Beam measurement design rules

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

Tabletop: In a cyclotron the machine itself is the analyzer, but any external beamline species check on the next machine can copy these modest slit and pole proportions.

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

Tabletop: A modern current-regulated supply meets this easily, but verify ripple and thermal drift: 0.1% of 5.9 kG is 6 G, comparable to the whole shim budget.

Most operators agree that a variation of less than 0.1 to 0.2 per cent is desirable ... After careful correction by use of sector-shaped and wedge-shaped shims, the errors were reduced to less than 0.1 per cent.

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

Tabletop: 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.

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

Tabletop: The beam follows the magnetic plane, not the machined one; with separate top/bottom coil circuits (or a resistor across one layer) the builder can steer it back to mid-gap.

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

Tabletop: The single strongest process lesson for a next machine: map first, shim from data - a weekend of Hall-probe mapping replaces months of trial-and-error beam chasing.

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

Tabletop: 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

Tabletop: 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

Tabletop: Sets a concrete stability target for a home magnet supply: a few parts in 10^4, achievable with a shunt, op-amp and pass bank.

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

Tabletop: A cheap DIY NMR gaussmeter (coil, oscillator, water sample) is a well-known amateur build and would let the builder set f = qB/2*pi*m exactly.

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

Tabletop: Budget several map-machine-remap cycles for a next machine's pole profile; it is normal, not a sign of a bad design.

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

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

Tabletop: Sets the metric (not the number - a cyclotron needs far less) by which the builder should present their own field maps: normalized deviation over the beam region.

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

Tabletop: 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

Tabletop: Free operational fix for run-to-run field shifts in a home cyclotron - important because resonance is set by B and the beam vanishes on a few-gauss error.

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

Tabletop: A 1/800 inch (0.03 mm) grid is more than enough for an 8-12 inch pole and is buildable from surplus stepper/leadscrew parts.

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

Tabletop: Directly applicable: any DIY gaussmeter-plus-stepper mapper on an 8-inch magnet needs this calibration or the map carries 1% systematic error.

Four needles were used to scale both dimensions; the fifth needle was used to break the symmetry, removing orientation ambiguities.

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

Tabletop: Trivially cheap (iron nails plus a few turns of magnet wire) and it ties the field map to the mechanical chamber center, which is what you actually need for placing the ion source and target.

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

Tabletop: Cheap insurance: an afternoon of cycling the homemade stage validates every field map you take afterwards.

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

Tabletop: 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

Tabletop: 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

Tabletop: The standard commissioning move for a next machine: B-field is the easy knob to sweep since the RF stays matched at fixed frequency.

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

Tabletop: Predicts the current-vs-radius profile the builder should measure, and the standard shim fix if a next machine loses beam before full radius.

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

Tabletop: 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.

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

Tabletop: A zero-cost field-quality diagnostic the builder can run on the existing magnet this weekend.

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

Tabletop: Inverted for the builder: their whole magnet is model-sized, so a dense XY hall-probe map on a ~5 mm grid with attention to probe positioning and current regulation (the two dominant error terms) is the equivalent discipline.

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

Tabletop: Directly applicable to a next machine's shimming: regulate magnet current (not just set it) while mapping, and index the probe mechanically, or the map noise will exceed the shim effects being measured.

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

Tabletop: When characterizing the dee resonator with a VNA or Q meter, treat the reading as a lower bound and keep leads/fixture capacitance minimal.

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

Tabletop: Exactly the measurement chain the builder needs for the LDMOS upgrade: calibrate their pickup at 5-50 W against a scope probe, then trust the pickup alone at 100-500 W.

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

Tabletop: 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

Tabletop: Lets the builder use an unshielded collector at nA levels: a ~100 uH-mH choke at the feedthrough kills 9 MHz pickup without blocking DC beam current.

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

Tabletop: Exactly sized for the reference machine's 100-500 W upgrade: a homebrew 30 dB coupler plus AD8307 boards gives continuous forward/reflected monitoring across their whole power range.

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

Tabletop: The builder already lives in this instrument ecosystem; a Bird 43 (or borrowed one) transfers absolute power calibration to permanently installed cheap sensors.

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

Tabletop: A free end-to-end check for the builder: the RF power at which beam vanishes measures the true dee voltage through pure geometry, independent of every probe.

Beam Inferred DEE Voltage

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

Tabletop: The builder can cross-check their 1.3 kV estimate by measuring where the first half-turn lands - the beam itself is the most honest voltmeter.

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

Tabletop: Essential for interpreting the reference machine's magnet scans: a peak at one-third field is a subharmonic, not a mystery species, and H2+ vs H+ vs They peaks can be disentangled this way.

the real voltage was roughly 11,300 times the pickup voltage ... the probe had to be recalibrated every time the frequency was adjusted.

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

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

a SWR of 1:1 and forward power of 15.43 W were measured

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

Tabletop: Reassurance for commissioning a next machine: hunt for first beam at tens of watts with a clean match before scaling power - beam detection, not power, is the bottleneck.

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

Tabletop: A cyclotron dee tank is narrowband, but the same rule holds: measure what the PA actually emits before designing filtering or worrying about RF interference from a garage machine.

At first this beam consists very largely of molecular ions, but after running for some time it changes over and becomes nearly all protons

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

Tabletop: Critical for p-B11: an unconditioned source delivers H2+ that behaves as half-energy protons, silently killing the expected alpha yield at fixed magnetic rigidity.

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

Tabletop: A triage rule for the reference machine's low-current debugging: measure current at small radius first; if it's already low there, more RF power won't fix it - the source will.

Higher frequency, lower H2 and base pressure, lower filament voltage

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

Tabletop: For the reference machine's current-hunting: before adding RF watts, cut chamber pressure and re-optimize filament bias - Houghton's 7x gain cost zero watts.

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.

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

Tabletop: Directly sets the gas-handling operating window for the reference machine and explains a common 'no beam' failure at too-good vacuum.

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

Tabletop: Gives the builder a sanity check: nA-to-uA beams need only uA-to-mA class discharges; if their beam/arc ratio is far below ~20% the extraction geometry is losing beam.

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

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

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

Tabletop: A used RGA head is arguably the single best diagnostic upgrade for a next machine - one spectrum 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

Tabletop: At the reference machine's ~1.3 kV dee voltage turn spacing is even smaller, so a bare, grooved copper collector (no thick shield) is essential or the probe reads zero while beam exists.

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

Tabletop: Judge a next machine first on internal-probe current at full radius; a 4:1 ratio between internal and extracted beam is historically normal, not a failure.

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

Tabletop: Gives the builder the extraction-voltage scale for a next machine: deflector kV requirements scale linearly with beam energy, so a ~100 keV beam needs only ~7 kV in the same geometry.

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

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

Tabletop: Prevents misidentifying beam in the reference machine's B-field sweeps: a peak at one-third the expected field is the same ion on the 3rd harmonic, not a new species.

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

Tabletop: Diagnostic rule: a sharp cutoff in the radial current profile means phase slip, not wall collisions - which points at field shape/Dee voltage rather than focusing.

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

Tabletop: Practical commissioning technique: the builder can confirm they are accelerating protons (not H2+ or contaminants) with only a magnet current sweep and an electrometer.

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

Tabletop: Sets expectations for pulsed diagnostics and duty-factor arithmetic on any measurement the builder makes with fast instrumentation.

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

Tabletop: The reference machine's Faraday cup inside the cyclotron fringe field gets free secondary-electron suppression; outside the field it needs an explicit suppressor bias or magnet.

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

Tabletop: The close-geometry, calibrate-with-a-known-alpha-source method is exactly how the builder should commission their PIPS geometry before hunting p-B11 alphas.

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

Tabletop: A radial probe (the reference machine's shielded Faraday cup on a linear feedthrough) is the workhorse diagnostic; falling current at some radius localizes where field shape loses the beam.

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

Tabletop: 5.9 kG corresponds to 25.1 MHz proton NMR; the machine's own resonance (f, e/m) also gives the average field to ~0.5%, a free sanity check.

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

Tabletop: A pulser check separates electronics noise (grounding, RF pickup from the 9 MHz drive) from true detector degradation without risking source contamination.

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

Tabletop: Slightly better-engineered alternative to the 9 V cup bias; easy to add to the reference machine's beam probe.

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

Tabletop: Directly applicable commissioning procedure; starting the search at small radius relaxes the resonance tolerance enormously.

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

Tabletop: Directly applicable; a 'beam' that stays constant while you detune B or RF is ion leakage to the probe, not orbiting protons.

The six-inch cyclotron has indicated a 7 microampere beam, at a frequency corresponding to about 800 kv protons.

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

Tabletop: Directly comparable scale; microamp-level internal beam is a realistic expectation for a next machine and the choke-protected probe is the right pickup.

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

Tabletop: Partially applicable: the p-Li gamma resonance needs ~440 keV, above the reference machine's 160 keV; a next machine reaching 0.5 MeV could use exactly this LiF-on-probe gamma check with their gamma detector.

At these energies beam intensities varied from 0.5 to 10 nA on target and beam resolution varied from approximately 60 to 70 keV.

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

Tabletop: The single most encouraging number in the batch: professional low-energy p-B11 data were taken at exactly the reference machine's nA beam scale.

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

Tabletop: When the builder converts PIPS counts to a 'cross section' they must divide by ~2 alphas per reaction - or better, publish counts-per-luminosity as this paper does.

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

Tabletop: The builder already owns the pieces: their Faraday cup/Keithley 617 integrates charge, and an Am-241 check source calibrates PIPS solid angle and energy scale.

energy at far left: T=.5087 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

Tabletop: Shows a phosphor screen plus this one formula suffices for energy-spread measurement at student-machine scale - no magnetic spectrometer needed.

The location of the ammeter in the circuit keeps it essentially at ground potential... Do not omit the 10 meg bleeder resistor.

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

Tabletop: The ground-leg metering trick is how the builder can safely log arc and extraction currents on the next machine without floating instruments at kV.

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

Tabletop: A one-component fix for honest current numbers on any Faraday-cup measurement the builder makes.

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

Tabletop: One battery fixes a systematic error in the main diagnostic the builder has; also gives a way to separate true beam from secondaries.

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

Tabletop: Calibrates expectations exactly at the reference machine's operating point (~160 keV) and names the three things that gate the next factor of 2-3: magnet current, cooling, RF frequency.

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

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

Tabletop: 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.

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

Tabletop: Sets the expected FEMM-vs-Hall-probe discrepancy for the reference machine's magnet: 1-2% mismatch is normal (unknown B-H curves, geometry error) and should be absorbed by a per-coil scale factor in the builder tool, not chased in the mesh.

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

Tabletop: Do not chase single-turn extraction: accept multi-turn with dE ~ 2*e*Vdee (~20 keV at 10 kV dee), which PIXE tolerates. (Spread and dB/B: botman p.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

Tabletop: The reference machine already probes the internal beam; adding a two-finger (or shadow-bar) differential probe turns the existing radial probe into the diagnostic that decides septum placement.

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

Tabletop: Start a next machine with the 0.5 mm x 5 mm slit: at 50-150 mA arc it made 230-590 uA at 40 kV; even derated ~30x for a 4 kV dee (V^1.5 scaling at fixed gap) that is ~10-20 uA available — four orders of magnitude over 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

Tabletop: Species purity is a tuning knob the reference machine has never had: run the PIG current-regulated at healthy gas flow for a clean proton beam at f = qB/2*pi*m, or starve it deliberately to hunt H2+ on harmonics. Removes the H+/H2+ ambiguity that has dogged the reference machine's run interpretation.

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

Tabletop: Directly applicable - a 0.1% relative radial map (differential Hall probe or flip coil) is the entry ticket to meaningful n(r) shimming on the next machine.

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

Tabletop: A modern LCR meter with lead-nulling does the same job on the reference machine's dee stem; knowing C-to-ground before pump-down predicts the ~9 MHz resonance and flags assembly errors.

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

Tabletop: At nA/sub-MeV there is no activation to survey - but the lesson stands: always check holder edges and apertures for beam strike (film, phosphor, or discoloration), since a large fraction of beam can miss the target.

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

Tabletop: Copy the C-target geometry but read it with phosphor screen or dental X-ray film instead of activation; a set of slotted witness targets at different radii gives the whole vertical envelope in a few runs.

in an effort to determine more definitely that the peaks, or 'pips,' shown in synchroscope photographs of the beam current are caused by precession of the beam.

Yeater, 184″ Cyclotron: Synchroscope Beam Pictures on Two Probes — MDDC-987 (1947) — p. 3

Tabletop: The FM pulse envelope is synchro-specific, but the two-azimuth probe comparison transfers: any structure that keeps a fixed phase relation between azimuths is orbit dynamics; anything common-mode is source or RF fluctuation.

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

Tabletop: Exactly the right probe pattern for the reference machine's chamber: an O-ring/Wilson-sealed sliding shaft with grounded shield tube; unshielded probes near a 9 MHz dee read RF pickup, not beam.

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

Tabletop: A next machine's extraction commissioning should start with on/off comparison images (film, phosphor, or CCD) at the channel exit; integrating detectors see sub-nA deflected beams that electrometers lose in RF noise.

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

Tabletop: No activation at tabletop energies - instead line the dee aperture with removable witness strips (paper, phosphor, anodized Al) and read burn/discoloration marks to find the loss radius; the localization logic is identical.

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

Tabletop: 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 mode run makes precession directly visible on a scope.

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

Tabletop: 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 even good 1950s machines lost most of the beam at extraction, 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

Tabletop: A tabletop ALC loop gets beam pulsing for activation or timing experiments for free - inject an offset into the amplitude setpoint; no mechanical or source-side hardware needed. The 1%/10 uA constant is specific to their circuit, 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

Tabletop: At the reference machine's nA scale calorimetry is unavailable, but the doctrine - never trust one beam-current method, and expect tens-of-percent disagreement between independent methods - is exactly the Faraday-cup vs electrometer-background cross-check discipline already used; 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

Tabletop: Directly usable on the reference machine's Faraday cup/probe - sweep a modest positive bias and accept the current only where it is bias-flat; near the source, gas ions and secondaries can dominate an unshielded collector by large factors. Scale the bias to the machine (tens of volts suffices for nA beams).

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

Tabletop: The linear beam-vs-dee-voltage check transfers to nA scale and is a good run-log plot for the reference machine; the 2-3x loading signature does NOT - milliampere beams absorb real RF power, whereas a nA beam is invisible in amplifier current, so use it only as an upper-bound sanity argument.

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

Tabletop: Same programme's RF paper (ucrl-3153 p.7) draws the identical moral - measure the quantity you care about at the electrode, not a correlate at the amplifier. For a next machine - derive tuning/phase feedback from the dee pickup, not from LDMOS drain current or forward power, which optimize at subtly wrong points.

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

Tabletop: Both halves are free instrumentation for a next machine - a three-point V(d) test during commissioning, and an insulated septum/ground-electrode current readout for beam steering (same trick as the reference machine's Faraday-cup practice).

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

Tabletop: Deflector voltage stability maps directly to extracted-beam steering stability; the lesson - regulation is limited by the divider, so buy/build the divider first - applies at any scale, and 0.01% is far beyond what a next machine needs (1% steers by ~1% of the deflection).

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

Tabletop: Two transferable halves: (1) semiconductor sensors near the chamber are a calibration-drift risk once neutrons appear; (2) a capacitive dee-voltage pickup is calibrated GEOMETRY — mechanically fix the probe-to-dee distance or every calibration is void. Bears directly on retiring the uncalibrated ~800 V nominal dee-voltage number on the reference machine.

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

Tabletop: The trick scales down perfectly — a nA-to-uA tabletop beam calorimeter (thermistor on an isolated cup) can be calibrated the same way with a surface-mount resistor dissipating known milliwatts. Electrical-substitution calibration converts any thermal sensor into an absolute beam-power meter.

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

Tabletop: The redundancy principle transfers even at nA — Faraday-cup current times computed energy should match any thermal or activation measurement; a persistent gap means secondary-electron error, wrong assumed energy, or beam missing the cup.

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.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 7

Tabletop: Fully transferable — witness marks on the reference machine's dee edges and probe shadows are a free orbit-centering diagnostic; an orbit center offset a few percent of pole radius is normal and correctable by moving source or dees.

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.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 16

Tabletop: Both the finding and the instrument transfer: stack 3-5 insulated foils as a segmented z-probe on the reference machine to see where the beam sits vertically, and spend tuning effort on the first turns — beam surviving to half radius will almost all reach full radius.

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

Tabletop: 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 dominate at weak arc — run the arc hard for protons. (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

Tabletop: 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 before "physics" runs; ORNL treated characterization as scheduled work, not overhead.

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

Tabletop: Directly actionable for the "~150 keV-class computed" number on the reference machine: convert computed to measured with two independent checks — Al foil range/transmission steps and, at higher current after the RF upgrade, cup calorimetry. One method is a claim; three in agreement are a measurement.

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.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 7

Tabletop: 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

Tabletop: 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; on any small machine almost all RF power is overhead, so chase Q and coupling, not amplifier watts, for efficiency.

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

Tabletop: Scale-honest — the reference machine's nA beams cannot melt anything, but the geometry trick matters for beam VIEWING (a grazing phosphor or foil intercepts more turns and lights up at lower current) and becomes thermally real on any 5-13 kV / uA-class upgrade path.

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

Tabletop: The reference machine's best-beam case (5.6x background on the Faraday cup) sits in exactly this evidentiary tradition — and the energy-threshold argument is the template for a source-species test: an observed nuclear signature whose threshold excludes the molecular-ion hypothesis is proof of species without a spectrometer.

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

Tabletop: Calibrates expectations for the reference machine's and a next machine's first runs — nA at full radius from uA-class first-turn current is what a real machine did at first beam; log the whole I(r) curve, because its shape (where the loss happens) is the tuning roadmap.

A carbon (graphite) target gave rise to 112-minute and 15-hour activities which are assigned to F 18 and Na 24 respectively.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 30 June 1952 — ORNL-1345 (1952) — p. 10

Tabletop: Below nuclear thresholds the 150-keV reference machine cannot use this — but it becomes the cheapest absolute energy check the moment any upgrade crosses a low-threshold reaction, needing only a GM counter and a stopwatch; the practice (identify by half-life, bound energy by threshold) is scale-free.

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

Tabletop: 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

Tabletop: Current bookkeeping is free diagnosis — on the reference machine, meter the puller and chimney drains separately from the Faraday cup; a weak beam with a hot puller is a geometry problem at the source exit, and no arc-power increase will fix it.

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

Tabletop: The control-experiment discipline transfers whole to any reference-machine or bench-scale target or activation claim — for every "the beam did X", run the identical setup minus beam; the 1339 quarter also flags their power-measurement accuracy as only +/-30%, a humbling uncertainty note worth copying into lab-book practice.

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

Tabletop: 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 rather than absolute B(r), and supply drift drops out of the shim iteration.

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

Tabletop: The one activation rule that DOES apply 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 null check that sub-MeV operation activates nothing — useful evidence for licensing conversations and for catching surprises if beam or species ever changes.

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

Tabletop: ENERGY SCOPE: relevant only when neutrons exist to be moderated. Standard Cd-difference technique to keep 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

Tabletop: Energy-independent technique. A 2-in lead collimator with a removable plug around a next machine's NaI turns it into a pointing instrument for finding X-ray leaks (RF multipactor, dee-liner discharge bremsstrahlung) on a running machine — the same aim/plug/subtract discipline at keV instead of MeV.

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

Tabletop: ENERGY SCOPE: Crocker's 10-24 MeV/nucleon beams at tens of uA made 100-500 r/hr targets; the sub-MeV reference machine makes none. But the instrument discipline transfers exactly: a logged GM/ion-chamber channel at the machine (the builder already logs Keithley current) gives prompt X-ray dose during RF conditioning and a defensible record for licensing.

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.

Cohen, Measurement of Beam Energy and Energy Distribution on an Internal Cyclotron Target — ORNL-1347 (1952) — p. 5

Tabletop: Verified on the page image, and 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. 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

Tabletop: At 150-170 keV protons the ranges are ~2-3 um Al, so foil steps become thin-film steps or the film is swapped for the next machine's PIPS behind a stepped degrader — but the architecture (stepped absorber + position-resolved detector + uncovered reference channel) and the arc-off/detune trick for nA-friendly intensity carry over directly. The film variant also maps radial beam width vs energy for free (p.9).

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

Tabletop: Scale the absolute numbers down with energy, but keep the shape of the claim — quote the high-energy edge with confidence, treat the low-energy tail as semi-quantitative. Same asymmetry applies to a PIPS-plus-degrader spectrum on a next machine, and to interpreting any resonance-yield curve taken with a spread beam.

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

Tabletop: ENERGY SCOPE: Cu63(p,n) threshold is ~4.2 MeV — closed on the reference machine and a next machine, so this exact reaction cannot be used below ~4 MeV. The transferable idea is using a steep, well-known excitation function as an energy discriminator: at a next machine's energies the B11(p,alpha) yield curve itself (or Al/Ni step degraders before the PIPS) plays that role, and the same triangular-unfolding trick applies to any stacked measurement.

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

Tabletop: Directly relevant methodological honesty for a next machine, where detector protection will likewise force attenuated or detuned beams for some measurements. Log the machine state (dee voltage, field, frequency, source position) alongside every energy measurement so diagnostic-mode and run-mode data are never silently mixed.

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

Tabletop: ENERGY SCOPE: C12(p,pn) needs ~20 MeV — the counting scheme is closed below threshold. Keep the geometry, swap the readout: a probe-tip mosaic of insulated segments read as Faraday collectors (or a scorched-film/thermal-paper witness at nA-uA-sec fluence) gives the reference machine and a next machine the same one-shot 2-D map of where the internal beam actually lands — directly useful for placing the B11 target and sizing its hot spot.

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

Tabletop: Table verified on page image. Energy-independent physics: on the reference machine or a next machine a differential probe (shadowed double tip) or the sectioned-target map gives dr, and with the known dee voltage that is a measurement of ion RF phase — the quantity a next machine's 5-G field tolerance is protecting. A rare direct 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

Tabletop: Directly usable on the reference machine now: a dee-voltage threshold scan vs radius separates center-region problems from field-error problems with no new hardware.

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

Tabletop: Direct transfer to the reference machine's probe/Faraday-cup work: an apparent current fall-off with radius can be instrumentation, not physics — swap probe material (their Al vs Ta test) before redesigning the machine.

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

Tabletop: Directly runnable on the reference machine with the existing probe hardware - measured turn spacing would convert the "~800 V nominal, uncalibrated" dee voltage into a calibrated energy-gain-per-turn number. Fig. 12 (PDF p. 41) shows the machine doing this at 9.2-12 kV dee-to-dee with 600 V dee bias.

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

Tabletop: Same artifact family as the reference machine's secondary-emission and background offsets on the Faraday cup; at nA scale a hot-wire thermionic term can dwarf the signal, so bias or shield the probe and log the baseline drift.

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

Tabletop: The reference machine's central tuning trap - a source tweak that fattens the inner-radius signal can starve the Faraday cup at full radius. Always score source changes at the outermost probe position.

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

Tabletop: A zero-cost magnet diagnostic for the reference machine or a next machine - enameled wire and a bench supply locate both the magnetic median plane (which need not be the geometric midplane) and the field center before any Hall-probe mapping campaign.

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

Tabletop: Direct prior art for the plan's educational variable-energy accelerator concept - vary energy with field/frequency plus a movable target (cf. the 44-inch spacer), and buy energy DEFINITION with a simple analyzed beamline 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

Tabletop: DIRECT trio of transfers: (1) budget alignment/tuning provisions into any multi-element line; (2) the floating-wire method (wire under tension carrying current I follows the trajectory of a particle with B-rho = T/I) is a superb zero-beam teaching-lab measurement of magnet optics; (3) their bottom line - 0.1 uA on target at ~0.2% energy spread (p.53) - is the achieved-performance benchmark for a first-generation small-machine analyzed beam.

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

Tabletop: SCALE-HONEST: geometry is energy-independent (it fixes E/E0 ratios, not E), so a palm-sized R ~ 5-10 cm version at a few hundred gauss would broad-range-analyze a next machine's ~170 keV protons identically - a compelling teaching-lab focal-plane instrument. The 5-ton, 14-kG original is MeV-class; copy the optics, not the iron.

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

Tabletop: DIRECT pairing of two ideas the reference machine already half-uses - (1) an error that scales rigidly with excitation is absorbed by end-to-end calibration; (2) loss of NMR (or Hall-linearity) signal quality is itself a diagnostic of entering saturation. Worth writing into the next machine's field-mapping procedure.

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

Tabletop: DIRECT and free at design time - a straight-through optical path (laser today) plus a permanent probe port turn alignment and field checks from teardown jobs into ten-minute jobs. A next machine's chamber/beamline port lists should include both.

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

Tabletop: DIRECT teaching-lab gold - one sealed alpha source and one afternoon calibrate the whole instrument, no beam required, and the equal-exposure trick measures the acceptance function that theory only estimates. Their peak-position convention (intercept of the straight high-energy edge with the baseline) is also the right lineshape-robust choice.

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

Tabletop: DIRECT for the teaching program - the 2026 equivalent is a small lookup app, but the doctrine stands; run-time decisions need precomputed inverse tables. (Their compute budget was an IBM 650; the curriculum can have students build the nomogram 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

Tabletop: SCALE-HONEST - kinematic broadening scales with (m_projectile/m_target) and aperture, not beam energy, so the trade is identical for a next machine's Rutherford-scattering station. The fix they note (close the entrance aperture when it matters) is the standard resolution-vs-count-rate knob students should learn to turn.

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

Tabletop: DIRECT and foundational for the experiment catalog - every cyclotron, including the reference machine at 9 MHz, delivers ~10-40 degree phase bunches at the RF period. The bunch structure is a measurable, teachable property (phase width vs turn number) and the enabling fact for every timing experiment on the machine.

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

Tabletop: The most directly transferable finding here: the machine's RF is a free timing fiducial at ANY scale. Reference-machine and next-machine experiments (beam-phase measurement, gated counting, TOF over cm-scale paths for keV protons) can clock everything off a capacitive sniff of the dee line; beam-derived triggers die exactly when you need them (low current).

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.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 13

Tabletop: DIRECT twice over: (1) never let the background-rejection threshold live inside the timing path (they tried; timing and efficiency fought); (2) a $50 Cs-137 check source turns "what is the threshold today?" into a 5-minute standardization - the calibration habit every counting experiment on a next machine should inherit.

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

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 11

Tabletop: 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.

Fulbright et al., A Fast Neutron Time of Flight System for Use with Cyclotrons — NYO-9360 (1962) — p. 12

Tabletop: DIRECT metrology doctrine - one calibration path is an assumption, two are a measurement. For a next machine's experiment gates (e.g., p-B or (d,n) yield claims), require a primary calibration plus an activation- or source-based cross-check, and quote the disagreement as the systematic.

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

Tabletop: The staging discipline transfers to every machine even where activation does not — low-duty, small-radius-first commissioning is also how you protect septa, collectors, and instruments; at a few hundred keV and above the activation logic itself starts to matter.

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

Tabletop: A model-calibration pattern the FEMM-based pipeline should copy — one deliberate known-geometry measurement (a wire loop, a known coil) in the actual gap pins the permeability/saturation assumptions the whole field model rests on.

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

Tabletop: 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.

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

Tabletop: 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.

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

Tabletop: Dee-voltage ripple modulates turn energy and orbit phase; put the envelope on a scope, log the percentage, and remember the excitation source (a cheap signal 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

Tabletop: A Faraday cup's reading depends on its stopping surface through secondary emission and backscatter; measuring the same beam against two stopper materials bounds that systematic without any absolute reference.

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

Tabletop: Ordinary graphite (and evaporated or pressed-powder targets generally) is not uniform at the percent level; a range-based or transmission-based density map of the actual target spot belongs in the error budget of any yield measurement.

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

Tabletop: 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

Tabletop: Yield calculations for a reaction target need atoms/cm2, which weighing gives directly; a micrometer or interference measurement of an evaporated film does not.

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

Tabletop: A used 1-ug-precision microbalance plus the free NBS weighing protocol is a complete sub-percent target-mass QA capability; the protocol, not the balance, is what removes the drift that dominates single weighings of sub-mg samples.

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

Tabletop: Treat the crystal monitor reading as a process gauge (right range, right rate), never the certified thickness; the crystal is heat-sensitive, so radiant load from the source shifts its frequency exactly when the reading matters most.

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

Tabletop: The one thickness method that needs no balance and works on a mounted film; a surface-barrier detector, a check-source alpha emitter, and an MCA are all standard home-lab equipment. Quote absolute thickness no tighter than the stopping-power tables allow.

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

Tabletop: A photodiode and lamp sort carbon stripper/backing foils into thickness bins in seconds — calibrate once against weighed foils and use it as the incoming-inspection tool.

The uniformity of thin foils can be determined by scanning the foil with a collimated beam of alpha particles.

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

Tabletop: The same alpha energy-loss rig with an XY-translated collimator becomes a uniformity mapper; a single-point thickness number hides exactly the wedge or crystallite structure that ruins energy resolution (see Abele et al., this volume).

This is all the calibration which is necessary since now only energy shifts are of interest.

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

Tabletop: The whole rig is a surface-barrier detector, preamp, biased amp and any old 512-channel MCA — Thompson wrote it up precisely so small labs could build it; the differential (shift-only) design makes absolute gain calibration irrelevant.

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

Tabletop: One spectrum yields thickness, uniformity and pinhole count simultaneously — run it on every target before it goes into the machine and again after beam exposure to quantify damage.

however uniform an evaporation may be, the parting agent produces an inhomogeneous 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. 134

Tabletop: If a target will sit tilted to the beam or feed a spectrometer, the release-agent choice is a resolution decision, not a convenience; standard single-point thickness QA cannot see this defect — only straggling-width measurement can.

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

Tabletop: Detergent-film release (Teepol-class) over salt release wherever the condensing metal tolerates it; and the alpha-straggling comparison is a complete bench-top target-quality metric using the same rig as the thickness measurement.

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

Tabletop: 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; budget with the Z^2 scaling when tempted by heavier beams.

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

Tabletop: Current density is the damage variable — halving the spot diameter quarters foil life at fixed current; any foil-life data from the literature transfers only through uA/mm2, so measure the actual beam-spot size before predicting.

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

Tabletop: An internal target wants the widest beam spot the measurement tolerates, an aperture that shadows the frame, and a multi-position holder; electrostatic wobble plates at kHz are trivial hardware on a small machine and equivalent to Corwin's mechanical rotation.

start with as large a beam spot as possible and slowly focus it smaller (Ramsay, "Alternatives to Thin Film Carbon Foils")

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

Tabletop: 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

Tabletop: A bench spectrophotometer (or a single calibrated LED/photodiode pair) measures foil thickness in seconds without an accelerator; cross-cite ornl-3021 for the films this gets applied to.

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

Tabletop: 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).

it was not possible to carry out accurate measurements with slides that had been coated with a soap-like parting agent (Rhoads, Stoner & Bashkin, "Calibration of Surface Densities of Metal Films by Optical Transmittance")

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

Tabletop: 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

Tabletop: A silicon detector at a fixed forward angle is cheap on any small machine; the scattering-peak-width-as-damage-gauge is the lightest possible target diagnostic and doubles as a luminosity monitor for excitation measurements.

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

Tabletop: A free diagnostic: ring the dee (impulse or drive-and-release), scope the pickup envelope, and look for a kink. A visible steep-decay segment localizes the multipactor band on YOUR machine and tells you whether nominal operating voltage sits inside it — the critical question for any dee running near a few hundred volts.

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

Tabletop: A diagnostic that costs a glance: if the chimney/hood top of a small source runs orange-hot, the arc power is exiting axially instead of ionizing gas — evidence for adding reflection (mirror or repeller) and a before/after check that it worked.

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

Tabletop: 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 an integrator, provided the flip is a true reversal.

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

Tabletop: Transfers verbatim to any ADC/integrator field mapper — calibrate at deflections spanning the readings, with the same input impedance, rather than trusting one scale factor.

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

Tabletop: A machined-spool primary standard plus a fluxgate-free comparison puts sub-0.5% absolute field capability in a home lab; it is the piece that turns a flip coil from a relative into an absolute instrument.

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

Tabletop: Sets the realistic error floor for coil-and-integrator absolute field measurement; a Hall probe certified to 0.1% is genuinely better than the classical chain, but only if its own calibration is traceable.

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

Tabletop: The classical answer to shimming with a wandering surplus supply — map relative structure differentially and pin the absolute scale with occasional flips; a modern two-channel Hall differential measurement inherits the same immunity.

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

Tabletop: The active-area rule for Hall mapping a shim edge: a 1-2 mm sensor is marginal where the gradient scale is a few mm (pole edge, shim step); position repeatability of the mapper jig belongs in the same error budget as the sensor.

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

Tabletop: Maps directly onto modern integrator front-ends — put the gain in the coil (turns), keep the electronics gain low, and treat offset/drift correction as part of every run, not a once-per-day calibration.

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

Tabletop: Zero-cost qualitative diagnostics for a home lab — a filing map locates stray-field lobes and leakage paths before any probe survey, and the discharge-follows-field trick is a natural cross-check in a machine that already runs a plasma source.

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

Tabletop: The discipline transfers whole: derive numeric field-map acceptance bands from orbit tolerance (phase-slip or centering budget) beforehand, so a survey ends in pass/fail per region instead of open-ended interpretation. Orbit-integral quantities beat point values when the beam only feels the integral.

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

Tabletop: Three habits for a home lab: repeat-trace to certify a mapping method, calibrate the current METER (it is usually the accuracy floor of a B-vs-I curve), and normalize survey data to a monitor reading so supply drift cancels out of shape maps.

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 (c. 1950) — p. 26

Tabletop: DIRECT — the differential trick ports to modern probes; two matched Hall/NMR channels read as a difference kill supply drift and thermal drift, the dominant error sources in a garage field survey. Same scheme reused on the full magnet with 28-turn, 0.607-cm-mean-radius coils (PDF p.30).

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 (c. 1950) — p. 42

Tabletop: DIRECT physics: a displaced/dished magnetic median plane steers the circulating beam into a dee lid at small gap heights. A tabletop analog of the dip needle (or vertical probe-pair difference) belongs in the survey plan; and keep deliberate shimming mirror-symmetric about the midplane unless correcting the median surface is the goal. 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 (c. 1950) — p. 86

Tabletop: The capacitive-paddle dee voltmeter is the same instrument Koeth calibrated on the Rutgers 12-inch and the missing calibration on the reference machine's "~800 V nominal" — a soldered paddle + defined-gap probe + diode peak detector, calibrated once against a real HV probe, converts dee voltage from folklore to data. The saturable- reactor trick survives as the Hall-effect/isolated-shunt principle: never bring an HV node to the meter.

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 (c. 1950) — p. 118

Tabletop: At nA-uA tabletop currents calorimetry is hopeless (uW-mW against watts of RF pickup) — the Faraday cup + electrometer choice the reference machine already made is the 1951 conclusion too. Calorimetry earns its place only at tens of watts of beam.