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Fundamentals of Vacuum Technology

Engineering Fluids Design

Fundamentals of Vacuum Technology
Dr. Walter Umrath
200 Pages

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Fundamentals of Vacuum Technology

Preface

This edition of the Fundamentals of Vacuum technology goes into great detail on manyopics. Among these are residual gas analyses at low pressures, measurement of low pressures, pressure monitoring, open- and closed-loop pressure control, and leaks and their detection. Included for the first time are the sections covering the devices used to measure and control the application of coatings and uses for vacuum technology in the coating process.

TOC

1. Vacuum physics Quantities, their symbols, units of measure and definitions . . . . . . . . . . . . . . . . . . . . . .9
1.1 Basic terms and concepts in vacuum technology . . . . . . . . . . .9
1.2 Atmospheric air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
1.3 Gas laws and models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
1.3.1 Continuum theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
1.3.2 Kinetic gas theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
1.4 The pressure ranges in vacuum technology and their characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.5 Types of flow and conductance . . . . . . . . . . . . . . . . . . . . . . . .15
1.5.1 Types of flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
1.5.2 Calculating conductance values . . . . . . . . . . . . . . . . . . . . . . .16
1.5.3 Conductance for piping and openings . . . . . . . . . . . . . . . . . . .16
1.5.4 Conductance values for other elements . . . . . . . . . . . . . . . . .18
2. Vacuum Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
2.1 Vacuum pumps: A survey . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
2.1.1 Oscillation displacement vacuum pumps . . . . . . . . . . . . . . . . .20
2.1.1.1 Diaphragm pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
2.1.2 Liquid sealed rotary displacement pumps . . . . . . . . . . . . . . . .20
2.1.2.1 Liquid ring pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
2.1.2.2 Oil sealed rotary displacement pumps . . . . . . . . . . . . . . . . . . .21
2.1.2.2.1 Rotary vane pumps (TRIVAC A, TRIVAC B, TRIVAC E, SOGEVAC) . . . . . . . . . . . .21
2.1.2.2.2 Rotary plunger pumps (E-Pumps) . . . . . . . . . . . . . . . . . . . . . .23
2.1.2.2.3 Trochoid pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
2.1.2.2.4 The gas ballast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
2.1.3 Dry compressing rotary displacement pumps . . . . . . . . . . . . .27
2.1.3.1 Roots pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
2.1.3.2 Claw pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
2.1.3.2.1 Claw pumps with internal compression for the semiconductor industry (ÒDRYVAC SeriesÓ) . . . . . . . . . . . . . . .33
2.1.3.2.2 Claw pump without internal compression for chemistry applications (ÒALLáexÓ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
2.1.4 Accessories for oil-sealed rotary displacement pumps . . . . . . .38
2.1.5 Condensers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
2.1.6 Fluid-entrainment pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
2.1.6.1 (Oil) Diffusion pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
2.1.6.2 Oil vapor ejector pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
2.1.6.3 Pump fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
2.1.6.4 Pump fluid backstreaming and its suppression (Vapor barriers, baffles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
2.1.6.5 Water jet pumps and steam ejectors . . . . . . . . . . . . . . . . . . . .45
2.1.7 Turbomolecular pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
2.1.8 Sorption pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
2.1.8.1 Adsorption pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
2.1.8.2 Sublimation pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
2.1.8.3 Sputter-ion pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
2.1.8.4 Non evaporable getter pumps (NEG pumps) . . . . . . . . . . . . . .53
2.1.9 Cryopumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
2.1.9.1 Types of cryopump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
2.1.9.2 The cold head and its operating principle . . . . . . . . . . . . . . . .55
2.1.9.3 The refrigerator cryopump . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
2.1.9.4 Bonding of gases to cold surfaces . . . . . . . . . . . . . . . . . . . . . .56
2.1.9.5 Pumping speed and position of the cryopanels . . . . . . . . . . . .57
2.1.9.6 Characteristic quantities of a cryopump . . . . . . . . . . . . . . . . . .57
2.2 Choice of pumping process . . . . . . . . . . . . . . . . . . . . . . . . . . .60
2.2.1 Survey of the most usual pumping processes . . . . . . . . . . . . .60
2.2.2 Pumping of gases (dry processes) . . . . . . . . . . . . . . . . . . . . .62
2.2.3 Pumping of gases and vapors (wet processes) . . . . . . . . . . . .62
2.2.4 Drying processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
2.2.5 Production of an oil-free (hydrocarbon-free) vacuum . . . . . . . .65
2.2.6 Ultrahigh vacuum working Techniques . . . . . . . . . . . . . . . . . .65
2.3 Evacuation of a vacuum chamber and determination of pump sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
2.3.1 Evacuation of a vacuum chamber (without additional sources of gas or vapor) . . . . . . . . . . . . . .66
2.3.1.1 Evacuation of a chamber in the rough vacuum region . . . . . . .67
2.3.1.2 Evacuation of a chamber in the high vacuum region . . . . . . . .68
2.3.1.3 Evacuation of a chamber in the medium vacuum region . . . . .68
2.3.2 Determination of a suitable backing pump . . . . . . . . . . . . . . . .69
2.3.3 Determination of pump-down time from nomograms . . . . . . . .70
2.3.4 Evacuation of a chamber where gases and vapors are evolved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
2.3.5 Selection of pumps for drying processes . . . . . . . . . . . . . . . . .71
2.3.6 Flanges and their seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
2.3.7 Choice of suitable valves . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
2.3.8 Gas locks and seal-off fittings . . . . . . . . . . . . . . . . . . . . . . . . .75
3. Vacuum measurement, monitoring, control and regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
3.1 Fundamentals of low-pressure measurement . . . . . . . . . . . . .76
3.2 Vacuum gauges with pressure reading that is independent of the type of gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
3.2.1 Bourdon vacuum gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
3.2.2 Diaphragm vacuum gauges . . . . . . . . . . . . . . . . . . . . . . . . . .77
3.2.2.1 Capsule vacuum gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
3.2.2.2 DIAVAC diaphragm vacuum gauge . . . . . . . . . . . . . . . . . . . . .78
3.2.2.3 Precision diaphragm vacuum gauges . . . . . . . . . . . . . . . . . . .78
3.2.2.4 Capacitance diaphragm gauges . . . . . . . . . . . . . . . . . . . . . . .78
3.2.3 Liquid-filled (mercury) vacuum gauges . . . . . . . . . . . . . . . . . .79
3.2.3.1 U-tube vacuum gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
3.2.3.2 Compression vacuum gauges (according to McLeod) . . . . . . .79
3.3 Vacuum gauges with gas-dependent pressure reading . . . . . .81
3.3.1 Spinning rotor gauge (SRG) (VISCOVAC) . . . . . . . . . . . . . . . .81
3.3.2 Thermal conductivity vacuum gauges . . . . . . . . . . . . . . . . . . .82
3.3.3 Ionization vacuum gauges . . . . . . . . . . . . . . . . . . . . . . . . . . .83
3.3.3.1 Cold-cathode ionization vacuum gauges (Penning vacuum gauges) . . . . . . . . . . . . . . . . . . . . . . . . . . .83
3.3.3.2 Hot-cathode ionization vacuum gauges . . . . . . . . . . . . . . . . . .84
3.4 Adjustment and calibration; DKD, PTB national standards . . . .86
3.4.1 Examples of fundamental pressure measurement methods (as standard methods for calibrating vacuum gauges . . . . . . .87
3.5 Pressure monitoring,control and regulation in vacuum systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88
3.5.1 Fundamentals of pressure monitoring and control . . . . . . . . . .88
3.5.2 Automatic protection, monitoring and control of vacuum systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
3.5.3 Pressure regulation and control in rough and medium vacuum systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90
3.5.4 Pressure regulation in high and ultrahigh vacuum systems . . .92
3.5.5 Examples of applications with diaphragm controllers . . . . . . . .93
4. Analysis of gas at low pressures using mass spectrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
4.2 A historical review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
4.3 The quadrupole mass spectrometer (TRANSPECTOR) . . . . . .96
4.3.1 Design of the sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
4.3.1.1 The normal (open) ion source . . . . . . . . . . . . . . . . . . . . . . . . .96
4.3.1.2 The quadrupole separation system . . . . . . . . . . . . . . . . . . . . .97
4.3.1.3 The measurement system (detector) . . . . . . . . . . . . . . . . . . . .98
4.4 Gas admission and pressure adaptation . . . . . . . . . . . . . . . . .99
4.4.1 Metering valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
4.4.2 Pressure converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
4.4.3 Closed ion source (CIS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
4.4.4 Aggressive gas monitor (AGM) . . . . . . . . . . . . . . . . . . . . . . . .99
4.5 Descriptive values in mass spectrometry (specifications) . . . .101
4.5.1 Line width (resolution) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
4.5.2 Mass range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
4.5.3 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
4.5.4 Smallest detectable partial pressure . . . . . . . . . . . . . . . . . . .101
4.5.5 Smallest detectable partial pressure ratio (concentration) . . .101
4.5.6 Linearity range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
4.5.7 Information on surfaces and amenability to bake-out . . . . . . .102
4.6 Evaluating spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
4.6.1 Ionization and fundamental problems in gas analysis . . . . . .102
4.6.2 Partial pressure measurement . . . . . . . . . . . . . . . . . . . . . . .106
4.6.3 Qualitative gas analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
4.6.4 Quantitative gas analysis . . . . . . . . . . . . . . . . . . . . . . . . . . .107
4.7 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108
4.7.1 Standard SQX software (DOS) for stand-alone operation (1 MS plus, 1 PC, RS 232) . . . . . . . . . . . . . . . . . . . . . . . . . .108
4.7.2 Multiplex/DOS software MQX (1 to 8 MS plus 1 PC, RS 485) . . . . . . . . . . . . . . . . . . . . . . .108
4.7.3 Process-oriented software Ð Transpector-Ware for Windows . . . . . . . . . . . . . . . . . . . . . . .108
4.7.4 Development software TranspectorView . . . . . . . . . . . . . . . .109
4.8 Partial pressure regulation . . . . . . . . . . . . . . . . . . . . . . . . . .109
4.9 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109
5 Leaks and their detection . . . . . . . . . . . . . . . . . . . . . . . . . .110
5.1 Types of leaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
5.2 Leak rate, leak size, mass flow . . . . . . . . . . . . . . . . . . . . . . .110
5.2.1 The standard helium leak rate . . . . . . . . . . . . . . . . . . . . . . . .112
5.2.2 Conversion equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
5.3 Terms and definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
5.4 Leak detection methods without a leak detector unit . . . . . . .113
5.4.1 Pressure rise test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
5.4.2 Pressure drop test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
5.4.3 Leak test using vacuum gauges which are sensitive to the type of gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
5.4.4 Bubble immersion test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
5.4.5 Foam-spray test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
5.4.6 Vacuum box check bubble . . . . . . . . . . . . . . . . . . . . . . . . . . .115
5.4.7 Krypton 85 test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
5.4.8 High-frequency vacuum test . . . . . . . . . . . . . . . . . . . . . . . . .115
5.4.9 Testing with chemical reactions and dye penetration . . . . . . .115
5.5 Leak detectors and how they work . . . . . . . . . . . . . . . . . . . .116
5.5.1 Halogen leak detectors (HLD 4000, D-Tek) . . . . . . . . . . . . . .116
5.5.2 Leak detectors with mass spectrometers (MS) . . . . . . . . . . . .116
5.5.2.1 The operating principle for a MSLD . . . . . . . . . . . . . . . . . . . .117
5.5.2.2 Detection limit, background, gas storage in oil (gas ballast), floating zero-point suppression . . . . . . . . . . . . .117
5.5.2.3 Calibrating leak detectors; test leaks . . . . . . . . . . . . . . . . . . .118
5.5.2.4 Leak detectors with quadrupole mass spectrometer (ECOTEC II) . . . . . . . . . . . . . . . . . . . . . .119
5.5.2.5 Helium leak detectors with 180¡ sector mass spectrometer (UL 200, UL 500) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
5.5.2.6 Direct-flow and counter-flow leak detectors . . . . . . . . . . . . . .120
5.5.2.7 Partial flow operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120
5.5.2.8 Connection to vacuum systems . . . . . . . . . . . . . . . . . . . . . . .121
5.5.2.9 Time constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121
5.6 Limit values / Specifications for the leak detector . . . . . . . . . .122
5.7 Leak detection techniques using helium leak detectors . . . . .122
5.7.1 Spray technique (local leak test) . . . . . . . . . . . . . . . . . . . . . .122
5.7.2 Sniffer technology (local leak testing using the positive pressure method) . . . . . . . . . . . . . . . . . . . . . . . . . . .123
5.7.3 Vacuum envelope test (integral leak test) . . . . . . . . . . . . . . .123
5.7.3.1 Envelope test Ð test specimen pressurized with helium . . . . .123
a) Envelope test with concentration measurement and subsequent leak rate calculation . . . . . . . . . . . . . . . . . . .123
b) Direct measurement of the leak rate with the leak detector (rigid envelope) . . . . . . . . . . . . . . . . . . . . . . . . .123
5.7.3.2 Envelope test with test specimen evacuated . . . . . . . . . . . . .123
a) Envelope = Òplastic tentÓ . . . . . . . . . . . . . . . . . . . . . . . . .123
b) Rigid envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
5.7.4 ÒBombingÓ test, ÒStorage under pressureÓ . . . . . . . . . . . . . . .123
5.8 Industrial leak testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
6 Thin film controllers and control units with quartz oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
6.2 Basic principles of coating thickness measurement with quartz oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
6.3 The shape of quartz oscillator crystals . . . . . . . . . . . . . . . . . .126
6.4 Period measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
6.5 The Z match technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
6.6 The active oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
6.7 The mode-lock oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . .128
6.8 Auto Z match technique . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
6.9 Coating thickness regulation . . . . . . . . . . . . . . . . . . . . . . . . .130
6.10 INFICON instrument variants . . . . . . . . . . . . . . . . . . . . . . . .131
7 Application of vacuum technology for coating techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
7.1 Vacuum coating technique . . . . . . . . . . . . . . . . . . . . . . . . . .133
7.2 Coating sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
7.2.1 Thermal evaporators (boats, wires etc.) . . . . . . . . . . . . . . . . .133
7.2.2 Electron beam evaporators (electron guns) . . . . . . . . . . . . . .134
7.2.3 Cathode sputtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134
7.2.4 Chemical vapor deposition . . . . . . . . . . . . . . . . . . . . . . . . . .134
7.3 Vacuum coating technology/coating systems . . . . . . . . . . . . .135
7.3.1 Coating of parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
7.3.2 Web coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
7.3.3 Optical coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136
7.3.4 Glass coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
7.3.5 Systems for producing data storage disks . . . . . . . . . . . . . . .137
8 Instructions for vacuum equipment operation . . . . . . . . .139
8.1 Causes of faults where the desired ultimate pressure is not achieved or is achieved too slowly . . . . . . . . . . . . . . . . .139
8.2 Contamination of vacuum vessels and eliminating contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
8.3 General operating information for vacuum pumps . . . . . . . . .139
8.3.1 Oil-sealed rotary vacuum pumps (Rotary vane pumps and rotary piston pumps) . . . . . . . . . . .140
8.3.1.1 Oil consumption, oil contamination, oil change . . . . . . . . . . .140
8.3.1.2 Selection of the pump oil when handling aggressive vapors .140
8.3.1.3 Measures when pumping various chemical substances . . . . .141
8.3.1.4 Operating defects while pumping with gas ballastÐ Potential sources of error where the required ultimate pressure is not achieved . . . . . . . . . . . . . . . . . . . . . . . . . . . .142
8.3.2 Roots pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142
8.3.2.1 General operating instructions, installation and commissioning . . . . . . . . . . . . . . . . . . . . . . .142
8.3.2.2 Oil change, maintenance work . . . . . . . . . . . . . . . . . . . . . . .142
8.3.2.3 Actions in case of operational disturbances . . . . . . . . . . . . . .143
8.3.3 Turbomolecular pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
8.3.3.1 General operating instructions . . . . . . . . . . . . . . . . . . . . . . . .143
8.3.3.2 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
8.3.4 Diffusion and vapor-jet vacuum pumps . . . . . . . . . . . . . . . . .144
8.3.4.1 Changing the pump fluid and cleaning the pump . . . . . . . . . .144
8.3.4.2 Operating errors with diffusion and vapor-jet pumps . . . . . . .144
8.3.5 Adsorption pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144
8.3.5.1 Reduction of adsorption capacity . . . . . . . . . . . . . . . . . . . . . .144
8.3.5.2 Changing the molecular sieve . . . . . . . . . . . . . . . . . . . . . . . .144
8.3.6 Titanium sublimation pumps . . . . . . . . . . . . . . . . . . . . . . . . .145
8.3.7 Sputter-ion pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
8.4 Information on working with vacuum gauges . . . . . . . . . . . . .145
8.4.1 Information on installing vacuum sensors . . . . . . . . . . . . . . .145
8.4.2 Contamination at the measurement system and its removal .146
8.4.3 The influence of magnetic and electrical fields . . . . . . . . . . . .146
8.4.4 Connectors, power pack, measurement systems . . . . . . . . . .146
9. Tables, formulas, nomograms, diagrams and symbols . .147
Tab I Permissible pressure units including the torr and its conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147
Tab II Conversion of pressure units . . . . . . . . . . . . . . . . . . . . . . . . .147
Tab III Mean free path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147
Tab IV Compilation of important formulas pertaining to the kinetic theory of gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
Tab V Important values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
Tab VI Conversion of pumping speed (volume flow rate) units . . . . .149
Tab VII Conversion of throughput
(a,b) QpV units; leak rate units . . . . . . . . . . . . . . . . . . . . . . . . . . .149
Tab VIII Composition of atmospheric air . . . . . . . . . . . . . . . . . . . . . . .150
Tab IX Pressure ranges used in vacuum technology and their characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150
Tab X Outgassing rate of materials . . . . . . . . . . . . . . . . . . . . . . . . .150
Tab XI Nominal internal diameters (DN) and internal diameters of tubes, pipes and apertures with circular cross-section (according to PNEUROP). . . . . . . . . . . . . . . . . . . . . . . . . . . .151
Tab XII Important data for common solvents . . . . . . . . . . . . . . . . . . .151
Tab XIII Saturation pressure and density of water . . . . . . . . . . . . . . . .152
Tab XIV Hazard classificationof fluids . . . . . . . . . . . . . . . . . . . . . . . . .153
Tab XV Chemical resistance of commonly used elastomer gaskets and sealing materials . . . . . . . . . . . . . . . . . . . . . . . .155
Tab XVI Symbols used invacuum technology . . . . . . . . . . . . . . . . . . .157
Tab XVII Temperature comparison and conversion table . . . . . . . . . . .160
Fig. 9.1 Variation of mean free path l (cm) with pressure for various gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160
Fig. 9.2 Diagram of kinetics of gases for air at 20¡C . . . . . . . . . . . . .160
Fig. 9.3 Decrease in air pressure and change in temperature as a function of altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161
Fig. 9.4 Change in gas composition of the atmosphere as a function of altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161
Fig. 9.5 Conductance values for piping of commonly used nominal internal diameters with circular crosssection for molecular flow . . . . . . . . . . . . . . . . . . . . . . . . . . .161
Fig. 9.6 Conductance values for piping of commonly used nominal internal diameters with circular crosssection for molecular flow . . . . . . . . . . . . . . . . . . . . . . . . . . .161
Fig. 9.7 Nomogram for determination of pump-down time tp of a vessel in the rough vacuum pressure range . . . . . . . . . .162
Fig. 9.8 Nomogram for determination of the conductance of tubes with a circular cross-section for air at 20¡C in the region of molecular flow . . . . . . . . . . . . . . . . . . . . . . . .163
Fig. 9.9 Nomogram for determination of conductance of tubes in the entire pressure range . . . . . . . . . . . . . . . . . . . . .164
Fig. 9.10 Determination of pump-down time in the medium vacuum range taking into account the evolution of gas from the walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165
Fig.9.11 Saturation vapor pressure of various substances . . . . . . . . . .166
Fig. 9.12 Saturation vapor pressure of pump fluids for oil and mercury fluid entrainment pumps . . . . . . . . . . . . . . . . . . . . .166
Fig. 9.13 Saturation vapor pressure of major metals used in vacuum technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
Fig. 9.14 Vapor pressure of nonmetallic sealing materials (the vapor pressure curve for fluoro rubber lies between the curves for silicone rubber and Teflon). . . . . . . . . . . . . . . .167
Fig. 9.15 Saturation vapor pressure ps of various substances relevant for cryogenic technology in a temperaturerange of T = 2 Ð 80 K. . . . . . . . . . . . . . . . . . . . .167
Fig. 9.16 Common working ranges of vacuum pumps . . . . . . . . . . . . .167
Fig. 9.16a Measurement ranges of common vacuum gauges . . . . . . . .168
Fig. 9.17 Specific volume of saturated water vapor . . . . . . . . . . . . . . .169
Fig. 9.18 Breakdown voltage between electrodes for air (Paschen curve) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
Fig 9.19 Phase diagram of water . . . . . . . . . . . . . . . . . . . . . . . . . . . .170
10. The statutory units used in vacuum technology . . . . . . . .171
10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171
10.2 Alphabetical list of variables, symbols and units frequently used in vacuum technology and its applications . . . . . . . . . .171
10.3 Remarks on alphabetical list in Section 10.2 . . . . . . . . . . . . .17510.4 Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176
10.4.1 Basic SI units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176
10.4.2 Derived coherent SI units with special names andsymbols . .177
10.4.3 Atomic units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
10.4.4 Derived noncoherent SI units with special names and symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
11. National and international standards and recommendations particularly relevant to vacuum technology . . . . . . . . . . . . . . . . . . . . . . . . . . . .178
11.1 National and international standards and recommendations of special relevance to vacuum technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
13. Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194

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