Safety design rules

The temperature coefficient of gap magnetic field was measured as about -0.07%/0C. Such coefficient is acceptable for normal work of cyclotron.

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

Tabletop: A PM cyclotron in an unheated garage will drift off resonance with the seasons: 10 degC swing = 0.7% field change, far more than the few-parts-in-10^4 the resonance wants.

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

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

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

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

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

Tabletop: The reference machine's magnet exceeds several of these thresholds; a simple sheet-metal or polycarbonate coil cover including the hot cooling fittings brings the machine to lab-standard electrical safety.

The velocity of the cooling medium ... should be sufficiently high to guarantee a turbulent flow but low enough (u_avg <= 5 m/s) to avoid erosion and vibration. A maximum permitted temperature of less than 60 C on the coil surfaces was found to be good practice.

Zickler, Basic Design and Engineering of Normal-Conducting, Iron-Dominated Electromagnets — arXiv:1103.1119 (2010) — p. 31

Tabletop: Gives hard numbers for a home chilled-water loop: exceed 5 m/s and you erode the tubing; exceed 60 C and the insulation ages fast.

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

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

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

The circulating pumps and heat exchanger are sized to handle a 1000-kw heat load, with the normal operating load being about 300 kw.

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

Tabletop: For a next machine dissipating ~1-5 kW, buy the chiller/radiator rated for ~3x that; margin is what makes long runs boring.

Water hoses should be at least one meter long and use nonconducting material to prevent current leakage from the magnet.

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

Tabletop: The reference machine's water-cooled copper-tubing coil sits at supply potential; a meter of plastic hose per lead and interlock-on-return are exactly the cheap practices that prevent shocks and detect a blocked circuit at home scale.

The normal set-point of Klixons is about 89 C... One thermal interlock is installed on each water circuit.

Tanabe, Iron Dominated Electromagnets, Lecture 9: Coil Fabrication, Testing and Electrical Safety (2005) — p. 5-6

Tabletop: A $5 thermal snap-switch soldered to the coil exit tube, in series with the magnet supply enable, is the single best protection against cooking the next machine's winding on a lost-water event.

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

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

Tabletop: If a next machine uses water-cooled coils at high voltage, tap water will leak current and corrode; a small DI cartridge loop is the fix.

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

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

Tabletop: Directly applicable; a next machine with tens of henries of coil inductance needs a freewheel diode/varistor dump path or it will arc its switchgear.

An alarm warns the operator when the coil temperature has reached a predetermined value, usually 70 to 80 C ... one to three hours are required for the temperature to reach equilibrium.

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

Tabletop: Directly applicable: put a thermocouple in the next machine's winding and log it; a coil that is fine at 30 minutes can still cook at 2 hours.

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

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

Tabletop: Directly applicable; the reference machine's beam-current, bias, and gauge lines all need feedthrough RC/choke filtering at 9 MHz.

The voltages employed on the various cyclotron components are deadly; proper precautions must be taken, even during preliminary testing ... Interlock switches on the power supply covers and grounding hooks

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

Tabletop: Directly applicable home-lab safety baseline for a next machine.

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

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

Tabletop: For any HV feed on a next machine (deflector, source bias): keep cable runs minimal - stored cable energy, not the supply, does the arc damage.

We've encased the resistor in a grounded shield, and the coax shields go through 68 Ohm, 2 watt resistors

Ponter, Beam Energy Measurements with a New HV Deflection System and Ion Source Upgrades on the Rutgers 12-Inch Cyclotron (2010) — p. 44-52

Tabletop: A ready-made HV-distribution recipe for the reference machine's deflector or PIG source bias; note even this shielding didn't stop arcs until the cable-energy fix - resistors limit damage, they don't prevent flashover.

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

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

Tabletop: Bring the reference machine's dee and extraction voltages up over tens of minutes on first pump-down, watching for micro-discharge pulses; a gap that arcs at 15 kV cold will often hold 20+ kV after patient conditioning.

I also added a limiting power resistor (20 ohms at 50w) in series with 50v to the TIP102 as a precaution...with this resistor in place, a short on the 12v line will limit the current and prevent a catastrophic failure.

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

Tabletop: Cheap fault-tolerance rules for any homebuilt high-voltage/high-current RF deck; voltage-derating the caps matters more with the reactive load a dee presents.

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

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

Tabletop: A directional coupler plus fast drive-cut on high reflected power is the single best defense when the cyclotron dee arcs or drifts off resonance mid-run.

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

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

Tabletop: After assembling the next machine, the builder should ramp dee voltage slowly and let a limited number of current-limited sparks condition the surfaces before declaring a voltage ceiling.

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

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

Tabletop: The edge-radius rule the builder needs when pushing dee voltage to 5-13 kV: radius all dee and stem edges so the enhanced edge field stays under ~half the material's breakdown value.

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

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

Tabletop: Perforation transfers directly (pressure inside an unvented dee can be much worse than gauge pressure); graphite armor matters only if a next machine reaches activation-capable energies.

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

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

Tabletop: Put an isolation valve between the gas bottle and the metering valve; forcing the tapered stem closed to seal will ruin the calibrated taper and still leak into the vacuum system.

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

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

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

D-D fusion can occur in an IEC device at voltages as little as 10 kV or less, but detectable fusion generally does not occur until voltages are at least 15 kV

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

Tabletop: Calibrates expectations for any sub-threshold nuclear signal at home: being physically above a reaction threshold is not enough; detection thresholds sit well above it.

The amateur is limited to the middle or D-D reaction which yields a split 50:50 reaction D+D to T + Proton, D+D to He3 + neutron

Hull, Fusor: An Easy to Construct Fusion Reactor Based on Inertial Electrostatic Confinement (2009) — p. 19-20

Tabletop: The reference machine's aneutronic p-B11 choice sidesteps even this; but if they ever runs deuterium in the cyclotron, D-D is the only license-free fusion fuel.

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

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

Tabletop: When the builder opens the chamber after sparking, the pit geography tells them whether to fix edge radii (perimeter pits) or surface contamination (random pits).

We coated the HV electrode with Aerodag G dry lubricant, which is also conductive and has low secondary electron emission coefficient.

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

Tabletop: A cheap surface treatment the builder can apply to deflector or dee edges if they hit breakdown limits near the top of their voltage range.

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

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

Tabletop: Directly reusable for the reference machine's dee/extraction HV monitoring; a divider-plus-panel-meter is safer and more trustworthy than reading the supply front panel.

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

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

Tabletop: A scrounger-grade current-limited HV architecture suitable for the reference machine's source-conditioning and glow-discharge cleaning supplies.

At voltages greater than 20 kV, the resulting x-rays can be hazardous.

Kovalchick, Deuterium Fusion Using Inertial Electrostatic Confinement (2012) — p. 25, 44

Tabletop: The reference machine's dee/extraction voltages are below this, but any HV conditioning or future higher-voltage upgrades cross the 18-20 kV line where viewport X-ray monitoring becomes mandatory.

Both light neutron and x-ray shielding are needed beyond this level and the planned fusor V will incorporate these upgrades.

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

Tabletop: Gives the builder a community-vetted numeric line for when a home nuclear device graduates from 'monitored' to 'shielded' - p-B11 alpha work stays far below it.

mainly fast neutrons are generated, and the permissible flux is 30-60 neutrons/cm2 s

Smirnov, The Cyclotron and Its Modeling — Phys. Part. Nuclei 52 (2021) — p. 16

Tabletop: At <=1 MeV protons the reference machine is below most (p,n) thresholds on common metals, so neutron shielding is a non-issue unless the builder targets Li, Be, or deuterated materials - then these numbers set the shielding scale.

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

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

Tabletop: A 3-5 kV, 5-10 kV/cm tabletop deflector sits ~300x below this limit; the practical amateur ceiling is set by feedthrough and edge-radius engineering (the ~26 kV/cm working rule), not bulk breakdown.

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

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

Tabletop: Direct amateur precedent: a 1 T / 472 keV university tabletop deflector at 28-32 kV; a next machine needs only ~1/10 the voltage, so generous edge radii make sparking a non-issue.

~0.1 Joules at 30 kV ... ~0.4 Joules at 30 kV ... The bottom plate and deflector electrode - no pitting on the electrode noticed.

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

Tabletop: Rutgers arced a 30 kV-rated feedthrough run at 35 kV and had to rebuild with the feedthrough inside vacuum plus a corona adapter - rate a next machine's feedthrough 2-3x over operating voltage.

All removable shielding blocks were stacked in two vertical layers so that no straight-through cracks remained.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 43

Tabletop: Transferable - stagger any shielding blocks on a next machine (concrete, water, borated PE) so seams never line up with the beam plane.

they cannot be opened without turning off the cyclotron oscillator or reducing the magnetic field from its resonance value.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 44

Tabletop: Directly applicable - interlocking RF-enable (and optionally magnet current) to the next machine's enclosure/cave door is a cheap, classic protection scheme.

All the adapters on the coil terminals are water cooled and supplied with thermal switches to protect the coil terminals from overheating.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 56

Tabletop: Directly applicable - thermal cutouts on a next machine's coil terminals/lugs (and dee stem cooling) are cheap insurance against a loose-joint meltdown.

The valves are automatically operated by compressed air cylinders and are controlled by vacuum gauges so that they will close when a leak occurs which the pump is not able to handle.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 58

Tabletop: Directly applicable - an interlocked isolation valve (even a spring-loaded solenoid gate) protects a next machine's diff/turbo pump from a chamber let-up.

this shielding was found sufficiently effective, the field being cut from 140 Gauss to less than 20 Gauss.

MacKenzie et al., Design of the Radio-Frequency System for the 184-inch Cyclotron — UCRL-64 (1948) — p. 20

Tabletop: Transferable - LDMOS amps, fans, and ferrite-cored parts near an 0.59 T magnet want a steel housing; remember the housing itself feels a large attractive force.

it has been used as an emission limiting device to protect the oscillator tubes when discharges occur in the tank and condenser.

MacKenzie & Waithman, R.F. System for Frequency Modulated Cyclotron — MDDC-1045 (1946) — p. 12

Tabletop: Directly applicable principle - fast current limiting/foldback in the LDMOS drain supply (plus VSWR trip) is the modern form of this arc protection.

a high intensity point (21 mr/hr) on the top outside edge of the copper foil holder, another high intensity point (18.5 mr/hr) on the foil just above the median plane

Reyenga, 184″ Cyclotron: Radiation Measurement of Breech Load Probe Head — MDDC-982 (1947) — p. 3

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

a sharp peak of radioactivity was found on the dee lip at the 82-inch radius, which gave additional evidence that the beam was spreading vertically in this region.

Sewell, Henrich & Vale, Some Operating Phenomena Associated with the 184-inch Cyclotron — MDDC-1092 (1947) — p. 3

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

protected by an interlocked air-cooling system, spark gaps at both ends of the half-wave transmission lines leading to the dee stems, and by an rf-dc fault circuit

Heusinkveld et al., Studies with a Three-Dee Three-Phase Proton Cyclotron — UCRL-3187 (1955) — p. 11

Tabletop: The rf-dc comparison is the tube-era ancestor of modern SWR/output-detect foldback and ports directly to the LDMOS upgrade (DC applied but no RF developing = arc or detune, kill drive); spark gaps at the feedthrough remain cheap insurance at 5-13 kV dee voltage.

In order to provide an adequate margin for day-to-day operation, a design value of 1.5 X 10^4 should be used.

Smith & Grunder, Electrical Design of Electrostatic Deflectors for Sector-Focused Cyclotrons — UCRL-10654 (1963) — p. 33

Tabletop: The single most quotable deflector design number, from an operating cyclotron with an in-tank vacuum no cleaner than an amateur's. Design a next machine's electrodes to 1.5e4 and treat anything above as commissioning margin.

it stores only 2-1/2 joules and, at most, this is distributed among 1200 diodes. ... There is so little energy in a spark from this rectifier that it will not puncture even a piece of 5-mil aluminum foil.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 28

Tabletop: The governing philosophy for any next machine's deflector supply - low stored energy is also the personnel-safety property. A sub-joule store at 50-100 kV is achievable and sufficient.

at the more sensitive positions of the crowbar current setting, the power supply can be turned off before a spark becomes visible.

Smith, Deflector Power Supply for Sector-Focused Cyclotrons — UCRL-10655 (1963) — p. 28

Tabletop: The feature to replicate in a modern build - a solid-state inverter driving a CW stack gives the same microsecond drive-kill for free (gate shutdown on an overcurrent comparator), and the threshold should be an operator knob used during bake-in, per UCRL-10654.

These tubes cannot be operated at plate voltages above 11,000 volts, even though rated at 16,000 volts, because, in operation, the plate voltage reversed in 0.3 us causing arcing between plate and grid.

Kerns et al., High Voltage Pulser for 184-inch Cyclotron Electric Deflector — UCRL-95 (1948) — p. 13

Tabletop: The derating discipline (waveform-specific stress, not catalog rating) transfers to every switching element an amateur uses - MOSFET/IGBT avalanche and dV/dt limits in a Marx or inverter play the exact role the 5C22 reversal limit played here.

We have not attempted to obtain particle beams for the cases discussed here as we do not plan to accelerate protons until the shielding vault is completed.

Jungerman, Kibbe & Peek, Central Region Studies for Incorporating an Axial Ion Source in the Davis 76-in. Cyclotron — UCD-CNL-49 (1966) — p. 7

Tabletop: Directly relevant to the plan's open shielding gate: species choice is a radiological control. Commissioning a new machine (or the reference machine's RF upgrade) on H2+ at the same B*rho halves the per-nucleon energy and keeps early tuning below neutron thresholds — the machine physics transfers to protons afterwards, exactly as Davis planned.

They permit, however, the backing of all three diffusion pumps by a combination of any two of the booster pumps, should any one of the booster or mechanical backing pumps become inoperative.

Foss et al., Cyclotron Component Design Technical Reports — TID-454 (1952) — p. 140-142

Tabletop: Scales down to one gauge and two relays - a foreline-pressure interlock that kills the diff-pump heater and an over-temperature switch on its casing are the two automatics that save an unattended amateur system.

a careful choice of materials of construction, for example, using as much aluminum as possible and very little stainless steel, should reduce the radiation problem significantly.

Boom, Toth & Zucker, Residual Radiation of the LRL 184-inch Cyclotron — ORNL-3158 (1961) — p. 18

Tabletop: ENERGY SCOPE: this is a 730-MeV 1-uA machine; at <1 MeV protons the spallation and (p,xn) channels behind it are closed and material activation is a non-issue. The principle activates only if the reference machine ever makes neutrons (d-D, p-Li) or exceeds a few MeV — then bake material choice in early, because it cannot be shielded in later.

Aluminum yields no long-lived activities, while Co58 is produced from copper ... Stainless steel produces two long-lived isotopes, Co58 and Mn54, while only Mn54 is induced in iron.

Boom, Toth & Zucker, Residual Radiation of the LRL 184-inch Cyclotron — ORNL-3158 (1961) — p. 18

Tabletop: ENERGY SCOPE: nuclide-by-material bookkeeping from 730-MeV spallation; every one of these production channels is closed at sub-MeV proton energy. Value to the builder is the pattern — inventory follows alloy content (Ni -> Co58, Cr -> Cr51) — worth knowing when reading other labs' activation numbers or planning any future >MeV or neutron-producing work.

foils of aluminum, copper, iron, and stainless steel were affixed at various positions on the walls of the cyclotron vault and on the cyclotron vacuum tank.

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

Tabletop: The one activation rule that DOES apply at any energy, because it is a measurement, not a prediction: a witness-foil pack plus the next machine's NaI/PIPS counters is a near-zero-cost null check that sub-MeV operation activates nothing — useful evidence for licensing conversations and for catching surprises if beam or species ever changes.

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

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

Tabletop: ENERGY SCOPE: relevant only when neutrons exist to be moderated. Standard Cd-difference technique to keep in the toolkit for any future neutron-producing experiment; meaningless for pure sub-MeV proton running.

To reduce the radiation by an order of magnitude one needs only 2 cm of lead - an amount that can readily be made into a portable shield.

Boom, Toth & Zucker, Residual Radiation of the LRL 184-inch Cyclotron — ORNL-3158 (1961) — p. 18

Tabletop: ENERGY SCOPE: a sub-MeV reference machine or next machine produces no residual gamma fields to shield; the transferable part is the sizing discipline — identify the actual photon energy first, then buy attenuation in half-thickness units. The same arithmetic sizes the Pb around a NaI detector against room background (0.6 cm/HVL at 662 keV Cs-137 scale).

the important source of radiation in the cyclotron comes from the gap and the structures in it, rather than from neutron-induced activities in the magnet yoke.

Boom, Toth & Zucker, Residual Radiation of the LRL 184-inch Cyclotron — ORNL-3158 (1961) — p. 12

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

use of a reliable radiation meter in the cyclotron near the targets ... takes much of the guesswork out of the question "How long should the target cool?"

McWalters et al., Radiation Exposures of Personnel at the 60-inch Cyclotron — UCRL-8276 (1958) — p. 16

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

Time is one of the most important factors in the amount of radiation received, and familiarity with the targets added to the speed of target setups and disassemblies

McWalters et al., Radiation Exposures of Personnel at the 60-inch Cyclotron — UCRL-8276 (1958) — p. 16

Tabletop: ENERGY SCOPE: the r/hr numbers are 20-MeV-machine numbers. The practice — rehearse any hands-on task near a hazard until it is a one-minute drill, and put a simple bench shield where hot items are worked on — is the cheapest safety hardware there is, and applies verbatim to a next machine's HV, RF, and any future activated-target work.

Finger films show that the hands receive about ten times as much exposure as the body for target operations; i.e., setting up and dismantling.

McWalters et al., Radiation Exposures of Personnel at the 60-inch Cyclotron — UCRL-8276 (1958) — p. 16

Tabletop: ENERGY SCOPE: measured on multi-MeV activated targets. Transferable geometry lesson at any scale: dose goes as 1/r^2 and the hands are at r ~ 0; if the reference machine or a successor ever handles activated or tritiated items, tongs and a ring dosimeter are the response, and the same 1/r^2 logic governs hands near an energized RF dee stem.

They are run only on Friday evenings and Saturday, and - if demands are high - on Sundays. For these bombardments a longer cooling time is required. A nominal time of 25 to 30 minutes is set

McWalters et al., Radiation Exposures of Personnel at the 60-inch Cyclotron — UCRL-8276 (1958) — p. 10

Tabletop: ENERGY SCOPE: deuteron (d,n) activation at tens of uA and ~20 MeV; no sub-MeV analogue. Keep the scheduling pattern: batch the nastiest operations (SF6 handling, HV conditioning, any future neutron work) into planned windows with a defined stand-down, rather than interleaving them with routine bench time.

An internal target (one that has been inserted into the tank on a probe) may emit more than 10,000 r/hr.

McWalters et al., Radiation Exposures of Personnel at the 60-inch Cyclotron — UCRL-8276 (1958) — p. 10

Tabletop: ENERGY SCOPE: 10-24 MeV activation levels, closed channels below 1 MeV. The design ordering survives: whatever intercepts full beam (probe tip, Faraday cup, B11 target holder) concentrates all consequences — on a next machine that means heat and sputtering now, and would mean activation first if energy ever climbs.

we have designed the shielding so that the limits for general population are observed in the regularly inhabited work areas adjoining the accelerator and experiment rooms.

Oak Ridge National Laboratory, A Proposal for the Mc² Isochronous Cyclotron — ORNL-3540 (1963) — p. 186

Tabletop: Directly transferable posture for a residential-basement machine: the family upstairs is 'general population'; design to the public limit at occupied locations, not the worker limit.

The extreme radioactivity induced in type 304 stainless steel makes its use undesirable, the use of an aluminum alloy is now being investigated.

Howard (ed.), Electromagnetic Research Division Semiannual, period ending 20 March 1953 — ORNL-1531 (1953) — p. 18

Tabletop: At reference-machine and next-machine energies activation is negligible, but the selection logic transfers to the planned higher-power machines and to the business plan's licensing story - prefer aluminum/graphite for probes, septa, and slits anywhere protons above a few MeV are contemplated.

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

Tabletop: 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.

Being mostly below ground level, the room will be easy to shield. Placing the room at the basement floor level will make it convenient to transfer heavy equipment.

Howard (ed.), Electronuclear Research Division Semiannual, period ending 20 March 1955 — ORNL-1884 (1955) — p. 21

Tabletop: Directly relevant to the plan's facility question and to any MeV-class educational machine - a basement corner with earth on two sides replaces feet of poured concrete, and siting next to existing utilities/controls is a cost line the ORNL study treated as seriously as the magnet.

A considerable amount of undesirable radiation will be produced by that part of the beam intercepted by the slit system.

Bromley & Bruner, The Design of a Focusing and Analyzing System for the 27-inch Cyclotron Beam — NYO-3823 (1954) — p. 5

Tabletop: DIRECT and cheap to honor at layout time, nearly impossible later. Even at 150-170 keV the slit is the hottest x-ray point on the line (thick-target bremsstrahlung at full beam power); a next machine should treat every defining aperture as a shielded component.

The oscillator must be stable enough to sustain an arc drawn from the dee face (simulating discharges in that region).

Anderson, Half-Scale Model Tests on the Three Quarter Wave R.F. System — UCRL-31 (1947) — p. 12

Tabletop: The arc test transfers verbatim to the planned LDMOS amplifier — prove the driver (and its protection) rides through a real drawn arc at the dee before trusting it in vacuum, where sparking during conditioning is guaranteed.

Secondary radiations produced as a result of the interaction of the primary beam with a target, portion of the accelerator, or the shielding most often determine the type and magnitude of the shielding.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 22

Tabletop: For the reference machine and a next machine the primary protons never leave the chamber; the machine's entire external radiation field IS secondary — dee-gap electron bremsstrahlung today, 11B(p,alpha) products and any (p,n)-capable contaminants at a next machine's energies.

The bremsstrahlung is approximately inversally proportional to the M2 where M is the mass of the incident particle. It is therefore usually insignificant for heavy particles.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 30

Tabletop: Confirms the program's standing model that dee-voltage electrons, not the proton beam, are THE radiation hazard on a sub-MeV proton cyclotron.

This radiation is soft and the shielding problem small. It is however important to be remindful of its existance and importance even at low energies of the incident particle. Instruments must be able to detect and measure this soft radiation.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 30

Tabletop: The reference machine's survey problem in one sentence: a ~10 kV dee makes sub-10-keV photons that ordinary GM/ion-chamber walls partly block — pancake/thin-window instruments are required to even see the hazard (pairs with the Ch. VI 150-keV response rule).

If we assume that the ion current "I" results in a reverse directed electron current of magnitude 0.2*I that is accelerated through 1/3 the terminal voltage we would usually get a very considerable x-ray production.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 31

Tabletop: Directly usable bounding recipe for a next machine's hazard analysis: treat the machine as an electron gun of 0.2x the circulating/source current at ~1/3 of peak dee voltage (multipactor and secondary electrons play the "back-streaming" role), then look up kV X-ray-tube output data for that current and voltage.

The % of the electron energy that is converted to X-rays upon complete stopping of the electrons ... 0.5 ... 0.265 ... 0.59 ... 1.34 ... 4.77 ... 6.21

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 23

Tabletop: Sets the scaling logic (efficiency ~ Z and E) even though sub-MeV values must be extrapolated downward: keep stray electrons landing on LOW-Z surfaces (Al, graphite) rather than W/steel to cut X-ray yield several-fold — an argument for aluminum dee/liner surfaces on product machines.

At very low electron energy (few keV), the intrinsic angular distribution is the same as from a radio-antenna, i.e., the intensity is greatest perpendicular to the direction of the electron beam.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 23

Tabletop: For dee-gap electrons accelerated axially/radially in the chamber, expect the soft X-ray leakage to peak SIDEWAYS from the electron paths — survey all around the chamber midplane and windows, not just along any assumed "beam" direction.

Because of the Coulomb barrier, proton cross sections for nuclear interaction are negligible below about 0.1 MeV. In light nuclei there are some exceptions which are of little interest here.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 48

Tabletop: Closes the neutron question for the reference machine at ~150 keV-class energies EXCEPT via the light-nuclei exceptions the chapter waves off — which here are exactly the deliberate 11B(p,alpha) target and any deuterium contamination (see Ch. IV rule).

For light and low-intermediate nuclei, (p,n) thresholds are of the order of an MeV. Neutron emission becomes the dominant reaction when the incident particle energy exceeds the threshold by about 1 MeV.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 48

Tabletop: The threshold-audit pattern for every machine energy bump: list materials the beam can strike, look up (p,n) thresholds, and confirm E_beam sits below them. At 170 keV (a next machine) every (p,n) channel on stable nuclei is closed by >600 keV of margin; the audit must be redone if energy ever approaches ~1.9 MeV (7Li(p,n) threshold 1.88 MeV).

H2(gamma,n)H1 ... 2.23 ... C12(gamma,n)C11 ... 18.7 ... O16(gamma,n)O15 ... 16.3

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 47

Tabletop: Fully closed at the photon energies of the reference machine and a next machine (<=keV-class bremsstrahlung, 429 keV 11B(p,alpha) line region), but the table is the permanent reference for why nothing photonuclear can happen on these machines — useful verbatim in the product hazard analyses.

Two of these reactions, the D(d,n)He3 reaction and the T(d,n)He4 reaction are exoenergetic and can be initiated at very low energies. Thus these two reactions can be produced in small Cockcroft-Walton accelerators.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 78

Tabletop: THE loophole in the "sub-MeV machines make no neutrons" argument: natural hydrogen is ~150 ppm deuterium, and D accumulates in beam-loaded surfaces, so a D-on-D source term exists in principle on any hydrogen machine. It keeps a neutron survey requirement honest even though the expected yield at tabletop beam densities is tiny.

In the slowing down process ... an insignificant amount of induced activity is produced as compared with the activity produced by thermal neutrons. Therefore the thermal cross section should be used for purposes of calculating the activity produced.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 78

Tabletop: The correct bookkeeping if a neutron-capable operation is ever run — inventory surrounding materials (Cu 3.9 b, W 34 b, Au 96 b thermal per Table IV-2) against thermal flux; also why activation on today's neutron-free machines is nil.

Only Na24 and perhaps K42 could present any kind of hazard. Because of the half-lives of these two isotopes, a shut down of three to five days will allow decay to very low levels.

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

Tabletop: Ready-made cooldown-scheduling logic for any future neutron-producing facility work; for the current machines it documents why the basement structure cannot become activated.

If large quantities of this isotope build up, it will be necessary to physically remove the activated shielding, so plans for this contingency should be made in the design of the walls.

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

Tabletop: Scope closed for the machine's photon energies (needs >12.4-MeV photons), but the design principle — never pour a monolithic shield you might someday have to demolish as radwaste — transfers to every enclosure decision.

The effective dose called the "Dose Equivalent" in units of rem is given by DE=D*QF*DF.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 110

Tabletop: The reporting convention every run-log radiation entry should follow once a next machine operates — a Faraday-cup-adjacent photon reading and any neutron check must be weighted before comparison to limits (modern practice replaces QF with wR but the structure is identical).

QF = 0.8 + 0.16 LET where LET is in keV/u.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 110

Tabletop: Lets the program derive its own weightings for odd radiations (the 11B(p,alpha) alphas at ~1.7 MeV/each have LET ~100 keV/um -> QF ~17, consistent with the alpha QF 1-20 table entry) instead of guessing; flag as the 1972 formulation of what is now wR.

X-rays, gamma rays, electrons or positrons 1 ... Neutrons, Energy < 10 KeV 3 ... Neutrons, Energy > 10 KeV 10 ... Protons 1 - 10 ... Alpha particles 1 - 20

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 111

Tabletop: HISTORICAL VALUES — cite for provenance but apply ICRP-103 wR in any real analysis (photons 1, neutrons 2.5-20 by energy, alphas 20). The photon QF=1 and alpha ~20 endpoints are unchanged, so the reference machine's photon surveys and internal-alpha reasoning carry over directly.

2.5 x 10-8 (thermal) 2 680 ... 5 x 10-1 11 27 ... 1 11 19

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 112

Tabletop: The number that turns any future neutron survey reading into a stay-time — a D-D contamination field of even a few n/cm2-s at 2.45 MeV is already a nontrivial fraction of a 1972 occupational week (modern limits tighten this ~5x for the public).

When the whole body is exposed to relatively non-penetrating radiation it may be assumed that the skin is the "critical organ" which determines the maximum permissible dose.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 116

Tabletop: Directly relevant to sub-10-keV dee bremsstrahlung, which barely penetrates the epidermis: the governing quantity for the machine's leakage fields is SHALLOW/skin dose, which is why survey instruments must be thin-window (Ch. VI) and why whole-body limits alone understate the right metric.

shall not exceed 5 rems multiplied by the number of years beyond 18. The dose in per calendar quarter shall not exceed 3 rems.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 116

Tabletop: CAUTION — HISTORICAL NUMBERS, superseded by 10 CFR 20 / NCRP 116 (5 rem/yr occupational, 100 mrem/yr public, age-proration abolished). Keep for reading-era context and for the still-valid design pattern: public-tier limits ~10-50x below occupational drive product-machine enclosure design, since customers are "general population."

Cyclotron positive ions 50-200 usec ... Microstructure at RF frequencies

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 123

Tabletop: The reference machine runs CW-RF but a beam bunched at 9 MHz; any future pulsed-RF operation (LDMOS duty-cycling) puts the machine squarely in this table — recheck every survey instrument's pulse response before trusting it.

the second term in the equation above becomes zero and the number of counts per second, as is expected, becomes the radiation source pulse rate.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 134

Tabletop: THE classic accelerator-survey trap and the reason the program's survey doctrine should prefer current-mode ion chambers over GM counters for any pulsed operation: a counter that reads "60 cps" at a 60 Hz pulse rate is telling you its saturation value, not the dose rate.

An approximation to the dose equivalent in a mixed neutron and gamma ray field can then be given by DE = Gamma + 1ON ... 10 = a conservative value for the quality factor

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 127

Tabletop: The cheapest credible mixed-field method for an amateur program — two chambers and a subtraction — and the fallback if a rem-ball is out of budget for future neutron-capable tests.

They obtained an accuracy of +-10% in measuring dose equivalent of neutrons over the range 0.04 to 10 MeV.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 127

Tabletop: Justifies planning on one moderated rem meter as the single neutron instrument — its energy band covers everything a D-D contamination source (2.45 MeV) or any near-threshold (p,n) could emit.

The ICRU has recommended a quality factor of 2 for neutrons between thermal and 10 KeV. This then rises to a peak of about 11 near 500 KeV before falling back to about 6 between 10 and 20 MeV.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 131

Tabletop: Any amateur-scale neutron leakage lives exactly in the worst band (keV-MeV), so never average it away with a thermal-flux conversion; modern wR moves the peak value to ~20 near 1 MeV, making this reasoning MORE conservative today, not less.

In a cavity ionization chamber the relative response falls off at low energies because of the effect of the thickness of the walls. Just above this energy the relative response can rise above unity because the effective atomic number of the walls exceeds that of air.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 130

Tabletop: The measurement-side half of the reference machine's X-ray problem: the machine's entire photon spectrum sits BELOW this misbehavior threshold, so an uncalibrated chamber reading of dee bremsstrahlung can err either direction. Use thin-window instruments with a low-energy calibration point (e.g. Fe-55 or an X-ray tube set) and record orientation.

Commercial mu metal shields, if properly used, will normally provide sufficient shielding against magnetic fields. To eliminate the effects of RF fields, aluminum foil or screening can be used.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 128

Tabletop: Written for exactly such a bench — a scintillator PMT near a 0.6 T fringe field and a 9-MHz (soon LDMOS) transmitter. The Keithley 617 grounding lore in the reference machine's as-builts is this rule independently rediscovered.

The most common cause of serious radiation exposures associated with accelerators, has been accidental (and sometimes intentional) entrance into the normally shielded target cell.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 144

Tabletop: The product-machine posture in one line: an educational cyclotron IS the "small shielded box with an interlocked lid" (Ch. I's phrase) — lid switch + beam-off interlock + machine-on light is the historically identified minimum for exactly this machine class.

Naturally no "line of sight" path for radiation would be permitted yet it is also necessary that the scatter path through the maze be considered.

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

Tabletop: The audit rule for every feedthrough, window, and joint in an enclosure — check sight-lines from the X-ray source point (dee gap) outward, then bound the one-bounce leakage.

it should never be convenient for an operator or an experimentor to remake an open interlock without someone actually going to the position of the break and, if the hazard no longer exists, reestablishing the interlock.

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

Tabletop: Design requirement for the product controller: a tripped lid/door input must latch and require a local (at-the-lid) action plus console reset — a firmware-only "clear fault" button recreates the exact failure mode this rule exists to prevent.

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

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

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

Teflon 5 x 104 ... Phenolic, Glass laminate >1 x 1010 ... Aluminum Oxide 1 x 1012

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 151

Tabletop: Counterintuitive and worth flagging in the next machine's design notes: PTFE, the amateur's default HV insulator, is the most radiation-fragile material on the list. Fine at the reference machine's dose rates, but in-chamber insulators near a future target station are better as ceramic or glass-filled phenolic.

a fail-safe design may typically use a complete path or presence of a signal to permit accelerator operation and an open circuit or loss of signal to disable operation.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 152

Tabletop: The normally-energized interlock-loop architecture verbatim — the product safety chain should be a series loop holding an RF/HV enable relay closed, so broken wires, unplugged connectors, and power loss all land in the safe state. Also the right pattern for the 1-uA beam-current interlock.

For interlocks, however, the loss of operating time must be preferred to the loss of safety.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 153

Tabletop: Two concrete requirements: (1) an FMEA-style enumeration of interlock failure modes with each shown to land safe; (2) latched annunciation: the controller must remember a mid-run lid opening even if reclosed, until deliberately reset.

This system uses a dual input which prevents the single key from disabling an interlock which affects personnel safety without the additional input provided by the Radiation Safety Officer's key.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 153

Tabletop: For a school machine the "RSO key" is the instructor key — service mode needs a physically distinct credential from the student/operator credential, plus a restore checklist entry before the next class runs. For the home lab, a logged service-mode jumper with a checklist line does the same work.

A person overlooked during the search before lockup must be able to positively defeat the beam instead of ineffectively shutting down some unassociated apparatus.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 153

Tabletop: In-enclosure e-stop requirement for any walk-in product installation; even for benchtop machines the classroom master kill must cut the actual hazard (RF+HV+source), not merely the controller, and the no-blame-for-pressing norm belongs in the curriculum.

After completion of the lockup procedure the person who has performed the survey should have seen every position capable of hiding a man.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 153

Tabletop: Trivially satisfied on a benchtop machine but a REAL checklist line for any walk-in enclosure a customer institution builds; belongs in the product installation manual's commissioning procedure.

Colors of lights should represent constant situations. ... Confusion with meanings of various audible alarms can be avoided by routine test alarms at programmed times. Too frequent tests, however, may do more harm than good (cry wolf).

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 154

Tabletop: The product HMI spec seed — a "machine on" beacon distinct from "RF enabled", consistent across every unit shipped, with an alarm-test entry in the curriculum's first lab.

one must be able to open these doors even after a loss of power. Some manual method of opening the door from inside and outside must be included in the design.

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

Tabletop: Scale-invariant egress principle — even an interlocked benchtop lid or a walk-in enclosure door must never imprison anyone on power loss; spring-return or manually liftable closures only.

Human safety should not be entrusted to one or more persons following a written routine. ... Even mechanized systems become routine after a time and hence may lose their effectiveness.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 155

Tabletop: The strongest possible source endorsement for the program's hardware-interlock- over-procedure stance (procedures complement, never replace, the interlock chain), plus a curriculum idea: occasionally rotate the interlock test scenario so student operators never go through the motions.

The recorded cases in which potentially lethal doses of radiation have been received have all involved highly experienced personnel. This accents the need for continuous education programs.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 17

Tabletop: Aimed straight at a two-person family lab and at teacher-operators: familiarity is the documented risk factor, and the visitor/helper (the "maintenance worker") is the documented victim class — brief every guest, and rehearse the rules even after years of clean operation.

There can be no substitute for the vigilance of personnel. Automatic devices, interlocks and remote area monitoring systems are essential but insufficient to do the job without personnel training.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 17

Tabletop: The counterweight to over-trusting the product machines' interlock chains — the curriculum's radiation-safety module is a safety SYSTEM component, not documentation overhead.

if proper safeguards are incorporated into the construction of the accelerator facility the cost of safety will be significantly lower then if such safeguards are superimposed upon already existing facilities.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 17

Tabletop: Why a hazard analysis belongs at desk phase rather than after first beam: the enclosure, interlocks and monitoring get designed into the machine rather than left to whoever installs it.

The oxygen from the air condensed in the liquid nitrogen, radiolyzed to ozone and left in concentrated form after the evaporation of the nitrogen presents a significant explosion hazard.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 19

Tabletop: Directly applicable to any LN2 cold trap on the diff-pump line if machine energies ever rise, and worth a line in ops procedures now — never let a trap that has sat in a radiation + discharge environment boil dry unattended (ozone also forms from HV corona, no radiation needed).

it may be necessary for the operations staff to act as the health physics staff as well. Though less then ideal, this condition will frequently be a "way of life". Under these conditions it is of paramount importance to define responsibilities and priorities.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 19

Tabletop: A 1972 acknowledgement, with conditions, of the small-facility reality in which one person is both operator and radiation safety officer. The conditions transfer to any teaching installation, and documentation should name the RSO-equivalent role and its decision rights.

indicate a confident Xray value of 13.8 +- 0.7 molecules of O3/100 e.v. in the radiolysis of oxygen. This value is used here.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 177

Tabletop: At the reference machine's beam powers the radiolytic term is negligible, but the SAME balance-production-against-exhaust model covers corona/discharge ozone from the HV and RF systems in a closed basement — nose-level ozone (odor threshold ~0.01-0.05 ppm) is the practical indicator, and 0.1 ppm the 1972 occupational line.

noted an approximate "half-life" for the ozone in their measurements at Rensselaer and Yale of 35 minutes.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 178

Tabletop: Practical basement rule: if ozone smell appears during an RF/HV session, a ventilated half-hour cooldown drops it ~2x, an hour ~4x — and the number lets the ops checklist give a real re-entry wait instead of "air it out."

Serious changes in the pressure differential on the up and down stream sides indicate that the filter has either clogged or ruptured.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 176

Tabletop: The delta-P-as-health-monitor pattern transfers to every filtered exhaust in the lab (pump exhaust filters, fume paths for boron sputtering later) — instrument the pressure drop, not the filter's appearance.

The threshold for (gamma,n) reactions are of sufficient magnitude to make the production of 13N and 15O of concern only to electron accelerators of energies in excess of 15-20 MeV.

Martin (ed.), Accelerator Radiation Protection — AD-755510 / USA-NLABS-TR-73-7, US Army Natick Laboratories (1972) — p. 176

Tabletop: Cleanly scopes air activation OUT of every current and planned program machine (the reference machine and a next machine, tiny, the 700-keV synchrotron) — cite this when a reviewer asks about activated air, and focus the air-handling design on ozone instead.

stopping the beam at r < 10 in. radius in graphite targets. This avoids neutron production and induced cyclotron radioactivity

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

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

with all workers averaging below 100 mrad/week, and most below 25 mrad/week for the 10 weeks of this activity

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 4

Tabletop: Dose scale is irrelevant to a 150 keV proton machine, but the pattern — cooling time, planned sequence, measured-not-assumed exposure — is the template for any future activated-hardware work and for the plan's licensing narrative.

We expect to use marble pole liners where possible, as in the past, to reduce sector iron, etc., activation

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 6

Tabletop: Below ~few-MeV protons activation is negligible, so this is a higher-energy note — but the general idea (choose what lost beam hits) already applies to sputter contamination and outgassing on any machine.

each wire will have its own thermocouple to sense any rise in the cooling water temperature which will shut off the current in the channel

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

Tabletop: Per-element thermal interlocks scale down perfectly — the same philosophy belongs on the next machine's RF amplifier dummy load, water-cooled dee stubs, and any powered septum, and matches the fail-safe interlock doctrine in the 1974 ORNL safety survey.

Since the underground beam stop is aimed away from the experimental areas, this greatly eases shielding, and subsequent background problems

Rainwater et al., The Columbia University Nevis Synchrocyclotron Major Modification — NEVIS-189 / R-774 / CU-295 (1971) — p. 3

Tabletop: Direction-dependence of secondary radiation is universal even though the 550-MeV numbers are not — orient any future target station and Faraday-cup dump so the forward cone points at mass, not people; a first-class rule for any facility layout.

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

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

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

The trend seems to be toward more elaborate systems which utilize solid state devices, fail-safe circuitry and self-checking circuits.

Ohnesorge & Butler, Recent Trends in Particle Accelerator Radiation Safety — CONF-741040-6, Oak Ridge National Laboratory (1974) — p. 2

Tabletop: Directly actionable for the next machine / tiny controls spec — an amateur interlock chain (door, HV, RF-enable, radiation monitor) should be fail-safe and self-testing; what was state of practice in 1974 is trivially cheap in 2026.

techniques of dealing with problems such as relay races, sneak grounds and power-supply crossties

Ohnesorge & Butler, Recent Trends in Particle Accelerator Radiation Safety — CONF-741040-6, Oak Ridge National Laboratory (1974) — p. 2

Tabletop: Fully transferable and cheap — one deliberate review pass asking "what unintended path can energize the HV or open the shutter" on the interlock schematic covers the classic amateur failure of a shared ground defeating an enable line.

There is often a safety officer appointed. Many installations have safety review committees.

Ohnesorge & Butler, Recent Trends in Particle Accelerator Radiation Safety — CONF-741040-6, Oak Ridge National Laboratory (1974) — p. 3

Tabletop: For a one-person program the transfer is external review — the archive's established cross-review protocol is exactly this committee function; for the planned educational-accelerator business a named safety officer and written program become literal requirements.

the As Low As Practicable philosophy can be adopted and put into practice only where there is a firm commitment by management to do so

Ohnesorge & Butler, Recent Trends in Particle Accelerator Radiation Safety — CONF-741040-6, Oak Ridge National Laboratory (1974) — p. 3

Tabletop: The governing philosophy (now ALARA in modern regulation) that any licensing narrative for the business plan must speak fluently; for the home program it means shielding and interlock decisions justified as "as low as reasonably achievable", not "under the limit".

Besides the neutron beam cone from the probe there was found to be a general spray of neutrons due to the deuteron beam grazing the interior of the dee.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 2

Tabletop: Wherever beam is lost - dee edges, septum, probe stalk, chamber wall - is a source; a survey plan that only looks downstream of the target will miss most of the emission solid angle.

Measurements with a BF3 proportional counter have indicated diffusion of slow neutrons through various access openings from the enclosure.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 2

Tabletop: Cable ways, viewport lines-of-sight, and door gaps are the paths that matter once any bulk shielding exists; thermal-neutron instruments answer a different question than fast-neutron ones and both belong in a survey.

These quoted measurements are made with Al-walled ionization chambers, and correspond to a deuteron beam of about 0.2 x 10-6 amp.

Moyer, Hildebrand, Knable, Parmley & York, Character of the Radiation Field and Shielding at the 184-Inch Cyclotron — AECD-2149, UC Radiation Laboratory (1947) — p. 2

Tabletop: A survey number without the simultaneous beam current is unusable later; log dose rate, location, instrument, and Faraday-cup current as one record so the map rescales when beam current grows.

This may happen before the operator can determine the sensor causing the fault condition. Therefore, a device was needed which could detect and store the location of a large number of possible faults.

Cyclotron Staff, Report of Cyclotron Operation 1 July – 31 December 1969 — NRL Memorandum Report 2103, Naval Research Laboratory (1970) — p. 22

Tabletop: Any interlock chain needs first-fault capture - even a latching relay or logged timestamp per sensor - or intermittent faults (thermal, flow, vacuum burps) become undiagnosable ghosts that waste whole sessions.

One is assigned as priority faults, errors which must be corrected to continue cyclotron operation ... The other is non-priority faults, such as the failure of a mechanical vacuum pump which may be bypassed and operation continued.

Cyclotron Staff, Report of Cyclotron Operation 1 July – 31 December 1969 — NRL Memorandum Report 2103, Naval Research Laboratory (1970) — p. 22

Tabletop: Hard-wire the safety-critical chain (radiation, HV enclosure, cooling on powered magnets) so it cannot be acknowledged away, and give everything else a bypassable alarm; a system where every fault stops the machine trains its operator to defeat interlocks.

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

Tabletop: A thoriated source and a -300 V bias produce a fresh, essentially massless (recoil-implanted) alpha source on demand; the 2.7 MeV spread between the 212Pb lines self-calibrates the spectrometer with no external standard. Ventilation for thoron is mandatory.

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

Tabletop: Grounding topology inside the evaporator is part of the recipe — the same charging physics that pits e-gun films will bite any deposition or beam system with floating fixtures near keV electrons.

The cleaning process is of utmost importance and each of the following steps contributes significantly to good 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. 257

Tabletop: Template for any compound that dissociates or splashes — pelletize the charge, chimney the boat, pre-warm the substrate with the source itself, and treat the color-temperature chart as the process instrument; valve off the diffusion pump so the compound vapor doesn't load the pump oil.

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

Tabletop: The route from purchased oxide powder to rollable or evaporable target metal; the two-page table is the reference to consult before buying any element as oxide.

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

Tabletop: Strongest is not best in metallothermic reduction; a controllable reaction that completes in minutes beats a violent one that contaminates the product.

exposed to the full beam intensity while the disc-driving motor was already switched off

International Nuclear Target Development Society Workshop — ANL/PHY-84-2, Argonne National Laboratory (1983) — p. 47

Tabletop: 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.

automatically turned on when the oscillator power is on and there is no dee voltage, but which is automatically turned off as soon as dee voltage appears.

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

Tabletop: DIRECT automation pattern: gate the starter on (RF enabled) AND (dee pickup below threshold). The dee capacitive pickup already present for voltage monitoring is exactly the signal needed, and the same logic doubles as a stall alarm — sparks repeating at 2/s means the machine is failing to start.

a check on the positions of the tanks in this quadrant showed that some of them had moved as much as 2.5 in. out of the gaps.

Wakerling & Guthrie (eds.), Magnets and Magnetic Measuring Techniques — TID-5215, Radiation Laboratory, University of California (1949) — p. 190

Tabletop: Anything ferromagnetic sitting in or near the gap on nominal-symmetry grounds (chamber, probe carriages, shim plates, tools) needs positive mechanical retention — the destabilizing force is invisible at the symmetric position and largest just when the part has already started to walk.

It is designed so as to take maximum advantage of naturally occurring shielding of a small ravine.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (c. 1950) — p. 5

Tabletop: Physics transfers even if the scale does not: mass is mass, and cheap mass (earth berms, water tanks, basement corners) is legitimate neutron/gamma shielding for a D-D-capable machine. Spec detail: PDF p.128.

Aluminum was chosen over stainless steel because of its short half-life property.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (c. 1950) — p. 46

Tabletop: DIRECT for any machine that will make neutrons: aluminum's activation products die in hours-days while stainless (Co-60 from cobalt traces) lives for years. Choose the beam-facing metal for the machine you hope it becomes, and TIG aluminum is proven UHV-adequate practice from 1951.

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

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (c. 1950) — p. 85

Tabletop: Solid-state amps moot the HV plumbing, but two transferable doctrines survive — pick the grounding scheme that keeps coolant out of the HV problem, and use source impedance (here transformer reactance) as passive inrush protection instead of active circuitry where a component's own rating allows it.

On the basis of cost it was decided to omit this refinement.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (c. 1950) — p. 90

Tabletop: The decision pattern (name the deleted protection, name the two things standing in for it, keep a commissioning-only resistor in the drawer) is directly reusable; contrast ucrl-9435, where the 88-inch — with 20x the stored energy — bought the full hard-tube-modulator protection instead. Scale decides.

it should be completely interlocked in such a manner that serious damage cannot occur due to any failure of the operator or of equipment such as water failure or a vacuum leak.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (c. 1950) — p. 95

Tabletop: DIRECT blueprint for a tabletop control panel or PLC: interlock- chain-ordered start, ready-light-with-reason indication (the diagnostic half most amateur panels omit), RF-enable as the terminal permissive, and a cooling run-on timer. Complements the ad-755510 interlock rules with the wiring-bookkeeping practice that keeps the system maintainable. Details pp.99, 107.

In this service it will open the anode circuit within 10 usec of a fault.

Smith, The RCA 6949 as a Self-Excited Cyclotron Oscillator — UCRL-9435, Lawrence Radiation Laboratory (1960) — p. 6

Tabletop: The modern translation is exact: LDMOS drain supplies want a fast electronic disconnect (the hard-tube modulator's descendant), a slower breaker layer, snubbers, and a matched/terminated dc feed. The dual-use insight — the series regulator IS the fast protection switch — carries straight into a solid-state dee supply. Cross-check ornl-2403's protection chapter; Smith's is the self-excited counterpart.

The rf-dc interlock compares the dee voltage with the amount of oscillator anode dc. If the ratio is too low, indicating the presence of an arc, the fault detector opens the anode circuit and recycles

Smith, The RCA 6949 as a Self-Excited Cyclotron Oscillator — UCRL-9435, Lawrence Radiation Laboratory (1960) — p. 7

Tabletop: DIRECT and cheap: a comparator on (dee pickup voltage vs forward power) with a ~1 s drop-and-retry turns dee sparks from session-enders into log entries, and is precisely the automation a conditioning campaign needs. The ratio form matters — absolute thresholds miss arcs that still draw full power.

If the circuit is made too fast, it takes too long to bake the resonators in. If it is made too slow, the spark damage to the dee and linear surfaces will be excessive.

Smith, The RCA 6949 as a Self-Excited Cyclotron Oscillator — UCRL-9435, Lawrence Radiation Laboratory (1960) — p. 7

Tabletop: A protection spec you cannot derive from electronics alone — the dwell time is chosen so each spark finishes cleaning the spot that caused it. For a tabletop supply: let a dee spark burn ~1 ms before the drop-and-retry, but trip amplifier-device faults as fast as the electronics allow. Two speeds, two purposes.

the resonator has to be vacuum-tight, automatically making it rf-tight.

Smith, The RCA 6949 as a Self-Excited Cyclotron Oscillator — UCRL-9435, Lawrence Radiation Laboratory (1960) — p. 8

Tabletop: DIRECT and comforting for a residential machine: a metal chamber dee system radiates almost nothing — EMI escapes via feedthroughs, viewports and the amplifier side, so gasket those and shield the drive chain and the neighbors' radios stay quiet. (The same reasoning applies to viewport mesh in the fusor literature.)