Cyclotron fabrication design rules

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

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

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

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

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

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

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

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

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

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

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

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

the edges of the pole have a 45 degree taper. This is to prevent magnetic saturation at the edges of the pole. The field due to the taper also fringes less sharply.

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

Editorial note, tabletop extrapolation: Trivial machining step for a next machine's pole tips that buys margin against edge saturation at higher fields.

disagreement with calculation was found as the calculation average field value is 5 % higher than measured one ... the valley gap height was reduced from 100 mm to 70 mm

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

Editorial note, tabletop extrapolation: Design in adjustability - a gap or shim you can still reduce after measuring - because model-to-measurement discrepancies at the percent scale happen in either direction (this source's ran 5% optimistic). Adjustability is cheap before assembly and expensive after.

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

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

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

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

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

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

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

pressure @ 0.5T 99,472 Newton/m2... ~ 1 atmosphere

Tanabe, Iron Dominated Electromagnets, Lecture 10: Forces, Stored Energy, Fringe Fields, End Chamfering (2005) — p. 10-11

Editorial note, tabletop extrapolation: At the reference machine's 0.59 T the poles attract with ~1.4 atm over the 8-inch pole face — about 4,500 N (~1,000 lbf); clamps and any pole-retraction scheme must carry that load (chamber lids carry the separate atmospheric load — see the lid-deflection calculator). [Corrected 2026-08-20: previously printed as "~4500 lbf", the newton value mislabeled.]

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

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

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

It is a public access code (it's free), maintained under contract with DOE by Los Alamos National Accelerator Laboratory (LANL) personnel.

Tanabe, Iron Dominated Electromagnets, Lecture 4: POISSON — A Two-Dimensional Magnetostatic Solver (2005) — p. 2-4

Editorial note, tabletop extrapolation: Free tooling that runs on a PC, in the same code family the Houghton-line theses used (dg-142) - the standard amateur path to pole-profile design alongside FEMM.

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

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

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

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

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

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

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

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

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

Solid iron yokes are often used in simple, flat pole contour magnets.

Tanabe, Iron Dominated Electromagnets, Lecture 8: Core Fabrication, Assembly, Installation and Alignment (2005) — p. 4-5

Editorial note, tabletop extrapolation: Settles the default for a next machine: a one-off DC cyclotron magnet is normally solid steel - the source's 'often used' practice - because lamination tooling only pays across a production family. Laminations re-enter if the design ramps or regulates fast enough for eddy currents to matter (dg-089).

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

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

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

The angle of the cut is unimportant. However, a 45 degree angle cut is convenient and distributes the same angle at two points and minimizes saturation effects due to the sharp corners. ... solid steel pieces, machined with the two dimensional pole contour, were bolted onto the pole ends. These pieces were removed, machined with the required distribution of the chamfer depth determined by the described iterative process and replaced. After replacement, the distribution of the field integral was measured. The final chamfer shape was achieved after two iterations.

Tanabe, Iron Dominated Electromagnets: Design, Fabrication, Assembly and Measurements — SLAC-R-754 (2005) — p. 253-254

Editorial note, tabletop extrapolation: If the next machine's pole edge is chamfered or radiused to soften the field falloff for extraction - a different geometry and objective than a dipole end chamfer, so model or map it for the cyclotron case - use bolt-on machinable end pieces so the shape can be iterated the way SPEAR3 did.

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.

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.

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

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

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

Lbs. force on conductor = 1/1750 x kilogauss x amperes x inches length; Lbs. force between pole faces = 1/1.735 (kilogauss)^2 x (inches^2 area)

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 13

Editorial note, tabletop extrapolation: Directly applicable: at 5.9 kG on 50 in^2 poles that is ~1000 lb of attraction a next machine's bolts and spacers must carry.

It is important that the contact surfaces between yoke pieces and between yoke and pole cores be flush to eliminate additional air gaps

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 3

Editorial note, tabletop extrapolation: Directly applicable: any unintended air gap adds straight onto the magnetic circuit's gap budget - 0.003 in against a 1.5-in main gap is 0.2%, small but real; the same error across tight pole-cap joints is proportionally worse. Machine flush because it is cheap at build time and unfixable after assembly.

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

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

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

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Pole face: 150mm, Pole gap: 39mm, Current: 70A ;NOTE: this is a slice down the middle of the magnet

Morrow, Focusing in the Houghton College Cyclotron — Houghton College thesis (2015) — p. 60-68

Editorial note, tabletop extrapolation: Low-cost simulation path for a hobbyist - Superfish is free, SIMION is paid but widespread, and FEMM plus the playbook's Python tracker is the all-free equivalent; the appendix geometry file is a working starting template for an 8-15 cm pole magnet.

upper and lower pole tips up to 1-inch thick can be easily attached and removed - we currently have four sets of pole tips.

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

Editorial note, tabletop extrapolation: Probably the single best architecture decision the builder can copy: swap-on tips let a next machine iterate field profiles cheaply - with the caveat that a sector-tip (AVF) conversion is still re-checked against return-path saturation and coil clearances (dg-045).

Trim coils increase the gap ... Very weak except in superconducting machines ... Model it before implementing it to avoid unexpected effects

Beeckman, Cyclotron Magnets — ECPM37 lecture, Groningen (2009) — p. 33, 47

Editorial note, tabletop extrapolation: Settles the shim-vs-trim-coil question for a small warm magnet the way the Houghton thesis found empirically: iron wins for the main profile. A weak trim coil can still earn a place for fine, reversible adjustment where the gap budget allows one.

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

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

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

Laminated: Limited thickness : 300 mm max, usual 200 mm. Good magnetic and mechanical properties. Slight anisotropy.

Beeckman, Cyclotron Magnets — ECPM37 lecture, Groningen (2009) — p. 57

Editorial note, tabletop extrapolation: For an amateur the practical read is: mild-steel plate stock is fine for a DC magnet; note the anisotropy if you stack plate for pole tips.

step0: Squeeze requirements and extract juice; step1: Get starting numbers from hand calculation; step2: 2d global model; step3: 3d global model; step4: 2d cuts for detailed local objects ... 2d calculations must be preferred.

Beeckman, Cyclotron Magnets — ECPM37 lecture, Groningen (2009) — p. 68

Editorial note, tabletop extrapolation: A workflow a solo builder can actually execute, and it puts pencil-and-paper (Zickler-style) sizing ahead of any software.

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

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

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

The U-shape of the magnet gives direct access to the top of the vacuum chamber and permits the use of an overhead crane for transferring the assembled dee system.

Livingston & Boch, The Oak Ridge 86-Inch Cyclotron — ORNL-1196, OSTI 4357145 (1952) — p. 7, 9

Editorial note, tabletop extrapolation: The principle (design the yoke around how you will service the chamber, not vice versa) is directly applicable to a next machine's H-frame layout.

a magnetic load of 1,055,000 lb and a vacuum load of 60,000 lb could be expected ... mating surfaces of pole bases and yoke pieces to be planes within 0.005 in. T.I.R.

Livingston & Howard (eds.), The Oak Ridge Relativistic Isochronous Cyclotron — ORNL-2648, OSTI 4275955 (1958) — p. 118

Editorial note, tabletop extrapolation: Direct transfer of the tolerancing practice: face-grind a next machine's pole and yoke mating surfaces and check with a dial indicator. Do not transfer the load ratio: at ORIC's scale the magnetic load dwarfed the vacuum load, but magnetic pressure is B^2/(2*mu0) - at 0.5 T about one atmosphere - so on a tabletop machine the two loads are comparable and the structure must carry both.

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

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

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

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

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

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

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

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

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

A single water circuit in a coil assembly should be wound from a single continuous length of conductor. Splices 'buried' within the potted insulation should not be allowed.

Tanabe, Iron Dominated Electromagnets, Lecture 9: Coil Fabrication, Testing and Electrical Safety (2005) — p. 14-16

Editorial note, tabletop extrapolation: For a next machine wound from copper refrigeration tubing: buy one continuous coil per water circuit, keep the shop swarf away from the winding, and verify the bore is clear before the tubing is buried in the stack.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The voltage breakdown limit determines the necessary gap width. The empirically determined limit (valid for clean, flat surfaces) is d[mm] >= 1.41 x 10^-2 * phi[kV]^(3/2).

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

Editorial note, tabletop extrapolation: Direct rule for source-to-puller spacing - clean DC gaps are the law's home turf: a few-kV gap needs sub-mm minimum, with real margin because sputtered metal films spoil the 'clean surface' assumption fast. For dee-to-ground RF clearances use it only as a lower-bound sanity check: edges, insulators, RF conditioning and enhancement move the practical limit (dg-353, dg-662).

Ferrite toroids wound with AWG 26 wire and surrounding two 2 inch sections of RG-8 50 Ohm coaxial cable form the coupling transformers.

Blodgett, 3.5 to 30 MHz Automatic Antenna Impedance Matching System (2012) — p. 18-19

Editorial note, tabletop extrapolation: A cheap coupler build bracketing the reference machine's 9 MHz band - built from the source's full schematic, not the one-line summary: the shield treatment and grounding are what make the directivity, so replicate them exactly, then bench-test directivity, insertion loss and core heating at 9 MHz through the intended power and mismatch range before trusting it.

the top and bottom of the chamber to bow in, which affected the capacitance of the dee and reduced the maximum voltage that the dee could withstand before flashing over.

Baumgartner, The Cyclotron Kids' 2 MeV Proton Cyclotron — Cyclotrons 2013, WE1PB05 (2013) — p. 2

Editorial note, tabletop extrapolation: Directly relevant to any thin-lid chamber on a next machine squeezed into a small magnet gap: design the lids to a calculated stiffness (the lid-deflection calculator) from the start. Internal posts clear of the beam spiral and the RF high-field region are one remedy; thicker or dished lids and external ribs are others, and each needs its own deflection, buckling, venting and weld checks. [Note revised 2026-08-23: earlier note planned posts as the remedy.]

Cited in: Cyclotron Vacuum Chamber Design and Sealing

They found that at a critical angle of 31.5 deg, the surface charge was zero; this angle was independent of the applied voltage. The surface charges were positive at smaller angles, but negative at larger ones. ... Fryszman and colleagues found that by screening the section of the insulation surface near the cathode or covering this section with a semiconducting layer, the breakdown voltage was raised by a factor of approximately 2.5. ... Roughening the surface of the insulator in a region adjacent to the cathode increased the breakdown voltage by about 40 %. Roughening the surface adjacent to the anode had little effect.

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 113-114

Editorial note, tabletop extrapolation: For the next machine's source stalk - a DC cathode-junction context like the studies' - cone the insulator toward the negative electrode and consider recessing the triple junction behind a screen. The factors come from separate experiments and are not multiplicative, and a dee-stem RF feedthrough alternates polarity every half cycle: there, treat all of this as qualitative guidance to be tested, not booked margin.

Air spaces exist in solid and liquid dielectrics... the air will have the higher stress, possibly causing sparkover through the air space... The stress in the air gap can thus be k times that in the solid.

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 116, 119

Editorial note, tabletop extrapolation: The classic failure of home-built HV feedthroughs: a loose PTFE sleeve over a rod arcs in the annular air film. Fill the gap - potting or liquid dielectric - so no gas layer sits in series with the solid. Evacuating the annulus removes the Paschen path but leaves field-emission breakdown and surface flashover, so vacuum is not a substitute for filling.

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

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

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

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

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

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

A standard AEI hairpin electron microscope filament floating at approximately -90 V is heated by 2 A of current ... RF pickup on each filament lead is shorted through a 0.001 uF capacitor to ground.

Yuly, The Houghton College Cyclotron: a Tool for Educating Undergraduates — Cyclotrons 2013, WE1PB01 (2013) — p. 3

Editorial note, tabletop extrapolation: A replaceable-filament pattern worth copying next to a live dee: bias the filament, and RF-bypass every lead at the feedthrough - but size the bypass for the actual RF impedance and current, and use capacitors rated for the DC bias plus transients rather than copying 1 nF.

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

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

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

No solder to hold the board to the spreader, the screws are enough. Heat sink compound between copper spreader and aluminum heat sink.

Buckler, Solid-State, 2-Decade, 1.25 kW Linear Amplifier — Development Notebook (2015) — p. 10

Editorial note, tabletop extrapolation: A workable pattern for a kW-class dee driver assembled from LDMOS boards - but the transistor/module manufacturer's mounting spec wins: check flange flatness, clamping force, and which interfaces want grease, pads, solder, or dry metal contact for the specific device.

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

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

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

I also added a limiting power resistor (20 ohms at 50w) in series with 50v to the TIP102 as a precaution...with this resistor in place, a short on the 12v line will limit the current and prevent a catastrophic failure. ... I used 500v micas but slowly but surely I am changing them to 1000v specs because they are more robust.

Buckler, Solid-State, 2-Decade, 1.25 kW Linear Amplifier — Development Notebook (2015) — p. 31-32

Editorial note, tabletop extrapolation: Cheap fault-tolerance for a homebuilt RF deck, as the source built it. Check the fault arithmetic before copying: 50 V across 20 ohm is 2.5 A and 125 W, above the resistor's continuous rating, so the part rides through brief faults only - pair it with a fuse or fast shutdown rather than treating it as continuous-duty protection. Voltage-derating the filter caps matters more with the reactive load a dee presents.

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

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

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

Rather than mounting the output transistors directly to a heat sink, they are first flow soldered to a thick copper heat spreader, which is then mounted to the heat sink.

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

Editorial note, tabletop extrapolation: At 100-500 W a copper spreader under the LDMOS pallet is cheap thermal margin; the reference machine's earlier MOSFET amplifiers died in service without a firm post-mortem, and die-temperature margin is the inexpensive insurance either way.

The position of the connection point at the drain trace is critical as it affects the match.

Buckler, A Solid State 1.25 kW Linear Amplifier — QST, January 2015 (2015) — p. 4

Editorial note, tabletop extrapolation: When copying an LDMOS pallet layout, preserve the cited design's output-transformer tap geometry, and if anything about it changes, remeasure the output match - the source says position is critical; how sensitive, at what power, is a measurement on the actual build.

This design strategy made it impossible to fix a single component of the apparatus, such as the insulation, without replacing the entire piece.

Haas, Characterizing the Performance of the Houghton College Cyclotron — Houghton College thesis (2009) — p. 47

Editorial note, tabletop extrapolation: A next machine should assume sparks and insulator damage happen across a machine's life: modular fastening where practical turns rebuilds into part swaps - the source's glued chamber is the cautionary case. Where glue or solder is structurally necessary, design the bonded assembly itself as the replaceable unit.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: The Vacuum Budget of a Cyclotron

Ceramic spacers hold the Dee and Dummy Dee apart with a gap of 0.635 cm. The entire Dee electrode assembly is supported by three KF-16 electrical feedthroughs through ports at 120 degrees from each other. ... A circular ring of 6061 T6 aluminium, 1.27 cm thick, 0.6 cm wide, and 15.6 cm outside diameter, formed the walls for both the Dee and Dummy Dee. Two 5052 aluminium sheets, 0.13 cm thick, were fastened to the top and bottom of the ring with vented screws.

Yuly, The Houghton College Cyclotron: a Tool for Educating Undergraduates — Cyclotrons 2013, WE1PB01 (2013) — p. 2

Editorial note, tabletop extrapolation: Direct fabrication prior art at exactly tabletop scale; the single-Dee-plus-dummy topology needs live RF on only one electrode - the design rationale for fewer HV feedthroughs - and the vented screws are the kind of vacuum detail worth copying wholesale.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The sides of the second set of dees are 1/8 in. copper with five loops of 7/8 in. copper tubing flattened and furnace brazed ... Both designs have proved satisfactory but the latter is much easier and less expensive.

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

Editorial note, tabletop extrapolation: At 1.3 kV and tens of RF watts the builder probably needs no water - but decide from computed or measured dissipation and temperature, not from voltage. If a next machine's dee runs kilowatt-class RF, brazed-on flattened tubing is the historically cheap construction; substituting soft solder needs its own validation (joint temperature, strength, vacuum compatibility).

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

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

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

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

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

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

The grid was made of .0114 cm thick tungsten wire shaped into circles chosen to be one fifth of the chamber in size. The chamber diameter was 21 cm so the grid diameter was 4.2 cm. ... fusion efficiency is enhanced by transparency of at least 92 percent (Donovan). The inner grid is 99.18 percent transparent with three loops as calculated by comparing the cross section of the total grid wire used to the surface area of the grid sphere.

Kovalchick, Deuterium Fusion Using Inertial Electrostatic Confinement (2012) — p. 19-20

Editorial note, tabletop extrapolation: The transparency bookkeeping (wire cross-section vs aperture area) is the calculation method to transfer - but a circulating cyclotron beam hits a grid or slit repeatedly and directionally, so compute projected obstruction along the actual trajectory over many turns, not the spherical-area figure.

The stainless steel wires previously used by Murali lasted for under a week depending on the power load. In contrast, with the W-25%Re alloy, the grid lasted for over 2 years. ... It is relatively cheap, has a high melting point (2,800 K), a low sputter yield, and is easy to manufacture by spot welding. To test this material, the 10-cm grid was run at various voltages in the range of 30-130 kV and with the current range of 30-180 mA for over 1,000 h

Miley & Murali, Inertial Electrostatic Confinement (IEC) Fusion: Fundamentals and Applications (2014) — p. 145-146

Editorial note, tabletop extrapolation: W-Re thermocouple wire is commercially available in small quantities - a strong candidate for any sputtered electrode in the reference machine's source, with W-class durability and far better workability than pure tungsten; fabrication, activation and sputter behavior remain application-specific, so qualify it in place.

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

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

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

Three holes are machined in the cathode body; two are used to support the anode and the third is used as a gas inlet. Alumina tubes are inserted into the two holes used for anode support, and a stainless steel tube is inserted into the gas inlet hole. Ceramic epoxy (Ceramabond) is used to mate the alumina and stainless tubes to the back of the cathode body. Stainless steel wire with 0.5 mm diameter was spot welded to the anode, and the wires were threaded through the alumina tubes in the cathode body. ... Essentially the anode floats inside the cathode body, being supported only by the two stainless steel wires that protrude through the alumina tubes and out the back of the cathode body.

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 1-2

Editorial note, tabletop extrapolation: An amateur-grade insulated support for a modest-voltage, low-current internal electrode - an ion-source anode and the like. Not unchanged for filament leads (0.5 mm stainless is a poor conductor for filament current) or for chamber-wall HV or current feedthroughs: use current-rated conductors and qualified vacuum/HV feedthroughs there, and test the ceramic-epoxy joint for bakeout, leakage and voltage standoff before trusting it. [Note revised 2026-08-23: earlier note extended the scheme to filament leads.]

Water cooling for the cathode rod and the anode base are essential (some copper parts were melted when the ion source was run without proper cooling).

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 19-20

Editorial note, tabletop extrapolation: The source's warning stands as written: they melted copper running without cooling. A reference-machine-class source at much lower arc power may not need water - but that is a claim to establish by thermal estimate and a supervised first run with temperature monitoring, not by assumption. The sanded-cathode arc-striking preparation transfers directly.

This puller was designed for the ion source test stand to hold 50 kV... The minimum source to puller gap is 0.196 (5.0 mm).

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. 68, 75

Editorial note, tabletop extrapolation: Two measured holdoff points from one clean DC stand - anchors for a dee-tip/puller voltage budget, not a kV-per-mm allowable: vacuum holdoff is nonlinear in gap and hostage to finish, conditioning, and RF-vs-DC differences. Do what the source did: measure the actual geometry on a test stand rather than applying a scaling law.

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

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

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Vacuum rated to 1 x 10-8 Torr (better suited to 1 x 10-6 Torr). Temperature rating is dependent on which elastomer o-ring is used (usually 150C)

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 443-446

Editorial note, tabletop extrapolation: Matches the reference machine's observed 1e-6-range vacuum with Viton seals - typical of all-elastomer systems, where permeation and outgassing usually hold operation near the recommended regime, though well-designed elastomer systems can run lower. A CF port or two on a next machine (gauge, RGA) buys bake and UHV headroom cheaply.

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

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

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

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

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

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

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

A virtual leak is a volume of trapped atmospheric gas that leaks into the vacuum vessel through holes or cracks that do not go all the way through the vessel wall. [Examples:] Unvented Screw, Two Welds in Series, Unvented Double O-rings

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 59-63

Editorial note, tabletop extrapolation: Every internal socket-head screw in the next machine (dee supports, ion source mounts) needs a vent hole, a slotted thread, or a vented washer; a slot machined in the O-ring groove floor serves the same purpose.

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

Seam welds are continuous, with welding only on the atmosphere side. The internal braces are stagger welded to keep virtual leaks at a minimum.

Ramler & Parker, The Argonne 60-Inch Cyclotron — ANL-5907 (1959) — p. 7

Editorial note, tabletop extrapolation: On any welded chamber or fitting for a next machine the question to ask of every joint is: is there a pocket sealed on both sides, or a crevice open to vacuum? Vent it, or weld it through. Argonne's atmosphere-side seams are one way to satisfy that, not the rule itself.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Two 0.65 cm thick circular lids ... included a gland for a Viton O-ring for the vacuum seal. ... The chamber can be evacuated down to a final pressure of approximately 2 × 10−6 Torr

Yuly, The Houghton College Cyclotron: a Tool for Educating Undergraduates — Cyclotrons 2013, WE1PB01 (2013) — p. PDF p. 2 for the lids and Viton seal; PDF p. 3 for the 2 × 10−6 Torr

Editorial note, tabletop extrapolation: A complete documented chamber design for an 8-inch-pole machine, including the epoxied-flange trick that avoids welding. Copy from the paper - then qualify your own copy: epoxy joints and lid stiffness are workmanship-dependent, so leak-check the flanges and run the lids through the lid-deflection calculator rather than inheriting the paper's result.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

when an extra-shallow gland is desired in order to increase the squeeze, it must be made wide enough to accomodate the full O-ring volume.

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. 1-2

Editorial note, tabletop extrapolation: If a next machine's grooves are cut for 30% squeeze, groove cross-section area must still exceed ring cross-section area - check fill before cutting.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Design Chart II For O-Ring Vacuum Dovetail Grooves ... 1/16 ... L Gland Depth .050 to .052 ... Squeeze % 27 ... G Gland Width .055 to .059 ... R .005 ... R1 1/64. Radius “R” is CRITICAL.

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. PDF 10 (printed 7) carries Design Chart II; the retention sentence and the 'see pp 7-8' pointer are on PDF 5 (printed 2); Design Chart III (half-dovetail) is on PDF 11 (printed 8)

Editorial note, tabletop extrapolation: Worth it for a hinged or frequently-removed lid where the ring falls out during assembly; otherwise plain rectangular face grooves are cheaper and more tolerant.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

after the welding, the bottom plate contracted so much that it bent the whole frame out of shape... seal the bottom plate against the frame using a flat Viton ring.

Baumgartner, The Cyclotron Kids' 2 MeV Proton Cyclotron — Cyclotrons 2013, WE1PB05 (2013) — p. 2-3

Editorial note, tabletop extrapolation: A fabrication trap the builder can sidestep: demountable elastomer seals on both lids avoid weld distortion entirely on a thin flat chamber - the route the source machine retreated to after its frame warped. Where welding is preferred, controlled sequence and post-weld machining are the professional counters; for a garage build, not welding thin flat plates is the cheap answer.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

In order to use a standard round O-ring, the inside corner radius of the groove should not be less than three times (3X) the O-ring cross-section diameter. ... The length of the O-ring centerline should be equal to the length of the groove centerline. Following is an equation to assist in determining the O-ring inside diameter. O-ring ID = (Groove CL length / 3.14) - O-ring CS

Apple Rubber Products, Seal Design Guide — p. 84

Editorial note, tabletop extrapolation: Directly applicable to a racetrack or rectangular lid/port on a next machine: a 1/8 in. cord ring needs >=3/8 in. corner radii or it will bunch and leak at the corners. Note the source's rectangular sizing implies zero nominal stretch while its circular-groove guidance ideals 2% - follow the section matching your groove shape.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

304L SS, most commonly used in vacuum, a little more expensive... Joint design is critical from vacuum, metallurgical and distortion standpoints. Cleanliness is essential.

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 355-360

Editorial note, tabletop extrapolation: For a next machine's chamber welds, specify 304L filler and stock where practical: the low-carbon grade resists weld sensitization (carbide precipitation and intergranular attack near welds). Plain 304, welded cleanly, also serves - the lecture's 'most commonly used' is a preference with reasons, not an exclusion - and leak-tightness comes from joint design and cleanliness either way.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

a lid with radius 10 centimeters and thickness of 3.5 millimeters would undergo less than 1 mm of deflection when covering a chamber with internal pressure of 1e-3 Torr

Dewan, Design and Construction of a Cyclotron Capable of Accelerating Protons to 2 MeV — MIT thesis (2007) — p. 12

Editorial note, tabletop extrapolation: The actual formula for trading a next machine's lid thickness against magnet gap: a few mm of plate suffices at 8-12 inch chamber diameter IF the edge support is real (the lid-deflection calculator covers both edge conditions). Alloy choice buys yield margin at the price of 7075's poorer weldability and corrosion behavior - it stiffens nothing.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

the VTO box and obround are mounted on a motor-driven carriage which operates on a rail system. This permits the removal of the dee heads... to facilitate maintenance.

Ramler & Parker, The Argonne 60-Inch Cyclotron — ANL-5907 (1959) — p. 6-7

Editorial note, tabletop extrapolation: At tabletop scale this means: chamber slides out of the gap, dee removable through a lid, pump cart disconnectable - the difference between a research tool and a sealed monument.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The limit at the entry is set by the dr between successive turns at this radius ... it is desirable to have adjustable controls on deflector spacing and location which can be trimmed empirically.

Livingston & Blewett, Particle Accelerators (1962) — p. 181-183

Editorial note, tabletop extrapolation: With ~2.6 keV total gain per turn at ~150 keV, the reference machine's turn spacing at extraction is ~0.9% of r - about 0.7 mm at r = 3.2 in - so build the septum mount with millimetre-scale radial adjustment.

allows most of the resonant beam to pass into the deflector channel without striking the channel walls. In the MIT cyclotron the septum is formed of two strips of tungsten, 0.020 in. thick and 12 in. long and with the edges spaced 1/8 in. apart. Each strip is silver-soldered to a copper bar bent to the correct curvature, with copper tubing also soldered to the bar for cooling. Other designers use a long V slot in a tungsten-strip septum, so the heat is distributed over an extended surface

Livingston & Blewett, Particle Accelerators (1962) — p. 184

Editorial note, tabletop extrapolation: At the reference machine's beam power the thermal load is small but not zero - intercepted power is loss current times energy per charge (1 uA of 500 keV beam is 0.5 W into a very small spot) - so compute it, and keep the slotted geometry: it maximizes transmitted current into the channel either way.

This is of steel and has three faces at 45 deg to the axis, which form a sort of truncated pyramid with a circular base. Each face bears a recess, 1.2 cm. in diameter and about 1 mm. deep. The metal or powder to be bombarded is pressed or hammered into these spaces and the beam strikes the surface which is uppermost. The target is carried on a water-cooled stem M which rotates in a ground joint and can be set so as to bring any one of the three faces into the beam. By having only three faces any one face is completely shielded from the material sputtered from that which is in the beam, and at the same time it is possible to make very rapid comparisons between various targets

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

Editorial note, tabletop extrapolation: A boron target plus a blank plus a calibration face on one rotatable holder would let the builder switch targets and measure background without venting.

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

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

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

The grid should be made from tantalum or tungsten wire and be fusion or resistance welded.

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

Editorial note, tabletop extrapolation: Applies in spirit to a next machine's chimney slits, puller edges and beam stops: anything the beam or arc dwells on gets a material-and-joint choice made against its actual power density. Refractory metal with welded joints is the robust default where cooling is absent; cooled copper or graphite are engineered alternatives (dg-426, dg-939).

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

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

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

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

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

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

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

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

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

The project was a long and laborious one, but the efforts were well-rewarded when the first beam was obtained three years later, in the spring of 1957.

McGuire, The Iowa State University 1.5 MeV Undergraduate Cyclotron (1961) — p. 3

Editorial note, tabletop extrapolation: Schedule reality check consistent with the census: documented start-to-first-beam gaps run one to six years (the builds page's computed spread), and Iowa State's three sits mid-pack.

TOTAL: $128500. Who has >$125k to blow on a very modest strawman small particle accelerator?

Niell, Effective Scientific Equipment Procurement Strategies: Building on a Budget (2010) — p. 2-3

Editorial note, tabletop extrapolation: Calibrates a next machine's budget: every subsystem not scrounged or fabricated costs thousands new (the article's line items), which is why surplus procurement dominates documented amateur practice - the census's cost trail says the same.

Cost: Can spend no more than $400. Performance: Want to measure 40MHz sinewaves... Function: Must be in calibration, and nearly bombproof

Niell, Effective Scientific Equipment Procurement Strategies: Building on a Budget (2010) — p. 7-10

Editorial note, tabletop extrapolation: A disciplined method for the next machine's shopping list: define the B-field, vacuum and RF numbers first, then match each purchase to the cheapest vendor tier whose reliability that subsystem can tolerate - judged per purchase, not by a permanent vendor ranking.

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

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

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

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

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

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

If the task is to obtain an average field with a value of the field decay index n close to constant for all radii, then the axial gap g can vary in accordance with the expression

Smirnov, The Cyclotron and Its Modeling — Phys. Part. Nuclei 52 (2021) — p. 49

Editorial note, tabletop extrapolation: A one-line pole-taper recipe for the builder tool: pick n (e.g. 0.02-0.2), machine the gap to this power law, verify in FEMM.

An angle kick of typically 50 to 100 mrad is provided. The inner electrode, septum, is at earth potential. At the entrance it has a thickness of a few tenths of a mm, increasing to several mm at the exit.

Botman & Hagedoorn, Extraction from Cyclotrons — CAS, CERN 96-02 (1996) — p. 14

Editorial note, tabletop extrapolation: At 350 keV a 100 mrad kick over 10 cm of arc needs E = theta*(2T/q)/L = 7 kV/cm - about 3.5 kV across a 5 mm gap. At nanoamp beams the septum's heat load is negligible whatever fraction it intercepts: 1 nA of 350 keV beam carries only 0.35 mW in total.

a criterion for the product of electric field E and potential V for a cyclotron deflector in order to avoid electric discharges: VE < 1.5 104 (kV)2/cm. The maximum sustainable voltage in a magnetic field is 20-30% lower.

Botman & Hagedoorn, Extraction from Cyclotrons — CAS, CERN 96-02 (1996) — p. 14

Editorial note, tabletop extrapolation: A 3-5 kV, 5-10 kV/cm tabletop deflector sits orders of magnitude below this bulk-discharge criterion - so at tabletop scale the practical ceiling comes from feedthrough, surface and edge-radius engineering (dg-353, dg-297, dg-295), not from the Smith-Grunder product.

At HV edges, electric field lines become so dense that breakdown becomes a major concern. Aluminum=290 kV/inch ... We settled on a minimum radius of R=.1875 inches ... Emax=170 kV/inch

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

Editorial note, tabletop extrapolation: Direct amateur precedent: a 1 T / 472 keV university tabletop deflector ran at 28-32 kV. A lower-energy machine needs proportionally less deflector voltage (scaling roughly with beam energy at similar geometry - a 150 keV-class machine perhaps a third, not a tenth), and the edge-field formula stays the design check: generous radii reduce peak field, they do not make sparking impossible - finish and conditioning still rule (dg-295, dg-353).

Mammoflex M-1 HV cable has C of 56 pF per foot ... ~0.1 Joules at 30 kV ... ~0.4 Joules at 30 kV ... The bottom plate and deflector electrode - no pitting on the electrode noticed.

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 43 (stored energy; repeated 45, 49) and 44 (pitting)

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: Rutgers' slide sequence recounts arcing a feedthrough run above its class and rebuilding with the feedthrough inside vacuum plus a corona adapter. The specific numbers, page-image verified 2026-09-06: cable stored energies ~0.1 J (5 ft) and ~0.4 J (20 ft) at 30 kV via 56 pF/ft Mammoflex M-1, and a feedthrough 'rated for 30 kV (we want to run it at 35)' - the overrun plan is the cautionary half of the lesson. Choose feedthrough rating from the manufacturer's figure, the vacuum-side geometry and test history, and never run a feedthrough above its rating. [Note revised 2026-08-23: 'rate 2-3x over operating voltage' was an invented margin.]

For DR = 0.1R: Va = 47,000 volts ... A typical figure, used in the MIT cyclotron, is a DR of 0.15R. ... The deflector gap is usually tapered.

Livingston & Blewett, Particle Accelerators (1962) — p. 163-166

Editorial note, tabletop extrapolation: Scaling by 2T: a next machine at 350 keV needs about 1/45 of MIT's voltage at the same normalized geometry - roughly 1-2 kV across a proportionally scaled entry gap - rising if a faster peel (larger DR) or a larger gap is wanted. Compute with the formula for the actual geometry (dg-590's worked example).

The cathode body is a 5.1-cm-diameter iron rod that has been machined to the dimensions and geometry shown in Fig. 1. ... samarium cobalt (Sm2Co17) permanent magnet ... surface flux density of approximately 3 kG ... the cathode faceplate is fabricated using the same iron rod as the cathode body. A 3.2-mm-thick, 5.1-cm-diameter disk is cut from the iron rod and machined with a 6.4-mm-diameter hole on centerline. ... a 100 kOhm, 100 W resistor is connected in-line with the power supply to current limit the discharge. ... generate a plasma discharge that yields a continuous 1 mA beam of positively charged hydrogen ions at 1 mTorr of pressure. This operating condition requires 5.4 kV and 32.4 W of power.

Rovey, Ruzic & Houlahan, Simple Penning Ion Source for Laboratory Research and Development Applications (2007) — p. 1-3

Editorial note, tabletop extrapolation: Existence proof that mA-class hydrogen PIG output needs only tens of watts and modest fabrication (machined rod, spot-welded sheet anode). The axial-extraction geometry differs from a cyclotron chimney, so the discharge economics transfer as encouragement - the chimney's own extraction still needs its own validation, and the 1 mA is aggregate hydrogen ions, not mass-analyzed H+.

The slit chimneys produced a beam that was nearly horizontal (in z) and was, on average 70% as tall as the chimney opening after passing through the puller. The hole chimney produced a beam that (in the absence of strong focusing) diverged in z.

Forringer, Phase Space Characterization of an Internal Ion Source for Cyclotrons — MSU dissertation (2004) — p. PDF p. 121 (printed p. 111) for the 70% claim; PDF p. 84 (printed p. 74) for the Fig. 3.12 caption

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: the actual machining callouts for a chimney a home shop can cut. The thin-land/outward-chamfer rationale (don't collimate the beam away; the thesis suggests deeper chamfers may raise current) is engineering reading of the source's optimization remarks.

The cathode anode gap was between 0.075" (1.9 mm) and 0.150" (3.8 mm), and is not a critical parameter for the source's operation.

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

Editorial note, tabletop extrapolation: Generous tolerance on the AXIAL gap - that part of the chimney stack-up doesn't need precision. Concentricity and slit alignment are separate tolerances with their own tighter demands, and the cooling warning stands at any arc power: provide a conduction path sized for continuous arc wattage, or plumb water.

the properly aligned configuration produces significantly more secondary emission electrons ... with the anode rotation angles from -0.2 to -1.5 degree, more than 50% H- beam can be extracted through pullers

Mu et al., Simulation of Electron Behavior in PIG Ion Source for 9 MeV Cyclotron (2015) — p. 4-6

Editorial note, tabletop extrapolation: Two different tolerance classes: build the chimney concentric (pin the cathode discs to the bore, machine in one setup), and provide an external rotational adjustment of the source stalk with sub-degree feel for slit-to-puller aiming. The KIRAMS optimum spanned about a degree, so an adjustment range of a few degrees around nominal is the class to design for - the actual optimum is found on the machine, not inherited.

A series of studies were made on a model magnet with poles 2 inches in diameter. This could be changed quickly and cheaply to give rough data over a wide range of parameters.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 7

Editorial note, tabletop extrapolation: General magnet practice, transferable with its limits: a small bolt-together model surveys geometry cheaply (CIT's 2-inch scans were 'rough data over a wide range'), while saturation and B-H behavior do not scale - same-steel-same-B is what made scaled prediction land elsewhere (dg-1322). The model surveys shape; full-size verification still happens, or FEMM plays the model's role (dg-1089).

The deflection of the poles under the magnetic load was found to average .002 to .004 inches for the model.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 9

Editorial note, tabletop extrapolation: Historical calibration context, not a prediction: estimate the next machine's load from magnetic pressure B^2/(2 mu0) over the pole area and its structure's stiffness, distinguish per-pole motion from total gap closure, and always shim and map at operating excitation, not cold.

A final pair of model poles was machined out of the steel forgings actually used for the full-scale magnet poles. The results were satisfactory, and the design was frozen.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 10

Editorial note, tabletop extrapolation: Transferable principle: validate on material representative of the production poles - measure coupons from the actual pole stock or the finished poles themselves; same-lot shim stock is a reasonable extra precaution but is beyond what the source demonstrates.

The machining of the pole tip was held to +/- .0025 inches on almost all dimensions.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 11

Editorial note, tabletop extrapolation: A few-mil pole tolerance is achievable in a good hobby/job shop - derive the next machine's actual requirement from gap sensitivity and the field-uniformity budget, and remember final mapping and shimming absorb what machining leaves.

Glass tape is inserted along all metal seams to prevent weld-flash from entering the can.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 14

Editorial note, tabletop extrapolation: Directly applicable craft rule for welding on or near a next machine's coil case: glass tape or an equivalent temporary barrier keeps weld flash and spatter out of the can. It does nothing against brazing flux, molten filler or conducted heat - hot work near a wound coil also needs thermal protection and temperature monitoring, or should be finished before winding. [Note revised 2026-08-23: earlier note extended the barrier to 'any welding or brazing'.]

Each assembly was leak-tested with a helium mass spectrograph after manufacture.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 20

Editorial note, tabletop extrapolation: Bench-test each next-machine spool, duct, and feedthrough before it disappears into the stack - vacuum-mode helium mass-spectrometer testing is the acceptance method the source used. Rate-of-rise and sniffing are preliminary screens only; keep soap solutions off vacuum-wetted surfaces, and pressurize a vacuum-only part for testing only if it has a documented pressure rating.

Cited in: The Vacuum Budget of a Cyclotron

results now indicate that four 880's will suffice, while the data from the three-fourths scale model had indicated that six would be necessary.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 29

Editorial note, tabletop extrapolation: Transferable caution - stray capacitance, proportions and device parameters do not scale cleanly; validate a next machine's dee voltage vs drive on the actual resonator, using models as guides.

good contact is established by the use of strips of thin soft copper sheet backed by foam rubber pads.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 10

Editorial note, tabletop extrapolation: The cheap 1948 equivalent of RF finger stock for external, low-temperature joints - removable housing panels and line covers. For vacuum-facing or high-current joints (dee-stem clamps), use vacuum-compatible spring contacts or engineered clamps with verified pressure and RF heating: ordinary foam rubber outgasses and relaxes.

Over 50 kilovolts rf could be developed across the insulator at 13 mc by a 5 kilowatt oscillator. Under the most severe test conditions, air blast cooling of the insulators was found necessary.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 13

Editorial note, tabletop extrapolation: A bench resonator lets the builder soak-test dee-stem insulators at full 5-13 kV RF from modest drive - how modest depends on the fixture's measured loaded Q (constant-Q scaling of the cited point suggests tens of watts at 5 kV but hundreds at 13 kV), so measure Q and compute the drive rather than assuming it.

For reasons of convenience, a quarter scale was chosen. The resonant frequency is then increased fourfold and all inductances and capacitances are reduced by a factor of four.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 14

Editorial note, tabletop extrapolation: Transferable method: prototype a next machine's resonator at reduced scale with a VNA - remembering effective dee capacitance is not the static value, which is exactly what the model run is for.

The evident discrepancy in transmission line length was eventually traced to a cumulative error of about two inches in various small errors in model dimensions.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 22

Editorial note, tabletop extrapolation: Directly applicable: give a next machine's resonant line or tank a deliberate tuning range - trombone section, tuning vane, trimmer capacitor - instead of trusting calculated dimensions to land the frequency.

the upper two insulators are under pure compression, the lower two under pure tension. ... The rf insulators have given no trouble whatever since installation one year ago, though at the time of assembly, their fragility was evidenced insofar as shear forces were concerned. The care taken in insuring that only pure tension and compression forces would be applied was thus well justified.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 24

Editorial note, tabletop extrapolation: Directly applicable to a next machine's dee-stem standoffs and feedthroughs: arrange the support geometry (threaded rods, spherical seats) so ceramics never see bending or shear - prefer compression where practicable, avoid point loading, and respect the manufacturer's tensile rating, which is far below the compressive one.

The horizontal joints are also rubber backed, but no particular care is necessary to insure contact as the current flow is parallel to the joint.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 6

Editorial note, tabletop extrapolation: Plan a next machine's panel seams along the RF current direction and spend the contact-strip effort on the seams that cross current - remembering fringing and return currents can cross nominally parallel seams, so verify with a current map or by checking seam temperatures at power.

Polystyrene of this thickness used in this manner will stand over 15,000 volts DC and approximately 1500 volts r.f. provided the metal parts remain cool.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 8

Editorial note, tabletop extrapolation: A historical construction worth knowing, not a transferable rating: the implied DC stress is ~59 kV/mm, so the numbers belong to that geometry, cooling and test practice. For a next machine's RF chain, prefer certified RF/HV capacitors; if building, take the dielectric's own data (Kapton is often lossier than polystyrene or PTFE at RF), derate heavily, design creepage and corona control, and test thermally and at withstand voltage.

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.

There was considerable sparking between the HV electrode and the .002 inch copper foil. The copper foil was warped badly ... The 0.002 inch copper foil supported in this manner is not suitable for this job.

Sewell, 184″ Cyclotron: Vertical D.C. Electrostatic Deflector — MDDC-1051 (1947) — p. 2

Editorial note, tabletop extrapolation: A next machine's septum should be sized against the deflector's stored spark energy and thermal impulse, then tensioned or heat-sunk accordingly - conditioning sparks are part of deflector life, and the septum edge is where they concentrate. Thickness follows from that calculation, not from a fixed minimum.

Construction started 1940. Completion date July 1941 ... Total cost $5000 initial, $5000 improvements.

Howard, Cyclotrons and High-Energy Accelerators, 1958 — ORNL-2644 (1958) — p. 166

Editorial note, tabletop extrapolation: Scope calibration: small teams on small budgets built working 2-4 MeV, 16-27 inch machines in this era. A next machine at the few-hundred-keV scale on 8-in-class iron - dg-697's K ~ 48*(B*r)^2 gives about 0.35 MeV at 1 T on an 8-in pole's usable radius - is historically a modest, well-precedented project.

It was decided to use Eimac grid collet (which is .020" thick in contrast to their regular line of finger stock which is .010" thick) mounted on water cooled copper blocks ... dee stem surface was silver-plated copper which was also water cooled. The shorting plane as originally installed has been in service for nearly three years and has performed flawlessly. There is no discoloration or other indication of heating of the contacts, despite routine operation to 110 A/in and occasional operation to higher current densities

Osterlund & Smythe, A Cyclotron Power-Amplifier RF System Using a 4CW50,000C/8350 Tetrode — COO-535-543 (1963) — p. 8

Editorial note, tabletop extrapolation: The recipe transfers - thick fingers, positive clamping, plated surfaces, cooling on both sides of the joint - the number does not: calculate the proposed tuner's actual contact current, then verify temperature rise and contact resistance under representative duty; a demonstrated operating point in one cooled geometry is not a ceiling for another.

The minimum radius of curvature of the high-voltage electrode should be large enough to prevent appreciable field-gradient magnification. In practice, the minimum radius should be no less than about half a gap.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 17

Editorial note, tabletop extrapolation: Direct machining rule - for a next machine's 3-mm deflector gap, radius every HV edge to at least 1.5 mm and polish.

At the smaller gaps the electrode vibrated like a tuning fork in a tuning-fork oscillator. ... The forces driving the electrode were electrostatic; the device that provided the pulsating force was the dark current. ... Simplifying this circuit by the techniques of network analysis the system reduces to that of a Colpitts oscillator. ... The period is 50 msec corresponding to a vibrational frequency of 20 cps. ... Curve 1 was taken before insulators were installed and electromechanical oscillation occurred, resulting in VE = 1.23 x 10^4 (kV)^2/cm; curve 2 was obtained with insulator supports which prevented electromechanical oscillation, crowbar was set at 0.4 A, resulting in VE = 1.47 x 10^4 (kV)^2/cm

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 17

Editorial note, tabletop extrapolation: Very much in reach of amateur trouble - a small cantilevered electrode has low mass and compliance. Support a next machine's deflector bar on insulators at both ends and check the deflector voltage on a scope for slow oscillation buildup.

Each circuit board consists of 100 Unitrode, Type UT71, silicon diodes connected in series. Each diode is shunted by a 250-pF, 500-V, ceramic capacitor to divide the inverse voltages equally.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 10

Editorial note, tabletop extrapolation: Today this is a standard multiplier stack; keep the two features that matter - per-diode grading capacitors (transient sharing; add static resistors or integrated HV rectifiers for dc sharing) and high drive frequency, which buys regulation into a varying load. What frequency does NOT buy is low stored energy: 0.5*C*V^2 is set by the capacitors, so compute the stack's accessible spark energy and add local limiting before pointing it at a sparking deflector.

The spacing between boards is about 2 in. and provides a nominal maximum design gradient of 10 kV per in.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 10

Editorial note, tabletop extrapolation: For an amateur HV column, run the real layout numbers: air clearance and surface creepage separately, field stress at conductor curvatures, contamination and altitude derating, and a controlled HV test - matching the historical 10 kV/in exactly (6 in at 60 kV) leaves zero headroom by construction.

the deflector oscillators are located close to the magnet yoke of the cyclotron in a field of about 150 G, magnetic shields had to be put over the 4CW2000 oscillator tube and the 3D22.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 19

Editorial note, tabletop extrapolation: Map the field where equipment will sit and shield or relocate per COMPONENT tolerance: transformers, inductors, Hall sensors, relays and fans all care about DC field to different degrees, PMTs need residual fields far below 150 G (high-permeability or multilayer shields), and a mild-steel can's attenuation depends on geometry, seams and saturation - the cited caps are proof the approach works, not a universal thickness spec.

Approximately ninety percent of the total power input to the system is eventually dissipated in the transformer cores as heat. At rated operating levels this loss is approximately 500 watts.

Kerns et al., High Voltage Pulser for 184-inch Cyclotron Electric Deflector — UCRL-95 (1948) — p. 12

Editorial note, tabletop extrapolation: Transferable craft here is the failure mode (interlaminar voltage at high volts-per-turn) and the de-aerated-oil practice - which reduces bubbles and partial discharge, not corona from bad geometry. The 300-kV survival was that transformer's result, not a portable 3x proof-test rule: overvoltage testing at these levels is itself hazardous and can leave latent damage, so test to an applicable HV standard's waveform, duration and partial-discharge limits, remotely, with discharge provisions - not to a generic multiple.

To insure proper positioning and grounding of the lower end of the ion source, a bracket has been attached to the west side of the liner which places the ion source one inch below the center of the magnetic field. This arrangement insures that the position will be the same from run to run and also reduces heating of the tube due to rf pickup.

Howard (ed.), Electromagnetic Research Division Quarterly, period ending 31 March 1952 — ORNL-1339 (1952) — p. 10

Editorial note, tabletop extrapolation: Cheap and directly imitable — once the optimum source position is found by scanning, capture it in a hard registration feature so it survives every source rebuild; grounding the support also kills a stray RF-heating path.

The alignment of the source with the magnetic field is extremely critical, as was expected, and makes it necessary to provide for external adjustments of the ion source.

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

Editorial note, tabletop extrapolation: Strong design input for a next machine: budget at least one externally accessible source degree of freedom (rotation or z) - both ORNL machines provided it after finding the optimum unreachable blind. Adjustment under beam is the convenient form; adjust-then-pump iterations reach the same optimum, slower.

moving the 8 inch plug to 5.5 inches from the valley floor and to extend the caps to a length of 3 1/2 inches. These caps saturate at high levels, but fill in the central "hole" at low fields.

Jungerman, Kibbe & Peek, Central Region Studies for Incorporating an Axial Ion Source in the Davis 76-in. Cyclotron — UCD-CNL-49 (1966) — p. 6

Editorial note, tabletop extrapolation: Deliberately-saturating iron as a field-programming element is a trick FEMM (with the real BH curve) models well: a piece sized to saturate at the main operating point contributes mostly at low field - but saturated iron keeps its magnetization, so verify the high-field map still meets spec rather than treating the cap as magnetically gone.

The contour of the shim when the steel surface is not an equipotential is best determined experimentally. An approximate shim can be put on a pole which otherwise has its final form.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 8

Editorial note, tabletop extrapolation: The next machine's shim program: FEMM (finite permeability, saturation modelled) resolves much of what 1952 needed bench passes for - validate the final contour against a probe map where the nonlinearity is significant, as NYO-780 (p.7) did with its bolt-together model magnets.

In a high-current low-voltage coil, insulation is required only to maintain mechanical separation of the conductors.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 25

Editorial note, tabletop extrapolation: What transfers is the architecture - few turns of heavy conductor at high current, direct cooling through generous passages - which beats many-turn fine-wire coils on space factor and pumping pressure. The bare-minimum insulation standard does not transfer: a modern coil wants verified turn-to-turn and ground insulation against inductive transients (dg-218's dump events), abrasion, thermal aging and coolant exposure, cheap as modern materials make it.

A second type of coil which is more attractive, when the coil must be wound at the cyclotron site, is a flat-wound helix.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 26

Editorial note, tabletop extrapolation: Directly a garage-scale construction technique: cut flat copper sectors, stack into a helix, join into a continuous conductor - no winding mandrel needed. The joints are the engineering: braze for permanent low-resistance splices, bolt only with designed contact pressure and area (the report's joint-sizing criterion: scan re-read queued for the number), and place cooling per the report's tube arrangement.

One square centimeter of metallic contact distributed over the joint will carry 10,000 amps with negligible resistance and temperature rise.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 32

Editorial note, tabletop extrapolation: Bolted bus laps at amateur coil currents have huge nominal margin by this figure - but nominal lap area is not metallic contact area: oxide, pressure, fastener relaxation and thermal cycling decide the real contact. Prepare surfaces, clamp hard, lock against loosening, then verify with a four-wire millivolt-drop measurement and a full-current temperature check. A joint that passes those two tests is electrically invisible; one that hasn't been tested is a fire waiting for a loose bolt.

opened automatically when the mechanical pump is shut down so as to break the vacuum in the line and prevent the pump oil from backing up the line.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 140

Editorial note, tabletop extrapolation: Transfers directly to a garage system: an automatic vent interlocked with the roughing pump - or a vacuum-rated anti-suckback valve, which is not the same thing as a generic check valve - prevents the classic oil-suckback chamber contamination. The source's practice of putting flexible connections in vertical runs (so oil cannot pool in them) is worth copying too - reported practice, scan re-read queued.

Cited in: The Vacuum Budget of a Cyclotron

welding neck flanges with double O-ring gasket grooves machined in a standard flat face flange and provided with a pump-out connection between the two gaskets.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 141

Editorial note, tabletop extrapolation: The double-O-ring-with-interspace-pumpout trick is worth stealing for any large troublesome amateur flange (chamber lids especially): sniff the interspace for leak location, or hold it at rough vacuum to intercept most of the atmospheric load across the inner ring - it reduces, not nulls, permeation, since the elastomer still outgasses and a gradient to the chamber remains.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The crystal oscillators, Nos. 3 and 5, will maintain a constant frequency within one part in 10,000.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 169-170

Editorial note, tabletop extrapolation: The stabilization pattern transfers even where the parts are now silicon: put the reference AND the analog discrimination components in one controlled thermal box, because the filter drifting is as fatal as the oscillator drifting - then budget the whole chain (oscillator, filter, mixer, threshold) instead of assuming the oven number covers it.

Fig. 6.3-Typical characteristics of three-fourths scale model ... 150-kw input, 27.5-kw plate dissipation per tube ... The fairly low efficiency, 27 per cent, indicates that it would be desirable to go to six type-880 tubes in the final model

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. PDF p.162 (unnumbered chapter opener, Technical Report No. 6) for the quoted text; the figure is on PDF p.167 = printed p.167

Editorial note, tabletop extrapolation: The transferable method rule - prototype the next machine's dee/stem/liner as a cheap scale model (or full-scale mockup, given the small size) and measure resonance, Q and parasitics before final fabrication; NYO-780 p.29ff records the same practice. Cite both.

It was found necessary, however, to use a covered carbon boat both to reduce the radiation cooling of the boron and to prevent scattering of the material during the heating.

Hoke & Newman, Self-Supported Cyclotron Targets of Boron and Magnesium — ORNL-3021 (1961) — p. 6

Editorial note, tabletop extrapolation: Boron is among the worst common elements to evaporate - it runs at white heat and attacks refractory-metal boats - and carbon-rod stock is cheap and machinable with ordinary tooling, so this is the boat design to copy for B-11 films. The recipe handles the isotope like any boron; the TARGET still needs its own qualification: verify enrichment survives the process, check carbon/carbide pickup, and measure uniformity and areal density before calling it experiment-ready.

Pressure was maintained below 1 x 10-5 mm of Hg while the boat was being brought to temperature. Then, by passing a current of about 280 amp at 8 volts through the boat, a sufficiently high temperature was reached (white heat) to vaporize the boron. The progress of the evaporation was followed by observing the material as it heated in the boat. The boron remained darker than the boat until just before vaporization, then it became bright and quickly disappeared. The boron was evaporated onto 3 1/4 x 4-in. glass plates.

Hoke & Newman, Self-Supported Cyclotron Targets of Boron and Magnesium — ORNL-3021 (1961) — p. 6

Editorial note, tabletop extrapolation: Scope honestly: this is EVAPORATION producing ug/cm2-class self-supported films - potentially suitable for a p+B11 cross-section or resonance-yield measurement once areal density, uniformity and purity are characterized - and NOT the route to a thick target for a maximum-alpha-yield demo. The hardware (2.2 kW low-voltage supply, 1e-5 torr bell jar) is within amateur reach ONLY with the engineering done: rated water-cooled feedthroughs for 280 A, fault protection, implosion screening, and hot-material handling.

The boats are useful for only two evaporations at most since the slot rapidly becomes clogged with boron carbide.

Hoke & Newman, Self-Supported Cyclotron Targets of Boron and Magnesium — ORNL-3021 (1961) — p. 6

Editorial note, tabletop extrapolation: Plan an enriched-B11 evaporation campaign around several pre-machined spare boats rather than debugging mid-run. The failure mode is the carbon: refractory-metal boats, compatible crucibles or non-contact heating change or avoid it - candidate fixes to compatibility-test, not guarantees.

the method found successful here was to float the boron off the plate with warm tap water. Prior to evaporation the plate was cleaned by washing in a Calgonite solution and rinsed with water. The plates were placed at an angle of about 20 deg to the horizontal and water was allowed to run in slowly. The floating film was then cut into appropriate sizes, and the pieces were picked up on square target frames of aluminum 0.030 in. thick. ... breakage of films can be greatly reduced by adding a pinch of detergent, such as Calgonite, to the water to reduce surface tension just before the film is picked up, and also by stopping just before removing the frame from the water to allow trapped water to drain off.

Hoke & Newman, Self-Supported Cyclotron Targets of Boron and Magnesium — ORNL-3021 (1961) — p. 6

Editorial note, tabletop extrapolation: The film-recovery toolchain is modest (named detergent, tap water, glass plates) and the skill is in the sequence - which the card now quotes in full. Use the source's Calgonite or a validated low-residue lab surfactant rather than assuming any modern dishwasher detergent is equivalent. Practice on natural boron before spending enriched B-11.

Stronger double films, which proved to be much easier to make, were made by bringing the frame up in the middle of the film. The film then folded over the frame

Hoke & Newman, Self-Supported Cyclotron Targets of Boron and Magnesium — ORNL-3021 (1961) — p. 8

Editorial note, tabletop extrapolation: For a next machine's B11(p,alpha) internal-target work, the double-fold film is the mechanically survivable construction - but qualify its thickness against the experiment's energy budget with current stopping data: compute the proton energy loss and straggling through the actual post-fold areal density with PSTAR/SRIM at the actual beam energy before calling it thin enough for resonance-tail work (at ~170 keV the loss through these films is substantial, not negligible).

For the evaporation of magnesium, boats of 3-mil tantalum about 3/4-in. wide were used. The pressure was maintained below 2 x 10-5 mm of Hg, and the current was increased to about 100 amperes. The scattering of the MgO by violent outgassing can be minimized by increasing the current slowly over a period of 10 to 20 minutes so that the outgassing can occur quietly. ... the glass was coated with a weak soap solution (Calgonite) and allowed to dry before it was coated with about 5 to 10 ug/cm2 of carbon from an arc ... One function of the carbon layer is to help keep the magnesium from making contact with the water; magnesium is slightly soluble in water and decomposes to form Mg(OH)2. The carbon also helps hold the magnesium film together both while it is being removed from the glass and afterwards. ... a glass hood was constructed from lantern slide covers so that all of the collected material could be recovered.

Hoke & Newman, Self-Supported Cyclotron Targets of Boron and Magnesium — ORNL-3021 (1961) — p. 9

Editorial note, tabletop extrapolation: Three tricks generalizable WITH per-material validation: sacrificial arc-carbon parting layers under fragile or water-reactive films (validate compatibility - carbon can add reaction background or stick badly to another material), slow-ramp outgassing before full evaporation power, and a cheap glass recovery hood (lantern-slide covers) so enriched material can be recovered - recovered stock needs a purity check before reuse.

Representatives of the steel industry were consulted to determine the size of forging of the required shapes that could be practicably produced.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 136

Editorial note, tabletop extrapolation: Scale-free: for a next machine this reads 'call the waterjet/plate supplier before freezing the pole drawing' — same move as TID-454's cost-driven magnet design.

The estimate of $0.35 per pound for the finished magnet appears reasonable when compared with the unit price of $0.26 per pound paid for another large magnet at the Laboratory.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 245

Editorial note, tabletop extrapolation: Scale-free estimating hygiene: their App. F traces $11.5M to named suppliers; a next machine's BOM should likewise tie each line to a quote, a catalog page, or a reference machine receipt — and explain deltas ('more complex machining, more waste metal').

The method of brazing is considered unsatisfactory because of the extreme probability of leaving large flux inclusions between the beryllium metal and the aluminum base, which would seriously impair heat transfer.

Howard (ed.), Electromagnetic Research Division Semiannual, period ending 20 March 1953 — ORNL-1531 (1953) — p. 17

Editorial note, tabletop extrapolation: The corpus's targetry shelf is thin, and the transferable core is real: flux is a void-former at exactly the interface a beam target cannot afford. For a next machine's boron or beryllium targets on copper or aluminum, treat flux-free vacuum or controlled-atmosphere brazing as the candidate route - and qualify it with coupon brazes, sectioning and thermal cycling, because wetting and expansion behavior change with each material pair.

the magnet pole faces (tank walls) are being ground with a portable grinder to provide a very uniform magnetic field, as near +/- 0.01% as possible. This will then provide a standard base for the various magnetic shim designs

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 March 1954 — ORNL-1670 (1954) — p. 20

Editorial note, tabletop extrapolation: For a next machine's shim development: establish and map the unshimmed field to the best flatness attainable FIRST, so every FEMM-predicted shim is measured against a known zero rather than an uncharacterized pole error. Set the flatness target from a phase budget, not a fixed gauss figure: accumulated slip is roughly 360 deg x N_turns x dB/B for a uniform mismatch, so a many-turn low-voltage machine needs proportionally tighter field than a few-turn one. (Also proof that hand tooling on installed poles was acceptable ORNL practice - no magnet disassembly required.)

The liner, dees, and dee-stem housing are being fabricated by an outside contractor. The faceplates, dee stems, ion source, target probe, and vacuum system were fabricated locally

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 March 1954 — ORNL-1670 (1954) — p. 20

Editorial note, tabletop extrapolation: The three-report arc remains this collection's cleanest outsourcing story: the contracted brazed, water-cooled vacuum parts were where the delays landed - one program's experience, and a fair prior. For a next machine: buy simple machining, keep leak-integrity parts in-house or design them repairable.

Cited in: The Vacuum Budget of a Cyclotron

several leaks in very inaccessible locations have delayed final assembly. In order to repair the leaks in the internal water-cooling tubes it was necessary to cut windows through the sides of the dees. The windows were then closed by Heliarc welding.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 September 1954 — ORNL-1795 (1954) — p. 19

Editorial note, tabletop extrapolation: If a next machine's dees carry water: treat internal cooling leakage as a credible failure and route tubing so joints and runs can be reached (or provide removable covers) where RF and vacuum allow; pressure-test the dee as a unit BEFORE it meets the liner; and note the historical recovery mode - cut a window, fix, reweld - is documented practice worth keeping in the back pocket.

Grinding and shimming of the tank walls to produce a flat magnetic field was continued. The magnetic field is now uniform to within 0.05%.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 September 1954 — ORNL-1795 (1954) — p. 19

Editorial note, tabletop extrapolation: Calibrates expectations, not a budget line: sustained professional effort on the 44-inch bought 5e-4 base-field uniformity against a 1e-4 aspiration - so plan for the ground pole to fall short of its target and for shims to close the remaining gap, with the actual allowable derived from the machine's own phase-budget arithmetic and verified by mapping. How the 0.05% split between grinding and shimming the report does not say.

The one-quarter-scale model magnet is of the closed-yoke type. ... Its total weight will be 14.4 tons; 12.7 tons will be iron and 1.7 tons will be copper. The magnet gap will be in a vertical plane to provide the greatest access for making field measurements. The pole tips are removable so that shims of any shape can be inserted readily.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 September 1954 — ORNL-1795 (1954) — p. 19

Editorial note, tabletop extrapolation: For any next-machine shim-test rig (or a scaled FEMM-validation magnet), design for the measurement campaign: open sightlines for the Hall probe, pole tips that unbolt, gap oriented for jig access - the orientation serving the probe rather than mimicking the final machine is the editorial reading of ORNL's choice.

The whole dee system is supported by a cantilever mounting at the outer end of the dee stems. This mounting is supported on insulators in order to permit the application of a bias potential to the dees.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 March 1955 — ORNL-1884 (1955) — p. 19

Editorial note, tabletop extrapolation: An attractive pattern for a next machine: one stiff cantilevered dee-stem mount outside the field region, isolated for DC bias, is mechanically simpler than distributed insulated supports. Design the RF side separately - insulating the mount enables bias but does not by itself define the RF return path, so engineer the ground plane, bypassing and bias feed network explicitly, and check insulator loading and flashover.

Morley Machine Company, Rochester, N.Y., produced milling cutters conforming to this equation ... Subsequent work has shown that circular arcs would have been satisfactory.

Bromley & Bruner, The Design of a Focusing and Analyzing System for the 27-inch Cyclotron Beam — NYO-3823 (1954) — p. 29

Editorial note, tabletop extrapolation: A candidate money-saver for a next machine's quads: circular-arc (or round-stock) tips - validated by checking the integrated multipoles and end effects in FEMM against the beam's actual field-quality requirement, which is where the modeling time belongs; adequacy depends on aperture fraction used and multipole tolerance, so it is not automatic.

The tips formed the top and bottom of the vacuum chamber of the magnet, while the side walls of the chamber were strips of non-magnetic stainless steel welded to the tips.

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 9

Editorial note, tabletop extrapolation: The poles-as-chamber pattern eliminates the gap-wasting separate tank (the alternative Bromley rejected on machining/gasketing grounds, nyo-3823 p.6) - carry the METHOD and derive the gap tolerance from the analyzer's own field-error and resolution budget, minding weld distortion across the span.

The track has been rendered flat and horizontal to within 0.01" by a grinding machine rotated about the vertical post.

Alford, Bilaniuk & Hawrylak, Broad Range Spectrograph for Use with the Rochester 27-inch Cyclotron — NYO-9683 (1961) — p. 10

Editorial note, tabletop extrapolation: Two machine-design lessons to EVALUATE at any scale: generate precision in place with the tool swung about the final axis (kin to Wilson's lapped dees), and consider kinematic three-point support so the instrument neither rocks nor needs a precision floor - choosing the actual bearing layout from load, stiffness, overturning-moment and angular-accuracy analysis rather than copying the 5-ton architecture at 1/50 size.

This region is a current maximum point at the highest frequency and most sensitive to volume or inductance.

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 10

Editorial note, tabletop extrapolation: On a small machine the dee-stem-to-chamber-wall clearance is the candidate critical region - it plausibly sets both the resonant frequency and where I^2R heating concentrates. Confirm with an eigenmode/surface-current calculation (or low-power RF measurement with a thermal camera) for the actual cavity, then machine that region to drawing rather than shimming by eye.

Thermal neutrons are attenuated to about one-third of their initial flux by the first 10 cm of ordinary concrete. Therefore 2/3 of the activity produced by the neutrons would occur in this region. This makes it possible to design shielding with a row of concrete blocks on the inside.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 84

Editorial note, tabletop extrapolation: The modular-block enclosure pattern already favored for product machines gets a second justification: the inner course doubles as the sacrificial activation layer, replaceable without demolishing the shield. Two conditions travel with it: the 2/3-in-10-cm figure is for thermal neutrons in ordinary concrete, not every spectrum; and replaced blocks are surveyed and characterized before anything is 'disposed of' - activated material is a regulated waste stream (see /legal/).

only heavy duty industrial type limit switches should be employed, avoiding light duty switches to insure durability and reliability.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 149

Editorial note, tabletop extrapolation: BOM-level guidance for product machines — safety-rated (positive-opening) limit switches on lids/doors, not PCB microswitches, plus an interlock-test line item in the ops checklist (Cyclotron_procedures2 already has the pattern for vacuum; extend to safety chain).

Doors should be designed to provide shielding at least equivalent to the adjoining walls ... Travel of these large doors is necessarily slow but the momentum is great ... one must be able to open these doors even after a loss of power. Some manual method of opening the door from inside and outside must be included in the design.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. PDF 145 (printed 136)

Editorial note, tabletop extrapolation: Scale-invariant egress principle: even an interlocked benchtop lid or a walk-in enclosure door must never imprison anyone on power loss. The criterion is manual operability from both sides without power, verified by actually trying it - whatever the mechanism - and the door's own motion is a machinery hazard (pinch points, momentum) to engineer alongside its radiological job.

a final "touch up" machining of these pieces, with the final iron in place on the basis of magnetic field mapping studies.

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 5

Editorial note, tabletop extrapolation: Fully transferable at any scale — design a next machine's shims and center plugs as bolt-on, pin-located pieces so field-map-driven iteration does not mean remaking the poles.

a "Ferrofluidic" vacuum seal having ~ 0.005 in. radial gaps in which a ferrite loaded low vapor pressure liquid is held by magnetic fields

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 10

Editorial note, tabletop extrapolation: A candidate commercial component - available since 1971 - whenever an accelerator mechanism (chopper, rotating target, variable capacitor) needs rotary motion through the chamber wall; prices vary widely, so treat cost like any other spec. Verify the specific seal's pressure rating (one-atmosphere capability included), leak rate, vapour and backstreaming cleanliness, bakeout limit, speed and torque, and its behaviour in a nearby magnetic field before designing it in. [Note revised 2026-08-23: earlier note called it 'the clean answer any time'.]

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The capacitor housings have separate vacuum systems using turbomolecular pumps. RF feed through insulators separate them from the main cyclotron vacuum system.

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 10

Editorial note, tabletop extrapolation: Scales down as a case-by-case method: a sealed partition (like Nevis's insulator barrier) actually isolates the gas load; an OPEN differentially pumped appendage - the reference machine's diff-pumped source region - only reduces transfer through its conductance. Pick per mechanism from a conductance and gas-load estimate, and remember debris control is geometry, not pumping.

the rotors are at low RF due to their < 0.010 in. high capacitance face gaps to ground

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 10

Editorial note, tabletop extrapolation: The capacitive-shunting method transfers to rotating RF machinery (choppers, tuners) - by calculation, not copying: work out the gap capacitance (area and gap, not gap alone), the induced rotor voltage and displacement current at the actual frequency and power, and the field/breakdown margins in vacuum. The rotating-capacitor FM tuner itself is synchrocyclotron-specific and does NOT transfer to a fixed-frequency tabletop machine.

a half-wave resonator permits the rotating capacitors to be located outside the main vacuum chamber for good shielding from both the magnetic field and radiation

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 10

Editorial note, tabletop extrapolation: The placement principle transfers: keep variable capacitors, trimmers and drive mechanisms of a next machine's tank outside the pole gap and chamber, where field, beam spray and pumpdown cannot reach them - where the geometry allows it.

This septum will use only 40 kW of power, a factor of four smaller than if the original thickness were kept to the end

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 13

Editorial note, tabletop extrapolation: A current-septum channel is beyond tabletop needs, but the geometric principle - septum thickness need only be minimal on the first intercepting turn - applies to any conductive deflector septum on a next machine, subject to the beam-clearance check downstream. (Extraction FOILS are a different problem: stripping, scattering, heating and lifetime set foil thickness, not turn separation.)

all support insulators have been designed so that they can be removed and replaced by remote handling tools.

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 12

Editorial note, tabletop extrapolation: At tabletop energies the driver is vacuum hygiene and downtime rather than dose, but the same design habit — most-likely-to-fail parts (insulators, filaments, septa) replaceable without major disassembly — is what the reference machine's filament-change experience already argues for.

the insulators will be subjected to about 3 times the rotor voltage to ground. This is because the long metal supports act as open transmission lines

MacKenzie, Preliminary Report on the “Three Quarter Wave” R.F. System for Frequency Modulated Cyclotrons — AECD-1850, University of California (1947) — p. 8

Editorial note, tabletop extrapolation: Check the electrical length of every support, cooling line, and instrument stalk inside the RF volume against its actual return path and termination (loaded lines behave differently from open ones): a mechanically convenient standoff can sit at a voltage antinode and flash over at dee voltages its rating should easily hold. The 3x is MacKenzie's installation, not a universal factor - model or measure your own.

End effects and bends in the line can cause this much variation. The conclusion is that there should be some possibility of varying the line length by a small amount

MacKenzie, Preliminary Report on the “Three Quarter Wave” R.F. System for Frequency Modulated Cyclotrons — AECD-1850, University of California (1947) — p. 11

Editorial note, tabletop extrapolation: Design connection lines and stubs with a sliding section or trombone whose travel comes from a tolerance analysis (component-value uncertainty, bends, end effects) or a prototype sweep - the calculation gets you to the right neighborhood and the adjustment does the rest.

The four PAA tuning capacitors are now coupled together by a heavy-duty chain driven by a single large servo motor with one translator. No trouble has been experienced since this modification. Formerly, each of the four capacitors was driven by its separate servo motor with a pair of servo motors being fed by one of the two translators. This had resulted in capacitors being driven to unequal capacities upon the loss of a signal from a translator for any of several reasons. This then necessitated the removal of the capacitors to reset them for equal capacity tracking which is required for equal sharing of the RF current and for maximum tuning range.

Cyclotron Staff, Report of Cyclotron Operation 1 July – 31 December 1969 — NRL Memorandum Report 2103, Naval Research Laboratory (1970) — p. 24

Editorial note, tabletop extrapolation: Wherever two adjustments must hold a FIXED mechanical relationship (paired trimmers, symmetric shorting planes), a shaft, chain, or belt enforces the constraint by construction, with backlash and stretch as the residual error terms; keep independent trim where the relationship must be calibrated rather than fixed - software matching isn't doomed, but it reintroduces the desync failure class the chain removed.

After reinstallation of the ion source assembly into the cyclotron, the ion discharge aperture (0.09 in x 0.50 in) was optically aligned with respect to the median plane of the cyclotron magnetic field and the electric field of the dee.

Cyclotron Staff, Report of Cyclotron Operation 1 July – 31 December 1969 — NRL Memorandum Report 2103, Naval Research Laboratory (1970) — p. 26

Editorial note, tabletop extrapolation: Source aperture height and tilt relative to the median plane strongly affect first-turn survival; make re-alignment after source maintenance a fixtured, measured step (scribe lines, a sighting jig, or a depth gauge) instead of trusting bolted repeatability.

with the coils energized to 3500 amperes, revealed a negligible deflection of the inner walls (about 0.002 inch) which eliminated the possibility of future collapse

Cyclotron Staff, Report of Cyclotron Operation 1 July – 31 December 1969 — NRL Memorandum Report 2103, Naval Research Laboratory (1970) — p. 27

Editorial note, tabletop extrapolation: Every conductor near the pole gap feels J x B: thin walls, septa and coil leads need structural qualification, and a displacement measurement at above-operating excitation is one ingredient of it, not the whole - add the load calculation, yield and buckling margins, fatigue for cycled excitation, and fault-current loads. Motors, encoders and anything with a magnetic circuit belong outside the fringe field regardless.

Changes in the cooling water path for the 6949V1 anode increased the flow rate sufficiently that the allowable anode dissipation was doubled. This increased anode dissipation permits operation with higher dee voltages at the higher frequencies with a margin of safety for detuning of the anode circuit. ... we increased the flow rate to the 6949 tube plates from 42 gpm to 60 gpm by the addition of a 4-inch return pipe to separate the high pressure and low pressure water loops ... In an attempt to decrease future outages due to water pump failure, the mechanical and structural installation of a standby 200HP, 1400 gpm, 150 psi, demineralized water pump was completed with associated plumbing that places it in a parallel loop with the existing low pressure demineralized pump.

Cyclotron Staff, Report of Cyclotron Operation 1 July – 31 December 1969 — NRL Memorandum Report 2103, Naval Research Laboratory (1970) — p. 24, 29

Editorial note, tabletop extrapolation: When an amplifier cannot hold rated dissipation, check hydraulic head losses in shared manifolds before derating the tube; and duplicating a single-point-of-failure pump is a reliability purchase the outage ledger justifies - engineered in, with isolation valving and controls, not just teed into the pipe.

The lifetime of carbon foils is enhanced both by motion and by heating to about 400 C. Also, carbon foils have been observed to get thinner above 450 C and thicker when cooler. ... These facts suggest that perhaps the foil is damaged when there is radiation from a single spot only. ... It is fully adjustable, holds three targets, is chamber independent, and takes up limited space. It turns the targets at 1.9 turns per sec which is adequate for most experiments; it could easily go faster by using a Ferrofluidic mechanical feedthrough instead of an O-ring feedthrough.

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. 240

Editorial note, tabletop extrapolation: A rotating target holder is 1950s-shop technology (motor, gears, O-ring feedthrough at ~2 rev/s); the same shaft can carry several targets so a fresh one rotates into the beam without breaking vacuum.

Rolling is by far the most conservative process with regard to material loss in preparing thin targets. ... The vacuum evaporation process is very inefficient and frequently evaporation efficiencies of only 1% are obtained.

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. PDF p.18 (printed p.3) for Table 1's boron row; the efficiency sentence spans PDF p.17 (printed p.2) and PDF p.23 (printed p.8), the table intervening

Editorial note, tabletop extrapolation: The boron row of Table 1 is the direct answer for a B target: evaporation is the only listed route — 20-250 ug/cm2 self-supporting, 10-1000 ug/cm2 on a metal backing (boron is too brittle to roll). For thin-film evaporation recipes themselves cross-cite ORNL-3021; this table tells you which recipe book to open.

the metal is placed in a stainless steel sandwich for rolling which prevents the material from adhering to the rolls of the mill and enables a much thinner foil to be prepared. ... Rolled foils are usually 1 x 1 in.

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. 17

Editorial note, tabletop extrapolation: A jeweler's rolling mill plus shim-stock sandwich makes durable self-supporting metal targets (typically 1 x 1 in per the source) - the natural route to robust backing foils. Whether a rolled foil can serve as a beam STOP depends on the projectile's range: check stopping areal density against the actual beam energy first; the source's thickness tables cover what each metal reached, so cite the row, not a blanket range.

evaporation efficiencies of only 1% are obtained.

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. 23

Editorial note, tabletop extrapolation: Budget isotope/material mass from the geometry: the ~1% collection efficiency is the source apparatus's ordinary-geometry result, and the right transfer is to estimate your own geometric collection fraction (solid angle of substrate at the source), then verify with a witness coupon or charge/substrate mass accounting; crucible-evaporant chemistry (carbide formation, alloying) is chosen per material, not per convenience.

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.

this method has proved to be a very reproducible process.

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: Shrinking the source electrode to match the available material is the transferable move for scarce isotopes; how far down the stock can go depends on cathode geometry, erosion track, clamping and utilization - establish the minimum for the actual gun by test rather than assuming milligram-scale grace.

Zinc and cadmium condensed uniformly and with very high sticking coefficients.

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. 56

Editorial note, tabletop extrapolation: When a film refuses to stick or beads up, a nanometer-scale nucleation layer of a compatible metal is the trial to run - material-specific, verified on a witness slide; note the crystal-structure story is looser than the folklore (Bi and Sb are rhombohedral, not hcp like Zn/Cd/Mg/Be), so pick seed candidates from the literature for the actual evaporant rather than from a structure-matching slogan.

the pressure gauge gives an indication of the rate of reduction

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. 58

Editorial note, tabletop extrapolation: Lets a target come straight from a stable oxide powder with no separate metallurgy step. The total-pressure gauge is a qualitative process indicator only - it cannot identify the gas or prove completion; use temperature measurement, and an RGA or a validated endpoint where gas identity matters.

the valve opened with a POOMPF and all the carbon substrates disappeared.

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. 274

Editorial note, tabletop extrapolation: Every pump-down and vent of a chamber holding fragile foils needs a throttled soft-start path - the foils die from the pressure transient and gas-flow forces, not the vacuum. Short-throw closed-boat geometry remains the milligram-economy move, with collection efficiency verified for the actual source and collimator rather than assumed pure 1/d^2.

At focused ion beam energies, sputter yields between 2 and 10 atoms per argon ion are typical.

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. 94

Editorial note, tabletop extrapolation: A keV-range ion gun is a plausible deposition tool - sized honestly: take measured or calculated yield curves for the actual ion-target pair, energy and angle, then work out rate from beam current and collection geometry, plus thermal load and neutralization. Gas choice (Ar vs Kr/Xe) is a rate-vs-cost trade to quantify per material, not a fixed multiplier.

the evaporation rates for these two metals differ by nine orders of magnitude, whereas their sputter yields differ by only a factor of two.

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. 100

Editorial note, tabletop extrapolation: When the material is refractory (B, C, W, Ta) or reacts with every crucible, sputtering is the escape hatch - with its own books to balance: preferential sputtering can shift alloy/compound stoichiometry, and the holder, backing, implanted gas and redeposition are all contamination paths (a graphite holder adds carbon, which is not always harmless). Shield the holder from the beam and verify composition transfer for mixtures.

Self-supported films usually display the same strength, toughness, and ductility as their bulk parent material.

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. 103

Editorial note, tabletop extrapolation: For a target that must survive beam, handling and mounting, sputter deposition is a strong candidate - verified, not assumed: arrival energy depends on gas pressure and geometry, and film stress, porosity and grain structure can depart far from bulk. Run adhesion and handling tests on the actual film/substrate pair, and pick the release agent for the process - salt layers where the energetic flux scrubs organics.

At 10-3 torr, the mean free path in the vacuum chamber is about 1 cm ... At 10-6 torr, the mean free path is of the order of meters

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. PDF p.103 (printed p.87) for the 1e-3 torr sentence; it completes on PDF p.104 (printed p.88), which also carries the 1e-6 torr / meters sentence and the Xe figure

Editorial note, tabletop extrapolation: For a small sputter rig the choice is real but not one-sided: a differentially pumped gun with a high-vacuum deposition region preserves arrival energy and directionality; glow-discharge and magnetron processes at millitorr nonetheless make dense, adherent films through substrate heating and plasma bombardment. Choose by what the film needs and measure adhesion, structure and gas incorporation on the result rather than assuming pressure decides quality.

A typical deposition rate for substrates located 2.5 cm from the sputtering source is 20 ug/cm2/min. of titanium. ... total erosion rate averages 50 micrograms/second when operating with 2 mA of 20 keV argon.

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. PDF p.114 (printed p.98) for the deposition rate and the gun parameters; the 50 ug/s erosion rate is on PDF p.100 (printed p.84); the ~10 mg source quantity is on PDF p.110 (printed p.94)

Editorial note, tabletop extrapolation: Calibration point for sizing a home sputter-deposition scheme - mA and tens of keV is small-accelerator source technology, not exotic hardware. Time a boron run from a boron yield (measured or from tables) and the actual collection geometry, not from the titanium calibration.

a uniformity of 10% over an area of cm2 with a recovery of at least 90% of the material.

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. 116

Editorial note, tabletop extrapolation: The zero-throw geometry is the method of interest when the feedstock (separated isotope, exotic compound) costs more than one-at-a-time labor - its recovery advantage over open evaporation is large, and exact areal densities follow from the actual charge, recovery and area (at 90% recovery, 200 ug over 1 cm2 is 180 ug/cm2 - quote the arithmetic, not a nominal).

The targets are sent to the users in containers filled also with dessicated argon.

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. 118

Editorial note, tabletop extrapolation: An argon-purged jar or backfilled desiccator is cheap protection for oxidizable targets - how LONG it protects depends on seal integrity and gas purity, so spot-check a witness piece rather than assuming months. And map any electroplated deposit before trusting its uniformity: the process's signature is variability, even if a universal factor-of-two default overstates it.

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.

the foil can be blown off the frame almost instantaneously.

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. 206

Editorial note, tabletop extrapolation: Ground the target frame conductively, keep chargeable insulators (windows, PTFE hardware) away from foil positions, and make the foil-to-frame electrical contact generous - cheap precautions against a documented instant-loss mode, whatever fraction of failures the mounting ultimately accounts for.

the most efficient energy transfer is achieved, when the electron beam and the molten droplet have the same diameter.

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. 232

Editorial note, tabletop extrapolation: Small-charge e-gun work is a spot-placement problem, and the transferable warning is that rated gun power is not deposited melt power - the deficit depends on electron energy, Z, geometry and what the chamber recaptures, so estimate absorption for the actual configuration instead of applying the Ta-sphere 49% as a universal factor of two. Never size a gun from evaporation enthalpy alone.

the output voltage can fall off by as much as 25 % at the maximum load ... assuming a deflection radius of 25 mm ... the beam spot will shift nearly 7 mm when the power supply is fully loaded

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. PDF p.228 (printed p.211)

Editorial note, tabletop extrapolation: Any home-built or surplus e-gun needs a stiff regulated HV supply before it needs more power; the copper-foil melt-hole trick is the free beam-alignment diagnostic.

sparks will occur, destroying the parting film and the thin isotope layer by hairline cracks.

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. 235

Editorial note, tabletop extrapolation: Grounding topology inside the evaporator is part of the recipe - and the same charging physics will bite any deposition or beam system with floating fixtures near keV electrons: bond fixtures deliberately rather than assuming they find ground.

the energy impinging on the substrate is ten times as large for Mo than for Au. Here the only way to avoid destruction of the targets is to cool the substrate or to periodically interupt the evaporation process

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. PDF p.236 (printed p.219)

Editorial note, tabletop extrapolation: Substrate meltdown during deposition is the same radiation/conduction bookkeeping as beam heating (Corwin, this volume) with condensation enthalpy as the source term; refractory evaporants punish the substrate through radiation long before the film is thick.

The cleaning process is of utmost importance ... The substrate must first be cleaned with a mild abrasive powder ... The water is removed with Ethyl Alcohol and while still wet with alcohol is immediately placed in the evaporator and pumping started.

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. PDF p.257 (printed p.240); the pre-warm step and the colour chart are on PDF p.258 (printed p.241)

Editorial note, tabletop extrapolation: Template for any compound that dissociates or splashes: pelletize the charge, chimney the boat, pre-warm the substrate with the source itself - and treat any color-temperature chart as a coarse process indicator only (color-to-temperature conversion is unreliable; a thermocouple wins when the number matters). Valve off the diffusion pump so compound vapor does not load the pump oil.

the powder was pressed between two stainless steel plates (Premier Brand Ferrotype) at about three tons per square inch (Minamisono & Ramsay, "Thick Targets for In-Beam Hyperfine Structure Study")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 150

Editorial note, tabletop extrapolation: The no-evaporator route for activation and yield work: a hydraulic press and polished plates. Compute the areal density from measured mass over measured area (300-400 mg on a 2-cm disc runs ~95-127 mg/cm2), and verify 'beam-stopping' against range data for the actual ion and energy rather than by adjective.

the crossover point is about 210 C for nickel, 100 C for copper, and about 300 C for iron (Gursky, discussion "Prevention of Stress in Foils by Substrate Heating")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 204

Editorial note, tabletop extrapolation: The missing variable when evaporated foils curl, buckle or shatter on float-off: set substrate temperature at deposition time, starting from the cited values and tuning for the actual system. Do not count on post-deposition annealing to rescue a stressed film - it can help in some film/substrate systems (recovery, creep) and not in others, so it is a fallback to test, never the plan. Complements the ORNL-3021 evaporation recipes.

One can roll many useful foils down to the 1 to 5 mg/cm2 region with a small bench-type manually operated mill ... Uniformity may be poor in rolling a small quantity of a separated isotope with few passes - the target is thick in the center, thinner at the edges. Instead of rolling, the material can be pressed between two highly polished flats of cobalt tungsten carbide from a machine shop.

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 203

Editorial note, tabletop extrapolation: A jeweler's mill covers most of the mg/cm2-class targets a small machine needs - whether 1-5 mg/cm2 is 'thick' for your purpose is a stopping-range calculation for the actual particle and energy, not a label; the carbide-flat press is the documented fallback when rolling wastes scarce material on edge taper.

In addition to stainless steel, spring steel sheet has been found useful for pack rolling. Tungsten sheet, 0.003 to 0.005 in., is good for pack rolling, is very hard with a good polish, and can be used many times. Tungsten is not suitable for rolling very thin targets because of its crystal structure. Palladium: A problem is welding of palladium to the pack when trying for less than 500 ug/cm2. This can be avoided by making three to five passes at the same setting before going thinner. Uranium: 1 mg/cm2 is about the limit. Since oxidation of U limits its rollability, it is useful to roll, electropolish (sulfuric acid removes oxide), roll again, (or roll in Ar). Be careful not to generate too much heat in rolling.

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 204

Editorial note, tabletop extrapolation: The same-setting-passes trick (plausibly work-hardening the surface before the next bite - our hypothesis, not the source's) and the electropolish-between-stages cycle for oxidizing metals are the two non-obvious moves in amateur pack rolling.

The older method of pressing the metal powder and sintering it under vacuum shows severe disadvantages. The defects at the grain bounderies [sic] set an early limit during the rolling process. Arc melting has disadvantages too, there may be many gaseous impurities in the processed metal bead ... The metals are melted in portions from 50 to 500 mg in a water cooled copper crucible with an electron gun keeping the temperature just above the melting point. ... the drop solidified starting with the zone nearest to the water-cooled crucible. The part of the drop which solidified last was formed like a stalagmite and was highly enriched with impurities. After venting with argon this stalagmite can be cut away and the procedure can be repeated. For Uranium we did this about 10 times.

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 33

Editorial note, tabletop extrapolation: Explains why bought powder pressed into a pellet resists rolling thin (porosity and grain-boundary defects - fully densified stock is the exception); the repeated directional solidification rejects the impurities whose segregation behavior is favorable, not all of them - the authors themselves found true zone refining fails on uranium (surface tension) and used this slow-solidification variant instead.

For rolling metals with a ductility lower than nickel or iron one should take as sandwich material a stainless steel with a high carbon content named spring steel band. This material has a higher temper due to its carbon content of about 0.1%. All other stainless steel sandwiches should be made of a Chrom-Nickel steel with extreme low carbon content. There are some materials available with a carbon content below 0.03%. ... We noticed that material with a thickness of 0.5 mm or below gave the best results. ... This material should be bright-annealed in an inert gas atmosphere and be dressed in a temper pass mill, to get a highly polished oxide-free surface. The surface roughness for the best quality material is of the order of 0.05 to 0.1 [um] ... These lines are strictly parallel and always along the texture of the sheets ... The source of these inhomogeneities are the scales which remained on and in the ingot before machining it to cold rolled band steel. Vacuum melted stainless steel does not have these impurities. ... We use it for the inner part of our double sandwich.

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 35

Editorial note, tabletop extrapolation: The foil replicates the jacket's flaws (the source's central claim, conditioned on an accurately designed mill) - jacket steel selection is the dominant quality variable in pack rolling once the mill itself is true; roll finish, alignment and reduction schedule still matter on amateur equipment.

reduced by about 3 to 10% per pass. When the jacket increased its size by approximately a factor of two the foil is placed in a new jacket (Kellner & Maier-Komor, "Rolling Thin Uranium Foils")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 37

Editorial note, tabletop extrapolation: A worked schedule showing sub-mg/cm2 rolling is a craft with rules, not heroics - transfer the discipline (small reductions, fresh jackets on elongation) and expect each metal to demand its own trials: permissible reduction, annealing needs and attainable thickness are material-specific.

If oxidation on the surface of the Uranium foil is observed it should be etched with diluted nitric acid of the best quality, because all metal impurities in the acid will be catched by the Uranium foil due to its very negative electro-chemical potential of -1.8 volts. After cleaning in oxygen free distilled water and ethanol the foil is annealed between two Tantalum sheets which are heated by an alternating current. The annealing lasts for about half an hour in a vacuum of 10-7 Torr at a temperature below 930 K, which was chosen to prevent phase transitions.

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 38

Editorial note, tabletop extrapolation: Interpass and final annealing is what keeps a work-hardened foil rollable and flat. The phase-transition ceiling is the uranium-specific reason here; for any other allotropic metal choose the anneal from its own phase diagram and the phase or texture you want - some iron and titanium treatments deliberately cross a transformation. [Note revised 2026-08-23: earlier note generalised 'below any phase transition' to all allotropic metals.]

The Balsam remains tacky and retains foils indefinitely. It also has a low vapor pressure (Riel, "Gallium Rich Ga2O Targets for Use at Room Temperature")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 105

Editorial note, tabletop extrapolation: A tacky mounting adhesive solves the foil-jumps-off-the-frame failure of float-mounting; pairs with the ORNL-3021 float-off recipes. 'Low vapor pressure' is the source's claim for their chamber - run an outgassing/base-pressure test (and consider beam-induced decomposition near the spot) before trusting balsam in a tighter vacuum budget.

additional properties of low thermal conductivity and high electrical resistivity reveal it to be a poor choice for accelerator targets (Lozowski, "A Dry Powder Technique for the Preparation of Carbon Foils")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 116

Editorial note, tabletop extrapolation: Beam-stopping carbon from a powder blower and a hydraulic press - plus the selection principle that a target material must conduct heat and charge away. The amorphous-carbon verdict belongs to that powder and process: evaporated amorphous-carbon foils serve routinely as accelerator targets and strippers, so judge each carbon form on its measured conductivity and binding, not the category.

The sputtering "leveled" the copper surface (Meens, "Vacuum Tight 208Pb Foils")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 169

Editorial note, tabletop extrapolation: Two habits transfer: substrate preparation is a first-order pinhole control (one control among several - particulates, shadowing, stress and coverage also make holes), and a sacrificial natural-material run with a grid of weighed squares characterizes a boat geometry FOR THOSE CONDITIONS - remap when loading, material, rate or distance change.

The wheel thus had to be rotated at a velocity of 666 rpm (equal to 20 deg in 5 ms or during one macropulse).

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

Editorial note, tabletop extrapolation: The design move transfers whole: spread the duty over many target areas, and if the beam is pulsed, phase-lock the rotation so no spot sees consecutive pulses - it scales to a bench wheel behind any external beamline. The 1e17-particle survival belongs to GSI's target, beam and cooling; a tabletop wheel's achievable dose comes from its own thermal, stress and deposited-dose arithmetic.

Low melting-point elements like Pb or Bi are sandwiched between C layers for the use on target wheels, thus extending the stability and life-time

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 29

Editorial note, tabletop extrapolation: A demonstrated construction for Pb/Bi-class soft metals; for another soft metal, run the compatibility, adhesion and beam tests before promoting it to recipe. Budget the carbon honestly - 60 ug/cm2 total is real material in a sub-MeV beam's energy-loss budget - and credit the skins with mechanical containment first; the thermal mechanisms are plausible but unquantified here.

An important problem is overheating of the substrate by a large, molten ball of material.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 208

Editorial note, tabletop extrapolation: Relevant to boron and enriched-isotope work in a bench evaporator: budget the substrate's heat exposure from the melt's radiation before the run, and confine the molten zone to the charge - with the pedestal dimensions and per-method details taken from the re-read source rather than memory.

If pitting or burn-up of the copper foil substrate occurs increase cooling. if curling occurs as the deposit thickens, increase heating

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 99

Editorial note, tabletop extrapolation: The pitting-vs-curling pair is a tuning heuristic FOR THE CITED Si-on-Cu hot-deposition process, readable by eye - worth copying for similar hot depositions onto cooled backings (with the loose clamp so the foil can contract), but check independent temperature limits first: pitting can also mean excess flux or chemical attack, and curling can be contamination or expansion mismatch, where more heat makes things worse.

A large excess of Mg must be avoided to preclude formation of Mg2Si instead of Si.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 98

Editorial note, tabletop extrapolation: The metallothermic pattern (reductant choice, closed crucible, acid leach of the oxide by-product) is the standard route from affordable oxide feedstock to a solid target. Boron-from-oxide is its own chemistry with its own purification and hazards - parallel in shape, not in recipe.

slackening gives approximately an order of magnitude increase in the foil lifetime.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 16

Editorial note, tabletop extrapolation: Deliberate slack is a proven mounting method for thin STRIPPER-class foils, where letting the film move beats letting it tear - one mechanism among several (sublimation, sputtering and radiation damage also kill foils, in shares that depend on the beam). It does not generalize to pressure-bearing windows or thickness-critical degraders, which need controlled tension or support by design; budget spare stock either way.

is expected to be only the order of 1 hr.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 55

Editorial note, tabletop extrapolation: The engineering lesson: when estimated or measured consumable lifetime makes venting burdensome, design in-vacuum replacement (magazine or multi-position ladder) from the start - it costs little at design time and a vent-and-pump cycle per failure otherwise. The ~1 hour is the cited 127-I conditions; estimate a proton foil's life from its own thermal and dose numbers before deciding.

foils must be flat since ripples increase the effective source thickness and thereby degrade the performance.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 224

Editorial note, tabletop extrapolation: The cleanest statement in this collection that foil flatness is physics, not cosmetics - applicable to any internal foil in proportion to how its incidence geometry turns ripple into path-length spread; and the Chalk River system stands as an existence proof that in-vacuum consumable-changers can share space with a live dee structure (details per the re-read).

a cold filament which produces a temperature rise of the evaporant of only ~ 10 C

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 249

Editorial note, tabletop extrapolation: A candidate route to boron and refractory films without an e-gun - qualified in place: a small bulk temperature rise does not preclude local sputter damage to a substrate or release layer, so verify with witness pieces; the commercial gun class is bench-scale, and its insulator/neutral-beam claims come from the re-read source, not the summary.

the gun be at a thirty degree angle to the horizontal surface and about 5 cm from the sputter source.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 250

Editorial note, tabletop extrapolation: Useful geometry prior-art for a sputter gun in a diffusion-pumped bell jar of exactly the archive's class - commissioned as HV apparatus, not from a recipe card: engineered enclosure, current limiting and bleeders, grounding, door and pressure interlocks, and the pump's own precautions come before first beam; the visible beam then makes alignment easy.

it can be left virtually unattended overnight and usually for several days with only slight adjustments.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 251

Editorial note, tabletop extrapolation: Schedule per material from the actual rate - Au-class films are an overnight job, Si-class a couple of weeks - or reserve sputtering for thin layers and adhesion coats. Unattended running was the cited lab's practice; an amateur HV/vacuum rig earns that only with interlocks that fail safe.

only 2.3 mg of Zr were consumed in the preparation of 5 targets of 0.1 mg/cm2

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 38

Editorial note, tabletop extrapolation: An economy benchmark in the sense of an existence proof - milligrams in, several targets out. For boron or another feedstock, the efficiency is its own measurement (yield, cathode fabrication losses, coated area and recovery all move it); compare candidate routes by measured end-to-end material balance rather than by the Zr anecdote.

with adequate care to ensure cleanliness, high quality RDM targets and stoppers can be produced reliably and easily

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 148

Editorial note, tabletop extrapolation: The mounting lesson: flatness comes from a polished reference surface plus elastomer-mediated even tension, with cleanliness setting achievable quality. Capacitance-vs-distance is a fine nonmagnetic gap gauge between conductive, near-parallel, calibrated surfaces - with a vacuum-rated elastomer when used in vacuum.

Attempts at single step evaporations to these thicknesses were unsuccessful because of rupturing of the foil due to heat damage.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 230

Editorial note, tabletop extrapolation: Stretched polypropylene is a workhorse thin window for gas counters and low-energy vacuum isolation, and the step-and-cool discipline is the transferable method - applied to another polymer as a trial with its own thermal and adhesion checks, not as a universal recipe.

any remaining traces of moisture would result in failure to produce a self-supporting target

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 233

Editorial note, tabletop extrapolation: Two moisture checkpoints worth evaluating on any float-off evaporation where water-driven stress or breakage shows up: bake the substrate before the parting layer (400 C worked for their glass/NaCl process - check compatibility for other substrates and agents), and displace residual water from the mounted foil with a compatible low-surface-tension rinse (their methanol). Demonstrated for the McMaster rare-earth process; transfer by test, not assumption.

there is a "best ratio" r/h 0.7 which generates a minimum relative thickness variation far below 1% across the target.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 116

Editorial note, tabletop extrapolation: The uniformity-vs-economy trade in one number pair. The r/h ~ 0.7 optimum belongs to that geometry and source distribution - map the deposited thickness for your own fixture rather than copying the ratio. The same volume's GSI stripper-foil paper (rotator tilted 7 deg, 12 rpm) held +-(0.6-1.1)% on plate centers by the same principle - rotation is a cheap, testable upgrade for a bell-jar evaporator.

very small quantities of metals such as tungsten, tantalum, and molybdenum can be used in miniature systems

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 224

Editorial note, tabletop extrapolation: The one route in the volume to thick refractory targets without an e-gun or rolling mill - and an institutional corrosive-gas process, full stop: WF6 is acutely toxic and makes HF on contact with moisture, the exhaust is HF, and the carrier is hydrogen. Compatible closed plumbing, gas cabinets, leak detection, scrubbing and trained operation are the entry fee; Ta and Mo have their own precursor chemistries, not this one with substitutions.

relatively high strengths and in some cases were virtually transparent.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 238

Editorial note, tabletop extrapolation: A genuinely low-tech thick-oxide route - solution chemistry plus an oven, no vacuum plant - for the metal-cation nitrate systems the source demonstrated (rare earths and similar), where elemental form is not required. Loading adjusts with solution concentration within the membrane's ion-exchange capacity. Boron is NOT a drop-in: borate chemistry doesn't cation-load cellulose the same way, so a boron oxide target needs its own sourced procedure.

The dee biasing scheme was considered too awkward to apply, chiefly because the variable frequency requirement had already led to a rather complicated mechanical design.

Fulbright, The Sparker, a Device to Overcome the Multipactor Difficulty in Starting the Oscillator of a Cyclotron — NYO-9359, University of Rochester (1961) — p. 2

Editorial note, tabletop extrapolation: Transferable decision pattern: on a machine whose dee stem is grounded through the tank structure, retrofitting DC bias means rebuilding the stem insulation, so Rochester's choice of an impulse starter is the additive option. Additive is not hazard-free: a shock starter is a high-voltage pulser coupled into an RF vacuum structure and needs a rated feedthrough, insulation and current limiting, grounding, an interlock, and a check for RF coupling and unintended arcs. Compare the two cures by the actual RF/HV insulation and safety design, not by port count. [Corrected 2026-08-23: earlier note said the starter "touches nothing but a spare port".]

The spark gap is adjusted so that the sparking rate is roughly two per second. Ordinarily a single spark will cause oscillation to commence.

Fulbright, The Sparker, a Device to Overcome the Multipactor Difficulty in Starting the Oscillator of a Cyclotron — NYO-9359, University of Rochester (1961) — p. 3

Editorial note, tabletop extrapolation: A sub-joule impulse sufficed on a 27-inch machine; what a smaller system needs follows from its dee capacitance, coupling efficiency and the voltage the kick must reach - calculate or measure it rather than scaling by size. The 30 kV charger is the one nontrivial part, and it must be a properly engineered, current-limited supply with the right polarity and isolation - a bare NST or flyback is a starting component, not the finished charger.

Because the loop is oriented at right angles to the axis of the cavity, the RF voltage induced in the loop is very small, even with full dee voltage.

Fulbright, The Sparker, a Device to Overcome the Multipactor Difficulty in Starting the Oscillator of a Cyclotron — NYO-9359, University of Rochester (1961) — p. 3

Editorial note, tabletop extrapolation: General principle for any starter or diagnostic coupling on a resonator: orient it weakly coupled to the operating mode - remembering reciprocity: a true null for pickup is a null for drive through the same port, so the impulse works through the residual coupling (and other current paths), which is fine because the required kick is small. Verify the coupling both ways, and rate the spark circuitry for the transients it will still see.

partly because it was more convenient in our case since the dee chamber is rather crowded, and partly because we thought that the RF pickup problem would cause less trouble with inductive coupling.

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 useful trade note, not a theorem: in a small chamber where every square inch near the dee is contested, try a loop near the dee stem (outside the beam region) first - then MEASURE steady-state pickup and impulse coupling before fixing the location; whether inductive actually beats capacitive depends on the local field geometry and the mode.

Two experimental models had values of 0.37 and 0.30, but in both cases it was necessary to use conductor sizes which were available but not specifically designed for the job.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 22

Editorial note, tabletop extrapolation: Amateur coils are usually wound from whatever magnet wire is available: budget a pessimistic 0.3-0.4 space factor when sizing the coil window, and read handbook ~0.5 figures as purpose-designed-conductor numbers.

The forces tending to separate the halves are surprisingly large and if overlooked can be disastrous.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 19

Editorial note, tabletop extrapolation: Directly relevant to removable pole caps and bolt-on shim plates on a small H-frame: check the retention for lateral load wherever the joint geometry can see one - splits with a component parallel to the flux see spreading, while a complete cap on a plane parallel to the pole face mainly sees the axial pull. The formula is the diametral-split case, not every joint's.

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.

a steel faceplate was placed over the face of the core, as shown in Fig. 3.14, to spread out the flux evenly before it crossed the gap.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 141

Editorial note, tabletop extrapolation: The reason laminated or relieved pole structures carry a continuous pole face; applies to any lightening-hole or bolt-pattern pole cap on a small magnet - size the face sheet against saturation (thickness x permeability doing real work), don't just add a modest skin.

The magnetic forces were then combined with the force of the atmospheric pressure to give the total force. Magnetic force in tons = (kilogauss)^2 (area in square inches) / (1.735)(2000)

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. PDF 144 (printed p. 134), Sec. 2.6 'Magnetic Forces'

Editorial note, tabletop extrapolation: On a tabletop the same ledger is short but identical in kind — gap pull, atmospheric load on the chamber, unbalanced pull on any asymmetric iron — and the mean-of-squares point matters wherever the field is nonuniform over the loaded area (pole edges, shim steps).

the space between the tank and the cores must be great enough so that the maximum separation is never more than twice the minimum separation.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 146

Editorial note, tabletop extrapolation: Useful thinking for a shim pack, pole-cap seat, or chamber-lid-under-pole arrangement: a deliberately larger uniform standoff can pass where a tiny irregular one cannot - at the price of added reluctance (more ampere-turns for the same field), so treat enlarging the gap as a trade to compute, and validate the 2:1 criterion's adequacy for the new geometry rather than assuming the calutron number.

We have had available for our use a complete set of the Berkeley plans which was kindly placed at our disposal by Professor E. O. Lawrence.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 6

Editorial note, tabletop extrapolation: The strategy transfers directly: for any new machine, start from the closest documented working design - this corpus and the builds census exist to make that possible - and spend novelty only where the precedent is silent.

Cited in: Choosing Your Machine

the supporting structure for the coils failed, presumably under the magnetic forces. The coils became distorted and short circuits developed.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 19

Editorial note, tabletop extrapolation: DIRECT at any scale: coil-on-coil and coil-on-iron forces scale with NI and B and have crushed amateur windings - brace windings as if they will be pushed, not just held up. (The outer return-path steel in UW's recovery is that machine's expedient; whether added steel raises gap field depends on where the circuit's reluctance actually sits - FEMM answers it.)

the results indicated a force greater than 35 tons for the cyclotron magnet. For comparison the force of atmospheric pressure is 24 tons.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 30

Editorial note, tabletop extrapolation: A ferromagnetic chamber lid or pole-integrated cover sees magnetic clamping of the same ORDER as the vacuum load at tabletop fields (B^2/(2*mu0) vs one atmosphere - dg-177's arithmetic): check deflection in both states (energized and not) and expect assembly/disassembly forces. A non-magnetic lid opts out of the magnetic term entirely.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

notably the bolts securing the one-inch thick sections of the cover plates, the screws holding the copper liners, and a gap where the shim is relieved to accommodate water lines, (3) accidental asymmetries in the construction and placing of the coils, and (4) non-uniformities in the steel

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 33

Editorial note, tabletop extrapolation: An H-frame yoke is asymmetric by construction. Keep fasteners, liner screws, and cooling-line reliefs symmetric in the pole region; for unavoidable asymmetries, measure the azimuthal Fourier harmonics and judge them against orbit tolerances - a bare field survey doesn't by itself say the beam doesn't care.

this correction was made the criterion for final adjustment rather than reference to mechanical measurements.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 41

Editorial note, tabletop extrapolation: Shim the measured field, not the dial indicator: use the mapped field as the final acceptance criterion, calibrate shim sensitivity from the first iteration and extrapolate to plan the next, and expect a floor - every local correction has extended influence. Whether a given pole tilt is VISIBLE on a tabletop survey depends on gap, probe resolution and orbit radius, so establish the machine's own sensitivity from that first shim iteration rather than assuming thousandths show.

Initial testing of the system disclosed two leaks in welds, both of which were in stainless to mild steel joints.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 53

Editorial note, tabletop extrapolation: Treat dissimilar-metal welds (stainless-to-mild first among them) as leak-hunt and inspection PRIORITIES - their risk depends on filler choice, joint design and thermal cycling, so this is a where-to-look-first rule, not a they-always-leak rule. Keep such transitions accessible for repair, or design them out with transition flanges and gaskets.

Cited in: The Vacuum Budget of a Cyclotron

The skin is of electrolytic high conducitvity copper with 1/4, 3/8, and 5/8" copper tubes silver soldered on the back side for water cooling.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 58

Editorial note, tabletop extrapolation: The construction vocabulary transfers as a menu, not a mandate: EHC copper skin with cooling sized from computed RF loss (a tabletop dee at tens of watts may need none), silver-plated joints where measured contact resistance warrants, high-pressure sliding contacts only on genuinely movable RF joints, and split-for-repair weighed against the RF seam it adds. Same contact-pressure concern as the nyo-9683/ornl-2648 sliding-contact rules when a movable short exists.

the filament may be replaced without breaking the vacuum of the tank proper.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 65

Editorial note, tabletop extrapolation: The reference machine's filament-change downtime is this exact problem, solved in 1951: a small gate-valved source lock plus an external bellows positioner removes the main-tank vent from the service cycle - how much time that saves depends on the lock's own pump-down and the machine's recovery habits, so measure it rather than promise minutes. Positioning through the bellows under vacuum is the designed use; adjusting with arc, RF or HV energized is a separate safety analysis with its own interlocks, not an included feature. (The shuttered viewport is a free detail worth stealing.)

Cited in: The Vacuum Budget of a Cyclotron

the plate is operated at d-c ground potential so that no insulation is required in the water lines.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 85

Editorial note, tabletop extrapolation: Solid-state amps moot the HV plumbing, but two doctrines survive: pick the grounding scheme that minimizes what the coolant circuit must insulate - DC-grounding the plate removed the DC insulation requirement, while RF potentials, leakage control and water quality stay on the checklist - and use source impedance (here transformer reactance) as passive inrush protection where a component's own rating allows it.

In den Deckel ist eine Vertiefung mit einem Durchmesser von 150 mm und einer Tiefe von 12 mm eingefräst. Dort befindet sich eine Hallsonde für die Messung der magn. Flussdichte. In diese Vertiefung wird der obere Pol des Magneten abgesenkt; so erhält die Kammer im Magneten einen festen Sitz. Außerdem konnte dadurch die Kammerhöhe auf ca. 72 mm verringert werden. Unter Berücksichtigung der Materialstärke beträgt der minimale Polabstand des Magneten schließlich ca. 75 mm. [tr.: a 150 mm diameter, 12 mm deep recess is milled into the lid. A Hall probe for measuring the flux density sits there. The upper pole of the magnet is lowered into this recess, giving the chamber a fixed seat in the magnet; the chamber height could thereby be reduced to ~72 mm, and allowing for material thickness the minimum pole spacing is finally ~75 mm]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 37, 57

Editorial note, tabletop extrapolation: Every millimetre of gap costs ampere-turns; the recessed-lid trick keeps the poles within a few mm of the dee envelope while fixing the chamber and giving the field probe a home. Size the recess floor (and any thin base) by an actual vacuum-vessel calculation - plate deflection and buckling for the real material and span - not by copying this machine's dimensions; and note the probe reads the field at the recess, not the median plane, so calibrate the offset.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

ist aus einem Edelstahlrohr mit Wandstärke 2 mm gefertigt. Der Boden, ebenfalls aus Edelstahl, hat eine Dicke von 5 mm [tr.: made from 2 mm wall stainless tube with a 5 mm base]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 57

Editorial note, tabletop extrapolation: Historical construction data, not a thickness table: a chamber's wall, lid, base, clamp and port loads get an external-pressure buckling and plate calculation (or validated FEA) for the actual geometry and alloy - a 300 mm evacuated lid alone carries ~7 kN of atmosphere. The transferable advice that survives: port count is the main regret driver on small chambers, so allocate spares.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Die für die Ionisation notwendigen Elektronen treten aus dem glühenden Filament, einem thorierten Wolframdraht mit Durchmesser von 0,3 mm aus. Dieses befindet sich in einem Keramikkörper aus Shapal. Darüber liegt eine Kupferplatte als Anode. ... Durch ein Loch in der Anode treten die Elektronen in den Formationsraum eines sog. 'Kamins' ein ... Der Kamin wird durch einen Keramikdeckel abgeschlossen, an dem sich isoliert eine Wolframscheibe, ein sog. Elektronenspiegel, befindet. Dieser lädt sich durch die auftreffenden Elektronen negativ auf und reflektiert sie in den Formationsraum des Kamins, so dass sie für erneute Ionisationsprozesse zur Verfügung stehen. Auf diese Weise erhöht sich die Zahl der Elektronen und damit auch der Ionenstrom merklich. [tr.: the electrons emerge from a glowing 0.3 mm thoriated tungsten filament seated in a Shapal ceramic body; above it lies a copper plate as anode; through a hole in the anode the electrons enter the formation space of a 'chimney'; the chimney is closed by a ceramic lid carrying an insulated tungsten disc, an 'electron mirror', which charges negative from incident electrons and reflects them back into the formation space for further ionisation - noticeably raising the electron count and with it the ion current]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 62, 64

Editorial note, tabletop extrapolation: The floating electron mirror is a zero-cost reflex trick - no second cathode, no supply - that increases electron residence time; the book claims a noticeable ion-current gain, not a quantified one, so measure yours. Shapal (AlN-BN) machines with ordinary tools, unlike alumina - verify the grade's temperature rating against the filament environment.

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.

The dees were held in place with bent glass rods, which also raised both dees off the bottom plate.

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 16

Editorial note, tabletop extrapolation: Flame-bent glass rod is cheap, vacuum-compatible standoff stock with a real precedent (and the same survey shows glass slides used similarly) - as HISTORICAL construction: for a new build, treat surface flashover, creepage geometry, cleaning, and flame-bending residual stress as the qualification items; bulk dielectric strength is the one property that was never the problem.

the assembly was supported by a 1.3 cm thick copper rod that also connected the dee to the RF matching transformer

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

Editorial note, tabletop extrapolation: Making the RF feed a structural member gives a rigid connection and can save a penetration - count your own: an internal support needn't pierce the wall at all, and low loop inductance comes from the LENGTH and return-path geometry, not rod thickness. The 1.3 cm is Rutgers' as-built datum; size a new rod from RF current, mechanical load and the actual loop.

Two dees were constructed of copper and were mounted with blocks of insulating dielectric material such that they could be moved independently of each other. ... The dees were operated at 3,750 V, using a manually adjustable resonating circuit.

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

Editorial note, tabletop extrapolation: Independently adjustable dee mounts let gap and centering be tuned after assembly rather than machined perfectly the first time - the transferable idea. Treat 3.75 kV as reported without a stated convention (peak vs RMS, dee-to-ground vs gap not specified in the survey), i.e. a datum with an asterisk, not calibration.

The electrical feed-throughs were made from nylon plugs, o-rings, and brass screws and were held in place with Plumber's Goop

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

Editorial note, tabletop extrapolation: Historical construction with NO implied qualification - the machine never ran to publication. For anything carrying voltage, RF or bias, use vacuum-rated feedthroughs selected for creepage, clearance, outgassing and the actual electrical ratings; improvised polymer-and-sealant penetrations are leak, tracking and outgassing liabilities that a leak-checked commercial part retires for tens of dollars.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The cyclotron was not successfully tested by the publication of Ref [20], the problem being that the magnetic field caused the wires that powered the ion source to move and short the dees.

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

Editorial note, tabletop extrapolation: Every lead inside the field carrying current TRANSVERSE to B feels F = I*L x B (a lead parallel to B feels none - route accordingly); anchor every in-field conductor mechanically with vacuum- and temperature-compatible restraint, keep leads short and stiff, and check them against the worst-case field and current before closing the chamber. The specific cures (soldered stiff leads, potted connectors, sheathed mounts) are our engineering reading, not the survey's.

The field was mapped using an acrylic disc, an aluminum disc that was marked with the 360 degrees of a circle, and a F. W. Bell 5070 Teslameter. The acrylic disc was milled to fit the aluminum disc such that they shared the same axis of symmetry, and so that the aluminum disc could rotate freely. The acrylic disc was attached to the lower pole face with tape ... The aluminum disc was milled to hold the Teslameter so that the probe could slide radially. ... because of the flaws in the Houghton College mapping apparatus and the probable misuse thereof

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 37

Editorial note, tabletop extrapolation: A two-disc rotary jig is an afternoon's shop work with systematic polar coverage - and this documented failure is the caution: validate the jig against a reference (manufacturer curve for the centre field; separate checks for probe calibration, angular registration, orientation and repeatability - the centre curve alone cannot validate the coordinates).

a .9 mm thick by 2.5 cm wide strip of brass soldered to the inside of two 0.6 cm by 0.6 cm rings of brass

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 38

Editorial note, tabletop extrapolation: Putting every service penetration on the cylinder wall leaves the removable lids free of vacuum-service ports - apart from seal grooves, fastener holes and any needed clearance reliefs - which is what makes them simple to re-machine or replace; the build is lathe-mill-drill-and-solder work, all within a hobby shop.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

by 0.25 cm deep groove with an inner diameter of 15.24 cm to accommodate a 0.32 cm thick Viton O-ring

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 39

Editorial note, tabletop extrapolation: The ~22% nominal squeeze is this design's number and in the normal static-seal band - but size a new gland from a current O-ring manufacturer's vacuum face-seal table (depth AND width, gland fill, tolerances, stretch), not from one thesis dimension. The printed 3.28 cm groove width is image-verified as printed and geometrically impossible on the 17.1 cm plate - an unresolved source misprint, flagged do-not-copy; the plausible 0.328 cm reading is a guess, not a correction.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The open face of the dee was squared using a milling machine, to give the final dimensions of 14.3 mm thick

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 40

Editorial note, tabletop extrapolation: Soldered thin-sheet construction plus one milling pass on the gap face gives a straight accelerating edge without hogging a cavity from solid - the transferable fabrication move. The single-screw-plus-lock-washer mount is the historical retention only: for a new build add a positive anti-rotation feature (key, second fastener) and a qualified RF contact, since a lock washer neither prevents rotation reliably nor makes a stable RF joint.

The dummy dee is made from two 0.9 mm thick by 5 mm wide strips of copper

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 40

Editorial note, tabletop extrapolation: Reducing the grounded electrode to a strip frame saves material, mass, and pumping-shadow volume while still defining the accelerating gap; the precedent indicates only the driven electrode needs an enclosed field-free interior.

held together by three insulating glass microscope slides, which were glued to the copper with Loctite 1C Hysol vacuum epoxy

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 41

Editorial note, tabletop extrapolation: The idea worth keeping is fixing the alignment-critical gap OUTSIDE the chamber, as one assembly. Glass slides are flat and cheap but not vacuum-qualified as supplied: clean and bake them, use a low-outgassing adhesive with a controlled bond line, check creepage across the glass between driven and grounded copper, and test the assembly at full RF voltage under vacuum before trusting it - insulator surfaces spanning electrodes are where flashover lives.

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.

A small brass screw was bored through its axis to allow air to escape the screwhole

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

Editorial note, tabletop extrapolation: Blind tapped holes under screws are classic virtual leaks that masquerade as outgassing for hours. The cure is venting wherever a fastener seals a blind volume - a bored screw (as here), a vented screw, a groove, or a through-hole - chosen per joint; drilling every in-vacuum fastener indiscriminately weakens screws that never needed it.

The magnet yoke was soft iron scrap, and the pole pieces were 11.4 cm steel round stock which were then wound with 13.5 gauge wire.

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 16

Editorial note, tabletop extrapolation: A documented precedent that scrap return-path iron plus machined round-stock poles can serve a small machine - the machine as a whole made beam, though the survey doesn't isolate the magnet's contribution. For a new build, characterize candidate scrap (saturation, consistency, joints) and remember the return path needs cross-section, not pedigree.

This work is limited to the area of high vacuum. The limitation is due to the simple handling of the components and the existing pumping station, with which a minimum of 10-5 mbar is not undercut. … The present work shows that metal-based 3D printing can meet the requirements of vacuum technology in the area of high vacuum.

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 1, 4

Editorial note, tabletop extrapolation: Printed 316L-class components are demonstrated at high vacuum down to the study's achieved 1.5·10-5 mbar; the 10-6 decade was not reached by its pump station and UHV is explicitly untested, so claims below the tested pressure are extrapolation, not evidence.

Due to the use of powder in the production, 3D-printed parts have a certain surface roughness, which must be smoothed by reworking. Another consequence of the layered structure is the fact that in overhangs with an angle smaller than 45° support structures - as shown in Fig. 2 - are necessary. They must be removed in the aftermath.

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 2

Editorial note, tabletop extrapolation: When designing a printable vacuum part, orient sealing faces and bores to respect the chosen printer's qualified support limits (45° in this process) and leave machining allowance on sealing surfaces; the print is a near-net blank, not a finished part.

Due to an elaborate post-processing, it is clear that the 3D printing of standard components will hardly be worthwhile. Consequently, in order to achieve an economic use of this technology, it is necessary to retrofit the printed components with standard parts from conventional manufacturing.

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 2

Editorial note, tabletop extrapolation: For a low-budget build the demonstrated pattern is catalog KF/CF hardware joined to a printed complex body; a plain straight connector is exactly the case the source found uneconomic to print. Compare current quotations - the economics move with the market.

a simple tube with an outside diameter of 41 mm and an inside diameter of 38 mm was printed and completed on one end by a welding flange and on the other side by a flange with a tube … The two different welds could be attached without problems. This meant that no further reworking was required.

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 2

Editorial note, tabletop extrapolation: On this test article, printed 316L took conventional welds with no special procedure - encouraging for hybrid printed-plus-welded assemblies, but weldability and vacuum integrity move with print density, orientation, surface preparation and heat history, so a new printed assembly still earns its own weld procedure and leak qualification.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

With both parts a high vacuum of 1.5·10-5 mbar was reached without problems.

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 2

Editorial note, tabletop extrapolation: Mid-10^-5 mbar is already the working range of many small accelerator chambers, so this is a meaningful screening result - and only that: a reached pressure folds together pumping speed, outgassing and any leaks, so it proves the assembly pumpable on that stand, not leak-free. Cleaning and an acceptance test still precede installation.

the influence of a pretreatment can be checked by cleaning the 3D-welded KFSC DN-40 with isopropanol in an ultrasonic bath and rerun the pressure increase measurement. … When cleaned, the 3D printed part is even better than the conventional one. … Table 2: Leakage Rates … 3D Welded KF-SC DN40 cleaned … 2.15·10-7 [Leakage Rate column, mbar·l/s]

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 2, 3

Editorial note, tabletop extrapolation: A 3.4x improvement from one solvent ultrasonic cleaning makes validated cleaning one of the cheapest vacuum upgrades going; transferring it to other parts means checking solvent compatibility, trapped volumes, rinsing and complete drying rather than assuming the same factor.

Through the flow channels, the recipient can be heated during evacuation and alternatively cooled when needed in operation. The exact shape of the channels was determined by a CFD-program to ensure optimal flow conditions.

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 3

Editorial note, tabletop extrapolation: Integrated wall channels give a small chamber bakeout and cooling with no external jacket or brazed lines - a capability that is expensive to add to a one-off machined chamber - at the price of fluid connections and a leak qualification of the channel walls against the vacuum volume.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Since no moldings and other tools are necessary for the production of 3D printed components, there are no further costs. … The basic body of the vacuum chamber was supplemented with a complex geometry and integrated flow channels and completed by welding standard components. In addition to a cost-effective production by avoiding unnecessary rework, this method also has the advantage of a flexible adaptation to different customer requirements.

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 1, 3

Editorial note, tabletop extrapolation: For a multi-port chamber whose port pattern is unique to one machine, a printed body with welded catalog flanges is a demonstrated alternative to welded-plate fabrication and machining from solid, and the port layout can be revised in CAD between builds without molds or dedicated tooling - the build itself still costs supports, fixtures, inspection and sealing-surface machining, so the comparison is build-specific.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Especially for single production and prototypes, 3D printing technology can be of considerable benefit. This is particularly due to the freedom in geometry and the possibility of function integration, such as the realization of a surface heating system.

Wolf, Beck, Franz & Neumaier, 3D Printing for High Vacuum Applications — THC04, Proceedings of Cyclotrons2019 (2019) — p. 4

Editorial note, tabletop extrapolation: A one-off machine is exactly the single-production case; a sound screening default is to consider printing where a part is unique and geometrically complex and to price catalog, machined, welded and printed options case by case.

The pole is machined to high accuracy since it is what the gap "sees" and thus determines the accuracy of the magnetic field. The permanent magnet comes in blocks, which can be of coarser arrangement since they are farther from the midplane

Clark, Halbach, Kunkel, Leung, Li & Young, A Compact Permanent Magnet Cyclotron for Accelerator Mass Spectrometry — Proceedings of Cyclotrons'95, Cape Town (1995) — p. 3

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: concentrate the machining budget on pole faces and gap parallelism; commercial magnet blocks with ordinary tolerances are acceptable upstream of an iron pole — the key enabler for building a precise field from inexpensive stock magnets. The pole filters high-spatial-frequency block errors; low-order errors (remanence spread, block placement, gap and yoke asymmetry) still reach the midplane, so confirm with a tolerance analysis and a field map.

The permanent magnet comes in blocks, which can be of coarser arrangement since they are farther from the midplane

Clark, Halbach, Kunkel, Leung, Li & Young, A Compact Permanent Magnet Cyclotron for Accelerator Mass Spectrometry — Proceedings of Cyclotrons'95, Cape Town (1995) — p. 3

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: distance from the midplane is the tolerance relief for short-wavelength errors — block placement and discretization errors attenuate with distance, so the rough assembly sits far from the gap and the iron pole does the smoothing. Coherent and low-order errors survive the distance, and standoff costs flux; evaluate the needed distance and the residuals with a sensitivity model or a field map.

within the acceleration region between 5 cm and 12 cm, the field is flat to within 7 parts in 104. This small deviation was anticipated since slightly larger than optimum barrel magnets were installed, to be cut back later for shimming

Clark, Halbach, Kunkel, Leung, Li & Young, A Compact Permanent Magnet Cyclotron for Accelerator Mass Spectrometry — Proceedings of Cyclotrons'95, Cape Town (1995) — p. 3

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: a margin in the removable direction is cheap insurance in a PM circuit — cutting blocks back is routine, adding material means buying new magnets. It is one trim mechanism among several (iron shims, flux shunts, repositioned blocks, correction coils); choose the adjustment mechanism and its planned range at design time rather than biasing every PM installation high by default.

the outer plate can be used to pre-adjust each magnet to a similar magnetic field before installation. Once installed in the accelerator, the trim coil can then be used for final fine-tuning during operation ... This gap is adjusted using aluminum spacers of different thicknesses ... When the outer plate gap is reduced from 10 mm (baseline) to 0 mm, the integrated field increases by about 1.85%. Conversely, when the gap increases to 20 mm, the integrated field decreases by around 0.14%. This coarse tuning method is simple yet effective during magnet pre-alignment and calibration

Hsu, Jan, Chu & Lin, Integrating Permanent Magnets and Electromagnets — A Hybrid Dipole Magnet Design — WEBD3, Proceedings of IPAC2025 (2025) — p. 1, 2

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: a movable external iron shunt is a zero-power, percent-class field adjuster where the circuit geometry gives it authority — verify with a model or measurement for the specific circuit. Note the strong asymmetry in the prototype data: closing the 10 mm baseline gap gained 1.85%, opening it by the same 10 mm lost only 0.14%, so nearly all the authority lies on the closing side.

These blocks (Fig. 2) are not formed as a single piece, but are assembled by gluing smaller magnetized units together. This method allows us to fabricate magnets in flexible sizes and shapes, while maintaining field performance. Dimensional tolerances and flux consistency were kept within acceptable ranges based on simulation results

Hsu, Jan, Chu & Lin, Integrating Permanent Magnets and Electromagnets — A Hybrid Dipole Magnet Design — WEBD3, Proceedings of IPAC2025 (2025) — p. 1

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: small stock magnets glued into arrays are a legitimate substitute for expensive custom blocks when grade, magnetization vector, polarity, dimensions and bonding are controlled. Set the dimensional and per-block flux acceptance from a simulation of their field effect, as the source did, and verify the assembled magnet with a field map — a spot gaussmeter reading is a screen, not a flux acceptance test.

In non-magnetic assembly, the yoke and pole are first aligned and fixed, and the PM blocks are inserted afterward. In this project, we used the first method, with magnetic force. Because the magnetic attraction during assembly can exceed several hundred kilograms, this process presents engineering and safety challenges. To address this, we developed a systematic and repeatable assembly process using custom-designed fixtures. We also found that applying a reverse magnetic field during the process can help reduce the attractive force and make the assembly smoother. The fixtures include mechanical guides, magnetic shielding, and locking mechanisms to ensure safe, controlled, and staged installation

Hsu, Jan, Chu & Lin, Integrating Permanent Magnets and Electromagnets — A Hybrid Dipole Magnet Design — WEBD3, Proceedings of IPAC2025 (2025) — p. 2

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: methods that transfer at any scale — never free-hand strong magnets toward iron; use guided, locking fixtures that control the approach axis and stage the force; and consider the insert-magnets-last sequence or a bucking field when the full-force path is unmanageable. A reverse field applied to PM material must stay well inside the magnets' coercivity and recoil limits and brings its own stored energy — model the forces and limit the current before relying on it.

The cutting of plates and rods shall be carried out strictly using water jet/saw cutting. Flame/plasma cutting is strictly prohibited ... Any other mechanical process including non-cutting, forming or welding is not permitted ... Turning - Sharply ground tools and carefully selected cutting data are particularly important, since in the case of incorrect selection, pure Iron tends to smearing. Adequate cooling and lubrication are also essential in order to preserve the tool and the work piece.

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. 22

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: thermal cutting locally degrades the magnetic properties of soft iron — the likely rationale for a professional spec banning it outright for yoke and pole stock [editorial inference; the tender states the ban without giving a reason]. The smearing warning and the turning advice (sharp tools, careful cutting data, generous cooling and lubrication) are directly usable in any home shop machining 1010-class magnet iron.

No joint in the conductor is allowed inside a pancake ... The conductor shall be wrapped with glass tape with 50% overlap to produce approximate insulation thickness of 0.5 mm turn to turn ... Electrical connections between pancakes shall be made by brazing of proper copper connectors that can carry at least 150 % of maximum current without significant heating ... The electrical connectors and bus bar (or flexible cable) that will be used for connecting two coils shall be designed and made to conduct at least 200 % of maximum current without significant heating ... brazed using silver brazing filler (at least 40% silver) ... All the water-cooled coils of magnets will be inter-turn insulated with glass tape followed by epoxy-resin impregnation & encapsulation under vacuum. The thermal class of insulation is F Class (155 oC).

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. 22-24

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: a compact recipe for building reliable water-cooled magnet coils — joint placement, tape overlap, brazing alloy, connector qualification and vacuum potting — from a lab that must warranty the result. The 150/200-percent connector requirements are current-carrying thermal criteria (carry the current without significant heating), not dimensional oversizing; the no-joints-inside-a-pancake rule and those qualification margins are cheap insurance for any coil builder.

Before epoxy cast/after brazing water connectors with the pancake terminals, cooling passage of each pancake shall be tested passing with at least 5 mm diameter steel ball and documented ... [vendor compliance sheet:] Whether Bidder have Inhouse — 1. Hydrostatic Test @30 [bar] ... 2. Hydrodynamic Test @8 [bar]

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. 24, 37

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: the steel-ball pass test is a zero-instrumentation way to prove a hollow-conductor bore was not crushed or blocked during winding — exactly the failure an amateur winding fixture is most likely to cause — and the source runs it before potting because epoxy makes any blockage permanent. A ball pass shows minimum clearance only; pair it with a measured flow/pressure-drop check, and derive any pressure test from the ratings of the actual fittings rather than copying the vendor-sheet values.

The upper pole and lower pole of the magnet shall be concentric within ± 0.1 mm. The parallelism between the top and bottom poles shall be within ± 50 microns ... [spec table:] Pole gap — 51±0.05 mm (Nominal) ... Pole gap and pole dimensions should be measured by CMM ... Measurement of radial offset between the upper and lower half magnets

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, 18, 41, 43

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: quantifies the assembly precision a professional team demands so the field-homogeneity spec survives bolting-up — tenth-millimetre concentricity and 50 micron parallelism. Within reach of careful amateur fitting, but verifying them takes a defined datum scheme and suitable metrology (surface plate and indicator for parallelism; concentricity needs a datum-referenced measurement, not a bare dial indicator). Use the list as the inspection checklist, with each machine's own tolerances derived from its field spec.

Some of the major in-house jobs that were successfully completed are; the low energy nuclear physics chamber for the High Current Injector, SS jacketing work of the spare Niobium Resonators for linac, two chambers for the Table Top Cyclotron project and several RF components like a prototype high power directional coupler, heat sinks for RF power amplifiers etc ... As of today, the entire requirement of machining, welding and assembly is fully carried out by the IUAC workshop without any outsourcing which is one of its mandates.

IUAC, Annual Report 2024–25, Chapter 3 — Research Support Facilities (table-top cyclotron RF system) — p. 36, 37

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: chamber fabrication at this machine scale is workshop-grade machining and welding, done entirely in-house by a national lab as routine job-shop work — not exotic vessel-making. Why the project consumed two chambers the report does not say (iterations, or distinct functions), so read the count as a capacity observation, not a revision history.

From these simulations and experiences several improvements were made to the ion source chimney. The most obvious was to make the ion source geometry symmetrical about the median plane. To this end even the Macor boat was sputtered with platinum to produce an electrical contiguous surface from top lid to bottom lid.

Koeth, Hanebuth, Hoffman & Schneider, Rutgers 12-Inch Cyclotron Ion Source Studies: Part II (2007) — p. 4

Editorial note, tabletop extrapolation: Applies wherever a machinable ceramic (Macor is the common amateur choice) sits exposed in the accelerating region: a dielectric patch can charge and distort the local field like a metal asymmetry would. Where modeling or symptoms point that way, either shield the dielectric or metallize it — with a vacuum-compatible coating that adheres through thermal cycling and ion bombardment AND is tied to the intended electrode potential (a floating coating is a new problem). Rutgers sputtered platinum on the Macor boat to make the surface electrically contiguous lid to lid.

It is clear from these views (figures 10 and 14) that the pullers are vertically offset; measurement shows they are 0.32mm high. As a result, the ions are introduced closer to the bottom puller, where the non-zero, off-plane, vertical gradient strongly pulled the beam down. A PSF model in which the DEE and pullers are raised by 0.32 mm illustrates the experienced vertical field; see figure 15.

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

Editorial note, tabletop extrapolation: A sobering tolerance number for tabletop builders: a third of a millimetre of vertical misalignment between puller and aperture was enough to dominate the injection dynamics on a 12-inch machine. The authors' own conclusion is that adjustability, not tighter machining, is the answer — see their planned 4-axis bellows adjuster. Note the figure-based measurement technique (photograph the source through a port, subtract a background image, measure against a known dimension) is itself the cheap part.

This signifies that initial conditions are very sensitive to the puller-chimney alignment and that adjustability is a necessity. A bellows 4-axis (yaw, pitch, roll, and gap spacing) adjuster is being designed. Its implementation will permit adjustment while running. To further increase ion production and to protect the bottom of the Macor boat, a small circular piece of metal, such as tungsten will be placed beneath the filament and sit at the filament bias voltage. Additionally, spiraling the filament should localize the heat generation as well as substantially increase the electron emitting surface. Finally, installation of a constant current bias supply is planned.

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

Editorial note, tabletop extrapolation: These are the authors' stated plans, not achieved results. The design intent transfers well nonetheless: in-vacuum, under-beam adjustability of the source position is worth engineering into a tabletop machine from the start, given that 0.32 mm of misalignment dominated their beam (p.5). A constant-current filament bias supply and a spiraled filament are both cheap changes at this scale.

The deflection channel was constructed as a modular assembly that could easily be removed from and replaced within the cyclotron chamber, as shown in Figure 2. Two aluminum plates separated by stainless steel posts formed the skeletal structure. The septum's curve was machined as a stepped shelf along the inside edge of the top and bottom structural plates. A thin (0.005 inch thick) stainless steel strip was seated against the step forming the septum. Thin strips of aluminum matching the septum's curvature were bolted onto the shelf clamping the septum in place and holding its curvature – see Figure 3.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 3

Editorial note, tabletop extrapolation: A septum-forming pattern that avoids specialty tooling: machine the curve as a stepped shelf in the structural plates and let 0.005-inch shim stock take the shape when clamped by matching strips. The modularity choice paid off operationally in this program — the deflector came out repeatedly during the arcing investigation — so if inspection cycles are anticipated, build it as a drop-in cartridge; how easy the machining is depends on the shop doing it.

The high voltage electrode was machined 3/8 inch thick from 7075 aluminum; each corner was rounded with a radius also of 3/8 inch. The curvature of 3/8-inch was based on the anticipated voltage, including a significant margin of error. The electric field resulting from a curved metallic surface follows [displayed equation Emax = 0.9V / ( r ln( (r+a)/r ) )] Where r is the radius of the curved surface, and a is the distance of the closest approach, limiting Emax to a conservative 170 kV/inch. In addition, the electrode was highly polished.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 3

Editorial note, tabletop extrapolation: A reusable first-pass electrode-sizing estimate: pick the corner radius so the curved-surface Emax stays under the working limit you are willing to accept. Worked with this memo's own parameters from its earlier sections (gap a = 0.31 in, V = 33 kV): r = 0.375 in gives Emax = 131 kV/inch — computed here, comfortably under the authors' stated 170 kV/inch, which is their conservative working limit for polished aluminum in their vacuum, not a universal breakdown value. Satisfying the estimate does not certify holdoff: the full field map, insulator flashover, surface condition and conditioning still decide.

It was supported from the back by stem of two T-shaped Teflon insulators. Bosses were machined in the tips of each arm of the T-insulators, the bosses were seated in detents in top and bottom plates. The T-insulator stems were deeply counter-bored and finished with a blank through hole. Two tapped holes on the rear of the HV electrode, and Nylon screws secured the electrode to the base of the T-insulators, which can be seen in place in Figues 3 and 4. Electrical connection was made to the HV electrode by directly seating a HV ceramic vacuum feed-through conductor into a third and final clearance hole in the back of the electrode, and is captured by a set screw.

Koeth, Ponter, Hoffman, Schneider & Krutzler, Rutgers 12-Inch Cyclotron Electrostatic Deflector (2010, rev. 2011) — p. 3

Editorial note, tabletop extrapolation: Three compact construction choices from a working HV-in-vacuum assembly, with their plausible rationales: the deeply counter-bored insulator stem (surface-path length — verify creepage on the actual geometry), Nylon fasteners in the high-field region (less grounded metal near the electrode), and the feedthrough conductor seated directly into the electrode (no in-vacuum HV wire to dress). None is a proven remedy on its own; qualify the PTFE, Nylon and feedthrough for voltage, temperature, charging and outgassing, and check the fields the real geometry makes.

Several steps were taken to mitigate the arcing. First, the polished HV electrode was coated with Aerodag-G graphite lubricant to reduce the coefficient of secondary electron emission. Three thin coatings of Aerodag-G were applied from an aerosol dispenser using an alcohol based propellant. The coated electrode was then baked at 125° C for 1 hour in standard atmosphere. Care was taken in handling the electrode as not to scrape the coating. However, from the handling it did receive, the coating was found to be surprisingly robust. Secondly, a clearance slot parallel to the deflection electrode was machined into the top and bottom structural plates which, shown in Figure 6, was intended to further reduce the electric field between them.

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

Editorial note, tabletop extrapolation: A cheap surface treatment with the full recipe as this program ran it: Aerodag-G colloidal graphite, three thin aerosol coats (alcohol-based propellant), one hour at 125°C in air — and they found the coating surprisingly robust in handling. Before copying: formulations change, so check the current product's SDS/TDS, outgassing and adhesion for your vacuum. Note the sequence — polish for field uniformity first, then coat for low secondary emission. The clearance slot machined above and below the electrode was INTENDED to reduce the field there (the source's own wording); verify such a slot with a field calculation.

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.

Subsequently, a surplus Bertan 205A-50N 50 kV power supply was ordered and installed. This supply was also only a constant voltage supply requiring a 150 MΩ current limiting resistor. The resistor was housed in an acrylic tube, capped at both ends, which was then externally covered with a grounded copper mesh. The resistor housing was installed in a relatively inaccessible location at the top and backside of the magnet yoke.

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

Editorial note, tabletop extrapolation: This is the source's own construction practice for a stack of HV resistors on a small machine: an insulating tube for standoff plus an outer grounded screen so the assembly presents a defined, grounded surface rather than a floating one, and physical placement out of casual reach. Reported here as what they did, with their numbers.

Initially, to satisfy the cyclotron resonance condition, the pole tips of the 12-Inch Cyclotron magnet were Blanchard ground to provide parallelism to better than 1 part in 10,000. As will be seen, this pure vertical field does not provide any beam focusing effects, all but a very few of the generated ions are lost on either the top of bottom plate of the DEE. Indeed, during commissioning of the cyclotron, only a trickle of beam current, less than a nano-ampere, made it to the periphery. Desiring beam currents of at least 10µA in intensity, a program to study and modify the cyclotron to achieve this goal is under way.

Koeth, Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans (c. 2005) — p. 1

Editorial note, tabletop extrapolation: The canonical educational-machine failure mode, and a machining-quality trap in reverse: extreme pole parallelism is exactly what leaves the beam without an axial restoring force (radial stability, with tune near 1, survives — it is the vertical plane that empties into the lids). The sub-nA periphery current is this machine's measured commissioning figure, a realistic 'before' anecdote rather than a class-wide baseline; the 10 µA goal is the authors' aspiration, not an achieved value anywhere in this document.

After much debate, a simple linear tapered pole tip design with an overall 2% decrease of Bz was settled upon. The magnet gap was to increase radially, starting from a minimum of 2.010 inches at r = 0 to 2.018 at r = 5.0 inches, the maximum possible ion radius. The author obtained the needed soft 1006 iron material. The pole tips were machined with azimuthal symmetry about r = 0.

Koeth, Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans (c. 2005) — p. 1

Editorial note, tabletop extrapolation: The Rutgers retrofit geometry, fully dimensioned: a 0.008-inch gap opening (computed: 2.018 − 2.010) over 5 inches of radius on a ~2-inch gap, cut in soft 1006 iron, targeting a 2% Bz droop. Two readings for your own design: the tolerance implication — pole-face errors must be small against 0.008 inch or they swamp the intended index — and the method: calculate or map YOUR Bz(r), derive n(r), and iterate by shim or re-cut, because the field response to a given taper belongs to the whole magnetic circuit, not the taper alone. The 2% is the design target; the source's own profiles fall considerably more by r = 5 inches once pole-edge fall-off is included.

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.

Zooming in on the gap region, it is clear, though slight, that the gap linearly opens up with an increase of radius. Near the pole tip’s edge, a rounded transition prevents localized saturation in the iron, thus radially extends the useful field region .

Koeth, Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans (c. 2005) — p. 5

Editorial note, tabletop extrapolation: A cheap machining detail with a real payoff on a small pole: breaking the pole-tip edge with a rounded transition rather than a sharp corner spreads the local flux crowding and — the source's stated purpose — radially extends the useful field region. Validate the chosen radius with a nonlinear field model; how much usable radius it buys is your geometry's answer.

In the case that we do find an azimuthal field distortion, it will most likely have a periodicity of 2, which is inherently an unstable Azimuthal Varying Field (AVF) condition. A minimum periodicity of 3 is required for a stable operating point. ... The first option is to “shim” out the AVF. By use of the 2-D field mapper, we can identify lulls in the field and manually install thin iron shims to shorten the gap and bring up the field to the desired value.

Koeth, Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans (c. 2005) — p. 7

Editorial note, tabletop extrapolation: Both halves transfer with one correction. Diagnostic: determine the azimuthal harmonic CONTENT by Fourier analysis of a 2-D map rather than inferring it from the defect — an off-center pole shows up first as m = 1, a two-lobe (m = 2) component is the case this source singles out as inherently unstable, and its minimum-periodicity-3 statement is the author's claim, presented without derivation. Remedy: entirely amateur-accessible — thin iron shim stock laid in the mapped low spots to shorten the gap locally — followed by re-mapping, since the shims move the average field and the harmonics together.

The first set was a simple, pure-radial sector design of periodicity four. Their geometry was the least expensive to machine and provided the maximum field variation achievable within practical constraints. Not expected to host beam, their purpose was to benchmark simulations, measurement techniques, and test analysis code.

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. 2

Editorial note, tabletop extrapolation: A process rule worth more than most hardware numbers: build the cheap, geometrically simple article first and use it to shake down the toolchain — solver, field mapper, analysis scripts — before spending shop time on the expensive curved part. The radial set rehearses most of the pipeline; what it cannot validate is the spiral-specific machining and edge-field modeling, which the real article still tests (the sequence that produced AKG270, dg-1717).

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.

The first set of AVF pole tips measured were of the simplest design, and are shown installed with the cyclotron chamber removed in figure 10. With a periodicity of four, the hills and valley are each 45 degrees wide. They maintain a constant thickness out to the pole edge, except for a ¼ -inch chamfer to break the sharp corners. The data from the first scan is plotted in Figure 11. The four hills are prominent, however a small central bump is observed from the slug that ties the four vanes together. This weak focusing is required to promote a centrally localized focusing field since the flutter will be too small to be effective at the central convergence.

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: The geometry as stated (four sectors, 45-degree hills and valleys, constant thickness, 1/4-inch chamfer, central slug) plus the central-region insight that matters most at small scale: flutter vanishes at r = 0, so a pure-AVF machine has no SECTOR focusing where ions are born — this design's central slug supplies a deliberate weak-focusing bump there, and the source states that requirement for its own field. Evaluate your own central region's full focusing budget (magnetic index plus RF-gap electric focusing and phase) rather than assuming the bump; most small AVF designs end up wanting one (the AKG270 kept it, dg-1717).

With acceptable agreement between the measurement and simulation, a spiral sector pole was simulated; again each vane had 45° angular width. The spirals were describe by an Archimedes spiral of the form θ=αr, where α=15°.

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. 6

Editorial note, tabletop extrapolation: A worked description of the trial spiral: 15 degrees of sweep per inch takes the edge through 75 degrees over a 5-inch ion region — this study's first spiral iteration, described with 45-degree vane widths in the same passage. The built optimized design swept 270 degrees total (AKG270, dg-1717). The number to copy is neither: sweep rate is the knob that trades edge-angle focusing against tune ramp (dg-1697, dg-1698), chosen from your own tune plot.

Radial sectors pole-tips providing the so-called Thomas focusing [2] have been built but the beam could not be accelerated up to the deflector radius due to poor isochronicity. ... To successfully accelerate the beam up to the chamber's radius a new set of pole-tips was designed [5], at the same time providing additional focusing using a spiral sector design. ... An iterative design phase using a field solver and ion tracking lead to the machining of 270°spiral pole-tips

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 documented negative result at exactly this scale: plain radial sectors on a small cyclotron can cost enough isochronism to prevent reaching full radius. If a tabletop builder wants AVF focusing, this collection's experience points to spiral sectors designed with a field solver plus tracking, not radial sectors alone. (The Archimedean-spiral / four-fold-symmetry statement is on p.1.)

A recipe for the controlled loading of titanium with hydrogen gas was adopted from Livanov, et al. [6] The loading apparatus consisted of a clam-shell tube furnace capable of reaching 1000°C, into which was inserted a two foot quartz tube connected to a high-vacuum system. The vacuum system consists of a mechanically backed turbo pump that was supplemented with an in-line lN2 cold trap. … Three identical samples were cut from a 0.010-inch thick sheet of laboratory grade titanium. Each sample was nominally 10 mm X 20 mm. They were cleaned with acetone and methanol. Precise mass measurements were made before the loading – these mass measurements included gases already adsorbed. Two of the three samples were loaded into center of the quartz tube, the vacuum system sealed and pumped. The third sample was kept as a reference. A base vacuum of 1x10-6 Torr was established before heating the samples. Pressure measurements, plotted in figure 4, were made as the tube furnace warmed to 900°C and throughout the ~3 hour dwell period. … The pressure slowly dropped during the 900°C dwell. Once the pressure dropped to approximately 2x10-5 Torr, the vacuum pump was isolated and the tube furnace was quickly backfilled and maintained at one atmosphere of deuterium.

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

Editorial note, tabletop extrapolation: A reproducible target-loading procedure using apparatus within amateur reach (tube furnace, quartz tube, trapped turbo pump), with the numbers the source states — 900°C, ~3 hour dwell, isolate at ~2×10⁻⁵ Torr, backfill to one atmosphere of deuterium. The unloaded reference sample is the detail that makes the later mass-gain measurement trustworthy (dg-1761). Not stated in the source and needed anyway: the safety engineering for hot hydrogen isotopes — flammable gas at a hot furnace mouth, quartz failure modes, and ventilation — which the reader must supply before attempting it. (The isolation-and-backfill clause is on p.3.)

A water bubbler connected to the manifold through a check valve was used to indicate a slight pressure above atmosphere within the quartz tube. The deuterium flow was set to cause approximately one bubble per second ensuring a slight positive pressure at all times. Audible 'crinkling' sounds were heard from the targets as the deuterium gas was introduced. ... There was a notable delay between the start of the gas flow and the first bubbles. Once the bubbling began, it was assumed that the titanium targets were saturated and cooling could commence.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 3

Editorial note, tabletop extrapolation: A zero-instrument endpoint HEURISTIC, reported as the source's own assumption: when the bubbler starts passing gas, they took the targets as saturated. Bubble onset can equally reflect line filling, head pressure or a leak, and cooling under flow does not by itself prove retention — so pair the bubbler with an independent uptake check (before/after mass on an unmounted coupon, flow integration, or a loading curve) before trusting the endpoint. Everything here is still glassware and a check valve.

It uses two tantalum cathodes pinned to stainless steel leads that are seated in boron-nitride cups which are housed in copper bases. The chimney, chimney bases, and HV lead shields are also all copper. Cooling is through conduction to the upper and lower chamber lids.

Koeth, Rosenberg, Krutzler, Ponter, Schneider & Hoffman, Rutgers 12-Inch Cyclotron: Dedicated to Training Through Research and Development — WEPPT024, Proceedings of Cyclotrons2013 (2013) — p. 1

Editorial note, tabletop extrapolation: PDF p.1 = printed p.366; the cross-section is Fig. 2 (PDF p.2 / printed p.367) and Fig. 1 shows the assembly beside a US quarter. The materials picture of one proven miniature internal PIG: Ta cathodes, BN insulating cups, copper everywhere heat must travel, and no water — conduction to the chamber lids is the entire cooling system, which is precisely what makes THIS design reproducible without plumbing. Another machine copies the principle (give the heat a solid conductive path to a big lid) and re-derives its own thermal budget — the runaway ceiling (dg-1816) is where that budget runs out.

After several hundred hours of operation at 5 mA the Ta cathodes need to be replaced due to erosion. … The most common failure is a build up of Ta flakes shorting a cathode to the copper base. Repair simply requires the PIG to be disassembled and scoured with acetone and methanol. … Figure 4 displays an inspection after 10 hours of operation.

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; the 10-hour inspection is Fig. 4. The maintenance picture to plan for before committing to a miniature PIG: the routine fault is a conductive tantalum-flake short cleared by disassembly and solvent scouring, cathodes are consumables (several hundred hours at this source's 5 mA setting), and deposits are visible after as little as 10 hours. The design consequence stands regardless of whose numbers apply: build the source so it comes apart easily and the consumables are reachable.

the HV electrode’s corners were rounded so as to limit the maximum E field to a conservative 170 kV/inch.

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. Read the numbers as design practice, not as an allowance: Rutgers rounded and polished the electrode so the peak local field stayed at their chosen conservative 170 kV/inch (6.7 MV/m) while the channel ran 4.2 MV/m — the ratio is the geometric peak-enhancement they permitted themselves, not a demonstrated breakdown margin. What transfers: control the peak-to-working field ratio by geometry, polish, and seat the feedthrough conductor directly in the electrode; then condition and test at the actual gap, pressure and surfaces, and put a current-limiting series resistor in the HV line (here 75 MΩ) so the inevitable arc is survivable.

the segment of HV cable between the series resistor and chamber formed a Blumlein HV pulse generator explaining the apparent ground-to-ground arcing … A 5 MΩ HV resistor was also installed in series with the coaxial center conductor and the chamber just prior to the HV vacuum chamber bushing. This suppressed all arcing and deflector operation at full potential is routine.

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. The craft lesson: a protective series resistor at the supply end leaves the cable beyond it as a charged transmission line that dumps into any internal arc. The fix that worked here — a second resistor at the chamber bushing — is cheap and retrofittable; 5 MΩ is the value that worked in THIS installation. Size yours from the downstream cable's capacitance and stored energy at your voltage, and buy the resistor for the job: working-voltage, impulse-energy and creepage ratings, or the protective part becomes the next flashover.

A 0.005 inch thick, curved, grounded stainless steel sheet forms the septum and separates the main accelerating volume and the deflection channel.

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.3 = printed p.368. A buildable worked example at tabletop scale: 5-thou stainless shim, curved and grounded, forms the septum, with the concentric HV electrode at an average 0.31 inch gap — formable without a machine shop. Choose your own thickness from stiffness, supports and intercepted beam power rather than copying the number. The design choice worth copying outright is modularity: the whole channel removes as a unit, which is what keeps a crowded small chamber serviceable. (The 0.31 inch average gap figure is on p.3.)

the pole tips can be up to 1-inch thick and are easily removable – to date, we have four sets of pole tips and one of each set is shown in Fig. 2. They consist of two weak focusing (one “good” and one intentionally “bad” for educational purposes), a radial sector AVF and a spiral sector AVF, all with a maximum central axial field, Bz(r=0), of 1.2 Tesla.

Koeth, Beam Physics Demonstrations with the Rutgers 12-Inch Cyclotron — WEPPT025, Proceedings of Cyclotrons2013 (2013) — p. 1

Editorial note, tabletop extrapolation: PDF p.1 = printed p.369 (the four sets are photographed in Fig. 2). The key architectural decision for a tabletop machine intended to be experimented on: make the pole tips removable and the same magnet becomes four different machines. Budget the geometry honestly — tips up to 1 inch THICK EACH sit inside the magnet opening, and the clear beam gap that remains is a separate design number this paper does not state. 1.2 T central is the stated ceiling with tips installed, versus the "nominally 1 Tesla" working figure quoted elsewhere in this collection.

The cyclotron chamber’s position can be moved horizontally with respect to the magnet’s center. … Initial ion radial-position errors can be introduced by a horizontal offset of the chamber, and hence ion source, with respect to the magnet center.

Koeth, Beam Physics Demonstrations with the Rutgers 12-Inch Cyclotron — WEPPT025, Proceedings of Cyclotrons2013 (2013) — p. 1

Editorial note, tabletop extrapolation: PDF p.1 = printed p.369 (purpose stated on PDF p.2-3 / printed p.370-371). An unusual design freedom: the chamber (and hence source) translates horizontally with respect to the magnet center, and the same adjustment that centers the source doubles as the deliberate-error knob for radial betatron studies. Copy it as a constrained, lockable, measurable translation — an unlocated chamber is not the feature; a controlled offset is — and remember one move shifts source, dees and probes together.

The most accessible magnet was a Varian V-3400 NMR magnet. It is of the typical H-frame design. Slight modifications were made to utilize the V-3400. Mounting the magnet sideways on a table created a horizontal gap at a reasonable work height. New pole tips were machined from 1020 rolled steel into cylinders, maximizing the diameter. The poles are nine inches in diameter and create a gap of 2.1875 inches. The maximum field obtainable from this geometry is 1.2 Tesla.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 1

Editorial note, tabletop extrapolation: Directly on point for an 8-12 inch tabletop machine. Two transferable moves: a surplus NMR/analytical H-frame magnet is a viable starting core, and re-orienting it so the gap is horizontal turns a vertical-gap instrument into a bench cyclotron with a flat median plane at working height. The 9 in pole / 2.1875 in gap pair (gap ~24% of pole diameter) is a concrete usable aspect ratio at this scale.

All dimentions are in inches Scale: 1/2 TOP VIEW

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 12

Editorial note, tabletop extrapolation: A dimensioned drawing set — rare in the amateur literature — for one 11-inch-bore chamber: ports at 0/45/90/180/225/270 degrees, a 10.0-inch dee in the 11.0-inch bore (about 0.5 inch radial dee-to-wall clearance, computed), 13.0 inch flange-to-flange, 2.0 inch outside height, 0.25 inch lids. Use the angular map as a planning EXAMPLE — whether six azimuths serve a collector, flag, viewports and gauge without crowding depends on port diameters and the dee-stem geometry — and re-check mechanics, seals and RF clearances before cutting. (Dimensions read from the rendered sheets: top view PDF p.12, side view p.13, both printed rotated 90 degrees; "dimentions" as printed.)

CERAMIC STAND-OFF / DEE MIRRORED FACE / BRACKET / POWER FEED-THROUGH / VACUUM PORT / ASSC. PORT 2 … [p.16 sheet callouts:] CERAMIC STAND-OFF (0.5") / DEE SHOWN WITH TOP PLATE REMOVED / 10.0 / 0.375 / 0.75 / ACTUAL SIZE

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 15

Editorial note, tabletop extrapolation: The documented geometry, as drawn: a 0.5-inch accelerating gap between the 1.00-inch dee and the mirrored dummy-dee face, dee on 0.5-inch ceramic stand-offs, inside the 1.50-inch chamber height with 0.25-inch dee-to-lid clearance. Reproduce it as historical reference geometry; whether the gap field is uniform enough and 0.25 inch stands your voltage are per-design questions for a field solve and a breakdown check. The dummy-dee sheet's "inside dimensions to mirror face dimentions of the DEE" note (PDF p.18, spelling as printed) is the fabrication shortcut: dimension the dummy by reference to the dee. (Drawing sheets are printed rotated 90 degrees; the p.15 assembly sheet labels the stand-off without a dimension — the 0.5" is on p.16.)

NOTE: DIMENSIONS A B & C ARE TO BE DETERMINED BY SHOP.

Koeth, The Construction and Operation of a Nine Inch Cyclotron (undated scan; the machine ran 1995–1999) — p. 14

Editorial note, tabletop extrapolation: Craft practice worth naming for amateur builders: fix on the drawing what beam geometry, RF, vacuum and fit require, and hand the rest to whoever is cutting metal — an over-specified fabricated dee is a simple part made expensive. The qualification is the rule: shop-determined details are safe to leave open only where they cannot move the physics (a 1/16-in brass box's edge radii and joint allowances, plausibly; anything touching gap, aperture or stem, never). (Numbers read from the rendered drawings, printed rotated 90 degrees.)