BASIC VACUUM PRACTICE

1
BASIC VACUUMPRACTICE
2
Why is a Vacuum Needed?
(Page 5 manual)
3
Why is a Vacuum Needed?
Atmosphere
(High)Vacuum
Contamination (usually water)
Clean surface
4
HOW DO WE CREATE A VACUUM?
5
VACUUM PUMPING METHODS
6
BAROMETER
Mercury 13.58 times heavier than water Column
is 13.58 x shorter 10321 mm/13.58760 mm ( 760
Torr)
10.321 mm
29,9 in
760 mm
WATER
MERCURY
(Page 12 manual)
7
PRESSURE OF 1 STANDARD ATMOSPHERE
760 TORR, 1013 mbar AT SEA LEVEL, 0O C AND 45O
LATITUDE
8
Pressure Equivalents
9
THE ATMOSPHERE IS A MIXTURE OF GASES
(Page 13 manual)
10
VAPOR PRESSURE OF WATER AT VARIOUS TEMPERATURES
(Page 14 manual)
11
(Page 15 manual)
12
Vapor Pressure of some Solids
(Page 15 manual)
13
PRESSURE RANGES
RANGE ROUGH (LOW) VACUUM HIGH VACUUM ULTRA
HIGH VACUUM
PRESSURE 759 TO 1 x 10 -3 (mbar) 1 x 10 -3 TO
1 x 10 -8 (mbar) LESS THAN 1 x 10 -8 (mbar)
(Page 17 manual)
14
GAS FLOWCONDUCTANCE
(Page 24 manual)
15
Viscous and Molecular Flow
16
FLOW REGIMES
Viscous Flow Distance between molecules is
small collisions between molecules dominate
flow through momentum transfer generally P
greater than 0.1 mbar Transition Flow Region
between viscous and molecular flow Molecular
Flow Distance between molecules is large
collisions between molecules and wall dominate
flow through random motion generally P smaller
than 10 mbar
-3
(Page 25 manual)
17
MEAN FREE PATH
MOLECULAR DENSITY AND MEAN FREE PATH
18
FLOW REGIMES
19
Conductance in Viscous Flow
Under viscous flow conditions doubling the pipe
diameter increases the conductance sixteen
times. The conductance is INVERSELY related to
the pipe length
(Page 28 manual)
20
Viscous Flow(Long Round Tube air)
d diameter of tube in cm l length of
tube in cm P1 inlet pressure in torr P2
exit pressure in torr
21
Viscous Flow(Long Round Tube nitrogen)
EXAMPLE d 4 cm P1 2 torr l 100
cm P2 1 torr
22
Conductance in Molecular Flow
Under molecular flow conditions doubling the pipe
diameter increases the conductance eight
times. The conductance is INVERSELY related
to the pipe length.
23
Conductance in Molecular Flow(Long Round Tube)
d diameter of tube in cm l length of tube
in cm T temperature (K) M A.M.U.
24
Conductance in Molecular Flow(Long Round Tube)
EXAMPLE T 295 K (22 OC) M 28 (nitrogen)
25
(No Transcript)
26
Series Conductance
RT R1 R2
SYSTEM
1 1 1
C2
C1
CT
C1
1 C1 C2
C2
CT
C1 x C2
CT C1 x C2
C1 C2
PUMP
(Page 29 manual)
27
GAS LOAD
Permeation
Outgassing
Real
Leaks
Virtual
Diffusion
Backstreaming
GAS LOAD (Q) IS EXPRESSED IN mbar liters per
second
28
Pumpdown Curve
101
10-1
Volume
10-3
10-5
Surface Desorption
Pressure (mbar)
10-7
Diffusion
10-9
Permeation
10-11
10 1
10 3
10 5
10 7
10 9
10 11
10 13
10 15
10 17
Time (sec)
29
Roughing Pumps
2
(Page 39 manual)
30
VACUUM PUMPING METHODS
Entrapment Vacuum Pump
Positive Displacement Vacuum Pump
Kinetic Vacuum Pump
Adsorption Pump
Reciprocating Displacement Pump
Rotary Pump
Ion Transfer Pump
Cold Trap
Getter Pump
Diaphragm Pump
Liquid Ring Pump
Piston Pump
Rotary Piston Pump
Turbine Pump
Liquid Jet Pump
Diffusion Pump
Sliding Vane Rotary Pump
Multiple Vane Rotary Pump
Axial Flow Pump
Gas Jet Pump
Diffusion Ejector Pump
Self Purifying Diffusion Pump
Vapor Jet Pump
Rotary Plunger Pump
Sputter Ion Pump
Radial Flow Pump
Roots Pump
Dry Pump
Cryopump
31
PUMP OPERATING RANGES
Ultra High Vacuum
Rough Vacuum
High Vacuum
High Vac. Pumps
Ultra-High Vac. Pumps
10-12
10-10
10-8
10-6
10-4
10-2
1
102
P (mbar)
32
VACUUM SYSTEM USE
9
8
1
7
8
5
4
7
2
6
3
3a
(Page 44 manual)
33
Rotary Vane, Oil-Sealed Mechanical Pump
(Page 45 manual)
34
Pump Mechanism
35
How the Pump Works
(Page 46 manual)
36
Pump Down Curves
37
OIL BACKSTREAMING
PRESSURE LEVELS LESS THAN 0.2 mbar
38
The Molecular Sieve/Zeolite Trap
(Page 48 manual)
39
Dry Vacuum Pumps
40
Blower/Booster Pump
(Page 61 manual)
41
One Stage Roots Blower Pump Assembly
42
VACUUM SYSTEM USE
(Page 62 manual)
43
Piston Type Pump
(Page 51 manual)
44
Piston design
(Page 50 manual)
45
Sorption Pump
46
Sorption Pump Components
(Page 54 manual)
47
Vapor Pressure
(Page 56 manual)
48
Cryo-condensation
49
Cryo-sorption
(Page 55 manual)
50
HIGH VACUUM PUMPS
3
(Page 63 manual)
51
VACUUM PUMPING METHODS
Entrapment Vacuum Pump
Positive Displacement Vacuum Pump
Kinetic Vacuum Pump
Adsorption Pump
Reciprocating Displacement Pump
Rotary Pump
Ion Transfer Pump
Cold Trap
Getter Pump
Diaphragm Pump
Liquid Ring Pump
Gaseous Ring Pump
Piston Pump
Rotary Piston Pump
Turbine Pump
Liquid Jet Pump
Diffusion Pump
Sliding Vane Rotary Pump
Multiple Vane Rotary Pump
Axial Flow Pump
Gas Jet Pump
Diffusion Ejector Pump
Self Purifying Diffusion Pump
Vapor Jet Pump
Rotary Plunger Pump
Sputter Ion Pump
Radial Flow Pump
Roots Pump
Dry Pump
Cryopump
52
PUMP OPERATING RANGES
Ultra High Vacuum
Rough Vacuum
High Vacuum
Roughing Pumps
Liquid Nitrogen Trap
Diffusion Pump
Turbo Pump
Cryo Pump
Ion Pump
Tit. Subl. Pump
10-12
10-10
10-8
10-6
10-4
10-2
1
102
P (Torr)
53
VACUUM SYSTEM USE
9
8
1
7
8
5
4
8
2
2
6
3
3a
54
Oil Diffusion Pump
55
Pump Construction
(Page 66 manual)
56
How the Pump Works
57
How the Pump Works
58
Release of Vapors
(Page 67 manual)
59
First stage vapors are separated from others
60
Pumping Speed
61
Maximum Tolerable Foreline Pressure
(Page 73 manual)
62
LN2 reservoir with baffles
(Page 78 manual)
63
How the LN2 Trap Works
Approximate Vapor Pressure (mbar)
Gas
Water (H2O) Argon (A) Carbon Dioxide (CO2) Carbon
Monoxide (CO) Helium (He) Hydrogen (H2) Oxygen
(O2) Neon (Ne) Nitrogen (N2) Solvents
10-22 500 10 -7 gt760 gt760 gt760
350 gt760 760 lt10 -10
(Page 79 manual)
64
VACUUM SYSTEM USE
LN2 COLD TRAP
(Page 80 manual)
65
Turbomolecular Pump
INLET FLANGE
ROTOR BODY
STATOR BLADES
HIGH PUMPING SPEED
HIGH COMPRESSION
BEARING
EXHAUST
HIGH FREQ. MOTOR
BEARING
(Page 81 manual)
66
Rotor - stator assembly
(Page 82 manual)
67
Pump Operation
Molecule
V
Moving Wall with Speed V
Principle of the Turbomolecular Pump
(Page 83 manual)
68
Roughing through the turbo
(Page 91 manual)
69
Pumping by Cryocondensation
70
Cryosorption in charcoal
(Page 98 manual)
71
Charcoal placement
72
Gauges
5
(Page 123 manual)
73
Gauge Operating Ranges
Ultra High Vacuum
Rough Vacuum
High Vacuum
Residual Gas Analyzer
Spinning Rotor Gauge
10-12
10-10
10-8
10-6
10-4
10-2
1
102
P (mbar)
74
Bourdon Gauge
75
How the gauge works
76
Heat Transfer Gauges

• Thermocouple gauge
• and
• Pirani Gauge

77
Thermocouple Gauge
78
How the gauge works
79
Ionization gauges
80
Ionization current is the measure of vacuum
81
Residual Gas Analyzer
82
How the RGA works
83
RGA SPECTRUM
84
RGA SPECTRUM
85
LEAK DETECTION

• 9

(Page 249 manual)
86
Introduction
87
Problems that appear to be Leaks
88
Trapped Volumes
89
Vented Screw
90
Double O ring sealed shafts
Atmosphere (760 torr)
Vacuum
91
Differential Pumping
Atmosphere (1013 mbar)
Vacuum
1 mbar
To Pump
92
PERMEATION LEAKS

• Permeation leaks are different than real leaks
  because the only way to stop them is to change to
  a less permeable material

93
One standard cubic centimeter/sec(std. cc/sec)
94
Leak rate of 1 x 10-1 std cc/sec
95
Leak rate of 1 x 10-3 std cc/sec
96
Leak Rates over Time
LEAK RATES
10 -1 STD CC/SEC --- 1 CC/10 SEC 10 -3 STD CC/SEC
--- 3 CC/HOUR 10 -5 STD CC/SEC --- 1 CC/DAY 10 -6
STD CC/SEC --- 1 CC/2 WEEKS 10 -7 STD CC/SEC ---
3 CC/YEAR 10 -9 STD CC/SEC --- 1 CC/30 YEARS
97
Permeation may occur lt1X10-8 std cc/sec
98
Why Helium is used
99
HELIUM

• Helium is very light and small
• Low concentration in air (0.0005)
• Permits dynamic testing
• Permits non-destructive testing
• Helium is safe

100
CONVENTIONAL LEAK DETECTOR
1
2
12
11
10
9
7
6
8
3
4
101
Ion Separation in Magnetic Field
Ion Source
Ion Gauge
To Pre-Amplifier
Magnetic Field Deflects He Ions 90O, other ions
more or less than 90O.
Lighter ions more
Collector
He ions pass through slit and are collected
Heavier ions less
102
Tracer probe leak detection technique
103
Leak detectors are calibrated with the
permeation leak