Cyclotron seals design rules

about 50 per cent thicker than the depth of the groove to allow for compression ... 1/4-in. gaskets have proved adequate for even the largest seals ... Conductivity for rf currents through such a seal can be assured by half-covering the gasket with a thin copper-foil strip. ... Most natural or artificial rubbers have unacceptable vapor pressures and also deteriorate when used with lubricating greases. Neoprene is free of these faults and is widely used in cyclotrons.

Livingston & Blewett, Particle Accelerators (1962) — p. 199-201

Editorial note, tabletop extrapolation: The copper-foil RF bridge over elastomer joints prevents mysterious Q loss and local heating and transfers directly. For the gasket itself, a modern machine should size grooves from the O-ring manufacturer's vacuum-service squeeze and gland-fill tables - the historical 1.5x ratio is the era's flat-gasket practice, not an O-ring spec.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

slipping a 1/4 in. pyrex tube completely over the 3/16 in. copper dee support rod from the dee edge to at least 2 inches beyond the seal

Wouters, General Recommendations for Design of Small Cyclotrons — UCRL-476 (1949) — p. 7

Editorial note, tabletop extrapolation: The cited machine's construction: a continuous Pyrex sleeve over the dee support rod, extending well past the seal for creepage. For a new machine, design stem insulation from peak RF voltage, surface-flashover behavior and the sleeve-to-stem annulus (sealed or vented?) rather than copying the geometry - and note glass sleeves bring their own charging and thermal-stress habits under RF.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

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

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

A double-gasket seal is frequently used with a pump-out connection to the space between gaskets. This arrangement makes it possible to test the seal for vacuum-tightness quickly and with certainty.

Livingston & Blewett, Particle Accelerators (1962) — p. 200

Editorial note, tabletop extrapolation: Worth adopting on a next machine's main lid: a guard-vacuum groove turns the worst leak hunt into a valve twist for TESTING; riding out a leak in service additionally needs the interspace continuously pumped with adequate speed, and only helps for leaks through the outer seal.

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

One butyl compound has been tested in face-type O-ring seals, using grooves that provide 15%, 30%, and 50% squeeze. It will be seen from the results plotted in Figure I that increasing the squeeze reduced the leak rate dramatically... at 50% squeeze the beneficial effect of the grease was not detectable. ... It is therefore recommended that dovetail or face type O-ring grooves be used whenever possible for static vacuum seals, employing a suitable vacuum grease as a sealing lubricant and surface coating in addition to a heavy squeeze on the O-ring.

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. 3-4

Editorial note, tabletop extrapolation: Cut a next machine's grooves toward the heavy end per the source's recommendation, but set the nominal from the ring manufacturer's static-vacuum gland tables under worst-case tolerances - 50% was a test point, not a design target; gland fill, compression set and assembly damage cap real designs. Grease is a crutch for light squeeze.

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

L = .7FDPQ(1-S)2 where: L = Approximate leak rate of the seal, std. cc/sec. F = Permeability rate of the gas through the elastomer at the anticipated operating temperature. Std cc cm/cm2 sec bar ... D = Inside diameter of the O-ring, inches. P = Pressure differential across the seal, lb/in2. Q = Factor depending on the percent squeeze and whether the O-ring is lubricated or dry. (From Figure II) S = Percent squeeze on the O-ring cross section expressed as a decimal. ... This formula provides only a rough order of magnitude approximation ... For convenience, the formula contains mixed units. ... The .7 factor provides dimensional homogeneity.

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

Editorial note, tabletop extrapolation: Computes the permeation floor of the 10-inch Viton lid seal - then convert to pressure via P = Q_gas/S_eff with the actual effective pumping speed, and remember outgassing and real leaks usually dominate above the permeation floor.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Vacuum Level: Approximately 1 x 10-6 torr ... Butyl .18 ... Nitrile 1.06 ... Nitrile 3.45 ... Fluorocarbon .07

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. 6

Editorial note, tabletop extrapolation: At exactly the reference machine's operating pressure, nitrile's high weight loss marks it a potential outgassing concern near feedthrough insulators, optics and RF surfaces - where the lost mass actually lands was not measured, so treat the ranking as a screening result and prefer the low-loss compounds (Viton's 0.1%-class loss is the cheap insurance) rather than claiming proven film deposition.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Butyl 6.5 @ 77F ... Fluorocarbon 12.7 @ 77F ... Silicone 238.0 @ 77F

Parker Hannifin, O-Ring Vacuum Sealing, Catalog 5705B (1998) — p. 7

Editorial note, tabletop extrapolation: Viton's placement plus its other properties is why it is the default; silicone's high permeability matters most when helium leak checking (He walks through silicone and fluorosilicone seals, confusing the sniffer) and in permeation-limited systems - compute the actual permeation gas load for the seal geometry before ruling a compound in or out, since at 1e-6 Torr with decent pumping the load is often ignorable either way.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

O-rings are typically compressed 15-20% of their diameter... the general criterion for high vacuum sealing to be a minimum initial contact pressure of 13 kg/cm2

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 337-338

Editorial note, tabletop extrapolation: The 2.7 kg/cm figure sizes the lid bolting: a 10-inch-circumference seal (25.4 cm) needs about 69 kg of clamping just for the ring - a 10-inch-diameter ring (79.8 cm around) needs about 216 kg - before atmospheric load helps. Size bolts and flange stiffness from the complete load and allowable-stress calculation.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

An unbaked Viton O-ring will have an initial outgassing rate of 10-3 Pa-m/s... After a 4-h bake at 150C and 12 h of pumping, this value is reduced to 4x10-7 Pa-m/s.

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 340

Editorial note, tabletop extrapolation: Argues for baking the assembled system under vacuum where the components allow it. An ex-situ pre-bake in a small vacuum oven helps only to the extent air exposure before assembly is minimized, and the payoff in chamber pressure depends on whether the rings dominate the gas load - budget the gas loads before promising an order of magnitude.

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

Grease is not needed to make a static seal between an elastomer and a metal surface. It will cause pressure bursts as trapped gas pockets are released.

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 340

Editorial note, tabletop extrapolation: Counters the amateur habit of greasing everything: on a clean, undamaged seat with proper squeeze, a dry Viton ring seals without grease's gas burden. A scratched flange is a repair item first; grease is the temporary expedient, not the standard practice.

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

This pressure rise is due to helium permeation. The permeation time is about 20 min for a typical Viton O-ring. ... First, do not attempt to leak check the system during baking. Second, helium background from a loaded O-ring will not decrease until it has been pumped from the gaskets. A coffee break may be required before proceeding.

O'Hanlon, A User's Guide to Vacuum Technology, 3rd ed. (2003) — p. 469-470

Editorial note, tabletop extrapolation: On an all-Viton chamber, spray briefly and wait: a slowly rising, broad He signal minutes after spraying is CONSISTENT WITH gasket permeation rather than a leak at the last joint - confirm by letting the baseline recover and re-testing for a prompt, reproducible local response before moving on.

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

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

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

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

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

Face-type o-ring seals are recommended. Use as heavy a squeeze as possible... Two o-rings in series can drastically reduce permeation.

Bertolini, Accelerator Vacuum and Mechanical Engineering — USPAS course, UCRL-MI-201847 (2004) — p. 71-74

Editorial note, tabletop extrapolation: To push an elastomer-sealed system's floor lower on a next machine, a double O-ring lid groove with a guard vacuum from the existing roughing pump attacks the permeation term specifically - the dominant elastomer floor once outgassing is conditioned down - for the cost of one groove and a hose barb. The guard reduces pressure-driven permeation through the inner seal (DARHT's numbers are that installation's); the inner ring's own outgassing remains, so the floor drops rather than disappears.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

For vacuum seals, O-rings must be comprised of elastomeric materials featuring low gas permeability, low weight loss under vacuum, and good compression set characteristics. ... With outstanding low permeability to gases, Butyl is especially effective in vacuum sealing applications. ... Employing a seal squeeze of up to 40% inhibits media flow through the seal... because of the decreased groove depth, increased groove width is essential.

Apple Rubber Products, Seal Design Guide — p. 84

Editorial note, tabletop extrapolation: Endorses heavier-than-usual squeeze on critical static vacuum joints when the groove is widened to take the displaced volume - within the compound's own application limits. A pre-bake ('post cure' in vendor language) to drive off volatiles before service is cheap insurance on silicone and fluorocarbon compounds.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

This stretch should be between 1%-5% with 2% as the ideal in most applications. A stretch greater than 5% is not recommended. The resulting stress on the O-ring will cause accelerated aging and cross section reduction.

Apple Rubber Products, Seal Design Guide — p. 11

Editorial note, tabletop extrapolation: When picking the AS-568 size for a non-standard groove (dee-stem feedthrough, viewport), size so the ring sits at ~2% stretch rather than swimming or straining.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

Apple Rubber Products, Seal Design Guide — p. 84

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Only two leaks were detected, and these were in the gasket seals. They were believed to be due to non-uniform thickness of gasket material.

Creutz, Design and Construction of Synchro-Cyclotron — NYO-780 (1950) — p. 24

Editorial note, tabletop extrapolation: A useful prior for a next machine's leak hunt: check O-ring/gasket joints first - while still testing welds and feedthroughs, since one chamber's tally doesn't make welds innocent; compression, gland condition and damage are additional gasket failure modes beyond thickness.

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

An auxiliary copper probe, shielded for RF pickup, was introduced into the main vacuum tank through a Wilson seal on the port near the ion source ... made adjustable as to its radial depth

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

Editorial note, tabletop extrapolation: Exactly the right probe pattern for the reference machine's chamber: an O-ring/Wilson-sealed sliding shaft with grounded coaxial shield tube and a defined exposed collector. Near a 9 MHz dee an unshielded probe's reading is dominated by RF pickup superposed on any beam signal - shield, then verify with beam-off RF-only background runs and filtering before crediting the remainder as beam.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The Buna N, chevron shaped vacuum seals between the cyclotron accelerator tank and the radial and azimuthal drive mechanisms ... were unreliable and displayed a short life expectancy.

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

Editorial note, tabletop extrapolation: For sliding or rotating shafts into the chamber, write a real dynamic-seal specification: compound, gland dimensions and squeeze, surface finish and land tolerance, lubrication, the motion profile, and an interseal vent or differential-pumping stage where leak-tightness matters - geometry, finish and compound all do real work, and a second O-ring buys redundancy at the cost of friction and a possible trapped-volume virtual leak.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

Double gaskets with a pump-out space between the two gaskets are used wherever possible for making seals at the joints in the system.

The University of Washington 60-Inch Cyclotron: Progress and Status Report of Design and Construction — AECU-1951, University of Washington (1951) — p. 51

Editorial note, tabletop extrapolation: Same guard-vacuum doctrine as ornl-1196/anl-5907: on a tabletop machine the pumped interspace is most worth its complexity on the largest lid and any joint opened often. Material translation: the 1951 Hycar parts are the nitrile (Buna-N/NBR) family; Viton/FKM is a DIFFERENT modern option chosen on temperature, chemistry, permeation and compression-set grounds, not a synonym. UW's leak record (two stuffing-box seals, one flat gasket, zero double-gasket joints) is favorable single-system experience for the ranking, not proof.

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

Aus Gründen der Spannungsfestigkeit der Durchführung ist U0 ≤ 3000 V [tr.: because of the feedthrough voltage rating, U0 <= 3000 V]

Prechtl & Wolf, Das Lehr-Zyklotron COLUMBUS — Mit einem Teilchenbeschleuniger Physik und Technik erleben, Springer (2020) — p. 42

Editorial note, tabletop extrapolation: A 5-15 kV dee upgrade is an insulation-coordination problem across the WHOLE RF path - feedthrough, stem supports, matching capacitors, connectors, plus contamination and conditioning state - with the feedthrough a frequent but not guaranteed weakest link. Specify every element for peak RF plus any DC bias, in vacuum, with tracking margin.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The first attempted vacuum chamber was made of curved sheets of copper that clamped around the magnet's poles. Using gaskets to seal the chamber, the machine produced a beam current of 1.5 microamperes. However, the system could not maintain vacuum and a new design was sought. The modified chamber consisted of a section of 16.5 cm brass tubing used as the wall of the chamber, and two 0.3 cm thick circular steel plates as the top and bottom. The bottom plate was soldered to the brass, the top plate was screwed to the bottom plate with a rubber gasket between the brass and steel to form a seal.

Cressman, The Design and Construction of a Small Cyclotron — Houghton College thesis (2006) — p. 15

Editorial note, tabletop extrapolation: A rigid soldered ring with one permanently sealed plate and one demountable gasketed plate is a simple chamber architecture with this documented precedent; the conformal clamp-around-sheet chamber has a documented vacuum-failure precedent. (The survey doesn't cost either build - 'low-cost' is our reading of brass tube and hand tools.)

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The faces of the chamber were annealed glass plates, with the external air pressure used to clamp them to the stainless steel ring, with vacuum grease to ensure a seal. ... [Knox:] like Niell, the external air pressure was used to seal the top plate to the rest of the chamber.

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

Editorial note, tabletop extrapolation: Atmosphere supplies ~10 N/cm2 of clamping - and the same pressure is an implosion load (~1.5 kN on a 15 cm glass lid). Historical construction, not a qualified design: before copying it, check plate stress and deflection for the actual glass and span, support the edges, retain the lid positively against venting transients, and put an implosion shield between glass and students. The visual access is real; so is the failure mode.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

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

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

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

Cited in: Cyclotron Vacuum Chamber Design and Sealing

the leakage rate is essentially attributable to the Viton flange gaskets and the material properties, for example the roughness of the surface, are not yet effective, they will have a decisive influence when the pressure falls below 10-7 mbar. How big this influence ultimately is, must result in appropriate tests, which require a much greater effort.

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

Editorial note, tabletop extrapolation: On an elastomer-sealed machine, gasket permeation can dominate the gas load, as it did in this test - but the crossover is system-specific, so build the gas-load budget (seals, wall outgassing, leaks, trapped volumes, pump speed) before deciding which term to chase; no universal pressure divides gasket-dominated from wall-dominated systems.

Cited in: Cyclotron Vacuum Chamber Design and Sealing

The chamber’s construction is of a stainless steel wall, accessory ports, and flanges. The top and bottom lids of the chamber are of 0.25 inch aluminum. The lids make a vacuum tight seal to the circular stainless steel wall with the use of 451 Viton O-rings. The accessory ports were TIG welded and are terminated in either CF2.75 or CF1.33 metal gasket seal flanges. The vacuum port on the chamber is a standard KF25 Viton 0-ring seal. … The chamber has an inside diameter of 11.00 inches and a wall thickness of 0.750 inches. The outside height of the chamber measures 2.00 inches and the inside height measures 1.50 inches. The DEE is 1.00 inch thick allowing for 0.25 inches of clearance between the top and bottom of the lid. The DEE wall is 1/16 inch thick brass. The DEE and chamber are symmetrical about the chamber's median plane.

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

Editorial note, tabletop extrapolation: A fully specified chamber at exactly this scale, whose internal consistency checks out: 2.00 in outside minus two 0.25 in lids = the stated 1.50 in inside; the 1.00 in dee leaves the stated 0.25 in per side. The elastomer-for-big-seals, metal-gasket-for-instrument-ports split is a pragmatic cost/performance pattern worth copying. Copy the PATTERN and re-derive the numbers: lid deflection under atmosphere, seal compression, and HV clearances are per-design calculations (the magnet gap this chamber fits — 2.1875 in — is on the magnet card, dg-1846-class).