VACUUM AND PLASMA SCIENCE AND
TECHNOLOGY
W7
High Vacuum Pumps
Turbomolecular, Cryogenic, Getter and Ion Pumps
Ming-Show Wong
Oct, 2015
TURBOMOLECULAR PUMP
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An axial flow turbine
for operation in the molecular flow range
consisting of a series of alternate circular rotor and stator disks
both of which have inclined blades designed to impart
momentum change to gas molecules in a preferential direction
• from the pump inlet to the outlet.
– Introduced in 1958 by Becker
– No hydrocarbon vapor backstreaming; no traps
– Need a backing pump
Turbo Pump
Trurbomolecular Pump for Corrosive Gas (Pfeiffer)
Pumping Mechanism of Turbomolecular Pump
• A molecular turbine that compresses gas by momentum
transfer from high speed rotating blades to the gas molecules
in a preferential direction from the pump inlet to the outlet
• It is a high speed molecular bat
• Rotor speed ranging from 24K to 60K rpm
– blades with a tip velocity near the thermal velocity of air
– rotating and stator blades are slotted at an angle
– gas molecules are transported from pump inlet to the outlet
• Work efficiently in the molecular flow region
– must be backed by an mechanical pump
Speed-Compression Relationship
Maximum Compression Ratio
K = Kmax = a12 / a21
Kmax ~ exp {Vb(M)1/2 / (2kNoT) 1/2 )
Shimadzu Turbomolecular Vacuum Pump
• CRYOGENIC PUMP A vacuum pump which operates by the
CRYOPUMP condensation and/or sorption of gas at surfaces
maintained at temperatures sufficiently low for the vapor
pressures of the condensed gases to be insignificant.
Cryopump
廠商 Austin
特性
Equivalent to CTI
Model: cryo-plex 8, cryo-plex 8Lp,
cryo-plex 10, cryo-plex 16
Pumping speed: 1500 l/s to 5000 l/s
Provide CTI equivalent spare parts kit
Exchange pump on request
Save 30% cost
冷凍幫浦
New On-Board TurboPlusVacuum Pumping System
• ION PUMP An electron device in which
ionization produces a significant rate of gas
removal. The ion pump is a “capture and hold”
type of pump.
離子幫浦(Ion Pump)
廠商 DUNIWAY
Pumping speed: 8L/s ~ 500L/s
Type: diode, triode
Varian Ion pump Equivalent
鈦昇華幫浦(Titanium Sublimation Pump)
廠商 Balzers
特性
Base pressure in the 10-12 mbar range
with titanium sublimation
High pumping speed for chemically
active gases
Remote control and simple manual
operation
ENTRAPMENT VACUUM PUMPS
• Capture
• Entrainment
• Getter
• Sputter Ion
• Cryogenic
Vacuum Pumps
Adsorption pump
Axial flow pump
Cryopump
Diaphragm vacuum pump
Diffusion pump
Ejector vacuum pump
Getter pump
Liquid ring vacuum pump
Piston vacuum pump
Radial flow pump
Roots vacuum pump
Rotary piston vacuum pump
Rotary plunger vacuum pump
Sliding vane rotary vacuum pump
Sputter-ion pump
Sublimation (evaporation) pump
Turbine vacuum pump, general
Turbomolecular pump
Vacuum pump, general
Cryogenic Pumps
• A vacuum pump which operates by the condensation
and/or sorption of gas at surfaces maintained at
temperatures sufficiently low for the vapor pressures
of the condensed gases to be insignificant
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entrapment by van der Waals or dispersion forces
any gas can be pumped
a clean form of pumping
release the absorbed gases after surface warming
– CONDENSATION The physical process by which a
vapor becomes a liquid or solid.
– ADSORPTION The process by which gas or vapor is
bonded on a solid or liquid surface; “sticking”.
Types of Cryogenic Pumps
• Liquid-N2-cooled molecular sieves pumps
– used as roughing pump
• Liquid nitrogen trap
• Liquid nitrogen or helium “cold fingers”
– boiling point of Nitrogen = 77.35 K
– boiling point of Helium = 4.125 K
• High and ultrahigh vacuum cryopumps
– cooled by liquid cryogens or closed helium gas
refrigerators
– extremely high pumping speed (107 L/s)
PUMPING MECHANISMS
• Cryocondensation:
– reduce the equilibrium or saturated pressure of gases by
lowering temperature; vapor condenses into solid and hold
• Cryosorption:
– allows a vapor to be pumped to a pressure far below its
saturated vapor pressure
• Cryotrapping:
– the dynamic sorption of one gas on and in the porous
frozen condensate of another
High Vacuum Gas
Refrigerator Pumps
(10-20 K)
(50-80 K)
(Charcoal
sorbent)
Pumping Speed &
Ultimate Pressure - (1)
• Pumping Speed
S = v    (1- Pult/Pc)
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v: 氣體的平均速度差
: Condensation Coefficient
Pult: 終極壓力
Pc: 腔體最初壓力
• Ultimate Pressure
– 假設為冷凝狀況
Pult. = Ps  (Tc/Ts)1/2
Tc=300 K
Ts=10 K
Pult = Ps  (300/10)1/2
= 3.16 Ps
= 2.0  10-11 Torr (for N2)
= 8.0  10-1 Torr (for H2)
Cryopump
廠商 Austin
特性
Equivalent to CTI
Model: cryo-plex 8, cryo-plex 8Lp,
cryo-plex 10, cryo-plex 16
Pumping speed: 1500 l/s to 5000 l/s
Provide CTI equivalent spare parts kit
Exchange pump on request
Save 30% cost
冷凍幫浦
New On-Board TurboPlusVacuum Pumping System
Medium Vacuum Sorption Pumps- LN-cooled
Sorption Pump
Specifications
Materials
Body and internal cooling fins Aluminum
Pump neck and connecting flange
Type 304 stainless steel
Dewar flask Standard: styrofoam
Option: stainless, type 304
Base pressure 1 x 10-3 Torr, with normal use
Recommended maximum pumping capacity SP-11
standard pump = 40 liters
Sieve requirements (Linde 5A) (SP-11) 3 lbs.
Liquid nitrogen required (approximate
amount in liters/pumpdown
from atmosphere) (SP-11) 5 liters
Heater power requirements 115 V, 50/60 Hz, 400 W
Number of heaters required per pump 1 heater
Bakeout temperature 250°C
Dual Sorption Pump Roughing System
includes:
Qty. Part Number Description
3 ea. A-1500-H 1-1/2" manual angle valve,
VitonR sealed, with 2-3/4" CF flanges
2 ea. SP-11 Pump assembly
2 ea. SPHT-11 Bakeout heater
1 ea. FL275150-VTC Double-sided flange
with TC tube and one up-to-air valve
1 ea. TE-150/S Fitting
1 ea. Set of necessary nuts and bolts
1 ea. FLP-1 Anti-seize lubricant
Partial assembly
Price $2,779.
Getter and Ion Pumps (I)
• Entrainment pumps.
• They operate by capturing gas molecules and binding
them to a surface
• The physical or chemical forces that bind molecules
to surfaces are sensitive to the gas species
• All gases are not pumped equally well
• Two or more entrainment processes are usually
combined to pump effectively a wide range of active
and noble gases
Getter and Ion Pumps (II)
• Often referred to as clean pumps
• Cleanliness in the sense that they do not backstream
heavy organic molecules
– as do diffusion or oil-sealed mechanical pumps
• In that sense entrainment pumps do contaminate
– for many applications, cleanliness is the freedom from
hydrogen, methane, carbon oxides, and inert gases as well
• Entrainment pumps may produce, or not pump, one or
more gas species
• The labeling of these gases as contaminants depends on
the application
• GETTER A material which reacts readily with
active gases to form stable low vapor pressure
chemical compounds, so as to remove these gases
from the gas phase.
– Titanium Sublimation pumps
– Non-evaporable Getter Pumps
• Typical getter materials
– evaporable: P, Sr, Ca, Ba, Ti
– nonevaporable: Zr, Ti, Hf, Th, rare earths, alloys based
on Zr and Ti
Ti Sublimation Pumps
• SUBLIMATION The process of transition
directly from the solid to vapor phase without
passing through the intermediate liquid phase.
• GETTER A material which reacts readily with
active gases to form stable low vapor pressure
chemical compounds, so as to remove these
gases from the gas phase.
Titanium sublimation pump
• An electrical current passes through a rod or wire of
titanium and heats it until its surface temperature rises
enough to slowly evaporate the metal.
– The resulting film of titanium covering all surfaces within a line-ofsight to the filament, reacts with the active gas molecules striking
them to form nonvolatile compounds.
– In this context, nitrogen, oxygen, hydrogen, etc. become active
gasses, reacting with the titanium film.
• After depositing the initial film, the current decreases
below evaporation level. When all the film has reacted, the
current increases again to deposit another film. Thus, the Ti
sub pump activates repeatedly, not just once.
鈦昇華幫浦(Titanium Sublimation Pump)
Base pressure in the 10-12 mbar range with titanium
sublimation
High pumping speed for chemically active gases
Remote control and simple manual operation
SPUTTER ION PUMP
• An electron device in which ionization produces a
significant rate of gas removal. The ion pump is a
“capture and hold” type of pump.
• basic components:
– a parallel array of short, stainless steel tubes; two plates
(typically titanium but occasionally tantalum) spaced a
short distance from the open ends of the tubes;
– a strong magnetic field parallel to the tubes' axes;
– a high voltage charge on either tubes or plates.
Sputter ion pumps: pumping mechanisms
• operate by ionizing gas within a magnetically confined cold
cathode discharge. The events that combine to enable
pumping of gases under vacuum are:
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Entrapment of electrons in orbit by a magnetic field.
Ionization of gas by collision with electrons.
Sputtering of titanium by ion bombardment.
Titanium gettering of active gases.
Pumping of heavy noble gases by ion burial.
Diffusion of hydrogen and helium into titanium.
Dissociation of complex molecules into simple ones for pumping ease,
e.g., CH4 breaks down into C and 2H2.
– Hydrogen is pumped separately. Carbon is no longer part of the
residual gas and resides in solid form.
Sputter ion pumps: pumping mechanisms (II)
• Burial is the basic means of pumping heavy noble gases
– Argon ions neutralized via glancing collisions with a sputter
cathode impact the pump wall and are coated with sputtered
titanium.
– Triode pumps are specially designed to maximize the kind of
collisions that produce energetic neutrals.
• Argon is permanently pumped on the wall behind the
cathode in these pumps.
– The wall area receives titanium for inert gas burial but,
because of a retarding electrical field between the cathode and
the wall, it is not subjected to ion bombardment and thus
gases are not resputtered
Standard Diode Pump
1. Permanent magnets
2. Pump envelope
3. Titanium cathodes
4. Anode cell array
5. Positive high voltage lead
Diode
Noble diode
Triode Pumps
1. Permanent magnets
2. Pump envelope
3. Titanium strip cathodes
4. Anode cell array
Triode
Star Cell
離子幫浦(Ion Pump)
廠商 DUNIWAY
Pumping speed: 8L/s ~ 500L/s
Type: diode, triode
Varian Ion pump Equivalent
Ion Pump: Basic Systems and PyraFlat Access Ports
Varian VacIon Plus 150
Applications of Ion pumps
¤ The universal choice for ultra high vacuum systems with
pressures between 1 x 10-9 to 10-11 torr and low gas loads.
¤ Used in research for: surface physics, surface analysis,
tribology, depth profiling, interface studies
¤ Clean, particulate- and oil-free, they offer reasonable
pumping speeds for all active gases.
¤Maintenance-free nature and long operating life for radio
nuclides or pumps mounted in inaccessible places.
¤Vibration-free operation makes their use in microscopy,
particularly atomic level SPM and STM, remarkably effective.
¤Ion pumps have four unpleasant characteristics that must be
judged according to their importance in the applications.
Ion pumps: four unpleasant characteristics
Their pumping speeds and abilities to permanently trap inert
gases, particularly helium, are not wonderful.
The diode pump converts carbon- and hydrogen-containing
compounds into methane, which it pumps only poorly.
The pump's inlet port must not point at any sensitive surface, e.g.
optical, electrical insulator, sample, or pressure measurement
devices. (covered by a thin film of titanium.)
The stray fields from the pump magnets, while not large, must be
considered when specifying these pumps for surface science
experiments involving low energy electron analysis