,000 gauss field to within +/-4 gauss of its nominal value.

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

Editorial note, tabletop extrapolation: A concrete precedent for a home magnet supply: a few parts in 1e4 is achievable with a shunt, op-amp and pass bank. What a given machine NEEDS follows from its turn count and phase budget (dg-273); this figure is the documented professional practice, not the requirement.

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.)

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.

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.

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.

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.

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.

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.

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.

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.

Approximately 1/8-scale model magnets were energized ... A complete grid of points 1/4 in. apart is thus obtained over the entire model.

Livingston & Howard (eds.), The Oak Ridge Relativistic Isochronous Cyclotron — ORNL-2648, OSTI 4275955 (1958) — p. 29, 31

Editorial note, tabletop extrapolation: Inverted for the builder: their whole magnet is model-sized, so a dense XY Hall-probe map - grid pitch chosen from the field structure you need to resolve - is the equivalent discipline, with an error budget drawn up for YOUR instrument chain (Hall calibration, angular alignment, temperature drift, positioning, current regulation) the way ORIC drew up theirs.

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 presence of the coil's distributed capacity causes the Q observed by the Q meter to be lower than the true Q of the coil

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

Editorial note, tabletop extrapolation: For the cited Q-meter method, treat the reading as a lower bound and keep leads and fixture capacitance minimal. A VNA measurement is a different animal: state whether loaded or unloaded Q is being extracted, calibrate and de-embed the fixture, and include the distributed capacitance in the fit - VNA errors can bias either direction.

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 P6015 probe introduced 3.0pF of capacitance; the tank circuit was indeed reduced in frequency corresponding to 3 pF

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

Editorial note, tabletop extrapolation: With the reference machine's ~78 pF-class dee, 3 pF is a ~2% frequency pull - enough to detune a high-Q tank, so calibrate with the probe on, then remove it and retune.

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.

The coupling factor is high, ~1000 or 30 dB, to minimize main line power loss ... enables 200 W power measurements using the AD8307 logarithmic detector IC

Blodgett, 3.5 to 30 MHz Automatic Antenna Impedance Matching System (2012) — p. 18

Editorial note, tabletop extrapolation: For the reference machine's 100-500 W upgrade: a homebrew 30 dB coupler plus AD8307 board works with a calibrated pad (10 dB or more) between them; include coupler tolerance and mismatch peaks in the level budget, and calibrate the chain end to end.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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 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.

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

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.

the ion revolution turn spacing near r = 4 inches, in a B-field of 1.0T will be just 0.04 inches, which is smaller than the 0.06 inch RF shield of the tip

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

Editorial note, tabletop extrapolation: At the reference machine's ~1.3 kV the turn spacing is smaller still, so geometry matters doubly: a thick tip costs single-turn radial resolution first, and a shield mounted AHEAD of the collector can shadow it into reading zero while beam exists - the quoted case. A bare, grooved copper collector is the safe default until turn-resolved measurements are wanted.

Emergent beam intensities up to 25 per cent of the resonant beam intensity have been obtained under optimum conditions ... practical operating intensities would in this case be limited to 80 or 100 ua.

Livingston & Blewett, Particle Accelerators (1962) — p. 182

Editorial note, tabletop extrapolation: Judge a next machine first on internal-probe current at full radius: documented machines commonly ran internal currents several times their extracted beam (MIT's optimum was 4:1), so a gap of that order is precedented rather than failure. The rung-by-rung extraction picture is dg-595's; the census cross-checks are dg-260's.

Our parameters: B=.976 T ... T=.472 MeV ... d=.291 inches ... Combining yields: Vd/d = (2T/R)(dR/(R+dR)) ... Vd = 32.531 kV

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 6 (R and dR on 7)

Editorial note, tabletop extrapolation: Gives the builder the extraction-voltage scale for a next machine: deflector voltage scales linearly with beam energy at fixed geometry, so a ~100 keV beam needs about a fifth of a 472 keV machine's figure in the same channel. Given the source's formula/number discrepancy (see formula field), size from the formula and confirm by measurement.

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.

Frame-by-frame analysis... revealed that ions nominally populate 40 degrees of the 360 degree RF cycle in our cyclotron.

Koeth, Undergraduate Education with the Rutgers 12-Inch Cyclotron (2015) — p. 9

Editorial note, tabletop extrapolation: Sets expectations for fast diagnostics and duty-factor arithmetic on any machine: measure your own bunch width (capacitive pickup, gated counting) and use it - 40 degrees is one measured machine's figure, not a constant.

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

At these energies beam intensities varied from 0.5 to 10 nA on target ... detected by eight silicon surface barrier detectors ... each detector subtending a solid angle of approximately 2.5 x 10^-4 sr.

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. PDF 3 (printed 359), continuing on PDF 4 (printed 360)

Editorial note, tabletop extrapolation: The single most encouraging number in the batch: professional low-energy p-B11 data at exactly the reference machine's nA beam scale. Whether nA suffices for a given measurement follows from the rate arithmetic - cross-section, solid angle, integration time (the experiments-by-energy worked examples) - not from precedent alone.

Cited in: Experiments by Energy Band

simulations show that out of the three emitted a-particles, on average 2.1 a-particles contribute to this peak at the 0.675 MeV resonance

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. 359-360

Editorial note, tabletop extrapolation: When the builder converts PIPS counts, publish counts-per-luminosity as this paper does. Extracting a cross section needs more than dividing by ~2: detector efficiency, angular acceptance, the alphas' angular/energy distributions and window effects all enter, and the multiplicity itself changes with beam energy and analysis window.

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

The highest proton energy obtained so far is about 160 keV, with a 3 pA peak near the correct magnetic field of 796 mT for 12.1 MHz.

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

Editorial note, tabletop extrapolation: Calibrates expectations exactly at the reference machine's operating point (~150 keV): currents fall steeply near a machine's energy limit, and the gating items the paper lists are the ordinary ones - magnet current, cooling, RF range.

Cited in: Choosing Your Machine

operating steadily for some time with 500 ua of 23 Mev protons on a 6 by 10 inch water-cooled aluminum target of the grazing-incidence type ... The highest level at which operation was stabilized long enough to permit calorimetric measurement gave a beam power of 41.7 kw.

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

Editorial note, tabletop extrapolation: Overkill at the reference machine's ~mW beam power, but the geometry trick transfers if a next machine ever puts tens of watts on a probe tip: tilt the target - and still do the cooling and stress arithmetic, since grazing only enlarges the footprint.

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.

This results in a phase acceptance of only a few degrees for the typical case of a few hundred turns.

Baartman, Cyclotrons: Why/How Are Their Dynamics Different? — JINST 18 T03005 (2023) — p. 10

Editorial note, tabletop extrapolation: Do not chase single-turn extraction on a small machine: accept multi-turn with spread of order the turn energy gain (~20 keV at a 10 kV dee - the simple-picture floor; turn overlap and precession can widen it), which PIXE tolerates. (Spread and dB/B detail: botman pp.11-14.)

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.

Table 3.4: Slit 0.010" 40 kV, 450 mA, 3.0 cc/min -> 227 uA; Slit 0.020" 40 kV, 150 mA, 3.0 cc/min -> 590 uA

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 88-91

Editorial note, tabletop extrapolation: Start a next machine with the 0.5 x 5 mm slit - at 50-150 mA arc it made 230-590 uA at 40 kV. A fixed-gap Child-Langmuir scaling to a 4 kV dee (V^1.5) would read ~7-19 uA, but treat that as a blackboard exercise, not available beam: RF extraction changes gap, meniscus and phase acceptance, so model the actual central region before booking any of it against the present 3 nA best.

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.

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 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

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

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

Internal Beam, Stable, ua 1000-2000 ... External Beam, Stable, 800 ua; 100 ua focused on target 15 ft from machine

Howard, Cyclotrons and High-Energy Accelerators, 1958 — ORNL-2644 (1958) — p. 107

Editorial note, tabletop extrapolation: If the reference machine sees nA, the gap to the historical uA-mA norm lives in source output and center-region transmission, not physics limits - and extraction cost most census machines most of their beam, so budget a next machine's external current pessimistically.

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.

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.

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.

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.

for a stability of 0.01% the temperature difference between resistors must be within about 3 C.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 21

Editorial note, tabletop extrapolation: Deflector voltage stability maps directly (first-order) to extracted-beam steering stability, so buy or build the divider first - and set the actual tolerance from a beam-clearance budget at the septum (beam size, orbit spacing, drift) rather than assuming either 0.01% is needed or 1% is fine.

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 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.

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 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.]

In dc tests the output of the source, measured after the beam had passed through a 180 deg path in the magnetic field, was: 8 ma of N+, 2 ma of N++, and 2 ma of N+++.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 24

Editorial note, tabletop extrapolation: The 180-degree bend uses the cyclotron's own field as a mass spectrometer with the RF off — on the reference machine this is precisely the source-species test geometry: source + static field + offset collector measures the H+/H2+/H3+ mix directly before any acceleration studies.

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.

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.

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

the ratio of Cu64 activity in the cadmium-wrapped sample (due only to fast particles) to that in the uncovered foil was ~1/1.6.

Boom, Toth & Zucker, Residual Radiation of the LRL 184-inch Cyclotron — ORNL-3158 (1961) — p. 15

Editorial note, tabletop extrapolation: ENERGY SCOPE: relevant only when neutrons exist to be moderated. The Cd-difference technique splits capture activation into below- and above-cutoff parts APPROXIMATELY - epithermal response and the wrapper's spectrum perturbation blur the split, which is why practice reports cadmium ratios rather than clean fractions. Keep it in the toolkit for any future neutron-producing experiment; meaningless for pure sub-MeV proton running.

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.

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 energy distribution of protons in the cyclotron beam is readily determined by measuring this excitation function and comparing it with the published data.

Cohen, Measurement of Beam Energy and Energy Distribution on an Internal Cyclotron Target — ORNL-1347 (1952) — p. 9

Editorial note, tabletop extrapolation: ENERGY SCOPE: Cu63(p,n)Zn63 needs ~4.2 MeV (verify against evaluated data at use time) - closed at reference-machine energies. What transfers is narrower than the note once claimed: the unfolding needs multiple independent response kernels, so a single B11(p,alpha) yield number constrains but cannot recover a spectrum; measurements at several calibrated degrader settings can build a response matrix, and a PIPS behind degraders is range spectrometry - a different, complementary method.

Cited in: Shielding a Small Cyclotron

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.

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.

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.

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.

such a cyclotron is feasible, that an energy definition of less than +/-10 kev could be achieved, and that deflected beams would be in the range of 1 to 10 ua

Howard (ed.), Electromagnetic Research Division Semiannual, period ending 20 March 1953 — ORNL-1531 (1953) — p. 19

Editorial note, tabletop extrapolation: Direct prior art for the plan's educational variable-energy concept: vary energy with field/frequency plus a movable target (cf. the 44-inch spacer), and buy energy DEFINITION with a simple analyzed beamline - accepting the current it costs - rather than machine perfection.

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.

an extension of the energy range much beyond 1.3 E0 requires an unreasonably large vacuum chamber at the exit of the magnet.

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 7

Editorial note, tabletop extrapolation: SCALE-HONEST only when the scaling is done: the geometry fixes E/E0 ratios, but reaching a given E takes B*R. For ~170 keV protons, B-rho ~ 0.06 T-m, so an R ~ 5-10 cm bench version needs roughly 0.6-1.2 T - iron-pole territory, not a few hundred gauss. Still compelling as a teaching-lab focal-plane instrument; copy the optics and size the field honestly.

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.

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.

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.

In scattering from light nuclei, this introduces appreciable kinematic broadening of peaks as the entrance aperture is opened.

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 8

Editorial note, tabletop extrapolation: For a next machine's Rutherford-scattering station the same knob exists: closing the entrance aperture trades count rate for resolution. State the broadening honestly - dE ~ |dE/dtheta|*dtheta depends on beam energy, angle and kinematics in general; only the FRACTIONAL elastic broadening at fixed masses and angle drops out energy-independent - so compute it for the actual geometry rather than quoting a mass-ratio shortcut.

the problem of obtaining a pulsed beam usually does not arise, because the beam of a conventional cyclotron is already naturally bunched.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 6

Editorial note, tabletop extrapolation: DIRECT and foundational for the experiment catalog: the reference machine at 9 MHz delivers phase-bunched beam at the RF period - a measurable, teachable property and the enabling fact for gated counting. 'Usually' is operative: time-of-flight at fine resolution, or experiments needing low repetition rate, can still require pulse selection or extra bunching - check bunch width and period against the experiment's timing demands.

the pulses are obtained in a way which makes them insensitive to beam current changes, and b) all reference pulses are smooth and identical in shape.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 6

Editorial note, tabletop extrapolation: The most directly transferable finding here: the machine's RF is a free, stable timing fiducial at any scale - clock gated counting and TOF off a capacitive sniff of the dee. A fiducial is not a beam-arrival timestamp: beam phase relative to the RF moves with field tuning, loading and cable delays, so calibrate the offset against a real beam signal - and re-calibrate after retuning - before treating RF zero-crossings as beam time.

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.

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.

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.

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.

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 output voltage of the radio-frequency oscillator for the cyclotron proved to vary with frequency and to contain undesired frequency components. At some particular operating frequencies, the undesired frequencies appeared as modulation of the dee voltage and could not be eliminated. These problems were solved by replacing the oscillator with a frequency synthesizer. ... The modulation on the dee voltage, defined as the peak-to-peak ripple riding on the RF voltage as a percentage of the peak RF value, has recently been reduced to about 0.5% from 1.5%.

Cyclotron Staff, Report of Cyclotron Operation 1 July – 31 December 1969 — NRL Memorandum Report 2103, Naval Research Laboratory (1970) — p. 25

Editorial note, tabletop extrapolation: Dee-voltage ripple modulates per-gap energy gain (and, through phase slip, orbit phase where the machine is off-isochronous); put the envelope from a calibrated RF pickup on a scope, log the percentage, and remember the excitation source - a cheap generator's spurs included - is a candidate cause before blaming the amplifier or resonator.

blocks of either of two different materials could be placed (without disturbing the vacuum system) immediately in front of the 2-inch brass stopping plate

Harvard University Cyclotron Laboratory, Quarterly Progress Report, 1 June – 31 August 1964 — p. 2

Editorial note, tabletop extrapolation: A cup's reading depends on its stopping surface through secondary emission and backscatter - a two-material comparison tests the SENSITIVITY to that choice, not the absolute error (both materials can be wrong the same way). For an absolute bound: verify full stopping, control geometry and contact, suppress electrons, and bring an independent current reference or a validated emission/backscatter calculation.

The density of various parts of the target was found ... by searching for the tail of the Bragg ionization curve.

Harvard University Cyclotron Laboratory, Quarterly Progress Report, 1 June – 31 August 1964 — p. 4

Editorial note, tabletop extrapolation: A range-based (or transmission-based) density map of the actual target spot belongs in the error budget of a yield measurement WHEN the required precision or the material's provenance makes nonuniformity plausible - stock and process vary, so let the required precision decide whether to map, and state the stopping-power and composition assumptions the map rests on.

In a typical charged particle experiment 100 na of beam loses 43 keV in a W = 380 ugm/cm2 PbCl2 salt target

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 238

Editorial note, tabletop extrapolation: A 1 uA, 170 keV proton beam fully stopped in an internal target deposits 0.17 W — forty times Corwin's example — into whatever spot the beam makes; the entire current limit of a thin uncooled target follows from this one number and the two removal channels (radiation, conduction) he works out next.

Linear measurements can lead to grossly erroneous values of atom content by virtue of included microscopic voids or a mixture of various crystal phases.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 27

Editorial note, tabletop extrapolation: Yield calculations need atoms/cm2, which weighing gives directly given composition; a micrometer or interference measurement of an evaporated film does not - use thickness methods only when the film's density and composition are independently established.

In almost every case the agreement was better than +-1%.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 30

Editorial note, tabletop extrapolation: A used microgram-precision balance plus the free NBS protocol is a strong target-mass QA capability - budgeted honestly: 1 ug of combined uncertainty is already 2% of a 50-ug sample, and a deposited mass obtained by difference doubles the exposure, so write the mass-dependent uncertainty budget (readability, repeatability, calibration, buoyancy, static) before promising sub-percent numbers at the light end. The protocol removes drift; it cannot remove the balance's floor.

the ultimate measurement remains the direct mass determination of the target after it has been removed from the vacuum system.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 36

Editorial note, tabletop extrapolation: Treat the QCM reading as rate-and-range control during deposition and take the certified number from pre/post weighing with the deposited area defined - a QCM calibrated in a stable thermal environment can be good, but radiant load from the source shifts its frequency exactly when the reading matters most, so the removal-and-weigh check is the arbiter.

most of these data have an accuracy of ~ +-10%.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 40

Editorial note, tabletop extrapolation: The one thickness method that needs no balance and works on a mounted film - with a surface-barrier detector and MCA. Quote absolute thickness no tighter than CURRENT stopping tables allow at the actual energies, combine straggling/calibration/fit uncertainties, and remember the alpha source is a regulated sealed source, not generic bench stock.

light intensity change is not a very useful technique for carbon films of thickness greater than 40 or 45 ug/cm2.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 43

Editorial note, tabletop extrapolation: A photodiode and lamp sort carbon stripper/backing foils into thickness bins as an incoming-inspection tool - calibrated against weighed foils and RE-checked periodically, since optical response drifts with lamp, alignment and film morphology; expect it to saturate out near the source's 40-45 ug/cm2 carbon ceiling.

The uniformity of thin foils can be determined by scanning the foil with a collimated beam of alpha particles. ... For targets having a thickness in the range of .5 to 500 mg/cm2, beta particles can be used to determine the target thickness profile ... Figure 19 illustrates a target thickness profile obtained by scanning a 58Ni rolled foil with beta-particles from a 204Tl source. ... For radioactive sources the surface of the sources can be scanned using a small collimating aperture and a silicon solid state detector

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 47

Editorial note, tabletop extrapolation: The same alpha energy-loss rig with an XY-translated collimator becomes a uniformity mapper. What it maps is AREAL DENSITY variation - a single-point thickness number hides the wedge or large-scale nonuniformity; fine crystallite structure below the aperture scale needs a straggling measurement instead (dg-1190).

This is all the calibration which is necessary since now only energy shifts are of interest. ... the vacuum must be maintained at a pressure of less than 10-4 torr to avoid a glow discharge caused by the detector bias voltage. Such a discharge can damage the detector.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 63

Editorial note, tabletop extrapolation: The whole rig is a surface-barrier detector, preamp, biased amp and a stable, linear MCA - Thompson wrote it up precisely so small labs could build it. Estimate fractional channel positions from adjacent-channel counts (peaks are Gaussian) and state the resulting channel uncertainty; whole-channel reading of a small shift is coarse. The pressure threshold for bias-induced glow depends on voltage and geometry - treat 1e-4 torr as his operating requirement and verify your own.

They show up as small unshifted peaks in the energy spectrum.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 65

Editorial note, tabletop extrapolation: One spectrum yields thickness plus uniformity and open-area evidence - run it on every target before installation. The unshifted peak measures unattenuated FRACTION, not a hole count; converting to open area needs the beam profile. Re-measuring after beam exposure quantifies damage - after the radiation survey and handling review that any post-irradiation work gets.

His analysis gave average crystallite sizes between 100 A and 2000 A and average surface roughnesses from 50 A to 1000 A depending on various parameters as parting agent material, temperature of the substrate, rate of evaporation, thickness of the parting agent. Recalling that carbon foils of 10 ug/cm2 or gold foils of 100 ug/cm2 have a thickness of nearly 500 A, one notices that the size of such a crystallite structure and the target thickness are of the same order of magnitude. This means that, however uniform an evaporation may be, the parting agent produces an inhomogeneous target. These nonuniformities are not detectable in a measurement of the target thickness profile with the standard method

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 134

Editorial note, tabletop extrapolation: If a target will sit tilted to the beam or feed a spectrometer, the release-agent choice is a resolution decision, not a convenience. Energy-straggling width is the sensitive test the source used; microscopy or profilometry can also reveal the structure - what cannot see it is a mean-thickness scan at aperture scale.

all targets should be produced with the use of Teepol as parting agent, or ... an organic parting agent with very little crystallite structure

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 143

Editorial note, tabletop extrapolation: Detergent-film release over salt release wherever the condensing metal tolerates it; and the alpha-straggling comparison is a bench-top RESOLUTION metric using the thickness-measurement rig - one axis of target quality, with adhesion, pinholes, large-scale uniformity and durability still needing their own checks.

With a proton beam, targetry is just no problem. One can obtain very nice high-resolution results.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 158

Editorial note, tabletop extrapolation: Direct license for a proton machine: target thickness and uniformity tolerances that dominate heavy-ion work are second-order for protons, so a thick-ish imperfect boron layer costs beam-energy definition, not feasibility. When tempted by heavier beams, budget with the Z^2-at-equal-velocity scaling and check real stopping tables (SRIM/NIST-class) at low energy, where effective-charge effects bend the simple law.

we have assumed that the foil lifetime is inversely proportional to the particle density incident on the target.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 205

Editorial note, tabletop extrapolation: Under that model, halving the spot diameter quarters foil life at fixed current - so measure the actual beam-spot size before predicting from literature data, and carry the companion variables when comparing (species and velocity, foil temperature and fabrication, motion/duty cycle for oscillated targets, vacuum contamination). The scaling is Yntema's stated assumption validated on his data, not a universal damage law.

Defocus whenever possible is the moral to this result.

Thomas & Karasek (eds.), Proceedings of the Fourth Annual Conference of the Nuclear Target Development Society — ANL/PHY/MSD-76-1, Argonne National Laboratory (1975) — p. 212

Editorial note, tabletop extrapolation: An internal target wants the widest beam spot the measurement tolerates, an aperture that shadows the frame, and a multi-position holder. Rastering and mechanical target motion are alternatives, not equivalents - rastering changes the optics and duty cycle while rotation moves material through a fixed beam - and each needs its own optical, aperture and HV check on a small machine before it is called easy.

start with as large a beam spot as possible and slowly focus it smaller ... Also the larger the diameter of the foil the greater the lifetime. The smaller the area of the beam spot the shorter the lifetime. Heating it evenly reduces the temperature gradient and probably makes the foil more elastic.

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 85

Editorial note, tabletop extrapolation: Directly usable at first target insertion — defocus onto a fresh foil, tighten the spot only as needed, and expect the smallest spot to have the shortest foil life.

if you weigh the frame without and with the foil, the error will be about 0.5 ug/cm2 because of adsorption and desorption effects (Maier-Komor, "A Rapid and Accurate Method for Measuring the Thickness of Extremely Thin Targets")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 157

Editorial note, tabletop extrapolation: A bench spectrophotometer measures foil thickness in seconds without an accelerator - as a CALIBRATED method: attenuation and reflectance are material- and wavelength-specific, interference and pinholes bend the simple law, so calibrate against weighed thicker foils and state the neglected effects. Where you draw the too-thin-to-weigh line follows from the 0.5 ug/cm2 floor and YOUR allowed relative error - 10 ug/cm2 is that line for a 5% budget.

the longer sputtering times required for thick targets produce higher temperatures, and higher rates (Stinson, "Nitrogen Targets Produced by Reactive Sputtering")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 67

Editorial note, tabletop extrapolation: Applies to any deposition where the source drifts hot — time-based thickness control needs either thermal steady state or an in-situ monitor (quartz crystal, witness plate).

For evaporated metal coatings (Al, Cr, Cu, Au, Ag, Sn, and Ti) we have developed curves of optical transmittance vs surface density that can be used to estimate surface densities to within about +-20%. ... measured at 5461 A ... it was not possible to carry out accurate measurements with slides that had been coated with a soap-like parting agent, since these would lose weight upon being placed in vacuo. ... It is certain that all of our coatings were contaminated either by oxide layers, burial of residual gas, and/or adsorption of active molecules. The curves indicate such effects by the extent of their non-reproducibility, most serious for the active species

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 164

Editorial note, tabletop extrapolation: Extends the carbon transmittance gauge to the metals a small lab actually evaporates; weigh calibration slides bare, never soaped — the parting agent is part of the tare and it evaporates.

broadening of the peak indicates target changes or damages

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 45

Editorial note, tabletop extrapolation: A silicon detector at a fixed forward angle is cheap on any small machine and the lightest target diagnostic going: baseline the peak width first (detector resolution, kinematic broadening and straggling all live in it), then read CHANGES as the damage flag. For luminosity, use the calibrated integrated peak yield at known cross-section and acceptance - the width tells you about the target, the counts about the luminosity.

the envelope of the oscillations was found to fall smoothly until the dee voltage had fallen to a value roughly 1/3 its maximum, then for a short time to drop steeply, then afterward to decay slowly once again.

Fulbright, The Sparker, a Device to Overcome the Multipactor Difficulty in Starting the Oscillator of a Cyclotron — NYO-9359, University of Rochester (1961) — p. 4

Editorial note, tabletop extrapolation: A free diagnostic worth running: ring the dee (impulse or drive-and-release), scope the pickup envelope through a calibrated divider, and look for a kink - a steep-decay segment is a candidate multipactor band on YOUR machine. Corroborate with pressure and conditioning dependence before labeling it multipactor (other nonlinear losses kink envelopes too), and don't transfer the 1/3 ratio - localize your own band and compare it with the operating voltage.

Cited in: Driving the Dee: RF Coupling

the top of the graphite hood glowed a bright orange color when the arc was operating, because of the intense electron bombardment.

Fulbright, A Hooded Arc Ion Source with a Magnetic Mirror Feature — NYO-9358, University of Rochester (1962) — p. 2

Editorial note, tabletop extrapolation: A diagnostic that costs a glance, used as a controlled A/B: at fixed arc power, cooling, surface state and sightline, an orange chimney-top says axial electron loss is real, and a change after adding a mirror or repeller says the geometry change did something. A black hood alone proves less - lower power, emissivity and sightline all dim the glow - so pair the glance with beam and arc-current numbers.

In accurate determinations of the absolute magnetic field intensity, only angular throws of 180 deg are considered satisfactory.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 72

Editorial note, tabletop extrapolation: The flip coil remains the cheapest absolute cross-check on a Hall probe - an NMR-free lab can tie its Hall calibration to a geometry-defined coil area plus a CALIBRATED integrator, provided the flip is a true reversal with aligned endpoints.

Field measurements may be made to 0.5 per cent accuracy by bracketing the deflections to be interpreted with deflections from the flux standard and then interpolating.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 45

Editorial note, tabletop extrapolation: The transferable method: calibrate at deflections spanning the readings, through the same signal path, rather than trusting one scale factor. For a modern ADC/integrator mapper that means multi-point calibration across the operating range; matched input impedance matters where source loading affects the transfer - check it rather than assuming either way. The 0.5% is the cited galvanometer arrangement's result.

As verified by practice, Eq. 68 holds true to at least 0.1 per cent accuracy when the diameter of the wire is small compared to the diameter of the cylinder.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 62

Editorial note, tabletop extrapolation: The piece that turns a flip coil from a relative into an absolute instrument - a machined-spool area standard any shop can make. What absolute field accuracy the whole home chain achieves is its own uncertainty budget (machining, winding, temperature, alignment, field nonuniformity, integrator) - build the budget, then claim the number it supports.

The value of X is 0.35 per cent, which is verified in practice.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 70

Editorial note, tabletop extrapolation: The cited chain's honest arithmetic - two ~0.25% terms RSS to ~0.35%, verified in practice - models how to audit any simple coil-and-integrator chain: enumerate the terms, RSS them, and treat any claim that beats the budget (sub-0.1% included) as unproven until its own budget shows the terms. A traceably calibrated chain can do better; a Hall probe certified to 0.1% is only better in a non-uniform cyclotron gap once its temperature, angle and positioning terms are in the budget too. Compare the two by a full uncertainty budget, not by the certificate. [Note revised 2026-08-23: earlier note made the 0.35% a general floor and the Hall probe 'genuinely better'.]

A 1 per cent change in the exciting current produces an error of only 1 per cent in the changes in the magnetic field.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 72

Editorial note, tabletop extrapolation: The classical answer to shimming with a wandering surplus supply: map relative structure differentially, pin the absolute scale with occasional flips. The cancellation assumes both coils see a common, effectively linear B(I) - check the local dB/dI, saturation and hysteresis on an iron magnet first. A two-channel Hall differential inherits the immunity only with simultaneous sampling and matched, temperature-stable channels.

It was desirable to know the magnetic field accurately to within 0.5 in. on the full-scale magnet. This corresponded to 1/32 in. on the models.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 73

Editorial note, tabletop extrapolation: For Hall-mapping a shim edge: the sensor's active area averages across the gradient, so where the gradient scale approaches the sensor size, either model the convolution or verify with a smaller probe; jig position repeatability sits in the same budget as its own line. Neither substitutes for the other.

Since drift is the most troublesome feature of a fluxmeter, the advantages of the low-sensitivity fluxmeter far outweigh those of the high-sensitivy fluxmeters for accurate, reliable measurements.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 58

Editorial note, tabletop extrapolation: Maps onto modern integrator front-ends as a conditional: putting gain in the coil (turns) and keeping electronics gain low reduces the relative weight of input-referred offset drift - but turns also add resistance, inductance and capacitance (noise, settling, bandwidth), so optimize the coil rather than maximizing it, measure the actual input-referred drift, and treat offset/zero checks as part of every run.

stainless-steel filings (being slightly magnetic) sprinkled in this area will arrange themselves along the lines of force without accumulation.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 81

Editorial note, tabletop extrapolation: Historical techniques worth knowing, deployed with modern care: filings near a strong magnet accelerate and infiltrate - use them sealed in a flat transparent container, never near open vacuum hardware or the pole gap; the discharge-tube method needs a sealed commercial tube plus mercury/UV/HV precautions, and the machine's own ion source is not a movable substitute for it. As qualitative first looks before a probe survey, both still earn their keep.

it was necessary for the values of the quantity integral h_z dx, experimental and theoretical, to differ by less than 3 cm, in terms of galvanometer deflection.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 87

Editorial note, tabletop extrapolation: The discipline transfers: derive numeric field-map acceptance bands from the orbit tolerance (phase-slip or centering budget) BEFORE surveying, so the survey ends in pass/fail per region. Use integral criteria where the beam observable demonstrably depends on the integral, and keep pointwise limits where local gradients, resonances or extraction physics bite - both kinds of band, each where it belongs.

A check of the accuracy of this method was made by determining the same line twice, and this check indicated that the error was not greater than 1/16 in.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 192

Editorial note, tabletop extrapolation: Three habits for a home lab, each with its honest scope: repeat-trace to establish a method's REPEATABILITY (absolute accuracy needs an independent reference); calibrate the current meter, usually the floor of a B-vs-I curve; and normalize survey data to a monitor reading so supply drift cancels out of shape maps - valid once shape invariance over the current excursion is verified and the hysteresis cycle is reproducible.

drifting of the exciting current, inaccurate flipping, inconstancy of the fluxmeter, and temperature effects

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 26

Editorial note, tabletop extrapolation: The differential trick ports to modern probes with its limits stated: two matched Hall/NMR channels read as a difference suppress the CORRELATED (common-mode) part of supply and thermal drift - each channel's independent drift, gain mismatch and temperature coefficient survive subtraction, so calibrate individually, synchronize acquisition, characterize the common-mode rejection, swap channels periodically, and anchor the percentage scale with an absolute reference reading.

an azimuthally symmetric field may still have a dish-shaped median surface.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 42

Editorial note, tabletop extrapolation: DIRECT physics: a displaced or dished magnetic median surface costs vertical aperture and can steer the circulating beam into a dee lid at small gap heights. Put a dip-needle analog (or vertical probe-pair difference) in the survey plan, keep deliberate shims matched top-and-bottom - and REMAP the median surface after shimming: symmetric shims avoid adding first-order asymmetry, but changed gradients can still move a pre-existing displaced surface. Needle details PDF p.44, map Fig. 3.13 p.45.

measured by means of a saturable reactor ... The dee voltmeters are of the series type coupled ... by a small capacity between the probe and a copper paddle soldered to the dee edge.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 86

Editorial note, tabletop extrapolation: The capacitive-paddle dee voltmeter is the instrument Koeth calibrated on the Rutgers 12-inch and the missing calibration behind the reference machine's ~1.3 kV: a soldered paddle + defined-gap probe + diode peak detector, calibrated IN SITU against an RF-RATED reference at the operating frequency - and recalibrated after any geometry, frequency, detector or cabling change (dg-307's Houghton data show the factor moves with frequency). The saturable-reactor trick survives as the Hall/fluxgate-sensor principle - never bring an HV node to the meter; a bare shunt is not isolated, it needs a rated isolation amplifier.

the direct measurement is preferable since for appreciable water flow the temperature difference is very small.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 118

Editorial note, tabletop extrapolation: Do the arithmetic before dismissing either method: P = I*E/q puts 1 uA at 0.1-1 MV at 0.1-1 W - readable by a thermally isolated calorimeter, invisible in high-flow cooling water. The Faraday cup with secondary-electron suppression remains the primary tabletop instrument (with energy known independently to convert current to power); calorimetry earns its place when isolation makes the temperature rise measurable, not at any fixed wattage threshold.

Diese vergrößern den gemessenen Strom und verfälschen damit das Signal. Dies spielt im vorliegenden Fall jedoch keine Rolle [tr.: these inflate the measured current; irrelevant in the present case]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 69

Editorial note, tabletop extrapolation: Secondary-electron emission inflates an unsuppressed cup's reading - fine when only the PEAK POSITION matters (the book's own point), not fine for absolute current: the yield depends on species, energy, angle and surface, so either suppress (dg-524), verify a current-vs-bias plateau, or state 'unsuppressed' beside every quoted beam current. No universal yield number exists to correct by.

Bei dem in Columbus verwendeten Faraday-Cup handelt es sich um einen Selbstbau, da ein Cup passender Größe nicht verfügbar war. Auf eine doppelseitige Platine, dessen eine Seite die Abschirmung darstellt, wurde auf der anderen Seite ein schachtelförmig gebogenes Kupferteil angelötet. Diese Anordnung ist auf ein sog. Semirigid-Kabel montiert, dessen Seele die Signalleitung bildet und das Detektorsignal verlustarm an den Verstärker weiterleitet und das gleichzeitig als Führungsstange dient, mit der der Cup in radialer Richtung bewegt werden kann. [tr.: the COLUMBUS Faraday cup is home-built since no suitable size was available: onto a double-sided PCB whose one side forms the shield, a box-shaped bent copper piece is soldered on the other side; the assembly is mounted on a semi-rigid cable whose core forms the signal line, carrying the detector signal to the amplifier with low loss and simultaneously serving as the guide rod by which the cup is moved radially]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 69-70

Editorial note, tabletop extrapolation: A movable shielded probe from PCB stock and semi-rigid coax is genuinely cheap and buildable in an afternoon - qualify it in place: vacuum-compatible feedthrough for a SLIDING cable, dark-current check with beam off, short exposed centre conductor and clean PCB edges so leakage doesn't swamp pA signals.

Aus diesem Grunde ist der Faraday-Cup unter einem Winkel von weniger als 90◦ gegen das Dummy-Dee montiert [tr.: the Faraday cup is mounted at less than 90 degrees to the dummy dee]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 70

Editorial note, tabletop extrapolation: The transferable move: orient the cup entrance normal to the LOCAL ORBIT TANGENT at the radius where the probe sits - computed or ray-traced for the actual field polarity and orbit (early displaced turns and spirals bend the simple theta-rotation picture) - and re-check whenever the probe moves radially.

Wir legen uns also mit einem geeigneten Detektor auf die Lauer und verändern das Magnetfeld solange, bis wir ein Signal erhalten [tr.: lie in wait with a detector and vary the field until a signal appears]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 69-71

Editorial note, tabletop extrapolation: Slow ramps help but don't grant immunity: characterize the electrometer/amplifier settling time and pick a sweep rate that resolves the narrowest expected peak - then confirm by comparing up- and down-sweeps (hysteresis and lag shift peaks in opposite directions). Correct the Hall reading to the median plane: a probe in the lid recess reads a different field than the orbit (the 1-7.5 percent class errors below), which moves every q/m assignment.

Der erste Peak erscheint bei einer Flussdichte von ca. 187 mT, der zweite kleinere bei B = 370 mT. Somit ergibt sich für Peak 1 eine spezifische Ladung von [2*pi*2.82 MHz/0.187 T] [tr.: the first peak appears at about 187 mT, the second smaller at 370 mT; from this, Peak 1 yields a specific charge of ... - the book carrying the assignment computation itself]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 71

Editorial note, tabletop extrapolation: On a 9 MHz machine the corresponding fields are 0.59 T (H+) and 1.18 T (H2+). A pair of peaks at B and exactly 2B is strong evidence CONSISTENT WITH H+/H2+ - not unique proof (D+ shares H2+'s q/m) - so confirm by frequency scaling or an independent species diagnostic before certifying the beam.

Ionen, die zufällig 1/3; 1/5; ... der Maximalgeschwindigkeit haben, werden jedoch ebenfalls resonant beschleunigt [tr.: ions with 1/3, 1/5 ... of the maximum velocity are also resonantly accelerated]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 71, 74

Editorial note, tabletop extrapolation: Odd reciprocal-field peaks are CANDIDATES for harmonic operation - same species, same probe radius assumed - and whether they are detectable depends on capture and gap geometry; treat them as one hypothesis in the peak ledger (dg-1426), not something every machine must show.

Peak 2 kann dadurch zustande kommen, dass der betreffende Ionenstrahl direkt in nur einem Halbkreis [...] in den Faraday-Cup gelenkt wird [tr.: peak 2 may arise from ions steered directly into the cup in one semicircle]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 74

Editorial note, tabletop extrapolation: On any machine, pull the probe beyond the single-semicircle reach before calling a peak resonant beam, and treat a peak that tracks sqrt(U0) as a direct-ion suspect - a clue, valid where the direct ions' starting energy actually scales with dee voltage.

Die Deutung der anderen, kleineren Peaks [...] ist nicht immer möglich und auch nicht ganz einfach [tr.: interpreting the other smaller peaks is not always possible nor simple]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 71, 74

Editorial note, tabletop extrapolation: Keep a running peak ledger (B, f, U0, gas flow, probe radius) across runs. Persistence at fixed B across U0 and flow changes is EVIDENCE toward species/harmonic assignments, and motion is evidence toward phase-spread or direct-ion artefacts - evidence, not a classification: confirm with frequency scaling and probe-radius scans (dg-1422, dg-1425).

Ein Steuergerät liefert eine zur Flussdichte proportionale Spannung, die für die weitere Auswertung verwendet wird [tr.: a controller supplies a voltage proportional to B used for evaluation]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 36, 70

Editorial note, tabletop extrapolation: A fixed probe reads ITS OWN location's field, not the median plane's: map the probe output against a median-plane measurement across the full operating range and both ramp directions (saturation and hysteresis bend the relation), fit the transfer curve, and carry its uncertainty into every specific-charge assignment - a one-point offset calibration is the minimum, not the goal.

Die spezifische Ladung ist sozusagen der Personalausweis eines Teilchens. Wenn wir diese kennen, kennen wir auch das Teilchen [tr.: specific charge is a particle's identity card]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 68-69

Editorial note, tabletop extrapolation: Connecting to the e/m fine-beam tube students already know turns first beam into an assessable experiment with a literature value and a computable error - the PROTON value being 9.58e7 C/kg. Teach the degeneracy honestly: q/m alone does not name the particle (D+, H2+ and He2+ all sit near 4.8e7 C/kg), so the identity card needs the source-gas and charge-state context too (dg-1422's candidate discipline).

The copper tube also shielded the collector from the RF signal.

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 17

Editorial note, tabletop extrapolation: A grounded slotted shield around the pickup is a sound and documented defense for beam readings taken inside a dee-drive RF field - one layer of several: pair it with shielded signal cable, verify the grounding actually sinks the induced current, and do a beam-off RF-only background run (dg-689's discipline) before crediting the residual as beam.

A phosphorescent screen could be inserted into the chamber in order to determine the vertical position of the beam.

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 17

Editorial note, tabletop extrapolation: A movable phosphor gives spatial (especially vertical) information a Faraday cup cannot - position and profile OBSERVATIONS that feed a focusing or median-plane diagnosis without uniquely proving one; pairs naturally with a viewport, and with the segmented-probe alternative (dg-790).

Peak A was a result of the quarter cycle effect, B was the third harmonic of resonant ions, C was caused by secondary collisions

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 12

Editorial note, tabletop extrapolation: When sweeping for first beam, a peak is not proof of fundamental resonance: check its position against prediction, look for companions (one-third field would support a harmonic assignment - absence doesn't refute the fundamental, since harmonic visibility depends on capture and geometry), and use a retarding potential or energy-sensitive check where possible (dg-502's discipline).

thermocouples are only reliable at pressures above about 10-3 torr

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 32

Editorial note, tabletop extrapolation: The allocation pattern transfers; the thresholds don't - take each gauge's usable range from its own manual. The placement lesson is real at small-machine conductances: measuring at the pump and inferring at the chamber can misstate the pressure the beam sees, so put the high-vacuum gauge where the answer matters (dg-475).

a Faraday collector has been built using the bellows and housing of a right angle brass Veeco valve ... The bellows can be moved 1.4 cm in and out, allowing to measurement of the beam current in the [chamber] ... On this screw was glued a 9.7 cm length of [glass tubing] ... [through the] hole was threaded a shielded MDC Vacuum Products KAP3 high vacuum coaxial cable that carried [the signal] ... The long glass tube insulates the collector from ground, while the wire used is shielded coaxial cable to prevent RF voltage from interfering with the current reading. (Fig. 29 caption; the figure annotates the travel as 1.36 cm where the text says 1.4 cm)

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 43

Editorial note, tabletop extrapolation: A valve body is a ready-made vacuum-tight linear feedthrough, so current-vs-radius comes nearly free. The glass standoff and grounded-shield coax address leakage and RF pickup - two major error sources; secondary-electron loss and interception geometry are separate ones, so treat the reading per dg-524/dg-508 before calling it beam current.

The top of the box slopes down, from 7.0 mm to 5.0 mm towards the glass rod

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 44

Editorial note, tabletop extrapolation: A sloped pocket can retain some backscatter but is NOT a substitute for a suppressor: secondary electrons leave at eV energies in all directions, so for quantitative current either bias a suppressor (dg-524's +9 V pattern), verify a current-vs-bias plateau, or carry a stated uncertainty. The thin-foil face acknowledging orbit shadowing is a real consideration for any cup parked in the beam plane.

An extractor system was designed with a negatively charged deflection plate, but the cyclotron also had a Faraday collector that was a small metal plate that could be inserted into the beam. ... The cyclotron was not successfully tested by the publication of Ref [20]

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 18

Editorial note, tabletop extrapolation: The design logic worth keeping: pair any extraction ambition with an internal probe so beam existence is confirmed independently of extraction working. 'Designed' documents intent - the extractor was never demonstrated (the machine never ran), so this is a proposed geometry, not a precedent.

the detector is set to a specific position and the magnetic field is continuously increased. With very specific magnetic fields, there are peaks in the beam current

Wolf & Prechtl, COLUMBUS — A Small Cyclotron for School and Teaching Purposes — THPO001, Proceedings of Cyclotrons2022 (2022) — p. 2

Editorial note, tabletop extrapolation: A B-sweep at fixed frequency is a q/m RESONANCE SURVEY - the cheapest species diagnostic a small machine has, not a full mass spectrometer: state the harmonic number, calibrate the field reading (dg-1428), and resolve the q/m degeneracies and harmonic ambiguities by field-ratio checks or frequency scaling (dg-1422/dg-1423) before naming species.

the two-day workshop can also analyse other peaks e.g., the peaks that correspond with the third or fifth of the nominal velocity.

Wolf & Prechtl, COLUMBUS — A Small Cyclotron for School and Teaching Purposes — THPO001, Proceedings of Cyclotrons2022 (2022) — p. 2

Editorial note, tabletop extrapolation: When a field-sweep spectrum shows unexplained minor peaks, check near ONE-THIRD and ONE-FIFTH of the main peak's field (f_RF = h*f_c, so B_h = B_1/h for the same species - lower field, not higher) as the odd-harmonic hypothesis, alongside contaminant-species and instrument checks; a matching position is a candidate assignment, not proof (dg-502's discipline).

The aim of this project is to deflect the ion beam and guide it through a Wien Filter to measure the speed and energy of the ions.

Wolf & Prechtl, COLUMBUS — A Small Cyclotron for School and Teaching Purposes — THPO001, Proceedings of Cyclotrons2022 (2022) — p. 3

Editorial note, tabletop extrapolation: A Wien filter is a realistic first external beamline element for a low-energy machine: it measures VELOCITY directly and yields energy only once the species is known (or paired with a separate analyzer) - which is exactly why it also cross-checks species assignments. It needs crossed electric AND magnetic fields; at keV energies both are modest, but 'electrostatic-only' it is not.

a linear translator was developed in order to move the detector, a Faraday-cup in a radial direction behind the dummy dee. In addition to the registered ions the corresponding x-position of the cup is measured, too … The ion source is located at position (-15, 5, 0) (all figures in mm), a Faraday-cup as an ion detector moves along the line y = -31 mm, the so-called sensor-line. This line extends parallel to the lower edge of the dummy dee with a distance of about 1 mm.

Wolf, Rueß & Prechtl, Simulation and Detection of the Helical Ion-Paths in a Small Cyclotron — MOB02, Proceedings of Cyclotrons2016 (2016) — p. 1, 2

Editorial note, tabletop extrapolation: A radially scanned cup with simultaneous position readout turns a single detector into a turn-structure probe, giving I(x) profiles that can be compared point-by-point against a simulated orbit bundle.

If B = 66 mT, the simulation predicts a set of closely spaced trajectories of H2+ - ions that have 1/5 of the maximum possible speed. This meets the corresponding measurement

Wolf, Rueß & Prechtl, Simulation and Detection of the Helical Ion-Paths in a Small Cyclotron — MOB02, Proceedings of Cyclotrons2016 (2016) — p. 3

Editorial note, tabletop extrapolation: This sharpens the false-beam trap for I(B) sweeps on hydrogen machines: a strong cup signal at an unexpected field may be partially accelerated H2+ on closely spaced slow orbits, and a first-turns simulation predicts where such impostor peaks should appear. Treat the simulation as one hypothesis, not a verdict - a Faraday cup is not species-resolving, so confirmation needs a q/m-dependent field-frequency scan or another species-sensitive check before a peak is accepted or discounted.

In the corresponding plot one can see how close the orbits are to each other. So it is obvious that at an Intensity-Plot I = I (x) in reality will be an almost continuous chart as shown in Fig. 6. This is qualitatively confirmed by the model, too.

Wolf, Rueß & Prechtl, Simulation and Detection of the Helical Ion-Paths in a Small Cyclotron — MOB02, Proceedings of Cyclotrons2016 (2016) — p. 3

Editorial note, tabletop extrapolation: Absence of clean turn separation in a radial probe scan is not by itself evidence of a fault: when turn spacing is small against beam width and probe resolution, a smeared continuous profile is the expected signature - though phase and energy spread, emittance and detector response smear it further.

In this experiment the beam is measured in dependence of the magnetic field at a fixed position of the detector. Here one can identify the ions in the beam … The Spectrometer-Plot (Fig. 8) shows the caluculated probability as a measure for the beam-current vs. the magnetic field and allows to simulate this experiment.

Wolf, Rueß & Prechtl, Simulation and Detection of the Helical Ion-Paths in a Small Cyclotron — MOB02, Proceedings of Cyclotrons2016 (2016) — p. 3

Editorial note, tabletop extrapolation: A fixed-cup B-sweep is a species diagnostic using hardware a small hydrogen machine already carries, separating proton from molecular-ion contributions; simulating the sweep first tells the operator which peak to expect where. The assignment rests on rigidity plus the assumed charge and energy, so overlapping peaks can stay ambiguous.

Three probes at 120 degrees apart can be used for beam detection ... Particles emerging from the accelerator are detected using a microchannel plate detector

Clark, Halbach, Kunkel, Leung, Li & Young, A Compact Permanent Magnet Cyclotron for Accelerator Mass Spectrometry — Proceedings of Cyclotrons'95, Cape Town (1995) — p. 1

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: multiple azimuthally separated probes let orbit-centering errors be reconstructed rather than inferred from one radial scan — given radial or position data at each azimuth; worth reserving the flange positions even if only one probe is built at first. A microchannel plate is a single-particle-class detector, suited to beam currents far below Faraday-cup sensitivity.

A sensitive electronic microammeter was connected directly between the target and ground, and its reading was taken as an indication of the relative number of protons hitting the target per unit time. The maximum beam current of this machine is about two microamperes. The second and probably more reliable method was to use a Geiger counter to measure the reaction counting rate from the Li7(p,γ)Be8 reaction occurring in the lithium target. The reaction rate is proportional to the beam intensity. The measured beam current has been found to be proportional to the counting rate but only an approximate indication of absolute beam current. The maximum counting rate was about 1500/min against a background of about 20/min ... the data from the beam current indicator served mainly as a check

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 2, 3

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: a nuclear-reaction counting rate is insensitive to the secondary-electron and leakage-current artifacts that plague bare target-current readings — the source itself found current only approximately proportional to count rate. A GM tube on a lithium target makes a cheap second, independent monitor where the rate is statistically significant for the actual current, geometry and detector; the Li7(p,γ)Be8 reaction is exothermic, its yield dominated by the strong 441 keV resonance (the source's 'threshold' wording on p. 488 is loose), and its ~17 MeV capture gammas are the same reason this reaction carries shielding obligations.

The magnet current was determined with a Type K potentiometer operating across a 0.0005 ohm manganin shunt. The center magnetic field (B0) was accurately correlated with the magnet current by means of a nuclear resonance gaussmeter. All field measurements were accurate and reproducible to better than four gauss out of 17,000.

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 3

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: current-based field setting calibrated against an absolute probe remains the economical pattern — run it with a fixed ramp/history procedure and periodic probe rechecks, since hysteresis, magnetic history, temperature and supply drift all move the current-to-field calibration. This 1961 undergraduate machine got few-gauss reproducibility from a shunt, a potentiometer and an NMR probe.

The frequency (f1) of the cyclotron r.f. supply was measured to five significant figures with a BC-221 frequency standard. The BC-221 was periodically calibrated against the frequencies of the radio station WWV.

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 3

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: frequency metrology by transfer from a broadcast standard, achieved with surplus gear. Modern counters exceed this trivially, but the lesson stands — calibrate the frequency reference and treat frequency as the best-known quantity in the resonance relation. Derive the accuracy actually needed from the allowed accumulated phase slip, and remember absolute field/energy bookkeeping needs the field map and orbit geometry too, not frequency alone.

The variable frequency oscillator was tuned to the resonant frequency (f1) of the dee-box, and the r.f. supply adjusted to produce a peak voltage of 10 Kv from dee-to-dee ... The target radius (r2) was fixed, and the beam tuned in by varying the center magnetic field strength (B0). Beam intensities were determined for different values of B0 within the tuning range of the beam. This procedure was repeated for various values of r2 between six and eleven centimeters.

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 3

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: sweeping B rather than f leaves the RF system at its tuned point, and the field sweep costs nothing but magnet-supply adjustment — on machines whose magnet is adjustable at all (a fixed-PM machine has no such knob). The intensity-versus-field curve at each probe radius is the fundamental commissioning dataset for a fixed-frequency, adjustable-field machine; families of curves at several radii help localize losses when combined with source-output normalization and independent diagnostics — they do not by themselves separate central-region loss from phase slip, source drift or vertical loss.

The vertical range of the beam was measured at different radii by the direct observation of the glow produced when a target coated with RCA 33-Z20A phosphorous was bombarded by the protons ... At present a program is in progress to determine the vertical excursions of the protons by employing nuclear emulsions to "photograph" the beam and to determine its energy and energy spread

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 3, 6

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: a phosphor-painted probe face is about the cheapest beam-position and beam-height diagnostic available where the current makes enough light — qualitative, interceptive, and to be read remotely (a camera through a viewport, not an eye near an operating machine). Nuclear emulsions, or their modern equivalents (radiochromic film, phosphor imaging), are the quantitative upgrade path, and need calibration before yielding beam size or dose. The source's own height study, run before the field was adequately regulated, was explicitly 'only qualitative'.

The magnetic field (B1) at which the ions are in exact cyclotron resonance at the r.f. supply frequency (f1) is given by the cyclotron resonance equation, B1 = 2πmf1/e (MKS units) ... The difference between the actual center field value (B0) and the field B1 at some larger radius r1 is defined as the tune-down (δB): δB = B0 − B1 ... Fig. 2 shows that with r2 less than 8 cm, δBm is observed to be zero. As r2 is increased, the peak of the resonance curve (Bm) is seen to shift to the right and δBm increases. This shift is in agreement with theory and is due to the drop-off of the magnetic field strength with increasing radius ... [Figure 2 axis label:] B1=16,830 gauss

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 3-5

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: tune-down versus probe radius is a beam-based check on the integrated field profile — how much extra center field the ions need to stay near resonance out to a given radius. Compared against a curve computed from the field map with an orbit-and-phase model (RF-frequency error, injection phase and centering included), it is an end-to-end consistency check of field survey plus orbit model, not a standalone field measurement. The source itself rates δBm as less well established than the curve widths, with uncertainties over ten percent possible from reading Bm off the graphs.

The experimental measurement of the width of the resonance curve shown in Fig. 2 was the most accurate part of the program. The curves were reproducible, and the maximum error in their widths amounted to only a few per cent. The value of δBm is not so well established as is the resonance curve width. The small magnitude of δBm coupled with an error of several gauss in determining Bm from the graph could produce uncertainties of greater than ten per cent.

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 6

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: quantities defined as small differences of large numbers (peak field minus resonance field) inherit gauss-scale absolute errors as tens-of-percent relative errors. Design commissioning measurements around widths and ratios where their component errors are controlled, propagate uncertainties explicitly, and treat peak-location-based quantities as soft — repeated fits beat single graph readings.

The study of the beam height was carried out before the magnetic field was adequately regulated, and the results are only qualitative ... The experimental measurement of the width of the resonance curve shown in Fig. 2 was the most accurate part of the program. The curves were reproducible, and the maximum error in their widths amounted to only a few per cent.

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 6

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: field-supply regulation bounds every beam measurement made through a field sweep — verify that field stability is small against the required measurement uncertainty before quantitative field-sensitive scans. Data taken before the supply is stabilized will likely have to be repeated.

The resonance curves have ions of greatest positive phase contributing to the extreme right of the curve, while ions of least positive phase contribute to the left of the curve ... Ions of least positive phase should be lost as r2 is increased. This is shown experimentally by the gradual shift to the right of the left-hand side of the curves with increasing r2.

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 6

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: the shape and edge motion of intensity-versus-field curves at successive radii encode which phase groups survive — information obtainable with nothing but a probe and a field sweep, read through the orbit model's phase convention. It is a model-mediated diagnostic: check source stability and rule out aperture, centering and transport changes before reading edge motion as phase acceptance.

The difference can be accounted for by the absorption of the aluminum foil covering the NaI crystal, and also by the fact that most of the N13 atoms are located below the surface of the carbon

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 10

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: window and source-layer energy loss can significantly bias an MeV-class endpoint measurement — model each layer's areal density between source atom and scintillator, alongside detector resolution, calibration and backscatter, before doubting the physics. Listing the absorbers explicitly is the difference between a validated measurement and a shrug.

The gradient, ∂B/∂r, of the magnetic field of the ISU cyclotron was measured with the field and gradient meter developed by Thoburn (5). The magnetic field, B, was obtained by numerical integration of this gradient.

Mueller, Proton Orbit Calculations for the Iowa State University Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 492–501 (1961) — p. 5

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: orbit quantities (focusing, phase slip) depend on the gradient, and numerically differentiating a noisy point-by-point field survey amplifies error — measuring the gradient directly, or fitting before differentiating, is the robust order of operations for gradient-dependent quantities. The integration to B(r) needs an absolute anchor (a calibrated field value at some radius) and accumulates probe baseline and spacing errors, so check the integrated map against independent absolute-field measurements. A two-coil differential probe is buildable at hobby scale.

Insulation resistance testing: The insulation resistance between the coil terminals and mandrel using minimum voltage of 1kV DC shall be measured and noted. Insulation leakage current testing (HiPot Testing): DC voltage of 1 kV shall be applied between coil terminals and mandrel for one minute and the leakage current shall be recorded. The main coils shall be hi-pot tested at 1 kV DC for 1 minute, and it should have less than 1µA leakage to the yoke ... Coil resistance and inductance measurements shall be made with a micro-ohmmeter resistance bridge at room temperature, with the coil temperature uniform throughout and steady state conditions prevailing.

IUAC, e-Tender 09/GOR/2024–25 — H-Dipole Water-Cooled DC Electromagnet for the Table-Top Cyclotron: Engineering Specification and Acceptance Tests (2024) — p. 27

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: concrete pass/fail numbers for magnet-coil insulation testing — 1 kV, one minute, under 1 microampere — as one lab's acceptance criteria. The method transfers; the voltage does not automatically: select proof voltage from the coil's working voltage, insulation system and an applicable standard, and treat any hipot test as hazardous work — current-limited rated equipment, guarded connections, controlled ramp and dwell, and discharge before touching. Run it before the coil is bolted into an expensive yoke.

The excitation curve (measured magnetic field versus current) of the electromagnet should be measured from 0 to maximum current of 220 A (10% higher than the nominal value of 200 A) at a step of 10 A, keeping the Hall probe positioned in the median plane of the magnet, at the centre of the pole. This excitation curve should be recorded at each excitation level of the current and the measured magnetic field.

IUAC, e-Tender 09/GOR/2024–25 — H-Dipole Water-Cooled DC Electromagnet for the Table-Top Cyclotron: Engineering Specification and Acceptance Tests (2024) — p. 13, 26

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: the transferable protocol is the shape, not the numbers — sweep in defined steps to a test current the design's ratings explicitly allow, probe fixed at a defined reference point, every level recorded with temperature and cooling conditions. Read saturation from the change in slope dB/dI of the recorded curve, not from an assumed percentage overhead; driving another magnet 10 percent past nominal without checking coil, cooling and supply ratings is not part of the method.

Field mapping in the median plane of the magnet should be carried out. Homogeneity of the magnetic field at different radial and angular positions w.r.t. the central field (B/B) shall be measured and compared with the results obtained using simulations. Deviation in the parallelism of the pole faces, deviation in the horizontal positions of (top and bottom) pole centres beyond the limit of the tolerances would be directly reflected by the loss of symmetry in the measured data of the magnetic field on the either sides of the pole centre.

IUAC, e-Tender 09/GOR/2024–25 — H-Dipole Water-Cooled DC Electromagnet for the Table-Top Cyclotron: Engineering Specification and Acceptance Tests (2024) — p. 43

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: treats the field map as a mechanical diagnostic, not just a pass/fail check — left/right asymmetry about the pole centre points to gap or centring errors before any disassembly, and comparing the measured map to the simulation closes the loop on the field computation the design was based on. Asymmetry is not a unique signature, though: rule out probe alignment and mapping-coordinate errors (repeat maps, reversed scan directions) before blaming the iron.

The magnet coil shall be excited using with rated current for 24 hours to achieve the maximum field of 1.2 Tesla for long term stability ... The long term temperature stability of the coils (48 hours) should be monitored together with the magnetic field to ensure no variation in the magnetic field is observed. Safety interlocks for testing the temperature sensors should be confirmed ... The local hot spots, evidence of overheating and other faults during the testing shall be recorded.

IUAC, e-Tender 09/GOR/2024–25 — H-Dipole Water-Cooled DC Electromagnet for the Table-Top Cyclotron: Engineering Specification and Acceptance Tests (2024) — p. 26, 43

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: couples thermal soak testing to field measurement — coil heating can move the field through gap-geometry changes and through supply-regulation limits (a current-regulated supply removes the resistance path but not the geometric one), so stability is proven with field and temperatures logged simultaneously. The transferable method is concurrent logging with staged current increases; set soak durations from the coil's measured thermal time constants and equipment ratings rather than copying 24/48 hours, and have fault protection validated before any long unattended run.

Pick-Up calibration has been performed using the Shunt impedance method, HV-HF Probe measurement. X-Ray Measurement via Bremsstrahlung radiation (done for HVDC) is currently in progress. Further testing of closed loop electronics, cooling system implementation, high power amplifier and modifications in the matching network are being currently being done.

IUAC, Annual Report 2024–25, Chapter 3 — Research Support Facilities (table-top cyclotron RF system) — p. 18

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: names three routes to the perennial small-cyclotron problem of knowing the actual dee voltage — circuit calculation from shunt impedance, a high-voltage RF probe, and bremsstrahlung X-rays. Cross-checking more than one is what separates a calibrated number from a nominal one (the reference machine's own dee voltage is exactly such an uncalibrated nominal). For RF fields the X-ray route needs care beyond reading an endpoint — electron trajectories, RF phase and detector response all enter — which may be why the source lists it as in progress rather than done.

Evidence to back up the accusation presented itself when, after a particularly long beam run, a spiraled discoloration appeared on the copper chimney. The discoloration began at the aperture and wrapped in the direction of the beam rotation and with downward pitch as shown in figure 1. The discoloration is taken to be tracks of ions launched during the early portion of the RF phase that were not energetic enough to clear the chimney. It was suspected that the slight vertical asymmetrical geometry of the ion source chimney was the cause of the vertical electric field. In obtaining the order of magnitude of the vertical field a slope of 4.3 degrees was calculated from the spiral track.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 1

Editorial note, tabletop extrapolation: Transferable to a small machine with an internal filament/chimney source: deposits and discoloration on the chimney are a free, retrospective record of where lost early-phase ions went. Photographing the chimney after a long run and measuring the spiral's pitch costs nothing and — as here, where the 4.3-degree track slope fed the field estimate of dg-1638 — can yield an order-of-magnitude number for the parasitic vertical field, PROVIDED the deposit's origin and timing can be argued. It is a track-pitch diagnostic, not a direct launch-angle measurement.

A chimney with three identical apertures was machined, one aperture was in the median plane as is typical of the normal ion source, and an aperture placed 2.5 mm above and below the median plane aperture. In addition to experiencing the vertical electric field the off-plane apertures gave the ions initial betatron amplitudes. The cyclotron was brought up to typical operating values – this time three stacked purple glows appeared fanning into the face of the DEE (figure 3). The intensity of the three apertures declined as they moved away from the filament, as plotted in figure 4. The off-plane sources intensity varied only +/- 7% from the median plane aperture.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 2

Editorial note, tabletop extrapolation: A cheap, highly copyable experiment: one extra chimney with three apertures (median plane, ±2.5 mm) turns the source into a deliberate initial-condition generator, and the glow-intensity profile (Fig. 4) is the control — the off-plane sources matched the median one within ±7%, so survival differences are attributable mainly to optics, at that level of control. Pick your own offsets from your machine's modeled or measured vertical acceptance and the betatron amplitude you want to launch, not by scaling 2.5 mm to your gap.

For instance, the placement of the radially adjustable florescent screen at its present azimuthal location was dictated by practical limitations. By happenstance this position was very close to the azimuthal location of the maximum radial betatron amplitude (turn-to-turn spacing is at its greatest), thus providing the ability to discern the axial betatron motion.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 2

Editorial note, tabletop extrapolation: A design rule worth applying deliberately rather than by luck, as it happened here: put the viewport/screen azimuth where turn-to-turn separation is greatest — that is where individual turns and the vertical oscillation can actually be told apart in a photograph. On a machine with only a handful of usable ports, model or measure the turn-spacing azimuth first and let that decide which port earns the diagnostic.

quickly losses the ability to distinguish the two different betatron paths. For a region of about 1.5 betatron periods (between 185 keV and 325 keV) the fluorescent screen intensity and turn to turn spacing were sufficient to capture an image useful for analysis. Calibration of the horizontal pixels indicates that the horizontal spacing of the two prominent betatron waveforms corresponds to a phase difference of 47 degrees.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 3

Editorial note, tabletop extrapolation: Realistic expectations for photographic beam diagnostics: this image was analyzable for about 1.5 betatron periods (185-325 keV) — below that the glow was too faint, above it the turns crowded together — and within the window a calibrated pixel measurement resolved a 47-degree phase difference between the two launched waveforms. Pixel calibration against a known internal dimension (here the 0.25-inch chimney) is the enabling trick; find your own machine's usable window empirically, since it belongs to the screen, exposure and beam intensity, not the class.

Operation was at 600 watts at 14.90 MHz with a magnetic field of 0.977 Tesla. Plugging this data into the SIMION model we were able to reproduce the following plot (figure 6). […] Peak vertical displacement from the median plane was approximately 9 mm in both measurement and simulation.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 3

Editorial note, tabletop extrapolation: The benchmark pattern to reproduce before trusting a tracker: one measurable, model-independent quantity — peak vertical excursion — agreeing between photograph and simulation at the ~9 mm precision reported (the memo states no uncertainty, so no stronger agreement claim is available). Note 14.90 MHz and 0.977 T are the proton fundamental (h = 1), a clean operating point; a machine at ~0.6 T sits near 9 MHz for the same harmonic (computed here).

A series of images were taken at differing RF input power levels. The ion beam's radius was calculated by using a calibration of the images pixels against the 0.25 inch diameter of the chimney. The initial energy of the ions (protons in this case) was determined from the calculated radius, magnetic field and the mass; and was then plotted as a function of input power. Twice the energy data was plotted against previously quoted peak-to-peak DEE voltages.[6] There is strong agreement with the older data; a slight increase in DEE voltage for a given power is seen – this is attributed to improvement in the Q from reworking the RF matching box.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 5

Editorial note, tabletop extrapolation: An independent, non-electrical dee-voltage calibration for any machine with a viewport — valuable precisely because divider and probe measurements are the usual error source at this scale. The physics of the factor of two, stated correctly: the imaged initial arc follows the FIRST gap crossing, so its radius measures the energy qV_peak; doubling converts V_peak to the peak-to-peak voltage the older rectifier data quoted. Identify which turn you are imaging and know the local field before applying it. Fig. 13 shows the resulting curve out to ~1400 W forward power against a theoretical curve with Rs = 0.8 Ohms.

Running the cyclotron with supplemental pumping, the hydrogen gas flow was increased to the point where the primary beam can be visibly seen via recombination. […] Figure 12 shows an intense beam spiraling to the left and downward while operating at 600 Watts. The beam is terminating at the leftmost portion of the chimney base. Secondary electron emission can be noted by vertical striations observed emanating from the ion beam's impact location.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 5

Editorial note, tabletop extrapolation: A deliberately dirty operating mode used as a diagnostic: with supplemental pumping in place, over-gas the chamber until the beam glows by recombination — this machine photographed an intense spiral (600 W) terminating on the chimney base, with secondary-electron striations marking the impact point. On a machine with a diffusion pump and an MFC the trick is free to try; whether YOUR beam becomes visible depends on gas excitation, optical access and background light, and the glowing trace is the beam path, not necessarily a single identified turn.

Presently proton beam currents of order 20µAmps can be focused onto the collector. The increased beam power has been duly noted; it is now sufficiently high to damage the Radeline fluorescent screen. The screen has blistered and no longer fluoresces near the median plane, rather glowing embers can be seen. […] Not directly pertaining to ion production, but worth mentioning is the installation of a reset-able minutes meter to track filament lifetime. Filament lifetime is presently the limitation in operating time.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 6

Editorial note, tabletop extrapolation: Two limits this machine hit that yours should be budgeted against, not assumed: its ~20 µA focused beam blistered the Radeline fluorescent screen at the median plane (screen survival is a power-density question — evaluate deposited W/mm² for your own screen, keep screens replaceable, and use a Faraday cup for anything quantitative), and its operating time was bounded by filament hours, tracked with a resettable minutes meter — a trivial addition that turns a nuisance into data and tells you whether filament life is YOUR limiting consumable.

Since this was much larger than the entering ion's radius of curvature of 4 inches, ions that entered the un-energized channel would impinge on the septum and quickly be lost, certainly unable to traverse the length of the channel. High voltage (HV) applied to the electrode generates a deflecting transverse electric field. Only an appropriate negative electric field will partially negate the magnetic field's bending force permitting the successful transmission of ions. A greater field will cause the ions to terminate on the deflector and be lost, and a lesser field will cause the ions to terminate on the septum, only ions of the correct q/m ratio and velocity will be permitted completely through the channel to be successfully detected.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 1

Editorial note, tabletop extrapolation: A useful commissioning property: with the channel un-energized the direct orbit ends on the septum, so ramping HV from zero and watching a signal grow is strong evidence you are steering real beam. Suppressed direct transmission is not a null instrument, though — scattered ions, secondaries, light leakage and pickup can all reach an exit detector, so take an HV-off background and shield the optics before crediting counts to extracted beam. The same geometry is what lets the channel double as a velocity/q-over-m filter (dg-1673, dg-1675).

It might be expected that the combined effect of the cyclotron's resonant acceleration and our embedded Wien Filter's velocity selection might separate the mass ambiguity. However, this is not the case, as the cyclotron itself acts a velocity filter at each of its radii. […] It also holds that at any given radius, both the deuterium and helium cover the same angular distance and thus must have the same angular velocity to keep in step with the oscillating RF voltage. Now it is easily seen that the velocity of either deuterium or helium will be the same at the entrance to the deflection channel. Note, while the two ions have the same velocity, they obviously do not have the same energy.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 2

Editorial note, tabletop extrapolation: Directly relevant to a hydrogen-fed tabletop machine, where the contaminant species of interest are H2+ and H3+ rather than deuterium and helium: an internal E x B channel will separate q/m = 1 from q/m = 1/2, but will not distinguish two species sharing a q/m. Species identification has to come from elsewhere (gas fill, source chemistry, or a downstream detector), a limit worth knowing before building the channel as a diagnostic.

Due to the extremely small geometry and cost of custom manufactured phosphor screens, we elected to produce our own screens. Mastering this technique has proven invaluable, allowing experiments with many different phosphors and target arrangements. […] Initially phosphor type P-22 green, the standard oscilloscope CRT phosphor, was used for maximum visual sensitivity. Using a settling technique, 1-inch square metal plates were coated with a uniform phosphor layer. The phosphor coated plate was attached to a metal carrier plate using electrically insulating screws – the phosphor plate was separated from the carrier plate by 1/8-inch to keep the capacitance reasonably low. … The screen was mounted at a 45° angle with respect to the incident beam and to the axis of a glass view port.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 4

Editorial note, tabletop extrapolation: Squarely a tabletop technique — custom screens at this size are disproportionately expensive, and settling powdered phosphor onto a 1-inch plate is small-scale bench work: treat the powder with respect (SDS, containment, no food surfaces). "P-22 green, the standard oscilloscope CRT phosphor" is the authors' description. The Fig. 7 caption enumerates what mastering the process enabled: directly coated carrier plates, solid plates on isolation plates, six identical strips, edge and central fiducial markings, and test strips carrying six different phosphors.

The center conductor of a coaxial cable was connected to the phosphor plate and the coax shield to the grounded carrier plate, the cable was routed to a BNC vacuum feed through connector. The electrical isolation and connectivity permits the phosphor plate to double as a Faraday collector. The low capacitance of the collecting plate should permit time-resolved electrical measurements of the impinging beam.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 4

Editorial note, tabletop extrapolation: Excellent value on a port-starved machine: one feedthrough and one insulated plate serve as viewing screen AND current collector. Two honesty limits: the electrical reading is NET collected current (secondary emission, charging and leakage bias it — suppress or calibrate before quoting microamps), and the time-resolved capability is the source's stated expectation from low plate capacitance ("should permit"), with real bandwidth set by the whole readout chain. The fiducial markings on the screen edges (Figs. 7 and 8 captions) are what turn the glowing spot into a position number.

Initial beam measurements were performed with the cyclotron operating at an RF frequency of 14.900 MHz at 400 watts input power and magnetic field of approximately 1 Tesla (the magnetic field is adjusted for maximum beam current on the original adjustable faraday collector). Once beam was established, the adjustable faraday collector was fully retracted, allowing the accelerated beam to encounter the entrance slit of the deflection channel. The deflector HV supply was slowly ramped while observing the phosphor screen. A clearly visible green spot appeared on the left most edge of the phosphor screen, and continued to move towards the right with increased HV until the maximum limit of the power supply was reached.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 5

Editorial note, tabletop extrapolation: A copyable extraction-TUNING order (not a full commissioning procedure — interlocks, remote observation and radiation monitoring are separate obligations): establish and optimize internal beam on the existing movable collector first, retract it, then ramp the deflector slowly with the phosphor screen as the live indicator. Separating the two optimizations matters on a small machine where field tune and deflector voltage are interactive. (The quoted passage begins on p.5 and its closing sentence is on p.6.)

The magnetic field was then approximately halved, 0.44 Tesla, and the measurements repeated. The RF frequency was held fixed at 14.900 MHz. The deflector voltage was stepped in 0.5 kV increments and a photograph of the phosphor screen was taken. Vertically stitching the sequence of images reveals the admittance of two different ions. Given the deflector voltage and magnetic field strength, the q/m values were determined. Accounting for the deflection voltage, analysis of the lower beam spot, centered at 6.0 kV, shows a q/m of 1.0 – the signature of a proton, H+. … A similar analysis was performed for the peak observed at 3.0 kV, corresponding to an ion with q/m of ½, such as 2H+ or 4He++.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 6

Editorial note, tabletop extrapolation: A genuinely cheap species diagnostic: a voltage step, a camera, and image stitching replace a dedicated spectrometer, with the 2:1 deflector-voltage ratio giving RELATIVE q/m directly. The source's own hedge carries the limitation: equal-q/m species (2H+, 4He++, H2+…) are indistinguishable by this measurement alone, and absolute identification still leans on the field and geometry calibration. Fig. 11 shows the resulting strip from 1.5 kV through 8.0 kV in 0.5 kV steps.

For the 12-Inch Cyclotron values, V=28 kV, ρ=4.125 inches, d=0.31 inches, ∆ρ=2.757 inches, εr=0.118 inches, we arrive at a ∆T=25 keV for a nominal 500 keV proton beam, a 5%. The resolution will be worse than this figure, as the entire entrance slit is admitting ions, which may have an angular component as well. These effects will be thoroughly studied in a future deflector document.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 7

Editorial note, tabletop extrapolation: For anyone whose internal deflector doubles as an energy diagnostic: apply the formula to YOUR channel — the ~5% here belongs to the listed Rutgers parameters, and the authors themselves call it optimistic (finite slit, angular spread). Worked checks: T_nom = (28 kV × 4.125)/(2 × 0.31) × (1 + 4.125/2.757) = 465 keV, consistent with the quoted nominal 500 keV; and subtracting the paper's own printed T+ and T− expressions yields a 2·εr factor and 24 keV, where the printed combined ΔT expression reads "1 +" — an apparent typesetting slip for "2", flagged here with both computations shown.

A high-voltage electrostatic beam deflection channel has been designed, constructed, and commissioned in the Rutgers 12-Inch cyclotron. A 500 keV proton beam has successfully been intercepted at it's nominal cyclotron radius of 4.0 inches and brought a radius of 4.5 inches in 43° of azimuth. This project has provided the experience necessary to confidently design an extraction channel for the 19-Inch cyclotron project. … [Figure 10 caption:] First image of 500 keV protons on phosphor screen.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 7

Editorial note, tabletop extrapolation: Read the achievement precisely: internal deflection onto a screen 0.5 inch further out in radius — not extraction from the chamber. For a small-machine builder that is the right first milestone: it proves the channel geometry, the HV system and the diagnostic before any attempt on the fringe field (the 19-inch extraction intent, dg-1676, is the stated next step).

An IEEE-488C GPIB interface has been purchased for the Bertan HV 205A-50N power supply, enabling remote computer control. There is a planned project to automate the sweeping of the cyclotron magnetic field and HV deflector while recording the beam current, effectively turning the cyclotron into a very sensitive accelerator based q/m spectrometer.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 5

Editorial note, tabletop extrapolation: Stated as a plan, not an achievement. The idea is well matched to a tabletop machine that already has a current-collecting screen: a two-axis sweep of field and deflector voltage recorded against collector current turns the manual photograph-stitching method (Fig. 11) into a quantitative spectrum with no new hardware in the vacuum. Modern equivalents of the GPIB link are trivial by comparison.

In order to achieve this difficult goal, a Hall probe was mounted on a platform that was threaded onto a long screw (~12 in.) whose motion was driven by a computer-controlled stepper motor. This entire unit was set upon three adjustable “leveling” screws protruding from an aluminum mounting fixture secured to the bottom pole of the magnet. An aluminum fixture was used as not to distort the field and likewise the measurement. The three leveling screws allowed adjustment to ensure the probe’s travel in the median plane.

Koeth, Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans (c. 2005) — p. 3

Editorial note, tabletop extrapolation: A buildable field-mapper: one lead screw, one stepper, three leveling screws, an aluminium fixture — with the craft detail being the three-point leveling, which keeps the scan at the intended median-plane HEIGHT (off-plane travel samples Bz at the wrong z; Br contaminates through probe tilt and cross-axis sensitivity, not height per se). The nonmagnetic rule extends past the plate: ordinary screws, lead screws and steppers are commonly ferromagnetic, so qualify every part near the gap or keep the motor remote, as any probe carrier near a 0.5-1.2 T gap demands.

The Hall probe was connected to a Gauss meter whose analog recorder output was the input for a multimeter. The output of the multimeter was fed into a data acquisition unit, and the number of steps taken by the motor was read by the computers serial port. A LabView program wrote the gaussmeter’s value and probe’s position into a text file. The gauss meter was calibrated against a very well known NMR magnet, and a precisely located “magnetic needle” gave the probe’s position calibration.

Koeth, Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans (c. 2005) — p. 3

Editorial note, tabletop extrapolation: Two calibrations, not one: absolute field against an NMR reference, and probe POSITION against a precisely located magnetic needle. Field calibration alone leaves the scan's radial origin unknown — and the interesting structure (taper, edge roll-off, n(r)) is all position-referenced. The magnetic-needle trick is cheap and is the same idea this group later industrialized into the coil-wrapped iron-needle field bumps of the 2011 AVF study.

Linear Fit to Tapered Pole Tips' B-field at 3 Coil Currents ... y = -0.0039x + 1.1624 R² = 0.9846 ... y = -0.0033x + 1.029 R² = 0.9846 ... y = -0.0025x + 0.7587 R² = 0.9862 ... Fig.1 Radial measurements at three different magnet currents: 20, 30, & 40A

Koeth, Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans (c. 2005) — p. 3

Editorial note, tabletop extrapolation: Hard numbers for a real 12-inch H-frame's excitation curve: about 0.76 T at 20 A, 1.03 T at 30 A, 1.16 T at 40 A — the tesla-per-amp halving between steps (0.0271 vs 0.0133 T/A) is THIS iron's saturation announcing itself. Computed honestly with P = I²R at fixed resistance: the 30→40 A step buys its 0.133 T at about 2.85× the incremental copper power per tesla of the 20→30 A step (700R/0.133 versus 500R/0.271). The fit slope is the normalized radial FIELD gradient, about −0.34% of central field per inch at 40 A — not the physical pole-taper angle. Where another magnet's payback ends is its own B(i) curve's business. (Fit values and R² read from the rendered Fig. 1; the 20/30/40 A assignment follows the curve intercepts, since the printed legend order is 30, 20, 40.)

As shown in Figure 13 the profiles of the measured field and the modeled field are precisely matched in the region utilized for acceleration. This is an encouraging result, as pointed out earlier; the measured field profile followed a single line directly facing the magnet, while the modeled profile followed a single line 90o azimuthally from the measured path. If there was to be a discrepancy between the measured and modeled data, it would have been expected to be at a maximum difference between these two paths. A discrepancy does become pronounced at a radius greater than 6-inches, the “lower” strength field is the measured field. This is just as one would expect, as the measured path does does not have a vertical yoke piece to coral in the field lines, and thus they leak out easier.

Koeth, Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans (c. 2005) — p. 6

Editorial note, tabletop extrapolation: A validation result with a built-in lesson about where the comparison stops being fair: measured (open-side azimuth) and modeled (yoke-side) profiles matched precisely inside the acceleration region and split beyond 6 inches, the open side reading lower — no yoke there to corral the return flux. Practice for an H-frame: take scans at several azimuths, compare like against like where possible, quantify residuals, and EXPECT 2-D/3-D disagreement in the fringe — interior agreement on one cut is encouraging, not proof.

Poor beam intensity motivated our search for an undesired azimuthal variation of periodicity two, which resulted in the 2-D Bz-field measurements of the weak focusing field shown in Figure 2. Since no detectable azimuthal variation was found, our quest to improve the beam intensity led us in other directions, including the ion source. [7]

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 3

Editorial note, tabletop extrapolation: A worked example of ruling a suspect out: disappointing current, a plausible magnetic culprit (m = 2 azimuthal error), a 2-D map to test it — and a null result, above the mapper's detection threshold, that legitimately DE-prioritized the field and sent the effort in other directions, including the ion source (where the real gains turned out to live, dg-1728). The transferable discipline is testing the measurable suspect before redesigning anything; a null map does not convict the source by elimination.

The newly written MatLab analysis code plots Bz about a circle of any requested radius in 5° increments – the center of the circle is intuitively chosen. Although the data lies on a rectangular grid, a MatLab provided 2-D linear interpolation routine was used to determine the field at any requested location. ... In the weak focusing case, the magnet center was determined by sweeping the center of the circle first in the x and then the y directions. The standard deviation of the values about the measurement circle was calculated and stored. After a sweep in x or y that included the magnet center, the data was fit to a parabola, from which the minimum standard deviation, i.e. the center locations, could be inferred as seen is Figure 4.

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 3

Editorial note, tabletop extrapolation: A reusable analysis for near-axisymmetric maps: you need not align the probe stage to the magnetic centre — find it afterwards in software by minimizing the azimuthal standard deviation of Bz (sweep the circle centre in x, then y, fit parabolas). The source applies it to the WEAK-FOCUSING case, where azimuthal uniformity is the expectation; on an AVF map the same minimization would chew on real sector harmonics, so centre those maps by fiducials or a symmetry-aware fit (the program's own N-harmonic method, dg-1792). On this magnet the correction moved the centre about half a grid step — (28.0, 27.0) to (28.5, 27.4), read from the rendered Figs. 3-5 annotations — and that half-step separated an apparent azimuthal error from a flat field (dg-1702).

– i.e. evaluation circle. The azimuthal analysis was then repeated, and the results are shown in Figure 5. Clearly each measurement point lies much closer to the average than was depicted in Figure 3. Comparison of the centers determined from the fit, show that the field is axisymmetric to 4 parts in 10,000.

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 4

Editorial note, tabletop extrapolation: Two things transfer: an existence proof — a 12-inch magnet with ground, tapered poles measured axisymmetric to 4 parts in 10,000, so that class of number is achievable — and the warning that an off-centre evaluation circle MANUFACTURES azimuthal signal (for a radially graded axisymmetric field, predominantly a first harmonic, with higher orders from curvature). Before concluding a small magnet has an azimuthal defect, re-centre the analysis (dg-1701) and re-run; this machine's apparent variation vanished exactly that way.

Our group custom designed and built a computer-controlled stepper-motor driven X-Y stage which utilized zero-backlash acme threads to sweep a magnetic field probe through the median plane. An F. W. Bell 7010 hall probe based gauss meter was used for the AVF measurements; the gauss meter was outfitted with an RS232 data port. The computer program which controlled the X-Y stepper motors also recorded the gauss meter data, fully automating the measurement process.

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 4

Editorial note, tabletop extrapolation: A named, buildable instrument set for a small pole map, with the load-bearing detail being ZERO-BACKLASH acme threads: a serpentine raster reverses direction every row, and lead-screw backlash then puts alternate rows out of registration (scan every row the same direction if your screws are ordinary, or measure the backlash). The meter needs more than a serial port: adequate range, resolution, stability and probe-orientation control, calibrated (this program's NMR-reference practice, dg-1684). The 7010's RS232 port is what let one program drive the stage and log the field together.

A Programmable Logic Controller (PLC) based machine-protection system was implemented to allow safe, un-attended operation of the 12-Inch magnet. In the event of high-temperature condition or a coil cooling-water flow loss for more than 10 seconds, the PLC will slowly ramp the magnet down and latch it off, requiring an operator to reset. The PLC safety system was necessary as the scans could take in excess of 24 hours: a standard measurement grid of 129 x 129 points equals 16,641 measurement points, each measurement required ~ 5 seconds totaling an excess of 23 hours scan time.

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 4

Editorial note, tabletop extrapolation: The source's own practice and thresholds, reported as such: 10-second flow-loss window, slow ramp-down rather than a trip, latching off until a human resets. The planning arithmetic transfers directly — points × (dwell + settle + motion) — and this machine's standard 129×129 map at ~5 s/point is a 23-hour job, which is why the protection exists: budget your own scan time honestly, and if it lands unattended, engineer fail-safe interlocks with a shutdown response derived from YOUR coil's thermal time constant and cooling failure modes, not copied from these numbers.

A result of a of field-bump calibration scan is shown in Figure 9, it also reveals the residual magnetization of the 12-Inch magnet. Four needles were needed to scale both dimensions; the fifth needle was used to break the symmetry, removing orientation ambiguities. The variation of the peak amplitudes indicate the probe was traveling in a plane slightly tilted with respect to the median plane. However, this effect seems to be insignificant in the measurement of actual AVF field. A vertical sensitivity study will be done. … To calibrate the hall probe’s position against the magnet’s mechanical center, magnetized iron needles were precisely placed around the pole tip to create field bumps, one such needle is displayed in Figure 8. The field-bump calibration was performed with the 12-Inch magnet deenergized. A full 2-D scan was completed; peaks found by fitting to the measured field bump were

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 5

Editorial note, tabletop extrapolation: A cheap, precise fiducial method for a field map: coil-wrapped magnetized iron needles placed around the pole tip make sharp, fittable field bumps, surveyed with the magnet DE-ENERGIZED so the main field is absent (the scan still sees the poles' residual magnetization — the same data doubles as a residual-field measurement, and unequal peak heights revealed the probe plane's slight tilt). The five-needle pattern is the craft detail: four for scale in x and y, a fifth asymmetric so the map cannot be mounted rotated or mirrored. Achieved precision is not stated; fit quality on your own bumps decides it.

The Maxwell 3D current was nearly set the same, differences between the two resulting average field reports were aligned by normalizing the simulated data central Bz value to exactly match the measured central value. ... Figure 14. Comparison of measured and simulated average field of the radial sector tips. Good agreement is noted over the range of the ions travel, at most 1% deviation is seen at r=2.5.

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 5

Editorial note, tabletop extrapolation: A quantified model-versus-measurement figure at the target scale, precisely bounded: after normalizing the simulated central Bz to the measured value, the AVERAGE-FIELD SHAPE agreed within 1% over the ion region (worst at r = 2.5 in). That is shape validation, not absolute-excitation validation — and not yet flutter, harmonic or tune validation, which need their own comparisons (dg-1721 does the 2-D map). The 45,000 A-turns for 1 T with these sector tips versus the Poisson model's 30,000 for 1.22 T with solid tips is suggestive of what valleys cost, but the two figures come from different codes and endpoints — measure the penalty on matched geometry before budgeting it. (The 45,000 A-t / 1 T / 0.25-inch-step statements are on p.5; the normalization sentence and Fig. 14 caption are on p.6.)

The off-center equilibrium orbits were experimentally verified using the wire-loop orbit technique.[7] 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. Myriad other stable orbits made it difficult to perform this experiment in the median plane; instead a clear acrylic sheet was placed on the bottom pole tip to provide a flat surface on

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 10

Editorial note, tabletop extrapolation: An outstanding no-vacuum, no-beam diagnostic: a current-carrying flexible loop settles onto stable orbit shapes of a real measured field for the price of magnet wire and a bench supply — a physical check on the tracker before the chamber ever pumps down. Physics to hold onto: the loop obeys T/ρ = I·B, so its effective rigidity is set by tension over current — circumference constrains which closed shapes are available but does not by itself select a particle energy (the source says as much; its extra orbits are the point of dg-1720). Practicalities: the acrylic sheet keeps the loop on a plane (not the median plane — a known offset), and 2.5 A in 30 AWG dissipates real heat, so current-limit, keep the duty short, and mind magnet forces. Setup as run: 30 AWG, 71 mm circumference, 2.5 A.

The energized wire loop simply needed to be tossed towards the gap and it would reproducibly snap to the nearest stable orbit, one such off-center orbit is show in figure 24. An overlay of five loop images demonstrating five stable orbits is shown in figure 25. This technique found another four orbits (for a total of nine) located even further away from the center. Since the wire-loop technique does not discriminate based circumference (only the loop’s tension will vary), the further outlaying orbits are most likely lower energy equilibrium orbits.

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 11

Editorial note, tabletop extrapolation: Interpretation guidance for the wire-loop method: the loop finds the orbit FAMILY, not one energy, so a bench survey should turn up more orbits than any single-energy simulation predicts — here nine against five, with the source judging the outliers 'most likely' lower-energy equilibria since the technique discriminates on tension, not circumference. Treat extra positions as candidates: compare against multi-energy tracking, and check loop mechanics (tension, friction, off-median-plane field) before either assigning an energy or reading a model discrepancy. (The figure references in this passage are off by one against the printed captions — the photographs are Figs. 25 and 26, not 24 and 25.)

Both plots were normalized such that the peak central fields were 1 Tesla – this required at most a 5% adjustment to either data set. Figure 29 subtracts the measurement from the simulation. ... Figure 29. Subtracting the measurement from the simulation reveals 14% discrepancies at the outer pole tip edge. The two agree within 1% in the ion region.

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 11

Editorial note, tabletop extrapolation: The most useful validation figure in this pair of documents, precisely bounded: after each map was normalized to a 1 T central peak (≤5% adjustment either way), the SHAPES agreed within 1% over the ion region and split by 14% at the outer pole-tip edge — cause not identified by the source, with fringe and edge effects the natural suspects but unproven. Budget trust accordingly: normalization means absolute solver accuracy is NOT bounded by the 1%, and the pole edge — exactly where an extraction deflector sits — earned measurement on this magnet and will on yours. (The measurement grid: 1/8-inch step at 30 A, from the rendered Figs. 27-28 plot titles.)

The project slated for Spring 2012 will develop a beam phase measurement probe. This experiment measures the beam arrival time with respect to the RF cycle. Measuring variations in the beam’s arrival time along a radial line is a method of characterizing the field’s isochronism. At the time of this writing, the authors are exploring an FFT based method to derive the radial and axial tune values from the SIMION simulations. Such a method would be quicker in the evaluation of the magnetic field configurations, reserving the tedium of trace space plot generation for only the most promising candidates.

Koeth, Hine, Hoffman, Krutzler, Ponter, Rosenberg, Ruisard & Schneider, Comparison of Azimuthally Varying with Constant Gradient Magnetic Fields with the Rutgers 12-Inch Cyclotron (2011) — p. 12

Editorial note, tabletop extrapolation: Both items are stated as the authors' intent at the time of writing, not results, and should be read as such. The beam-phase-probe method is nevertheless a described technique a tabletop builder can adopt: radial variation in arrival phase is a direct, measurable isochronism error. The FFT tune-extraction point is a workflow recommendation for anyone running an orbit tracker — screen candidate fields by tune, then spend trace-space effort only on survivors.

We normalized the measured field profile for the three different operating currents: 20, 30, and 40 Amperes. Each field profile, as one would expect, had a peak field at r = 0. The data was linearly scaled to bring this peak field to unity. The simultaneous plotting of these normalized profiles, as shown in Figure 2, confirms that the field index's (n's) profile does not vary with field strength, even into the beginning of the saturated régime. This generously allows for just one analysis of the field profile.

Koeth, Hanebuth, Schneider & Hoffman, Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron (2006) — p. 3

Editorial note, tabletop extrapolation: Useful economy for a small-magnet builder: map the pole-tip field at a few excitations spanning the operating point, and if the normalized profiles overlay, one field analysis serves — WITHIN that tested range and magnetic history. This magnet held profile shape from 20 to 40 A, into the beginning of saturation; deeper saturation, hysteresis state or a changed excitation history can bend the profile, so remap when leaving the verified window.

The profiling of the radial dependence of the magnetic field between the pole pieces was executed with a Hall probe mounted on a computer controlled motorized platform. A LabView program wrote the Hall probes value and probe's position into a text file. ... The LANL Finite Element code Possion Superfish's (PSF) [6] output was compared to our measurement. Strong agreement between the McClain & Friedman's measurement with the PSF justified the use of the computer model for further analysis, see figure 3. [3]

Koeth, Hanebuth, Schneider & Hoffman, Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron (2006) — p. 3

Editorial note, tabletop extrapolation: The measure-then-validate-then-model workflow to copy with FEMM or Superfish: the model earns trust for downstream analysis only after a mapped Hall-probe profile agrees with it (here the downstream use included the field-index work of the following sections). Note the source prints "Possion Superfish" (a typo for Poisson Superfish); the quote is transcribed as printed.

It was calculated that the required RF power for the first revolutions of ions to clear the chimney (with the cyclotron operation at 14.900MHz) was 165 watts as plotted in figure 7. [4,7] Confirmation of the ions source model came from establishing beam with 300 watts of RF power and slowing decreasing RF power. Beam intensity decreased with decreasing RF power, but at 170 watts the beam current abruptly dropped to zero.

Koeth, Hanebuth, Schneider & Hoffman, Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron (2006) — p. 4

Editorial note, tabletop extrapolation: A rare validated model-vs-measurement pair at this scale: predicted 165 W first-turn chimney-clearance threshold, measured abrupt cutoff at 170 W. Diagnostic reading: beam that fades then DROPS to zero as RF power falls, near a modeled clearance threshold, is consistent with the first turn striking the source structure — check dee voltage, RF stability, source output and tuning before assigning the cause, since phase-acceptance loss and resonator instability can also end beam abruptly.

This caps thickness was greater than the turn-to-turn spacing of the ion revolutions at a radius greater than 2.1 inches when operating at 14.900MHz with a DEE voltage of 7,500 Vp-p. Such a thick tip would prevent the ions from hitting the sensitive portion of the ion collector, rather the ions would just return to chassis ground. A new, simpler, Faraday cup was installed. It simply consists of an unshielded aluminum block. RF suppression was still a concern, so externally a notch filter, with -100dB of rejection at 14.900MHz, was installed in the Faraday cup line that connects to the electrometer. An RF choke was also installed in this line, just before the electrometer connection.

Koeth, Hanebuth, Schneider & Hoffman, Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron (2006) — p. 4

Editorial note, tabletop extrapolation: A specific, easily repeated mistake: a grounded shield that projects into the incoming beam path intercepts ions before the collector once its effective radial thickness exceeds the local turn spacing — compute Δr(r) (dg-1740) before designing any probe tip. This machine's solution moved RF rejection out of the vacuum entirely (bare aluminum block collector; -100 dB notch filter plus RF choke in the electrometer line); suitably thin or recessed in-vacuum guarding remains an option the memo simply did not need.

We then set the camera to a 15 second exposure and scanned the florescent screen slowly. The resulting image, Fig 10, clearly showed periodic behavior about the median plane with increasing frequency and decreasing amplitude as r increased. This was immediately identified as betatron motion.

Koeth, Hanebuth, Schneider & Hoffman, Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron (2006) — p. 5

Editorial note, tabletop extrapolation: An almost free beam-dynamics diagnostic: a phosphor screen on a manual radial feedthrough plus a long-exposure camera through a viewport records vertical betatron structure across the scanned interval in one frame, no electronics. It is a QUALITATIVE record as taken; a tune number additionally needs calibrated radial coordinates and peak-spacing analysis (dg-1741 is this memo's own worked version).

The radial position of several peaks from the observed vertical betatron motion were recorded: ro = 8.6 cm (338keV) r1 = 9.2 cm (387keV) r2 = 9.6 cm (421keV) Relevant operating conditions: fo=14.8640 MHz (B = 0.977 Tesla) RF power = 300 Watts Magnet Current = 28.28 Amps … Precise “tuning” of the magnetic field yielded a peak beam current reading of 20nAmps.

Koeth, Hanebuth, Schneider & Hoffman, Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron (2006) — p. 5

Editorial note, tabletop extrapolation: A calibrated benchmark set for the 100 keV-1 MeV band: field, frequency, radius, energy and beam current quoted together. The radius-energy pairs are internally consistent with E = q²B²r²/2m at B = 0.977 T (computed check: 8.6 cm gives 338 keV, 9.2 cm gives 387 keV, 9.6 cm gives 421 keV), so they can sanity-check another machine's energy bookkeeping.

Using a fourth order polynomial fit and our equation for ∆r(r) we can create table 1. The first measured peak of the vertical betatron oscillation was at ro = 8.6cm, and we denote that as the start of the betatron period. We then allow one RF period, hence one ion revolution, to process, after which, using our equation for ∆r(r), we reevaluate the new radius and that radius' field index n. It can easily be shown that the fraction that the betatron period advances at a given n is just sqrt(n). … Integer values of fractional betatron periods indicate the full completion of a vertical betatron oscillation. … Noting the radii at which these occur the reader immediately sees the same values that were observed at r1 and r2 as reported in section V.

Koeth, Hanebuth, Schneider & Hoffman, Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron (2006) — p. 6

Editorial note, tabletop extrapolation: A worked piecewise-tracking recipe implementable in a spreadsheet — no orbit code — and checked by its authors against the streak photo: integer betatron periods land at the observed r1 and r2. The tabulated n values over 8.6-9.7 cm run 0.025 to 0.042 (Table 1, read from the rendered page). Table 1 prints 9.2 cm in two consecutive rows (n = 0.031 and 0.033) — most likely rounding of nearby unrounded radii rather than a misprint.

Radial betatron oscillations were not noticed as their period in the regime of low field index n is comparable to that of the ion revolution frequency.

Koeth, Hanebuth, Schneider & Hoffman, Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron (2006) — p. 7

Editorial note, tabletop extrapolation: Expectation-setting for a weak-focusing machine: at small n, νx = √(1−n) is near 1, so radial betatron structure barely advances per turn and hides in a fixed-azimuth screen view — this memo saw none. It is a visibility statement, not an absence: turn-resolved diagnostics or the slow 1−νx beat can still expose radial motion (the program's later precession work, dg-1840, is exactly that physics put to use).

Magnetic maps have been measured using a home-made magnetic measurement table and stepper motors electronics with a digital Gauss-meter. The magnetic centers of the sector focusing pole-tips are identified using a field harmonic analysis on a set of circles with different radii; indeed the non-structure harmonics are minimal at the magnetic center.

Hernalsteens, Ponter, Beaudoin, Koeth, Ruisard & Miller, Betatron Tune Characterization of the Rutgers 12-Inch Cyclotron for Different Magnetic Poles Configurations (2016) — p. 1

Editorial note, tabletop extrapolation: Answers a practical question for any tabletop AVF build: the true magnetic center of a sectored pole-tip set need not be its mechanical center, and a harmonic analysis on circles finds it — the non-structure harmonics minimize at the magnetic center. The home-made stepper table and digital gaussmeter are the hardware the Rutgers group used; the mapping accuracy and harmonic resolution a given magnet needs must be established for that magnet.

The design of the source, a cold cathode Penning Ion Gauge (PIC) source, is reported in Ref. [4]. The aperture is circular with a 0.8mm radius and it can sustain a current of 5mA. A modified source chimney featuring an aperture offset along the vertical axis was built in order to provide a beam with an initial axial offset.

Hernalsteens, Ponter, Beaudoin, Koeth, Ruisard & Miller, Betatron Tune Characterization of the Rutgers 12-Inch Cyclotron for Different Magnetic Poles Configurations (2016) — p. 1

Editorial note, tabletop extrapolation: A spare chimney with a deliberately off-median aperture is a simple, purpose-built way to launch coherent axial oscillations for tune studies — the launch half of the measurement. Extracting a tune still needs adequate transmission and a diagnostic that resolves the oscillation turn by turn (here, the phosphor radial probe). The source prints the acronym "(PIC)" where "PIG" is standard; quote transcribed as printed.

The instrumentation is based on a phosphor coated screen mounted on a radial probe system. The probe is manually displaced along the chamber's radius by the operator. A view port next to the radial probe allows to take images of the beam induced luminescence of the screen with a DSLR camera. The camera is set for long exposure shots (up to 5 seconds) while the operator maneuvers the radial probe. These beams images then feature a vertical and radial 2-dimensional picture of the beam. ... This measurement technique requires to calibrate the beam images to transform their pixel grid into coordinates in the usual frame of reference centered on the central axis of the magnet. To reach that goal, calibration pictures of the radial probe are taken each time a new set of data is taken.

Hernalsteens, Ponter, Beaudoin, Koeth, Ruisard & Miller, Betatron Tune Characterization of the Rutgers 12-Inch Cyclotron for Different Magnetic Poles Configurations (2016) — p. 2

Editorial note, tabletop extrapolation: A demonstrated low-cost turn-by-turn diagnostic: phosphor screen on a linear feedthrough, a viewport, a consumer DSLR on long exposure. The per-dataset probe calibration image is the detail that makes the images quantitative — the source uses it to transform the pixel grid into magnet-centered coordinates. Turn resolution on another machine still depends on its turn spacing, light yield and optics (the source's own dee-voltage tradeoff, dg-1750, is the knob).

The accelerating voltage is adjusted to find a balance between two characteristics of the beam image: if the voltage is not large enough the radial turn to turn separation is too small and one cannot distinguish between two consecutive turns in the beam image, if the voltage is too large then the length of the turn by turn signal is reduced.

Hernalsteens, Ponter, Beaudoin, Koeth, Ruisard & Miller, Betatron Tune Characterization of the Rutgers 12-Inch Cyclotron for Different Magnetic Poles Configurations (2016) — p. 2

Editorial note, tabletop extrapolation: Practical operating guidance for anyone doing turn-resolved imaging on a small machine: dee voltage is the knob that trades turn separation against the number of turns in the field of view. Consistent with the turn-spacing relation Δr ≈ m·ΔE/(q²B²r) for energy gain ΔE per turn (equivalently m·ΔV/(qB²r) with ΔV the effective accelerating voltage) from the same program's 2006 betatron-motion note.

These data were in turn fitted with an harmonic signal using a moving window technique. The fitting technique takes the measurement errors into account: lower weights were associated with the data points corresponding to large beam envelopes, as the determination of the centroid of these data points are not as precise as those were the beam is at a focus. Image-by-image examination of the fit quality showed that the best results are obtained using a 5-point window. That relatively low number of data points allowed to extract frequency information for many radial position as the typical signal length is around 15 turns long.

Hernalsteens, Ponter, Beaudoin, Koeth, Ruisard & Miller, Betatron Tune Characterization of the Rutgers 12-Inch Cyclotron for Different Magnetic Poles Configurations (2016) — p. 2

Editorial note, tabletop extrapolation: Calibration context from the Rutgers analysis: their typical signal was ~15 turns and image-by-image checks favoured a 5-point moving window. On another machine, pick the window by fit residuals and uncertainty (synthetic-signal tests are cheap); the transferable part is the method — error-weighted moving-window harmonic fits with envelope-dependent weights — not the two numbers.

The best linear fit in the measurement range reads νa = (0.086 ± 0.001) + (0.0012 ± 0.001) · (r − 45), where r is the radius expressed in millimeters in the range 45 to 80mm. The 90 % confidence interval is also shown revealing that the measurement resolution is sufficient to confirm the observed linear trend. ... The equation of the fit of the magnetic results (in the beam based measurement range) reads νa = (0.088 ± 0.004) + (0.0015 ± 0.0002) · (r − 45).

Hernalsteens, Ponter, Beaudoin, Koeth, Ruisard & Miller, Betatron Tune Characterization of the Rutgers 12-Inch Cyclotron for Different Magnetic Poles Configurations (2016) — p. 3

Editorial note, tabletop extrapolation: A validated model-versus-measurement pair for a weak-focusing machine in the target class: this machine's field map predicted its beam's axial tune within the measurement errors. For THIS field the fits put νz ≈ 0.09–0.13 over 45–80 mm (n ≈ 0.008–0.02) — comfortably below the n = 0.2 Walkinshaw coupling band that this collection's weak-focusing rules treat as the ceiling (dg-003, dg-138); another machine's margin comes from its own n(r), not these numbers. The printed slope uncertainty (±0.001 on a slope of 0.0012) is nearly as large as the value and looks like a source misprint given the stated 90% confidence in the trend.

It is interesting to note that the measurement technique that we use readily provides a turn-by-turn envelope beating information. This is contrasting the usual case of synchrotrons where that kind of data is not as easily accessible. This provides a second and independent mean of measuring the betatron tune. Indeed it is well known that the envelope beating signal has a frequency which is two times the betatron tune. ... Within the measurement errors the envelope-based result matches very well the centroid-based tune values.

Hernalsteens, Ponter, Beaudoin, Koeth, Ruisard & Miller, Betatron Tune Characterization of the Rutgers 12-Inch Cyclotron for Different Magnetic Poles Configurations (2016) — p. 3

Editorial note, tabletop extrapolation: A free cross-check for a machine already taking streak images: the envelope beats at 2ν, so fitting its modulation gives a second, independent tune number to compare with the centroid fit. One caution the source's comparison sidesteps: with once-per-turn sampling the 2ν component can alias, so fit it modulo the turn frequency and use the centroid tune (or an expected range) to unwrap before halving.

The target, located at the end of a radial probe, is electrically isolated and connected to a BNC vacuum feed through. A short coaxial cable connected the target's signal to the input of oscilloscope's vertical amplifier. With 1MΩ input impedance, a 1µA beam current creates a 1V deflection. The rise time, as well as decay time noted in the beam current (lower) trace of figure 1 is an artifact of the RC response of the measurement circuitry, which utilized a low pass filter to suppress RF pickup from the DEE. The actual ion source current profile is prompt.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 2

Editorial note, tabletop extrapolation: A dead-simple current diagnostic for a pulsed machine: isolated target, BNC feedthrough, 1 MΩ scope input — 1 µA reads as 1 V. Three qualifications before trusting the number: it is COLLECTED current (secondary-electron emission makes it differ from incident beam unless suppressed or calibrated), the pulse must be long against the circuit RC for the trace to reach V = IR, and — the source's own warning — the visible rise and decay edges belong to the RF-suppression filter, not the beam.

The cyclotron was tuned for maximum deuteron beam current on the radial probe, which was set to radius of 4 inches – this is just prior to the beam entrance into the deflection channel.[6] The probe was then fully retracted, allowing the beam to enter the deflection channel. … A deflector voltage of 16 kV placed the deuteron beam onto the phosphor screen, confirming the energy at 250keV. After fine-tuning of the RF and magnetic field the beam's stability was monitored for a few minute period. Neutrons were not detected. ... The radial probe was slowly inserted until neutrons were detected. The target position was adjusted for maximum measured neutron dose rate, which was found to be at a radius of 3 inches, for an inferred energy of 150 keV with a measured beam current of 100nA, as respectively depicted in figures 8 and 9. This was the crossover point of increasing beam energy and decreasing beam current.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 4

Editorial note, tabletop extrapolation: A counter-intuitive operational result: the best NEUTRON position was not the highest-energy position — dose rate peaked with the target at 3 inches (~150 keV, 100 nA), the crossover of rising energy and falling current. Two honesty notes: the maximum is of measured dose rate at a fixed detector, and moving the target also moves the source-detector geometry, so scan radius with geometry-corrected readings and simultaneous target current; and the 250 keV no-neutrons observation was beam-on-PHOSPHOR, not a controlled deuterated-target comparison at that energy. The method — scan the movable target for yield rather than assuming maximum radius — is the transfer. Note the Fig. 9 beam-current axis is labelled microamps while the text quotes 100 nA at r = 3 inches; the axis label appears to be a source misprint and no rule here relies on Fig. 9's magnitudes.

While not as sensitive as the other two tubes, the 12-4 was the primary diagnostic as its BF3 tube was unaffected by the magnetic field and could be positioned arbitrarily close to the cyclotron chamber. The second and third detectors were photomultiplier based detectors; one being a Ludlum Model 42-4 LiF(Eu) scintillator, and the third detector a Ludlum Model 42-2 proton recoil detector. When positioned sufficiently far away from the cyclotron magnet, neutrons were detected by both, however, an approach closer than two feet of the magnet gap either greatly reduced or otherwise extinguished the photomultiplier tube signals.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 4

Editorial note, tabletop extrapolation: Concrete siting guidance from one instrumented machine: its gas-filled BF3 rem-ball worked arbitrarily close to the chamber, while its two PMT-based instruments (LiF(Eu) scintillator, proton-recoil) lost or degraded signal inside roughly two feet of the magnet gap, and its NaI(Tl) spectrometer failed close-in even with a mu-metal shield (sited ~three feet out; that sentence is on p.6). The pattern — gas tubes tolerate fringe field, PMTs suffer — is a sound prior, not a law: test each complete detector-plus-electronics assembly in the actual fringe field before committing to a layout. (The companion 2020 draft ran a 3He tube close-in, its own separate data point.)

At this location the 1.6 cm diameter X 2.5 cm tall BF3 tube was 29.5 cm away from the target. Assuming the most favorable orientation of the cylindrical BF3 tube, the maximum area of the detector is taken to be 4 cm2; the actual effective area may have been as much as one half that, or 2 cm2. Sitting at a radius of 29.5 cm, the tube only intercepted 4 cm2 out of the available 10,930 cm2 4π spherical surface – yielding a geometrical efficiency of 3.7x10-4.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 5

Editorial note, tabletop extrapolation: The solid-angle bookkeeping any yield estimate needs, with its assumptions visible: 3.7e-4 is an upper-bound geometric factor under the most favorable assumed orientation (the source's own 2 cm² alternative gives 1.8e-4 — a factor-two spread the source acknowledges rather than bounds). The arithmetic checks (4π × 29.5² = 10,935 cm²; 4/10,935 = 3.7e-4). A real response number still needs intrinsic efficiency, moderation and angular response on top of geometry.

Several tests were performed to ensure the detectors' response were to neutrons. First, the target was inserted so as to only intercept the low energy deuterons – the detectors ceased their counting. Second, with the target the position of greatest production rate, the ion source was gas starved, beam current decreased as well as the measured neutron dose rate. Finally, the cyclotron's magnetic field was slightly adjusted to break the optimized magnetic resonance acceleration condition, and again the neutron fluence followed the diminishing beam current. … All three detectors responded in unison for the duration of each pulse when operating in RF pulse mode.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 4

Editorial note, tabletop extrapolation: A reusable falsification protocol: every claimed detection should switch off with a beam parameter, three independent ways here. It demonstrates beam correlation — strong support, not proof, since RF pickup can also track tune and beam loading; the remaining discriminators are a calibrated-source response check, an RF-only background run, and moderator/absorber tests. For a machine surrounded by kilowatt RF, this discipline is what separates a count from pickup.

the cyclotron was pushed into its shortest pulsed mode operation yet, with only 230 RF cycles at 7.15 MHz (an RF drive pulse of 30 us duration), which resulted in the generation of a 10us beam-on-target pulse after the 20us ring up time. With such a short pulse duration, the pulse repetition rate could safely be increased up to 200pps (200Hz). Figure 2 shows the RF pulse structures on an oscilloscope with a time base of 10us/div: the upper trace is driving RF pulse, lower trace is actual DEE voltage, note the ring-up-time is due to the high Q of the tank circuit.

Koeth, Gilde & Moroch, Measurement of Neutron Diffusion Time from Fast Pulsed Systems (draft, 2020) — p. 2

Editorial note, tabletop extrapolation: Quantifies the price of a high-Q resonant dee for pulsed work on a tabletop machine: two thirds of a 30 microsecond drive pulse is spent ringing up, leaving 10 microseconds of usable flat top. A builder planning fast pulsed operation must budget the ring-up time explicitly. 230 cycles at 7.15 MHz is 32 microseconds, consistent with the stated 30 us. Draft report. (The quoted passage opens on the last line of p.1.)

The target was position for a nominal 100keV incident deuteron beam energy (r=0.067m). ... When operating in this fast cyclotron-pulsed mode with a 10us duration of beam-on-target time, an average of 5 D-D fusion neutrons were produced. During most cyclotron pulses, these neutrons would completely miss the detector altogether, with approximately 1 out of 250 cyclotron pulses registering a neutron. The likelihood of more than one striking the detector per cyclotron pulse was vanishing small. This was crucial to the measurement.

Koeth, Gilde & Moroch, Measurement of Neutron Diffusion Time from Fast Pulsed Systems (draft, 2020) — p. 2

Editorial note, tabletop extrapolation: Radial target placement doubles as an energy selector: at fixed field the incident energy follows radius (the 100 keV at r = 0.067 m figure checks against E = q²B²r²/2m at the stated 0.96 T — computed ≈99 keV), and yield follows the energy-dependent D–D cross-section. Detected rate also depends on intercepted current, target loading and geometry, so calibrate yield against position rather than assuming it — and the method requires a movable radial probe, which not every machine has. Draft report. (The quoted passage begins on p.2 and continues on p.3.)

After being positioned, the 3He detector was calibrated by placing a NIST calibrated 252Cf sealed neutron source at the face of the deuterated target, thus giving the ability to quantify peak neutron production from the cyclotron during operation. Care was taken not to disturb the 3He detector geometry to maintain the calibration. During a 5 second CW run of the RF at full operating power, the DEE voltage and ion source production rate were adjusted for an average neutron production of 500,000 neutrons per second, which were considered to be isotropic.

Koeth, Gilde & Moroch, Measurement of Neutron Diffusion Time from Fast Pulsed Systems (draft, 2020) — p. 3

Editorial note, tabletop extrapolation: An in-situ absolute-efficiency calibration: a calibrated source at the target face, the detector geometry then left undisturbed. This is the source's own practice and its own reported yield, not a general dose statement — and a ²⁵²Cf spectrum is not a 2.45 MeV D–D spectrum, the source and beam spot are not spatially identical, and D–D emission at finite deuteron energy is not exactly isotropic, so a quantitative D–D yield still needs response and geometry corrections. Draft report.

A preliminary demonstration of the neutron diffusion effect is given by a digital oscilloscope set to infinite persistence which recorded the electronic pulses generated from the detection of neutrons over numerous cyclotron pulse events. … The upper yellow trace in figure 4 is the rectified reference of the actual RF “on time” pulse … The lower blue trace displays the pulses from the 3He detector NIM electronics, which are seen to continue to arrive long after the cyclotron RF is off. After 5 minutes of acquisition at 100 pulses per second a total of 250 neutrons events are observed. One can see the slowest neutron took 550us after production (RF off) to reach the 3He detector. This is not a quantitative measurement, since many of the neutron detector pulses overlap and blur their individual arrival times.

Koeth, Gilde & Moroch, Measurement of Neutron Diffusion Time from Fast Pulsed Systems (draft, 2020) — p. 3

Editorial note, tabletop extrapolation: A zero-cost first look before building any timing electronics: infinite persistence on a two-channel scope already shows whether the physics is there — and the source is explicit that this stage is not quantitative. The Fig. 4 caption says "in excess of 500 us" where the text says 550 us. Draft report.

To quantify the thermalization and diffusion time, an Ortec model 567 time-to-amplitude-converter (TAC) was employed as outlined in figure 5. … In the present case, the full-scale time window was set 1ms. The TAC then delivered a proportional output pulse, ranging from 0 to 10V, corresponding to a time period of 0 to 1ms. Thus, if the period between the start and stop pulse was 500us, then the TAC would then output a 5V pulse. The TAC output was then binned by a multi-channel analyzer (MCA) to generate the temporal profile. The MCA used was an Ortec EZMca set to a conversion gain of 512 channels. If the time between start and stop pulses exceeded 1ms, the TAC simply reset without triggering an output pulse, and awaited a new start pulse, thus ignoring cyclotron pulses that did not result in a detected neutron. A ten-point calibration of MCA channel-to-time interval calibration of the TAC-MCA system was performed with 70, 100, 200, …, 900uS time intervals generated from a Tektronix arbitrary waveform generator. … To perform the measurement of neutron thermalization and diffusion time, a TTL pulse synchronized with the beginning of the RF pulse started the TAC clock, and the NIM pulse arising from the 3He detector registering a neutron provided the stop pulse.

Koeth, Gilde & Moroch, Measurement of Neutron Diffusion Time from Fast Pulsed Systems (draft, 2020) — p. 4

Editorial note, tabletop extrapolation: The source's TAC/MCA timing method, built from ordinary NIM modules. Two behaviours matter: an interval exceeding the 1 ms full scale resets the TAC with no output — which conveniently ignores the ~249 of 250 no-detect pulses, but also truncates any genuine event arriving later than 1 ms — and the ten-point AWG-generated calibration is what makes the histogram's time axis trustworthy. Detector conditioning, discriminator settings and grounding are not in the excerpt; treat this as the method's skeleton, not a complete recipe. Draft report.

The neutron propagation from the target, through the chamber wall, through approximately 8 inches of air, and then finally diffusing through the polyethylene before entering the 3He is the measured quantity. That process, presumably dominated by the duration spent in the polyethylene is long compared to the 10us RF pulse (the time window in which a neutron could be produced). The multichannel analyzer's binning created a histogram of cyclotron pulse-neutron detection time intervals over a 1-hour period of acquisition, or 720,000 cyclotron pulses. Figure 6 shows a fit to the data, yielding a measured diffusion time of approximately 94us.

Koeth, Gilde & Moroch, Measurement of Neutron Diffusion Time from Fast Pulsed Systems (draft, 2020) — p. 4

Editorial note, tabletop extrapolation: The headline number — but it is an effective decay constant of the complete target-to-detector timing distribution in this one assembly (chamber wall, ~8 inches of air, then the polyethylene), which the authors presume is polyethylene-dominated. What transfers is the strategy: delayed counting can separate neutron events from the RF transient — with the usable quiet window measured on each machine, not assumed from the 94 µs. 720,000 pulses in one hour is consistent with the 200 pps quoted earlier in the draft. Fit value read from the rendered Fig. 6 image (p.5). Draft report.

Additionally, the response of the NIM electronics to the detection of a genuine nuclear event results in a deadtime on the order of 10us or longer. … Although the neutron production window may be short (10us or less), the neutron transportation time from the source to the detector is relatively long, with a characteristic time of 100us, which affords the pulsed plasma experimenter the opportunity to "look" for neutrons in a quiescent period after the pulsed event. … 5 minutes of neutron events were collected with all cyclotron systems operational, including the pulsed RF, except the Ion Source Discharge power supply was shut off and no neutrons were detected during that time.

Koeth, Gilde & Moroch, Measurement of Neutron Diffusion Time from Fast Pulsed Systems (draft, 2020) — p. 1

Editorial note, tabletop extrapolation: The draft's transferable conclusion: moderator transport delays neutrons past the transient-and-deadtime window, so NIM-based counting survives pulsed operation. The everything-on-but-the-ion-source background run is a clean, cheap control — but it is one partial control (removing the discharge also removes discharge-borne transients), so a per-installation timing spectrum and a pulser/deadtime check still belong in the plan. Draft report.

holds a 5-inch radius DEE and dummy DEE with a peak applied RF voltage of 10 kV and tunable frequency 2 - 30 MHz.

Ruisard, Hine, Koeth & Rosenberg, The Rutgers Cyclotron: Placing Student's Careers on Target — WE1PB02, Proceedings of Cyclotrons2013 (2013) — p. 1

Editorial note, tabletop extrapolation: PDF p.1 = printed p.291. A self-consistent parameter list for a machine at exactly this scale: 5-inch dee radius inside 12-inch poles, "10E-5 Torr" as printed — read as 1×10⁻⁵ Torr, the operating pressure the companion paper WEPPT025 states unambiguously — and a reported 10 kV peak applied dee voltage over a tunable 2–30 MHz range. The single-dee-plus-dummy-dee topology and the every-diagnostic-is-also-a-current-collector pattern are the parts worth copying; the numbers are reference-machine parameters, not targets.

Difference analysis reveals a 14% variation between simulation and measurement. However, the discrepancy is <1% within the ion region.

Ruisard, Hine, Koeth & Rosenberg, The Rutgers Cyclotron: Placing Student's Careers on Target — WE1PB02, Proceedings of Cyclotrons2013 (2013) — p. 4

Editorial note, tabletop extrapolation: PDF p.4 = printed p.294. A rare model-versus-measurement pair at tabletop scale, and the lesson is the split: a 14% global mismatch coexists with sub-1% agreement where the beam lives. Score a FEMM/Elmer validation over the ion region so a usable model is not condemned by its periphery — but keep the full-aperture residual map and read it: where the big errors sit (and whether they are fringe, boundary or saturation artifacts) matters for extraction and for trusting the model's edges.

The geometric center was identified using an FFT-based analysis that maximizes the fourth harmonic and minimizes all others.

Ruisard, Hine, Koeth & Rosenberg, The Rutgers Cyclotron: Placing Student's Careers on Target — WE1PB02, Proceedings of Cyclotrons2013 (2013) — p. 4

Editorial note, tabletop extrapolation: PDF p.4 = printed p.294. A purely computational alignment method for anyone with a mapped field: for an N-sector pole, choose the origin that concentrates power in the N-fold symmetric harmonics (N and its multiples are legitimate structure; everything else is error or mis-centering). It removes the guesswork from registering a hand-built mapper's frame to the pole — then cross-check against mechanical registration and, once beam exists, closed-orbit behaviour, since a construction error can put the symmetry center away from the orbit center.

A 30 AWG 7 cm radius wire loop was energized with 2.5 amps and placed in the magnetic gap … Four additional orbits were found at higher radii, beyond the four seen in simulation. These are likely lower energy equilibria, as the wire loop technique does not strictly correlate circumference to ion orbit energy (due to an additional degree of freedom, tension).

Ruisard, Hine, Koeth & Rosenberg, The Rutgers Cyclotron: Placing Student's Careers on Target — WE1PB02, Proceedings of Cyclotrons2013 (2013) — p. 4

Editorial note, tabletop extrapolation: PDF p.4 = printed p.294. An almost free diagnostic: hookup wire, a couple of amps and an acrylic spacer reveal a pole-tip set's equilibrium-orbit structure with no vacuum, RF or source. Run it as the controlled demonstration it was: 2.5 A through 30 AWG dissipates about 0.9 W in the fine wire, so use a fused, current-limited low-voltage supply, keep the duty short, secure the (nonmagnetic) leads, and keep hands clear while energized. Carry the authors' own caveat with the method: wire tension is an uncontrolled degree of freedom, so a loop's circumference does not map cleanly onto a beam energy — they found four MORE orbits than simulation predicted for exactly that reason.

The photos shown in Fig. 9 demonstrate betatron motion of a proton beam in a ½ Tesla field, with fRF = 7.8 MHz. … All images were gathered using the radial P-22 Phosphor probe and a DSLR camera. … In the spiral pole tips, the motion quickly reaches a focus, due to the comparatively stronger weak-focusing central region. … for DEE powered at 100 Watts.

Ruisard, Hine, Koeth & Rosenberg, The Rutgers Cyclotron: Placing Student's Careers on Target — WE1PB02, Proceedings of Cyclotrons2013 (2013) — p. 4

Editorial note, tabletop extrapolation: PDF p.4 = printed p.294 (the 100 W dee power is the Fig. 9 caption, PDF p.5 / printed p.295; the subscript in "fRF" is printed as f with subscript RF). A phosphor-tipped radial probe, a viewport and an ordinary DSLR turn a pole-tip set's vertical focusing behaviour into a photograph — at half a tesla, within amateur reach. Read it as the qualitative first check that a new taper focuses (this paper's own comparison: adiabatic tightening on the weak-focusing tips, fast focus on the spirals with their stronger central gradient), then quantify with calibrated radial scans or tune measurements before believing details of the image.

Over a decade of experimentation has been focused on transverse beam measurements without any knowledge of the longitudinal behavior. This is because the large residual electric field of the radio frequency (RF) accelerating potential makes standard electronic beam phase and bunch length measurements impossible. RF filtering permits average beam current measurements, but removes any time structure within an RF cycle.

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 1

Editorial note, tabletop extrapolation: PDF p.1 = printed p.299. Why a small machine cannot simply put a pickup in the chamber and read phase: at these radii a probe sits inside the dee's residual field, and the fix that recovers a current reading (RF filtering) is exactly the one that erases the RF-cycle time structure. Whether a carefully shielded electronic pickup could do better on some machine is untested here — this program's answer was to go optical.

We have developed an optical based measurement that is insensitive to DEE voltage using a fast (3 ns) phosphor screen viewed by a gated camera to create “time sliced” images which longitudinally profile the beam. The phosphor plate is located on the end of a radial positioner that can sweep the entire chamber radius and hence any ion revolution. … This optical method mitigates measurement difficulties due to interfering RF fields near the accelerating gaps, and enables measurements to be made arbitrarily close to the ion source.

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 1

Editorial note, tabletop extrapolation: PDF p.1 = printed p.299 (conclusion on p.3/printed p.301). The central transferable idea: convert a longitudinal measurement that residual RF spoils into an optical one — the paper's own claims are that it mitigates the RF-field interference near the gaps and reaches anywhere the radial probe does, including the central region. A radial positioner already exists on most small machines as a beam probe; the added cost is the fast phosphor and the gated camera, the camera being the expensive item.

The 0.944-inch diameter ZnO:Ga doped “fast” phosphor deposit was layered between a 0.050 inch thick quartz substrate and a 1000 Å aluminium coating. The plate, mounted at the end of an adjustable radial probe, was electrically isolated for average beam current measurements. The fast phosphor screen has a 1/e relaxation time of 3 ns

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.300. The reported layer stack for a fast beam-imaging target at tabletop scale — named phosphor (ZnO:Ga), quartz substrate and thickness, 1000 Å Al coating — with deposition, thickness of the phosphor itself, and optics not specified. The dual role (image plus isolated current reading) is worth copying where practical, remembering an isolated target reads net collected charge: secondary-electron emission must be suppressed or calibrated before that number is treated as beam current.

we believe that the aluminium backing attenuated the proton beam and therefore reduced signal from the beam

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 3

Editorial note, tabletop extrapolation: PDF p.3 = printed p.301. Directly relevant at tabletop energies: 1000 Å (100 nm) of aluminium in front of the phosphor is a real energy-loss layer for protons near 100 keV, and its fractional effect decreases as energy rises toward 1 MeV. The authors present attenuation as a belief, not a measurement; before copying the fix (thinner backing, or beam-side phosphor), evaluate the layer with PSTAR/SRIM at the actual beam energy.

Operation at 7.8 MHz was a compromise between maximum achievable proton energy and extending the RF period so as to maximize the time resolution

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.300. A tabletop machine running at a few MHz is accidentally well suited to this measurement: at lower cyclotron frequency a fixed gate width spans fewer RF degrees (Δφ = 360·f·Δt), so the same 3 ns camera gate buys finer phase resolution. Direct computation gives 3 ns of a 128.2 ns period = 8.42 degrees; the paper's 9 degrees is its rounding of that.

The cyclotron RF was operated in pulsed mode at a frequency of 20Hz to permit instantaneous high power (thus high DEE voltage)

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.300. The most portable RF trick in this collection for an amateur whose dee voltage is limited by amplifier and tank heating rather than by breakdown: pulse the RF and gate the measurement late in the pulse. Estimate the amplitude ring-up as τ ≈ Q_L/(πf) and put the gate several time constants in; choose repetition rate and duty from measured voltage and thermal limits — the 20 Hz here is what Rutgers' hardware wanted, not a design number.

Due to the extreme sensitivity of the camera, and weak light of the phosphor, it was necessary to create a light-tight optical transport between the chamber viewport and the camera … 900 integrations per time step, a complete run of 44 time steps required over half an hour.

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.300. A realistic cost-of-measurement anchor: at Rutgers' own settings the arithmetic is 44 steps × 900 integrations / 20 Hz = 1,980 s — 33 minutes of stable operation (source, RF and field all required to stay put). Another machine's run length scales with its signal-to-background ratio, camera and beam current; the light-tight enclosure exists because the phosphor light is weak and the camera extremely sensitive — measure your own signal level before deciding it is optional.

This serendipitously provided a direct measure of the turn-to-turn (nth to nth+1) phase shift at a given radius.

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.300. Tabletop machines have small turn-to-turn spacing, so a partially intercepting probe is common — a double-peaked signal should raise the adjacent-turns hypothesis early, tested cheaply by changing probe insertion depth or plate size and watching whether separation and relative amplitude respond as turns would (species content, radial oscillations and bunch structure can also double a peak). Rutgers deconvoluted the two peaks with a dual-Gaussian fit and took the more intense (n+1) peak as the turn of interest.

we observe a tendency for bunch length to decrease with a rising magnetic field.

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 3

Editorial note, tabletop extrapolation: PDF p.3 = printed p.301 (Table 1; the 91 mm probe radius and ~100 keV termination energy are on PDF p.2). Rare published bunch-length numbers for a tabletop machine at almost exactly the 100 keV end of the target class: a beam tens of RF degrees long, with the measured means falling as field rises — the source states this as a tendency. The tabulated ±0.03 T is comparable to the spacing between the three field values; if that uncertainty were independent per row the settings would barely be distinguishable, so either it is largely common-mode (calibration) or ±0.003 T was intended — an unverified hypothesis, reported here as such with the printed value preserved.

Our phase shift observations agree qualitatively with simulation, but absolute agreement is yet to be achieved.

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 3

Editorial note, tabletop extrapolation: PDF p.3 = printed p.301. Honest calibration expectation for a tabletop builder running a tracker against a real machine: trends matched, absolutes did not. The input the authors chose to go measure was the dee voltage — the same poorly-known quantity on most amateur machines — but field map, source initial conditions and RF phase are equally capable of owning an absolute discrepancy; calibrate the important inputs before assigning blame to one.

during the experiment, current to the magnet was not continuously increased so as to follow the hysteresis loop.

Gonski, Burcher, Lazarov, Krutzler, Koeth & Beaudoin, A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron — WE1PB04, Proceedings of Cyclotrons2013 (2013) — p. 3

Editorial note, tabletop extrapolation: PDF p.3 = printed p.301. A direct warning for any iron-cored tabletop magnet: the search procedure an operator naturally uses (find resonance, then step up and down) is exactly what breaks hysteresis reproducibility, and Rutgers name it as a contributor to their error bars. The primary remedy is procedural — pre-cycle the magnet and approach every setpoint from the same direction; a calibrated Hall probe (or NMR where homogeneity permits) then verifies the field at the radii that matter, rather than substituting for the discipline.

The best arc stability was found for the smallest (0.031 inch) circular aperture.

Koeth, Rosenberg, Krutzler, Ponter, Schneider & Hoffman, Rutgers 12-Inch Cyclotron: Dedicated to Training Through Research and Development — WEPPT024, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.367. Two things transfer: the zero-RF characterization method (DC-bias the dee as a collector and sweep pressure, arc current and aperture — no RF system needed to commission a source), and 1/32 inch as the best-stability aperture AMONG THOSE TESTED here, i.e. a candidate for your own sweep rather than a design value. The Fig. 1 photograph shows an assembly with a 0.7 × 4 mm slitted aperture; whether that configuration was operated is not stated in this paper.

As expected, the collected ion current follows the arc current and extraction voltage.

Koeth, Rosenberg, Krutzler, Ponter, Schneider & Hoffman, Rutgers 12-Inch Cyclotron: Dedicated to Training Through Research and Development — WEPPT024, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.367; currents read from the rendered Fig. 3, axes beam current (µA) versus DC dee voltage (kV). Two cautions before transfer: these are DC-extracted source currents into a biased dee, NOT accelerated beam on target — and a DC-biased dee is not mass-selective, so the collector current lumps protons with H2+ and friends (the same source's 5:1 species ratio, dg-1817, says how much that matters). The rising trend with extraction voltage holds over the measured range; beyond it, extraction can go plasma- or space-charge-limited, so measure rather than extrapolate. The "H Pressure 111" label is an uncalibrated instrument reading, so the hydrogen pressure for this curve is not recoverable.

Rapid sweeping operation of the cyclotron has shown simultaneous generation of protons and +H2 ions in a 5:1 ratio.

Koeth, Rosenberg, Krutzler, Ponter, Schneider & Hoffman, Rutgers 12-Inch Cyclotron: Dedicated to Training Through Research and Development — WEPPT024, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.367 (printed notation is a leading-superscript "+H2"; transcribed as printed). Species fraction is first-order on a small machine: H2+ at half the charge-to-mass ratio accelerates at a different frequency and appears as a second resonance. The transferable method is the sweep — run the RF quickly across the band and see which resonances light up; no mass spectrometer needed for identification. The 5:1 proton-to-H2+ figure is this machine's result under its conditions, and resonance amplitudes fold in acceleration and detection efficiency, so treat ratios read this way as qualitative until independently analyzed.

The deflection channel has a nominal radius of curvature, ρ1, of 7 inches and tangentially intercepts the cyclotron beam at a radius, ρo, of 4.0 inches and transports it to a radius of 4.5 inches over 43° of azimuth.

Koeth, Rosenberg, Krutzler, Ponter, Schneider & Hoffman, Rutgers 12-Inch Cyclotron: Dedicated to Training Through Research and Development — WEPPT024, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.367. A dimensioned energy-analyser example at tabletop scale, with the governing combined-field orbit relation in closed form. Because the electric field selects velocity at known magnetic rigidity, it yields an absolute energy number rather than the inferred radius-times-field estimate. Before rescaling: the relation as written is the ideal nonrelativistic form and its sign follows the chosen field direction (with ρ1 > ρ0 the deflecting field opposes the magnetic bending) — define the convention, then check the design with a field map or trajectory run, since gap, fringes and orbit geometry set the real calibration.

In a 1 Tesla field, a potential of 33 kV is required to produce a transverse electric field of 4.2 MV/m

Koeth, Rosenberg, Krutzler, Ponter, Schneider & Hoffman, Rutgers 12-Inch Cyclotron: Dedicated to Training Through Research and Development — WEPPT024, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.367 (gap on PDF p.3 / printed p.368). The three numbers are mutually consistent on computation — 4.2 MV/m across 0.31 inch (7.9 mm) is 33 kV, and the paper's own formula with ρ1 = 7 in, ρ0 = 4 in, B = 1 T returns 4.2 MV/m for the computed ~494 keV proton at 4 inches — so the set can be trusted as a worked example. Another machine recomputes from its own orbit radii, field and electrode gap; the voltage scales with the gap and the geometry, and can land well above or below this.

This was verified by simulation: 385, 405, and 425 keV ions were admitted to the deflector resulting in a comparable target image … The bands are compilations of revolutions. Ions with sufficient radial extent in the nth turn are captured by the channel and form the outer (right most) band in Fig. 8. Those not intercepted continue on for another revolution, nth+1, of acceleration, and thus have a greater rigidity and hence are deflected less forming the second band, and so it goes for the third band, or nth+2 turn. … Considering the finite width of the deflector entrance slit and channel, the resolution has been calculated to be 10% at 500 keV.

Koeth, Rosenberg, Krutzler, Ponter, Schneider & Hoffman, Rutgers 12-Inch Cyclotron: Dedicated to Training Through Research and Development — WEPPT024, Proceedings of Cyclotrons2013 (2013) — p. 3

Editorial note, tabletop extrapolation: PDF p.3 = printed p.368. A small machine can display individual turns as separate bands on one screen — the source's own account: outermost band the nth turn, successive bands nth+1 and nth+2 at greater rigidity, verified by admitting 385/405/425 keV ions in SIMION. Two metrics must not be conflated: adjacent-band SEPARATION (~20 keV here) is an image-structure statement, while the calculated 10% at 500 keV (~50 keV) is the absolute-energy resolution set by the entrance slit and channel width — so the screen resolves turn structure without being a 20 keV spectrometer. Band spacing tracks energy gain per turn; converting it to dee volts needs the gap-crossing count and phase, not just the image.

To estimate a local average tune, Qz, the student notes the radial locations of two adjacent axial peaks and divides by the number of revolutions within that interval. When the radial beam spot is wider than the turn-to-turn spacing, overlap prevents a direct count of individual turns; peak DEE voltage is used to estimate the number of turns within the corresponding energy (radial) increment. By definition, the measured tune directly follows from the ratio of vertical oscillations to revolutions.

Koeth, Beam Physics Demonstrations with the Rutgers 12-Inch Cyclotron — WEPPT025, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.370 (the printed text reads "can beam measured", a source typo for "can be measured"). A tune measurement needing only a phosphor probe, a viewport and a camera on long exposure — no gated camera, unlike we1pb04's phase method. The dee-voltage fallback is the practical part, and it is an ESTIMATE: turns-per-energy-increment follows from an energy-gain-per-turn model (effective voltage, gap crossings, phase), so calibrate that model before trusting the count on a machine where turns overlap early.

Figure 3a is a SIMION simulation of ions crossing a radial reference plane in our “good” poletips’ WF field, showing the beam coming to a focus near the DEE edge, where n=0.2. … The increased frequency of the axial oscillation with radius is a display of the growing field index, n. Both a) and b) exquisitely demonstrate adiabatic damping … The reader can estimate from Fig. 3a that Qz≈0.09 at r=65 mm.

Koeth, Beam Physics Demonstrations with the Rutgers 12-Inch Cyclotron — WEPPT025, Proceedings of Cyclotrons2013 (2013) — p. 2

Editorial note, tabletop extrapolation: PDF p.2 = printed p.370 (Fig. 3a axes: axial height ±6 mm versus radius 0-110 mm). A concrete worked example, not a class expectation: this machine's good weak-focusing set runs νz ≈ 0.09 mid-radius with millimetre-scale axial excursion, the oscillation frequency rising with radius as n grows, and both simulation and photograph showing adiabatic damping. Damping means the beam tightens vertically as it gains energy — which ARGUES the vertical acceptance question is decided early, near the source; verify it by tracking or measuring the envelope over the full radius, since apertures, field errors and resonances can still bite downstream.

in six thousand or 2 gauss. Practically though, the field control was less than the theoretical as variations in cooling water temperature would change the resistance of the coils. The DC power system being voltage regulated then caused changes in the magnet current and of course the magnetic field.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 2

Editorial note, tabletop extrapolation: A cautionary rule with a number attached: the DAC chain promised 2-gauss setability (one part in six thousand), and the VOLTAGE-regulated supply handed that away to the chiller — cooling-water temperature moved coil resistance, hence current, hence field. Current regulation removes that specific path; hysteresis, yoke temperature, ripple and calibration remain, so a claimed field stability is demonstrated by measurement (or closed on a Hall/NMR probe), never promised by the DAC's step size. (The sentence begins on p.1: "...theoretically the magnetic field could be adjusted to one part..."; "Telsa" is a source typo.)

A precision shunt of 1.00 mOhm was inserted into the magnet DC power lead, a 5 digit Keithly DVM measured the voltage drop across the shunt. A Bell 620 Hall Effect Gaussmeter measured the field, while another Keithly DVM measured the 620's recorder output. The Hall Effect probe was located centered, flat against the surface of the bottom pole piece. An HP85 HPIB based computer was employed to slowly ramp the magnetic field while, while reading the values of the two meters. … The data was then recorded to an IBM PC disk via an RS232 link.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 2

Editorial note, tabletop extrapolation: A cheap, reproducible B-versus-I measurement arrangement: precision shunt + DVM for current, Hall gaussmeter read at its recorder output by a second DVM, a computer ramping slowly and logging both. Two craft details worth copying: the probe flat against a pole face is a REPEATABLE mechanical reference (one point, though — median-plane mapping is a separate job, dg-1683-class), and slow single-direction ramps respect hysteresis. Add probe calibration and an uncertainty estimate before calling the curve a calibration. (Spellings as printed: "Keithly", doubled "while".)

Because it is mounted directly on a chamber accessory port, the gauge is in a significant magnetic field while the magnet is energized. Since the operation of the ion gauge utilizes low energy ion currents, even the slightest magnetic field will alter the ion current incident on the collector. This ion current change thereby guarantees erroneous pressure readings.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 3

Editorial note, tabletop extrapolation: A failure mode that bites anyone who mounts an ion gauge on the chamber inside the yoke — and is easy to misread as a real pressure excursion when the magnet ramps. The physics: fringe field bends the gauge's electron and ion trajectories, shifting its calibration by amounts that depend on field, orientation and gauge geometry (the source's "guarantees erroneous readings" is its emphatic version). Remedies in preference order: mount the gauge on a stub outside the fringe field; characterize the gauge at operating current; or, as this machine did, set the leak with the magnet off and hold the mechanical setting — accepting blindness to gas-load changes mid-run, which argues for interlocks on what you CAN see.

For this cyclotron the non-loaded Q was about 1600. The measured Q of the tank circuit is somewhat less due to loading, denoted as QL. Looking at the voltage developed on a capacitve pickup very loosely coupled to the DEE, a sweeping RF signal was injected into the transmatch. ... fr was found to be 13.60 MHz. Because the response is measured in voltage rather than power, delta-f is measured at 70.7% of the maximum height, which was found to be 90kHz. Thus the QL of the tank circuit was measured to be 150, a very reasonable QL for a tank circuit of this type.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 4

Editorial note, tabletop extrapolation: A complete bench procedure: sweep RF into the transmatch, watch a very loosely coupled capacitive pickup, and take Δf at 70.7% of maximum height — the detail people get wrong, since a VOLTAGE response uses 1/√2 of peak, not half height. This resonator measured QL = 150 (13.60 MHz / 90 kHz = 151, consistent) against an unloaded ~1600; your own chamber-as-tank number depends on conductor losses, coupling and loading, and is a twenty-minute measurement by this method. (Spelling "capacitve" as printed; source cross-reference misprint: p.4 says the Q sweep is 'shown in Fig.3' — the sweep is Fig. 4; Fig. 3 is the RF block diagram.)

The high voltage capacitor, denoted as C1, was charged to the peak RF voltage through the rectifier and bled off by the high impedance resistor network. A DMM with a high input impedance was placed across R2 to measure the developed voltage. The ratio of R2 to R1 is 1:9.1E+5, thus the peak DEE voltage is: V(D-peak) = 9.1E+5 x V(r2)

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 4

Editorial note, tabletop extrapolation: A workable absolute dee-voltage measurement built from a rectifier, a capacitor, two resistors and a DMM — which is to say, a HOMEMADE high-voltage RF probe, and it deserves probe-grade engineering: voltage-rated component strings, enclosure, a verified discharge path, remote reading. Its accuracy hangs on diode drop, leakage and the resistors' voltage coefficient, and the signal is small — at 1700 V peak the R2 reading is about 1.9 mV (computed), so calibrate the chain and estimate its uncertainty before quoting dee volts from it. The resistor values are read from Fig. 5 (R1 = 750 MΩ, R2 = 820 Ω); 750E6/820 = 914,600, consistent with the printed 9.1E+5.

As expected, the peak DEE voltage rises as the square root of the applied RF power, Fig.6, and the peak induced voltage is linearly proportional to the peak DEE voltage, Fig.7.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 4

Editorial note, tabletop extrapolation: The method transfers, the number does not: measure YOUR dee voltage against forward power and expect approximate √P scaling while coupling and loaded Q stay fixed — this resonator's curve ran ~500 V near 4 W to ~1700 V at 60 W (points read from the rendered Fig. 6, 0-2000 V / 0-80 W axes; they bracket, not define, one exact coefficient). The practice worth copying outright: calibrate the cheap capacitive pickup against the rectifier divider once (Fig. 7's linearity), then use the pickup as the day-to-day reference. (The quoted sentence is the last line of p.4 and continues on p.5.)

This faraday collector was constructed from a 3/8 inch brass slug and is suspended as well as isolated in a coaxial arrangement by a Teflon spacer inside a 1/2 inch hollow copper cylinder. The copper cylinder forms an RF shielded housing for the brass slug. The copper cylinder has a 0.185 inch slit diametrically traversing one half of the hollow portion near the tip. This slit exposes the brass slug centered inside and is positioned such that it is only exposed to positively accelerated ions, while any negative ions hit the grounded RF housing.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 7

Editorial note, tabletop extrapolation: A buildable Faraday cup that solves the two problems a beginner hits — RF pickup swamping the picoammeter, and wrong-species contamination — with one piece of copper tube: the grounded housing is the RF shield, and the one-sided slit accepts only ions arriving from the correct azimuthal direction. The readout of record ran RG-174 through a coaxial feedthrough to a Keithley 610CR electrometer (per the same section's text beyond this excerpt), and the source notes a small positive bias suppresses secondary electrons while too much deflects the protons — calibrate your own bias by watching the reading turn over. Lengths and the bias arrangement are not fully dimensioned in the document; treat as a demonstrated layout.

It is mounted such that the collector can be inserted radialy with a two inch travel, effectively determining the maximum ion radius. The minimum measurable ion radius, maximum insertion of the collector is 2.50 inches while the maximum ion radius, minimum collector insertion is 4.50 inches. A plot of beam current against radius, Fig.10, shows that the beam current linearly drops off as the radius grows.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 7

Editorial note, tabletop extrapolation: The cheapest radial beam-profile monitor a small cyclotron can have: the movable collector doubles as the radius-defining aperture, so one linear feedthrough yields current-versus-radius — an INVASIVE measurement, with energy then inferred from radius and the calibrated field rather than selected. On this run, collected current fell about eightfold from ~16 nA near 2.6 in to ~2 nA at 4.5 in (read from the rendered Fig. 10) — this machine's outer-turn attrition under its own source and pressure conditions, a shape to expect, not a universal loss factor. ("radialy" as printed.)

However, after a short period of ion bombardment the luminescence ceased. This is due to the charging of the screen, the strong electric field that developed deflected the incident proton beam off target. The screen charging issue was resolved by sputtering approximately 50 Angstroms of gold over all of it's surfaces and ensuring a connection to ground. Such a thin layer of metal is almost completely transparent yet conductive. After metallization the beam indeed re-appeared and remained on the screen without any deflection

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 7

Editorial note, tabletop extrapolation: A classic trap with a cheap fix: an insulating phosphor flag charges under beam until its own field steers the beam away — brilliant, then dark. The method transfers: a thin grounded conductive over-coating that preserves light output; ~50 Å of sputtered gold is the value that worked HERE (film continuity at 5 nm depends on substrate and deposition, so verify conductivity, grounding and light yield on your own screen). The photograph (Plate 5) carries a 1.2 cm scale bar across the beam spot — a rare direct beam-size datum at this class.

In run 91699C the resonant frequency was tuned to 13.590 MHz. Other parameters for run 91699C are listed below: fr 13.590 MHz / Forward RF Power 16 Watts / Theoretical B-field 0.889 Tesla / H2 Pressure in tank 5.1E-5 Torr / Filament Current 5.75 Amps / Filament Voltage 5.0 Volts / Filament Bias -320 Volts / Filament Emission 21.0 microAmps / Max. Ion Radius 7.0 cm / Max. Ion Energy 184 keV

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 8

Editorial note, tabletop extrapolation: The single most valuable calibration point in the wave for a 100 keV-1 MeV tabletop design - a complete achieved operating point, not a design target. The energy is internally consistent: with B = 0.885 T (the measured peak) and r = 0.070 m, E = (qBr)^2/(2m) computes to 184 keV, matching the printed value. Note the whole machine ran on 16 W of RF and 21 microamps of filament emission. The forward slashes in the quote separate table rows; the microamp symbol is printed as a Greek mu.

The measured ion peak at 0.885 Tesla tightly corresponded with the theoretical value to 0.6%. ... However an unexpected peak at 0.449 Tesla developed. ... After an investigation into the matter, it was determined that indeed singly charged protons were being accelerated. ... the RF frequencies required for acceleration of the ions at the low magnetic fields, developed from excitation of higher frequency modes of oscillation in the tank circuit. ... If the applied frequency were double that of the fundamental, on it's second crossing of the gap the ion would receive a de-acceleration, thus gaining zero net acceleration. However, if the RF frequency were triple that of the fundamental it is seen that the electric field direction is again in sync with ion's travel. This effect holds true for any odd multiple of the fundamental cyclotron frequency.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 8

Editorial note, tabletop extrapolation: The most instructive diagnostic story in the document, with one open number. A builder ramping the magnet while watching a collector WILL see spurious low-field peaks and will suspect contaminant species; this source traced its extra peak to the RF tank ringing on harmonic modes, protons confirmed. Unresolved, computed here: 0.449 T is almost exactly half of 0.885 T — at fixed drive frequency that is an even multiple of the ion's fundamental, which the source's own two-crossing argument says gives zero net acceleration; a third-harmonic peak would sit near 0.295 T. So the qualitative lesson (check the RF spectrum and recompute candidate resonances via B = 2πmf/(qh) before blaming ion species) stands, while this particular peak's mechanism needs a nonideal ingredient the source does not supply. The author's reported consequences — harmonic operation sharpens the field peak; suppressing tank harmonics improves efficiency — were stated intent, not achieved results. Ellipses mark omitted intervening text.

Although considered obsolete in this day, the HP85 proved to be an extremely versatile piece of test equipment. It's ability to control any HPIB ready unit has made possible a flexible data control and acquisition system. The simple HP Basic language allowed even the most novice programmer to exercise complete equipment control. Although the processor is slow, speed was not an issue as the magnetic field needed to be ramped even slower. Future needs that may arise from active feedback certainly would require a faster computer.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 7

Editorial note, tabletop extrapolation: The controls-architecture lesson survives the obsolete hardware: when the acquisition loop is bounded by how fast you dare ramp the magnet, a slow, simple, well-understood controller on a standard instrument bus wins — and the logging-here, analysis-elsewhere split (HP85 logs, PC stores and analyzes, per the p.2 calibration chain) is the same split a modern builder should make. The author's own caveat carries: feedback, protection and fast diagnostics impose different timing budgets than a slow scan.