Cyclotron targets design rules

Targets and their assemblies normally emit about 100 to 500 r/hr 5 minutes after bombardment ... The intensity of radiation by the exit strip averages about 10,000 r/hr, and the deflector about 500 r/hr.

McWalters et al., Radiation Exposures of Personnel at the 60-inch Cyclotron — UCRL-8276 (1958) — p. internal-target and external-target figures on PDF p. 10 as cited; deflector/exit-strip figures on PDF p. 15 (section 'Maintenance')

Editorial note, tabletop extrapolation: ENERGY SCOPE: these are 10-24 MeV activation levels. The design ordering survives: whatever intercepts full beam (probe tip, Faraday cup, target holder) concentrates the consequences. On a sub-MeV machine that is heat and sputtering today - and activation joins the list via thresholdless capture on some materials, light-element targets, or any deuteron operation, growing first at these same components if energy climbs.

Cited in: Shielding a Small Cyclotron

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.

A photographic film is covered with a stepped absorber (made by folding an aluminum foil), wrapped in aluminum foil, and exposed directly in the cyclotron beam.

Cohen, Measurement of Beam Energy and Energy Distribution on an Internal Cyclotron Target — ORNL-1347 (1952) — p. 6

Editorial note, tabletop extrapolation: At 150-170 keV the material budget dominates everything: compute proton range and straggling with PSTAR/SRIM through the CUMULATIVE areal density - wrapping foil, absorber steps, emulsion overcoat, detector dead layer - before trusting any variant, since micron-scale layers can stop such protons outright. The architecture transfers (stepped degrader + position-resolved readout + reference channel), but an ordinary PIPS is a single channel: use per-step exposures, a scanned detector, or a segmented one, and establish low-current operation for the actual ion source rather than assuming the arc-off trick.

each carbon foil was broken into 1/2-inch sections, along previously made scorings, and counted in a Geiger counter.

Cohen, Spatial Distribution of Current on an Internal Cyclotron Target — ORNL-1348 (1952) — p. 5

Editorial note, tabletop extrapolation: ENERGY SCOPE: C12(p,pn) needs ~20 MeV, so the activation readout is closed at tabletop energies. Keep the geometry, swap the readout - a probe-tip mosaic of insulated segments read as Faraday collectors gives a one-shot 2-D map IF built properly (guarded insulation, secondary-electron suppression, RF isolation, calibrated electrometers); a witness material (film, phosphor) needs calibrating at the actual energy, spot size and vacuum before its image is trusted. Either way the map decides where the B11 target goes and how big its hot spot runs.

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.

a beryllium target is bombarded with protons, approximately 1 neutron for 50 protons is obtained.

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

Editorial note, tabletop extrapolation: SCALE-SCOPED - this 2% yield is a ~20-MeV number; at the reference machine's and a next machine's energies (0.15-5 MeV) p-Be yields are orders of magnitude lower. Useful as the upper anchor when building the shielding/licensing dose model for any future MeV-class educational machine.

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

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

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

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

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

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

the target appears transparent and all of the radiating surface of a solid may not be present in a thin film.

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

Editorial note, tabletop extrapolation: Radiation is the only cooling channel a self-supporting foil in vacuum really has at the spot: solving Corwin's equation for a stopped 0.17 W beam on a 0.03 cm2 spot with e = 0.1 gives roughly 1200 C equilibrium - above most evaporated films' damage points and hot enough to anneal or evaporate many (boron itself melts higher, but its substrate and adhesion rarely survive) - which is why the spot is enlarged or the film backed (dg-1160).

so a metal target could conduct the heat away with a 12 C rise in temperature.

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

Editorial note, tabletop extrapolation: The 100x conductivity gap between salts/insulating compounds and metals is the single biggest lever on target survival: a boron film on a thick copper or silver backing is conduction-cooled through the backing, while the same film self-supported is radiation-only (dg-1159). Thickness enters linearly, so doubling film thickness halves the rise at fixed power.

The equilibrium temperature of the beam spot circle for the high speed rotation limit is 65 C.

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. 239

Editorial note, tabletop extrapolation: Rotation or beam wobbling is a heat-spreading method worth serious money on an internal target - Corwin built a three-target rotator to use it - but the gain factor is his geometry and material: rerun the equation with the actual tabletop spot, circle, thickness and emissivity, and remember a rotating mechanism in vacuum is real engineering (bearings, feedthrough, balance), not a trivial add-on.

the temperature can rise only 39 C before that part of the target is out of the beam.

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: Sets the rotation-speed design check: compute the per-pass peak excursion (P/mc x dwell) against the allowable rise, and where the revisit period is not long compared with tau, run a periodic transient-heat calculation - the pulse train settles to a periodic steady state whose peak, not a simple ratchet criterion, is what must clear the material limit.

With thicker targets the conduction limit will not change while the radiation limit will rise.

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: For a beam-stopping target the deposited power saturates at P = I*E/q, so further thickness adds no heat - then COMPARE the loss paths for the actual design instead of assuming conduction wins: a heat-sunk metal backing usually makes conduction dominant, but emissivity, temperature and interface resistance decide, so run both terms once.

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

it is equally important to know what species are present and in what concentration.

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. 52

Editorial note, tabletop extrapolation: For a reaction-yield target the practical home-lab measures are material pedigree (certified purity), clean processing, and a background run on a process-matched blank backing - which catches backing and process backgrounds but NOT impurities arriving with the active deposit, so where composition is critical they reduce risk rather than replace assay. Check, for the actual projectile and energy, which contaminant reactions and scattering peaks could land in your signal region - carbon and oxygen are the usual suspects but not automatic offenders.

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.

A large portion of the 220Rn gas is created as positive ions which are attracted by the -300 volt collecting potential

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. 61

Editorial note, tabletop extrapolation: The physics is elegant - the 2.7 MeV spread between the 212Pb lines self-calibrates a spectrometer with no external standard - and the procedure is not an amateur recipe: an open 228Th container means thoron gas, plated-out daughters and removable contamination, and possessing 228Th in usable quantity is licensed activity in most jurisdictions (/legal/). For the program's spectrometer calibration the appropriate form of this idea is a commercial sealed or electroplated check source.

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

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

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

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

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

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

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.

Some targets may be hydroscopic, while others may oxidize rapidly.

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. 84

Editorial note, tabletop extrapolation: The load-lock principle scales down to one target: a valved transfer pot REDUCES atmospheric exposure for Li, Ca or boride targets - how much depends on its achievable pressure, residual water and oxygen, pump backstreaming and valve sequencing, so qualify the pot against a sacrificial target before trusting it with the real one.

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

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

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

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

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

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

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

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

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

using a carbon substrate produces a lot of difficulty because of the contaminant reactions observed from carbon

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. 164

Editorial note, tabletop extrapolation: For reaction-yield measurements, run the blank-backing background and prefer a backing whose own beam reactions are energetically closed or distinguishable at YOUR energy; compare backing stopping powers with current tables at the actual projectile and energy rather than a remembered ratio. Flatness of the mounted foil matters as much as its thickness distribution.

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

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

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

radiative heating of the foil to a temperature of approximately 500 C. The increase in observed lifetime was about a factor of 40. ... There was no substantial difference between annealed and non-annealed foils.

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.206 (printed p.190)

Editorial note, tabletop extrapolation: Concurrent annealing is the transferable idea: a small radiant heater on a carbon stripper/target holder is a cheap experiment with a large historical payoff - run it as an experiment, monitoring actual foil temperature, outgassing and vacuum cleanliness, rather than booking the 40x (which belongs to the cited foil, beam and conditions). Keep hydrocarbons out of the vacuum or the beam writes a thickening carbon spot on every foil.

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.

Defocus whenever possible is the moral to this result.

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

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

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.

It has always bothered me that a film should ever break at its thickest port [sic]; (Ramsay, "Alternatives to Thin Film Carbon Foils")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 81

Editorial note, tabletop extrapolation: When a thin internal target or probe foil dies, read the wreckage before assigning the cause: the radial-crease/thickened-spot signature points to Ramsay's stress mechanism, while melting, sputtering, charging marks or a failed frame each tell a different story - the mechanisms coexist and beam conditions pick the winner.

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

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

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

two of the targets did not break (Ramsay, "Alternatives to Thin Film Carbon Foils")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 80

Editorial note, tabletop extrapolation: When a self-supporting film keeps failing, an evaporated metal layer is a cheap experiment - with its costs computed first: at sub-MeV proton energies 10 ug/cm2 of gold contributes real energy loss and straggling (run the stopping numbers), ultrathin layers may not be continuous, and the backing adds its own reaction background. Try it; measure what it costs the experiment.

too high a temperature can cause nitrogen diffusion into the tantalum substrate resulting in a target with a poorly defined thickness (Stinson, "The Preparation of Nitrogen-15 Targets")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 96

Editorial note, tabletop extrapolation: Any reacted-layer target (nitride, oxide, deuteride) on a metal backing needs its own temperature study - the failure modes differ by system (substrate diffusion here; desorption or decomposition for deuterides) - and a smeared depth profile shows up downstream as degraded resonance width or energy resolution, which is the cheap check that the window was respected.

Iron forms a carbide if a graphite boat is used (Heagney & Heagney, "Reduction Techniques for Isotopic Materials")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 98

Editorial note, tabletop extrapolation: The route from purchased oxide powder to rollable or evaporable target metal - consult the per-element table before buying any element as oxide. A hot hydrogen furnace is its own hazard class: inert purge before and after H2, flow and flame management, and per-element vapor and hydride toxicity are prerequisites the table assumes rather than teaches; the report's apparatus description is the checklist seed, not the whole checklist.

Usually better than 90% of the metal can be deposited on the cathode (Heagney & Heagney, "Reduction Techniques for Isotopic Materials")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 100

Editorial note, tabletop extrapolation: For milligram-scale enriched material the deciding metric is END-TO-END recovery fraction, not speed - cathodic deposition is one term in it (dissolution, transfers and electrode handling take their shares), so weigh the whole chain for each candidate route rather than assuming electrolysis beats furnace reduction whenever plating works.

Deuterated polyethylene could not be used because of its rapid deterioration under bombardment (Meens, "Deuterated Titanium Targets on Thin Backings")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 106

Editorial note, tabletop extrapolation: The standard durable chemistry for d-beam or D(p,..) work - with durability measured, not assumed: TiDx targets still lose deuterium, blister and sputter as current density rises, so establish the lifetime at the actual beam parameters. CD2 remains usable where its measured lifetime covers the run - 'lowest current only' is a tendency from the cited experience, not a threshold.

The maximum allowed beam current is about 20 particle nA for the HgS-ta[rget] and about 1 particle nA for the amalgam target (Friebel et al., "Preparation of Isotopically Enriched Mercury Targets")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 121

Editorial note, tabletop extrapolation: The compound-beats-volatile-element lesson transfers; the factor of twenty does not - it belongs to that beam, spot, thickness and cooling. For a sub-MeV proton or deuteron machine, compute deposited power and target temperature for the candidate compound directly. The elastic-peak tail is a useful in-beam flag for target quality once detector response, straggling and backing effects are excluded.

They are cooled from the edges by connecting to a copper block with silver paint (Maier, discussion of "Preparation of Isotopically Enriched Mercury Targets")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 200

Editorial note, tabletop extrapolation: The simplest conductive-cooling geometry for a target that cannot be water-backed - a cold finger to the frame plus a conductive-paint joint. What temperature the target actually runs at is beam power times the total thermal resistance: compute it or measure it in beam; the joint and film resistance can be anywhere from negligible to dominant, so no stock kelvin budget applies.

the reaction with mercury oxide runs into an explosion (Friebel et al., "Preparation of Isotopically Enriched Mercury Targets")

Fifth Annual Conference of the International Nuclear Target Development Society — LA-6850-C, Los Alamos Scientific Laboratory (1977) — p. 127

Editorial note, tabletop extrapolation: Strongest is not best in metallothermic reduction: a controllable reaction that completes in minutes beats a violent one that contaminates the product. Mercury adds its own layer - at these temperatures Hg is mobile, toxic vapor, so the paper's sealed-retort integrity, condensation path and exhaust handling are part of the method, and mercury work sits behind fume containment at any scale.

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 holder ring was split to prevent eddy currents in the ring from rf (Ramsay, discussion of "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. 201

Editorial note, tabletop extrapolation: An internal target probe near the dee gap lives inside the machine's own RF field; a closed metal frame is a shorted turn that heats and perturbs. One saw cut interrupts the loop PROVIDED nothing bridges it - target foil, conductive deposits, or mounting hardware across the gap re-close the turn, and a narrow gap still passes some capacitive current - so verify RF heating after assembly.

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

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

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

the 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.

Heating the carbon foil and graphite support frame to an ambient temperature of 450 +-150 C increased its lifetime by about a factor of 4 (Thomas, DenHartog, Bicek & Yntema, "Lifetimes of Carbon Stripping Foils")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 24

Editorial note, tabletop extrapolation: A heater ring or slow rotation stage on a foil holder is a cheap candidate life-extender - for carbon under heavy beams it has a strong record; for other target materials, adhesives and beams, heating can as easily hurt (oxidation, adhesive failure, evaporation), so test it with heat-load and vacuum checks rather than booking a multiplier. The gradual-tear behavior of heated carbon is a bonus where it holds: warning instead of sudden loss.

Periods of sixty seconds have produced encouraging results while six second periods showed very little improvement in foil lifetimes. The longer cycling times may afford the foil a relaxation time. This relaxation time may also be a contributing factor in the increased lifetimes for foils which are moved.

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 25

Editorial note, tabletop extrapolation: Relevant to any interlock or chopping scheme meant to spare a target: two time points bracket, but do not measure, the relaxation constant - if chopping is the plan, scan the off-time on the actual foil rather than assuming tens of seconds is the magic number.

Rolled target foils withstand due to their crystalline structure longer a heavy ion beam than evaporated targets (Kellner & Maier-Komor, "Rolling Thin Uranium Foils and Other Exotic Isotopic Metals")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 32

Editorial note, tabletop extrapolation: Where a target must survive sustained current, prefer rolled, electrodeposited or annealed material over as-evaporated film where practical - but crystalline order is one factor among several. Target survival is set by beam power density, stopping range against thickness, backing and adhesion, thermal conductivity and cooling, sputtering, melting and stress; size the thickness, backing, cooling and current density from a stopping-power and heat-load calculation (dg-1211), and treat the rolled-versus-evaporated choice as a durability bonus on top of that, not a substitute for it.

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.]

In the first experiments the Uranium foils were destroyed by a heavy ion beam during the first 1 or 2 hours. The monitor spectrum showed almost pure Uranium oxide. ... The problem was a poor vacuum of 10-5 Torr in the scattering chamber which allowed oxidation similar to the effect in an ion getter pump. In the next experiment the vacuum was in the 10-6 Torr range due to an additional cryo-pump and the targets lived much longer, but one could see still in the monitor spectrum, that oxidation took place.

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: A 1e-5-torr-class chamber actively burned this reactive uranium target under beam - the beam spot acting like a getter pump. For any reactive target, budget life against chamber pressure (and specifically oxygen/water partials), expect oxide growth in the monitoring spectrum as the early warning, and treat the uranium numbers as that experiment's calibration, not thresholds.

Even, tough films, easy thickness control and production of self supporting targets are other advantages inherent to the process (Stinson, "Nitrogen Targets Produced by Reactive Sputtering of Tantalum and Titanium") ... Tantalum nitride targets with a thickness of 36 ug/cm2 were produced by sputtering for eight minutes. Titanium nitride targets of the same thickness required 32 minutes. ... the sputtering rates range from 1 to 1.5 ug/cm2.min for tantalum nitride, and from 3 to 4.5 ug/cm2.min for titanium nitride.

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 68

Editorial note, tabletop extrapolation: Sputter deposition is the durable-target counterpart to the ORNL-3021 evaporation recipes - slower, but the film adheres and survives beam heating; backing choice and beam-power suitability still get verified per design rather than assumed from the process name.

Hydrocarbons crack during the sputtering process and deposit car[b]on or form carbides with the refactory [sic] metals used (Stinson, "Nitrogen Targets Produced by Reactive Sputtering")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 62

Editorial note, tabletop extrapolation: The same cracking chemistry threatens any glow discharge backed by an untrapped oil diffusion pump - hydrocarbon backstreaming can contaminate whatever the discharge sees. Condition the discharge on a closed shutter before exposing the workpiece (removes initial cathode contamination), and control CONTINUING contamination with a working cold trap/baffle or oil-free pumping - the shutter trick does not cure ongoing backstreaming.

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

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

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

Evaporated films of carbon, titanium, nickel, or gold of 0.01 to 0.2 mg cm-2 are used to protect the uranium layers from oxidation (Folger & Klemm, "Uranium Sandwich Targets of 0.1 to 100 mg-cm-2")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 70

Editorial note, tabletop extrapolation: Two transferable patterns, each with arithmetic attached: a cover layer buys shelf life and in-beam oxidation resistance at an energy-loss cost that is NOT negligible at sub-MeV energies (0.2 mg/cm2 of gold takes a real bite - run the stopping numbers for the actual beam and cover); and a thick copper chip spreads heat but sinks it only through a designed low-resistance path to actual cooling.

Tank pressure above 4 x 10-6 torr made the targets more brittle and shortened their shelf life (Ellsworth, "Preparation of 3/4-in Dia. Self Supporting 182W and 184W Targets for Cyclotron Bombardment")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 81

Editorial note, tabletop extrapolation: Transfer the method - control pressure, rate and substrate temperature, then calibrate stress, adhesion and shelf life on the actual material - not the tungsten numbers: the 4e-6 torr boundary and the rate-stress trend are that process's results, and residual stress can move the other way in another material/substrate system.

in cases of poor heat conduction temperatures up to 3000 C occur and exceed therefore the melting points of most of the usual target materials (Tietsch, Feist, Bethge & Schopper, "A High Density Windowless Gas Jet Target")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 82

Editorial note, tabletop extrapolation: The checklist stands: conduction, charge relief and structure all have to be engineered as current rises, and a gas target is the limiting alternative when no solid survives - trading foil failure for nozzle, flow-stability and differential-pumping engineering rather than achieving unbreakability.

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.

small impurities of nearly all metals in the order of magnitude of a few hunderd [sic] ppm largely enhance the brittleness (Friebel, Frischke, Grossmann & Maier, "Preparation of Isotopically Enriched, Self Supporting Chromium Targets")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 112

Editorial note, tabletop extrapolation: When a foil cracks in the mill, suspect chemistry before technique - assay or provenance-check the stock before burning days on rolling variables. The few-hundred-ppm sensitivity is chromium's measured result; treat other brittle metals as innocent until their own data convict.

in equilibrium the maximum tolerable water content of the hydrogen atmosphere is 540 ppm (Friebel et al., "Preparation of Isotopically Enriched Chromium Targets")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 110

Editorial note, tabletop extrapolation: The template for judging whether tank-grade gas is good enough for any reduction or annealing atmosphere: compute the equilibrium H2O/H2 ratio at the furnace temperature before blaming the furnace - then verify the DELIVERED atmosphere (dew point or oxygen potential at the work zone), since a purifier's outlet spec says nothing about downstream leaks and outgassing.

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.

a cooling system for the target material post is required (Baumann & Wirth, "A Heavy Ion Sputtering System with a Penning-Ion-Source")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 127

Editorial note, tabletop extrapolation: The same arithmetic sizes cooling for beam stops, probes and targets on a small machine: compute the flux from the actual current, spot and duty (mm-scale spots reach 100 W/cm2-class loading at mA-and-tens-of-kV operating points, not automatically at tens of uA), then get temperature from a stated thermal model before deciding whether cooling is needed.

the source ran with a stable ion beam intensity for 165 hours without any trouble (Baumann & Wirth, "A Heavy Ion Sputtering System with a Penning-Ion-Source")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 125

Editorial note, tabletop extrapolation: The filament-free argument is the same one that favors PIG sources inside a cyclotron, and the documented design point (geometry, discharge mode, gas flow, stability) is valuable prior art - as a demonstrated result, not a category win: PIG cathodes still sputter and erode, chemical resistance is gas- and materials-specific, and whether <30 W runs uncooled depends on where the watts concentrate and what the mounting conducts. Check those for the actual build.

a constant current density of 250mA/cm2 ... the deposition rate is about 3.6ug/cm2. min. ... the yield in the case of platinum is about 20%. However, it happens that platinum is lost as a residue in elementary form in the bath.

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 133 (printed = PDF) for the quoted conclusion; the numbers are on 131-132

Editorial note, tabletop extrapolation: Electroplating joins rolling on the durable side of the durable-vs-evaporated divide, and it works at milligram scale with a beaker and a regulated supply - for platinum by this process on this evidence; other metals earn the durability label with their own beam tests.

the foil breakage time is dependent on the total number of bombarding ions (Livingston, Berry & Thomas, "Thin Carbon Foil Breakage Times Under Ion Beam Bombardment"; reprint of NIM 148 (1978) 125)

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 152

Editorial note, tabletop extrapolation: Plan foil replacement by integrated charge where the fluence law holds - and verify it holds: dose-rate heating, spot profile and mounting can break the current-independence outside the tested window. Thickness buys nothing in beam life WITHIN the cited range, so choose it from mechanics, handling and dispersion - not as a lifetime lever.

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

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

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

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 trap is essential; the gas is not absorbed otherwise (Gursky & Sherwood, "Hydriding of Titanium Cones for a Sputter-Ion Source")

Proceedings of the Sixth Annual Conference of the International Nuclear Target Development Society — LBL-7950, Lawrence Berkeley Laboratory (1978) — p. 57

Editorial note, tabletop extrapolation: The bench recipe for Ti-H or Ti-D loaded pieces - executed as a hydrogen process, not a casual one: hydrogen-rated containment and plumbing, leak checking, ventilation and ignition control, and a trap that gets inspected (an LN2 trap can concentrate oxidants if purification fails). Tritium is a different world entirely - licensed containment, monitoring and recovery - and is not an amateur variant of this recipe.

If the beam is focused to an area of about 0.2 cm2, the resulting specific energy depositions amounts to 1 kW/cm2.

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

Editorial note, tabletop extrapolation: The reference machine at ~3 nA / ~150 keV deposits ~0.5 mW - no realistic solid target is troubled by half a milliwatt. Rerun the two-line arithmetic at every upgrade, using the energy LOST IN the target rather than incident beam power where targets are thin: a 10 uA / 1 MeV machine puts up to 10 W into a mm-scale spot, which is rotating-target or water-cooled-backing territory.

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.

survived a bombardment of Au ions of an energy of up to 15 MeV/u and intensities of up to 1 uA, rotating with 1333 rpm ... exposed to the full beam intensity while the disc-driving motor was already switched off ... producing zones of molten Au

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. PDF p.47 = printed p.38 (Folger, Sec. 3.3 'Improved Rotating Target-Disc for Fragmentation-Reaction Experiments')

Editorial note, tabletop extrapolation: Folger's before/during/after SEM sequence is the reference picture of beam kill on a metal foil. Any moving-target scheme needs a rotation-OK permissive in the beam interlock chain: a stalled wheel concentrates the whole designed-for-distributed load on one spot.

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.

Additional features of such multi-layer targets appear to be their enhanced thermal and/or electrical conductivity. Both thermal gradients and electrical charge generated in or on the target during bombardment appear to be shunted to the relatively heavy frame surrounding the target. This improved energy transfer tended to significantly increase target lifetime under bombardment. Accumulation of energy was also reported to cause local melting of the target material as evidenced by significant broadening of scattering peaks.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 140

Editorial note, tabletop extrapolation: Two transferable ideas: treat the frame as the heat sink and design the film-to-frame conduction path deliberately; and watch the elastic-scattering (or yield) peak width online as a degradation warning - broadening flags trouble worth investigating (melting is one cause; thickness change, roughening, charging and detector drift are others).

Representatives from Argonne National Laboratory indicated their partial success using a thin layer of copper (ca. 500 ug/cm2 or less). With this protection, it was observed to take five minutes before any significant amounts of oxygen or moisture were detected. The minimum thickness of copper required was indefinite, but 'it could possibly be as thin as 100 ug/cm2'. The overcoating was successful with lithium layers of 500 ug/cm2 on pin-hole free nickel substrates. ... others in the group indicated only marginal success with gold coatings. The thickness suggested for the gold layer was 30-40 ug/cm2.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 140

Editorial note, tabletop extrapolation: Sets the realistic SCALE for air-handling of reactive targets - minutes, not hours - from one measured case (Li under Cu, with 'partial success' and detection-limited timing): use inert transfer where possible, validate each target/overcoat pair, and remember overcoat nuclei scatter too, so the coating choice is coupled to the experiment.

broadening of the peak indicates target changes or damages

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

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

target heating can be a problem and efforts are made to diffuse the beam on the target.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 58

Editorial note, tabletop extrapolation: Spot size is a powerful cooling knob - average flux is P/(pi*r^2), so doubling the radius quarters it - but use it inside a checked budget: compute beam power and allowable target temperature first, confirm the full swept or defocused beam still lands on target (not the holder), and treat active cooling, temperature monitoring and beam-trip protection as their own requirements rather than things defocus postpones.

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.

they would slowly curl and fracture

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 100

Editorial note, tabletop extrapolation: Plan target fabrication against the run schedule, not the calendar, for any film KNOWN to carry stress - and qualify rather than generalize: store finished targets under vacuum or argon, inspect periodically, and learn each film type's actual shelf behavior from a witness piece instead of assuming a universal use-within-weeks rule.

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).

no method seems superior to the arc evaporated foil.

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

Editorial note, tabletop extrapolation: Two lessons: distrust any foil-lifetime or target-durability claim not measured under your own beam and current density, and settle fabrication-method questions with a side-by-side test on the actual machine rather than the literature's confounded comparisons.

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.

This prevents target damage by gas out-rush.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 159

Editorial note, tabletop extrapolation: Even a desiccator-scale target store benefits from the transferable habit: throttled first venting/roughing near fragile foils (the source's restrictor-valve recovery). The legacy failure list is instructive where the corresponding hardware exists - IF the store or target uses water cooling, monitor flow and let a hazard assessment decide whether the monitor must interlock beam or heating rather than just alarm.

thermal runaway would occur and the stored beam would be lost.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 218

Editorial note, tabletop extrapolation: Directly relevant to the synchrotron campaign, not the cyclotrons: compare target heating with the circulating current and intercepted fraction - a nanoamp of circulating current is a nanoamp at the target - and apply the traversal multiplier where it belongs, to how fast the stored inventory or injected charge is consumed.

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.

NO QUOTE — paper IV-1 is reprinted from Nucl. Instr. and Meth. 206 (1983) 361-366 with North-Holland permission; finding paraphrased, cite the journal article.

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 210

Editorial note, tabletop extrapolation: NOT a tabletop construction example. Actinide targets - arc-melting the alloy, mounting it, putting it in a beam - are licensed radiological-laboratory work: contamination control, shielding, dosimetry, fission-product and activation handling, and radioactive-waste management, on top of the licence itself. Keep this rule as a literature example of matching host-material physics (crystal symmetry, conductivity, heat sinking) to what a measurement needs, and as the rights-boundary marker for this volume; the transferable idea is the matching, never the material. Cite the journal article (Nucl. Instr. and Meth. 206 (1983) 361-366) for the paraphrased finding. [Corrected 2026-08-23: earlier note called this merely "marginal technically" for a proton machine, which understated the hazards that actually decide it.]

A copper target will be placed in the chamber, which will as a result of the beam be impregnated with deuterons. More ions from the beam will collide with the trapped deuterons, undergoing one of two reactions, d(d,n)3He or d(d,p)3H. Since neutrons are the desirable result of the reaction, no extraction system will be required. ... the outgoing neutrons will be produced with 2.8 MeV. The electrically neutral neutrons will pass through the chamber walls and can then be used for inelastic scattering measurements.

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 48

Editorial note, tabletop extrapolation: A beam-loaded (drive-in) copper target avoids separately fabricating a deuterated target and removes extraction from the critical path. Physics notes on the thesis's numbers: D(d,n)3He neutrons at ~150 keV bombarding energy are angle-dependent, roughly 2.1-3.0 MeV in the lab - 2.8 MeV is one point on that curve, not the spectrum - and the thesis does not analyze dose or shielding beyond its concrete room, so the radiological planning is entirely on the builder.

The maximum energy of the current cyclotron, using (6), is 150 keV for deuterons, which puts the cross section near the maximum. ... [the d(d,n)3He reaction is] exothermic with 2.227 MeV released for each deuteron pair.

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 49

Editorial note, tabletop extrapolation: Working back from the excitation curve converts machine energy from a bragging number into a requirement - the transferable design move. D-D is the standout low-energy neutron reaction because its cross-section is already usable near 100 keV; take Q-values and cross-sections from live evaluated data (per site policy), not from the thesis's figures.

The Li7(p,Y)Be8 resonance reaction has a threshold energy of 0.441 Mev and has a large cross section ... A thick (0.5 mm) Li7 target was attached to the target and r2 was set so that the energy of the protons would be about 1 Mev ... The NaI crystal was located about fifty centimeters from the target ... The scintillation spectrometer was calibrated using the unresolved (1.25 Mev) Y-rays from Co60 ... The reaction actually yields two high energy Y-rays, the 17.5 Mev one and also one of energy of 14.5 Mev ... it had an abundance of 30%, as determined by the relative counting rates

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 7-9

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: the strong 441 keV resonance puts high yield within reach of even modest machines, and a ~17 MeV gamma is a distinctive high-energy signature — though NaI response at 15-18 MeV is pair-production-dominated and needs calibrated interpretation (the source's own 15 MeV pulse-height reading needed a +0.5 MeV pair-escape correction and still sat 2 MeV low, within their stated uncertainties). Yield versus target radius maps beam energy against the resonance once target energy-loss and beam-spread corrections are applied; a gamma-onset reading is not a threshold measurement, because capture occurs below the resonance too. Photons this energetic exceed photoneutron thresholds in nearby materials — assess shielding, dose and activation before running the experiment.

The samples to be bombarded were machined (dry) in the form of thin wafers (1 mm thick) from spectroscopic carbon. The target radius was set so the energy of the protons would be only slightly greater than the threshold energy for the reaction. This was done to minimize the absorption of the β+-particles leaving the sample, thus providing the maximum flux at the counter. The sample was then bombarded for about one half-hour. After bombardment, the activated sample was removed from the machine and taped to a two-inch NaI crystal scintillation counter located in a lead house for minimum background. The counting was done for fifteen-second periods every minute for one half-hour ... A plot of the natural logarithm of the counting rate versus elapsed time has a slope equal to 0.693/T1/2, where T1/2 is the half life for the decay ... gave T1/2 = 10.3±0.3 min. The average value of three such determinations also yielded a half life close to 10.3 min. for the N13. This is in reasonable agreement with the published value of 10.1 min.

Burns, Experimental Program with the Iowa State University Undergraduate 1.5 Mev Cyclotron — Proceedings of the Iowa Academy of Science 68(1), 483–491 (1961) — p. 9, 10

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: off-line activation counting decouples the measurement from accelerator-correlated pickup — the machine only has to run for the bombardment, and a known half-life gives a self-grading answer. Barely-above-onset bombardment as a technique for keeping activity near the surface is a subtle, transferable target-design trick.

In the case of a centered orbit, the proton will strike the target when r0 exceeds rt, the target radius. Target energies would be approximately single-valued for centered orbits for which E = mv2/2 = [r0 e B(r0)]2/2m. However, off-center protons may strike the target whenever r0 + δr exceeds rt. It is then possible to have heterogeneous target energies since r0, and consequently E, may vary. Therefore, any simplified method of off-center orbit study must include a means for considering heterogeneous target energies.

Moses, Proton Orbits in a Small Cyclotron — Proceedings of the Iowa Academy of Science 70(1), 403–414 (1963) — p. 12

Editorial note, tabletop extrapolation: Editorial note, tabletop extrapolation: quoted beam energy from radius alone assumes centered orbits — a distribution of orbit offsets and betatron phases both shifts and broadens the energy arriving at a probe. Propagate the measured or assumed offset distribution through the local energy-radius relation, or read impacts from tracked trajectories; threshold-reaction measurements near the target radius smear accordingly.

Primarily dedicated to proton acceleration, the cyclotron's Radio Frequency (RF) systems was retuned to 7.15 MHz to satisfy the magnetic resonance acceleration condition for deuterons having a q/m of half that of the single a.m.u. proton. A new, externally coiled, tank circuit inductor was wound to bring the DEE's 78 pF capacitance into resonance. The coupling loop was adjusted to present the RF power amplifier with a pure 50-ohm load.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 1

Editorial note, tabletop extrapolation: Species matters and it can change the RF plant, not just a dial: at fixed field, deuterons run at about half the proton frequency, and the resonator plus matching network must reach it — on this machine that meant winding a physically new tank inductor, because the existing tank could not tune an octave down. The 78 pF dee capacitance is this 12-inch machine's measured value; use it as a sanity anchor, not a design number.

Many nuclear reactions produce neutrons, but perhaps the simplest is d-d reaction, with a broadly peaked cross section at a mere 180 keV. With an incident energy beam, in the regime of 180 keV, the reaction d(d,n)He3 reaction produces 2.45 MeV neutrons quasi-isotropically.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 1

Editorial note, tabletop extrapolation: The species distinction is the load-bearing radiological fact: deuterons on a deuterated target make fast neutrons at only ~180 keV, while common stable targets have (p,n) thresholds above 1 MeV (7Li(p,n) at ~1.88 MeV is among the lowest) — so a sub-MeV proton machine's neutron picture hinges on verifying the beam really is protons (deuterium contamination opens the D–D channel), what the beam actually strikes, and the truthful maximum energy; no blanket neutron-free claim follows. The cross-section characterization and the quasi-isotropic 2.45 MeV figure are the source's own: at finite beam energy the neutron energy is angle-dependent, and quantitative cross-section shapes should be taken from evaluated data at design time, not from this description. The source states its laboratory move was what provided the radiological controls to permit fast-neutron generation (abstract, 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.

After the loading, each target was again precisely massed, both indicating an increase of 56 mg. Table 1 summarizes the mass and dimensional increases. It is worthwhile to note that the compression of the same quantity of gaseous deuterium into a volume of the titanium sample would result in a pressure of 20,000 PSI! With that in mind, it is understandable that the titanium would swell. Determined by the mass measurements, greater than 220% (atomic) deuterium loading has been achieved in our samples.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 3

Editorial note, tabletop extrapolation: What two real coupons did, not an acceptance limit: 56 mg gained each and roughly 10% linear growth on 10×20 mm, 0.010-inch titanium. Recomputed assuming every milligram gained is deuterium, the two samples give D/Ti ≈ 2.17 and 2.22 — bracketing the stated >220% and close to stoichiometric TiD2 — but mass gain is not deuterium-selective (oxide and adsorbates ride along), so an independent composition check is needed before certifying a load. The swelling is hydride-phase lattice expansion; the source's 20,000 PSI compressed-gas figure is a vividness argument, not the mechanism. The finished target is brittle and dimensionally changed — mount accordingly. Table 1 (p.3) prints 4% for the #2 height change and 10% for the #2 width change, but the tabulated dimensions give ~10% and ~4.7% respectively — the two percentages appear transposed in the source.

The targets were prepared in February of 2008, and were mounted to sample holders using a silver epoxy and were stored at atmosphere until their use in April 2017. Because of their attachment to the target holders, periodic mass measurements could not be taken, thus there is no knowledge of the deuterium retention.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 3

Editorial note, tabletop extrapolation: Two lessons for a small target program: these targets, stored at atmosphere for nine years with retention unmeasured, were the ones the same paper's April 2017 runs then used to produce detected neutrons (dg-1763, dg-1767) — so long storage did not kill them, though how much deuterium survived is unknown by the source's own admission. And the mounting scheme is why: silver-epoxied to holders, they could never be re-weighed. Mount so the coupon can come off the holder for weighing, or keep an unmounted witness coupon from the same loading batch.

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

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

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

With an RF duty factor of 25% (RF on for 125 ms twice a second) an average dose rate of 20 mrem/hour was measured. Using the health physics standard of 8.2 n/sec/cm2/mrem/hour for 2.45 MeV neutrons, a peak isotropic neutron production of 10 million neutrons per second can be inferred. The average dose rate increased linearly with the RF pulse repetition rate. The duty factor was briefly raised to 100% where the measured average dose rate reached 80 mrem/hr.

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

Editorial note, tabletop extrapolation: The source's measured and inferred numbers for its own machine and detector placement — not a dose limit or a shielding recommendation. The methodological transfer, stated correctly: local fluence rate = dose rate × the 8.2 (n/s/cm² per mrem/h) factor for 2.45 MeV neutrons; isotropic source strength S_avg = fluence × 4πr²; peak S = S_avg / duty factor. Worked with the source's numbers at its 29.5 cm detector radius: 20 × 8.2 = 164 n/s/cm²; × 10,935 cm² = 1.79e6 n/s average; ÷ 0.25 duty = 7.2e6 n/s peak — the source's ~1e7 on rounding. (Starting from raw counts instead, divide by intrinsic efficiency × A/(4πr²).) Dose scaling linearly with duty factor held at fixed pulse amplitude and tune. Verified against the rendered page image (all radiological numbers re-read from the 150 dpi render).

The energetic neutrons of the d-d reaction must be moderated to thermal energies to before the can be absorbed by the target nuclei. The foils were taped to a 45 mm thick polyethylene moderator and placed directly outside of the glass view port which was the nearest to the Ti:D target. ... The half-life of Ag110 is 24.6 seconds; the half-life of Ag108 is 2.42 minutes. Their short half-lives quickly bring them to equilibrium during irradiation, however, they make the subsequent decay measurements challenging. Indium is also commonly used for activation analysis. In115 à In116m is a metastable state with a 54.2 minute half-life, thus requiring a longer irradiation time, and of course, improving the decay measurement. … The irradiation time of the indium foil was approximately 6.5 minutes, a fraction of the time needed to achieve activation saturation; yet, the peak-induced activity was at an order of magnitude above background. … The theoretical curve is a single exponential decay constant, with a half-life of 54.2 minutes, with initial count rate of 153 counts per minute above a background of 24 counts per minute.

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

Editorial note, tabletop extrapolation: Practical foil selection for a setup with only a Geiger counter: indium's 54.2-minute half-life is forgiving of a slow walk from machine to counter; silver's 24.6 seconds is not. The 45 mm polyethylene block is what THIS setup used to raise the thermal component at its geometry — thermalizing 2.45 MeV neutrons takes many hydrogen collisions and the emerging spectrum depends on geometry and surroundings, so size a moderator by transport estimate or test, not by copying 45 mm. On the signal: the source calls its indium activity 'an order of magnitude above background'; the printed fit values give 153 cpm net over 24 cpm background — 6.4× net, 7.4× gross — its own rounding, worth knowing when planning counting statistics. (The indium numbers are on p.6.)

The fission chamber used was a spare Westinghouse WL6376A, HEU 235U lined tube intended for reactor nuclear instrumentation. Approximately 1 gram of 235U lined an argon-filled proportional tube. The detector bias and signal are split with a preamp, the HV bias was +1100 V, the signal was conditioned with a pulse shaping spectroscopy amplifier, and distributed to an oscilloscope for observation and scalar/timer for counting. ... These occurred at a rate of approximately 1 fission event per RF pulse.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 8

Editorial note, tabletop extrapolation: Reported as the source's own experiment and instrumentation, with no recommendation attached: an HEU-lined legacy fission chamber is specialized regulated material — possession, transfer and disposal rules must be verified for any such device, whatever its surplus provenance. What transfers is the method (optimize with the sensitive detector first, then bring in the insensitive instrument) and the calibrated fact that this complete configuration — this beam charge per pulse, target, moderator and ~1 g chamber — produced about one fission event per RF pulse; the rate belongs to the whole configuration, not to 150 keV alone.

Settling a personal pursuit for the author, a small 1 MeV proton cyclotron, modified to accelerate deuterons up to 400 keV, has demonstrated the ability to generate neutrons through the d(d,n)He3 reaction.

Koeth, Neutron Production with a 12-Inch Cyclotron (2017) — p. 8

Editorial note, tabletop extrapolation: One demonstrated operating point, precisely stated: a nominally 1 MeV proton 12-inch machine, retuned, accelerated deuterons to 400 keV and generated D–D neutrons. Other machines land elsewhere as field, radius, RF voltage and phase acceptance dictate. The listed future work (isotope identification, other low-energy reactions, beam-loss reduction) is the author's stated intent, not accomplished work; the source's printed reaction "F16(p,alpha)O16" is a misprint, the physical reaction being 19F(p,alpha)16O.

The typical 12-inch cyclotron configuration to produce D-D neutrons through beam-on-target operation uses a long-pulsed mode with a duty factor of about 10% for RF thermal considerations given the passive cooling of the RF matching box components. However, the heretofore "pulsed mode" operation typically used beam-on durations of order 150ms - a lifetime as far as nuclear processes go.

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

Editorial note, tabletop extrapolation: In the Rutgers system the duty-factor limit lived in a specific place — passive cooling of the matching-box components, not the dee and not the amplifier — at about 10% duty and ~150 ms beam-on. The transferable step is identifying which component limits a given machine's duty factor by loss estimate and temperature measurement, not the 10% figure itself. Draft report.

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

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

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