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BASIC VACUUM PRACTICE. Why is a Vacuum Needed? To move a particle in a (straight) line over a large distance (Page 5 manual)

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Presentation on theme: "BASIC VACUUM PRACTICE. Why is a Vacuum Needed? To move a particle in a (straight) line over a large distance (Page 5 manual)"— Presentation transcript:

1 BASIC VACUUM PRACTICE

2 Why is a Vacuum Needed? To move a particle in a (straight) line over a large distance (Page 5 manual)

3 Why is a Vacuum Needed? Contamination (usually water) Clean surface Atmosphere (High)Vacuum To provide a clean surface

4 HOW DO WE CREATE A VACUUM?

5 VACUUM PUMPING METHODS

6 BAROMETER WATER MERCURY 760 mm Mercury: 13.58 times heavier than water: Column is 13.58 x shorter : 10321 mm/13.58=760 mm (= 760 Torr) 10.321 mm 29,9 in (Page 12 manual)

7 PRESSURE OF 1 STANDARD ATMOSPHERE: 760 TORR, 1013 mbar AT SEA LEVEL, 0 O C AND 45 O LATITUDE

8 Pressure Equivalents Atmospheric Pressure (Standard) = 0 14.7 29.9 760 760,000 101,325 1.013 1013 gauge pressure (psig) pounds per square inch (psia) inches of mercury millimeter of mercury torr millitorr or microns pascal bar millibar

9 THE ATMOSPHERE IS A MIXTURE OF GASES PARTIAL PRESSURES OF GASES CORRESPOND TO THEIR RELATIVE VOLUMES GASSYMBOL PERCENT BY VOLUME PARTIAL PRESSURE TORR PASCAL Nitrogen Oxygen Argon Carbon Dioxide Neon Helium Krypton Hydrogen Xenon Water N 2 O 2 A CO 2 Ne He Kr H 2 X H 2 O 78 21 0.93 0.03 0.0018 0.0005 0.0001 0.00005 0.0000087 Variable 593 158 7.1 0.25 1.4 x 10 -2 4.0 x 10 -3 8.7 x 10 -4 4.0 x 10 -4 6.6 x 10 -5 5 to 50 79,000 21,000 940 33 1.8 5.3 x 10 -1 1.1 x 10 -1 5.1 x 10 -2 8.7 x 10 -3 665 to 6650 (Page 13 manual)

10 VAPOR PRESSURE OF WATER AT VARIOUS TEMPERATURES T ( O C) 100 25 0 -40 -78.5 -196 P (mbar) 1013 32 6.4 0.13 6.6 x 10 -4 10 -24 (BOILING) (FREEZING) (DRY ICE) (LIQUID NITROGEN) (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 FLOW CONDUCTANCE (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 1013 mbar (atm)1 x 10 -3 mbar1 x 10 -9 mbar # mol/cm 3 MFP 3 x 10 19 (30 million trillion) 4 x 10 13 (40 trillion) 4 x 10 7 (40 million) 2.5 x 10 -6 in 6.4 x 10 -5 mm 2 inches 5.1 cm 31 miles 50 km

18 FLOW REGIMES Mean Free Path Characteristic Dimension Viscous Flow: is less than 0.01 Mean Free Path Characteristic Dimension Molecular Flow: is greater than 1 Mean Free Path Characteristic Dimension Transition Flow: is between 0.01 and 1

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) C = 1.38 x 10 2 x d 4 x P 1 + P 2 (l/sec) 2l d = diameter of tube in cm l = length of tube in cm P 1 = inlet pressure in torr P 2 = exit pressure in torr

21 Viscous Flow (Long Round Tube; nitrogen) EXAMPLE: d = 4 cm P 1 = 2 torr l = 100 cm P 2 = 1 torr C = 138 x d 4 x P 1 + P 2 (liter/sec) 2 l C = 138 x 256 x 3 (liter/sec) 2100 C = 530 (liter/sec)

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. C = 3.81 x d 3 x T M l (l/sec)

24 Conductance in Molecular Flow (Long Round Tube) EXAMPLE: T = 295 K (22 O C) M = 28 (nitrogen) C = 3.81 x d 3 x T M l (l/sec) = 3.81 x d 3 x 295 28 (l/sec) l = 12.36 x d 3 l

25 EXAMPLE: T = 295 K (22 O C)d = 4 cm M = 28 (nitrogen) l = 100 cm C = 3.81 x d 3 x T M l (l/sec) = 3.81 x d 3 x 295 28 (l/sec) l = 12.36 x d 3 l = 12.36 x 0.64 = 7.9 (l/sec)

26 SYSTEM PUMP C1C1 C2C2 Series Conductance R T = R 1 + R 2 1 = 1 + 1 C1C1 C2C2 CTCT 1 = C 1 + C 2 C 1 x C 2 CTCT C T = C 1 x C 2 C 1 + C 2 (Page 29 manual)

27 GAS LOAD Outgassing Leaks Virtual Real Backstreaming Diffusion Permeation GAS LOAD (Q) IS EXPRESSED IN: mbar liters per second

28 Pumpdown Curve Pressure (mbar) Time (sec) 10 -11 10 1 10 3 10 5 10 7 10 9 10 11 10 13 10 15 10 17 10 +1 10 -1 10 -3 10 -5 10 -7 10 -9 Volume Surface Desorption Diffusion Permeation

29 Roughing Pumps 2 (Page 39 manual)

30 VACUUM PUMPING METHODS Sliding Vane Rotary Pump Molecular Drag Pump Turbomolecular Pump Fluid Entrainment Pump VACUUM PUMPS (METHODS) Reciprocating Displacement Pump Gas Transfer Vacuum Pump Drag Pump Entrapment Vacuum Pump Positive Displacement Vacuum Pump Kinetic Vacuum Pump Rotary Pump Diaphragm Pump Piston Pump Liquid Ring Pump Rotary Piston Pump Rotary Plunger Pump Roots Pump Multiple Vane Rotary Pump Dry Pump Adsorption Pump Cryopump Getter Pump Getter Ion Pump Sputter Ion Pump Evaporation Ion Pump Bulk Getter Pump Cold Trap Ion Transfer Pump Gaseous Ring Pump Turbine Pump Axial Flow Pump Radial Flow Pump Ejector Pump Liquid Jet Pump Gas Jet Pump Vapor Jet Pump Diffusion Pump Diffusion Ejector Pump Self Purifying Diffusion Pump Fractionating Diffusion Pump Condenser Sublimation Pump

31 PUMP OPERATING RANGES 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 110 +2 P (mbar) Rough Vacuum High Vacuum Ultra High Vacuum Venturi Pump Rotary Vane Mechanical Pump Rotary Piston Mechanical Pump Sorption Pump Dry Mechanical Pump Blower/Booster Pump High Vac. Pumps Ultra-High Vac. Pumps

32 VACUUM SYSTEM USE 1 2 4 6 5 9 8 8 7 1 2 3 3a 4 5 6 7 8 9 Chamber High Vac. Pump Roughing Pump Foreline Pump Hi-Vac. Valve Roughing Valve Foreline Valve Vent Valve Roughing Gauge High Vac. Gauge 7 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 2 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 1 2 3 4 5 6 7 8 9 10 11 12 Chamber Foreline Roughing Valve Roughing Gauge Roughing Pump Foreline Foreline Valve Foreline Gauge High Vacuum Valve Booster/Blower Vent Valve High Vacuum Gauge 1 9 3 12 4 11 5 2 6 7 8 10 (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 Sliding Vane Rotary Pump Molecular Drag Pump Turbomolecular Pump Fluid Entrainment Pump VACUUM PUMPS (METHODS) Reciprocating Displacement Pump Gas Transfer Vacuum Pump Drag Pump Entrapment Vacuum Pump Positive Displacement Vacuum Pump Kinetic Vacuum Pump Rotary Pump Diaphragm Pump Piston Pump Liquid Ring Pump Rotary Piston Pump Rotary Plunger Pump Roots Pump Multiple Vane Rotary Pump Dry Pump Adsorption Pump Cryopump Getter Pump Getter Ion Pump Sputter Ion Pump Evaporation Ion Pump Bulk Getter Pump Cold Trap Ion Transfer Pump Gaseous Ring Pump Turbine Pump Axial Flow Pump Radial Flow Pump Ejector Pump Liquid Jet Pump Gas Jet Pump Vapor Jet Pump Diffusion Pump Diffusion Ejector Pump Self Purifying Diffusion Pump Fractionating Diffusion Pump Condenser Sublimation Pump

52 PUMP OPERATING RANGES 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 110 +2 P (Torr) Rough Vacuum High Vacuum Ultra High Vacuum Roughing Pumps Turbo Pump Diffusion Pump Cryo Pump Ion Pump Tit. Subl. Pump Liquid Nitrogen Trap

53 VACUUM SYSTEM USE 1 4 6 5 9 8 8 1 2 3 3a 4 5 6 7 8 9 Chamber High Vac. Pump Roughing Pump Fore Pump Hi-Vac. Valve Roughing Valve Foreline Valve Vent Valve Roughing Gauge High Vac. Gauge 7 3 3a 2 8 2

54 Oil Diffusion Pump

55 Pump Construction (Page 66 manual)

56 How the Pump Works

57

58 Release of Vapors (Page 67 manual)

59 First stage vapors are separated from others

60 Pumping Speed 10 -10 10 --3 10 --1 Pumping Speed (Air) 1234 Inlet Pressure (Torr) Critical Point 1. Compression Ratio Limit 2. Constant Speed 3. Constant Q (Overload) 4. Mechanical Pump Effect

61 Maximum Tolerable Foreline Pressure (Page 73 manual)

62 LN 2 reservoir with baffles (Page 78 manual)

63 How the LN2 Trap Works Gas Approximate Vapor Pressure (mbar) Water (H 2 O) Argon (A) Carbon Dioxide (CO 2 ) Carbon Monoxide (CO) Helium (He) Hydrogen (H 2 ) Oxygen (O 2 ) Neon (Ne) Nitrogen (N 2 ) Solvents 10 -22 500 10 -7 >760 350 >760 760 <10 -10 (Page 79 manual)

64 VACUUM SYSTEM USE LN2 COLD TRAP (Page 80 manual)

65 Turbomolecular Pump ROTOR BODY HIGH PUMPING SPEED HIGH COMPRESSION EXHAUST HIGH FREQ. MOTOR INLET FLANGE STATOR BLADES 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 123456123456 Chamber Turbo Pump Roughing Pump Vent Valve Roughing Gauge High Vac. Gauge 1 6 7 4 3 2 5 2 (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 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 110 +2 P (mbar) Rough Vacuum High Vacuum Ultra High Vacuum Bourdon Gauge Thermocouple Gauge Cold Cathode Gauge Capacitance Manometer Hot Fil. Ion Gauge Residual Gas Analyzer Pirani Gauge Spinning Rotor Gauge McLeod Gauge

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 QUADRUPOLE HEAD CONTROL UNIT

82 How the RGA works

83 MASS NUMBER (A.M.U.) RELATIVE INTENSITY NORMAL (UNBAKED) SYSTEM H2H2 H2OH2O N 2,, CO CO 2 (A) RGA SPECTRUM

84 MASS NUMBER (A.M.U.) RELATIVE INTENSITY SYSTEM WITH AIR LEAK H2H2 H2OH2O N2N2 CO 2 (B) O2O2 RGA SPECTRUM

85 LEAK DETECTION 9 (Page 249 manual)

86 Introduction

87 Problems that appear to be Leaks Outgassing Leaks Virtual Real Backstreaming Diffusion Permeation

88 Trapped Volumes

89 Vented Screw

90 Double O ring sealed shafts Atmosphere (760 torr) Vacuum

91 Differential Pumping Atmosphere (1013 mbar) Vacuum To Pump 1 mbar

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 <1X10 -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 3 4 5 6 7 8 9 10 11 12 Test Piece Test Port High Vac. Pump Roughing Pump Fore Pump RoughingValve Test Valve Pump Valve Spectrometer Tube Cold Trap Roughing Gauge Vent Valve 7 6 12 4 5 1 3 8 11 2 9 10

101 Ion Separation in Magnetic Field Ion Source To Pre-Amplifier Collector Magnetic Field Deflects He Ions 90 O, other ions more or less than 90 O. He ions pass through slit and are collected Lighter ions: more Heavier ions: less Ion Gauge

102 Tracer probe leak detection technique

103 Leak detectors are calibrated with the “permeation leak”


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