III. Vacuum Pumps - UC Davis Physics
Transcript of III. Vacuum Pumps - UC Davis Physics
III. Vacuum PumpsIII. Vacuum Pumps
MechanismGas transferGas capture
FunctionFunctionRoughing (backing, mechanical pumps)
Rotary vaneSorption Rotary lobe Scroll ScrewSorption, Rotary lobe, Scroll, Screw
High vacuumOil diffusion, Turbomolecular, Cryo, Ion
AuxiliaryTitanium Sublimation, LN2
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IIIIII--A. Roughing: Rotary Vane Pump A. Roughing: Rotary Vane Pump (Gas Transfer)(Gas Transfer)(Gas Transfer)(Gas Transfer)
Single-stage10-2 torr
Dual-stage10-3 torr
Speed: 1-100 cfmOil: lubricant, coolant, sealant, contaminationForeline trap: copper gauze, molecular sieve, LN2Pumping reactive/flammable/O2 gas:
Chemically inert fluid: Fomblin PFPE (perfluoropolyethers)
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Chemically inert fluid: Fomblin PFPE (perfluoropolyethers)Ballast valve; Gas bubbler; Venting (anti-suckback); Exhaust; Vibration
Roughing: Sorption Pump Roughing: Sorption Pump (Gas Capture)(Gas Capture)( p )( p )
10-3 - 10-4 torr10 10 torrOil free, no moving partsDrawback:
Initial cooling
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gLimited capacity, need regenerationGas selective- difficulty w/ inert gases
Roughing: Diaphragm Pumps Roughing: Diaphragm Pumps (Dry, Gas Transfer)(Dry, Gas Transfer)( y, )( y, )
< 10cfm
1-10 torr
Exhaust into atmosphereExhaust into atmosphere
Low cost
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Kurt J. Lesker
Roughing: Roots (Rotary Lobe) Pump Roughing: Roots (Rotary Lobe) Pump (Dry, Gas Transfer)(Dry, Gas Transfer)( y, )( y, )
RootsGas transfer0.01-10 torr(10-4 torr when backed) Handle high gas loadsHandle high gas loads
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Kurt J. Lesker
Roughing: Other Dry PumpsRoughing: Other Dry Pumps
Kurt J. Lesker
ScrollG f
ScrewGas transferGas transfer
10-2 torr12-25 cfm
Gas transfer10-3 torr30-320 cfmMay handle aggressive gases
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May handle aggressive gases
IIIIII--B. High Vacuum: Oil Diffusion PumpB. High Vacuum: Oil Diffusion Pump(Wet, Gas Transfer)(Wet, Gas Transfer)( , )( , )
Momentum transfer
10-7 -10-8 torr or better30 L/s - 50,000 L/sOil: Very low vapor pressure
O2 resistantBaffles & LN2 trap
Kurt J. LeskerBaffles & LN2 trap
Advantages: Inexpensive, simple, non-gas-selective, durable, quietDisadvantages: oil backstreaming (LN2 trap, baffles)
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upright, load < 300mtorr, need backingslow start/shut-down
High Vacuum: Turbomolecular PumpHigh Vacuum: Turbomolecular Pump(Dry, Gas Transfer)(Dry, Gas Transfer)( y, )( y, )
10-7 -10-10 torr10 -10 torr 50 L/s - 3500 L/sCrossover P: ~ 1000 mtorr
Gas selective: Easy w/ heavy moleculesdifficulty w/ H2, He
High speed, screenOften verticalOften verticalBearings
Ceramic M ti ll l it t d
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Magnetically levitated
High Vacuum: Cryo PumpHigh Vacuum: Cryo Pump(Dry, Gas Capture)(Dry, Gas Capture)( y, p )( y, p )
Cryo-condensation + cryo-sorptionClosed-cycle He cryocompressor10-9 torr or betterAny orientationNo backing neededNo backing neededCrossover P: ~ 500 mtorr
Gas selecti e: diffic lt / HeGas selective: difficulty w/ HeRegeneration & replacement
KJL
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KJL
UHV Pump: Ion PumpUHV Pump: Ion Pump(Gas Capture)(Gas Capture)( p )( p )
KJLKJL
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Chemical reaction w/ Ti (getter) + burial (ion implantation)
Reactive gases All gases
10-12 torrCross over P: ~<1mtorrAny orientationAny orientationClean, bakeable, vibration-freePermanent magnet: ionization; heavy
Gas selective: difficulty w/ inert gasLow throughput
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Ti refurbish necessary
IIIIII--C. Auxiliary: Titanium Sublimation PumpC. Auxiliary: Titanium Sublimation Pump(Dry, Gas Capture)(Dry, Gas Capture)( y, p )( y, p )
Sublime Ti-Mo, continuous/pulseChemical reactionGas selective: no inert gasGas selective: no inert gasBetter at LN2:
Pump speed & heat insulationProper partitionOperates < 10-6 torr
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Auxiliary: LNAuxiliary: LN22(Gas Capture)(Gas Capture)( p )( p )
Cryopumping
LN trapLN2 trapCryopanel
Continuous LN2 feed$0.25 /L
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