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BASIC VACUUM PRACTICE.

Published byLucinda Andrews Modified over 6 years ago

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Presentation on theme: "BASIC VACUUM PRACTICE."— Presentation transcript:

1 BASIC VACUUM PRACTICE

2 To move a particle in a (straight) line over a large distance
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? To provide a clean surface Atmosphere
(High)Vacuum Contamination (usually water) Clean surface To provide a clean surface

4 HOW DO WE CREATE A VACUUM?

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

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

7 Atmospheric Pressure (Standard) =
Pressure Equivalents Atmospheric Pressure (Standard) = 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

8 THE ATMOSPHERE IS A MIXTURE OF GASES
PARTIAL PRESSURES OF GASES CORRESPOND TO THEIR RELATIVE VOLUMES GAS SYMBOL PERCENT BY VOLUME PARTIAL PRESSURE TORR PASCAL Nitrogen Oxygen Argon Carbon Dioxide Neon Helium Krypton Hydrogen Xenon Water N2 O2 A CO2 Ne He Kr H2 X H2O 78 21 0.93 0.03 0.0018 0.0005 0.0001 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)

9 VAPOR PRESSURE OF WATER AT VARIOUS TEMPERATURES
T (O C) 100 25 -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)

10 (Page 15 manual)

11 Vapor Pressure of some Solids
(Page 15 manual)

12 GAS FLOW CONDUCTANCE (Page 24 manual)

13 Viscous and Molecular Flow
Viscous Flow (momentum transfer between molecules) Molecular Flow (molecules move independently)

14 MOLECULAR DENSITY AND MEAN FREE PATH
1013 mbar (atm) 1 x mbar 1 x mbar # mol/cm3 MFP 3 x (30 million trillion) 4 x (40 trillion) 4 x 10 7 (40 million) 2.5 x in 6.4 x mm 2 inches 5.1 cm 31 miles 50 km

15 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)

16 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.

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

18 Pumpdown Curve 10+1 10-1 Volume 10-3 10-5 Pressure (mbar)
Surface Desorption 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)

19 Roughing Pumps 2 (Page 39 manual)

20 VACUUM SYSTEM USE 9 1 Chamber 8 2 High Vac. Pump 3 Roughing Pump 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 8 1 7 8 5 4 7 2 6 3 3a (Page 44 manual)

21 Pump Mechanism

22 OIL BACKSTREAMING 2 PRESSURE LEVELS: LESS THAN 0.2 mbar

23 The Molecular Sieve/Zeolite Trap
(Page 48 manual)

24 Cryo-condensation

25 Vapor Pressure (Page 56 manual)

26 Cryo-sorption (Page 55 manual)

27 HIGH VACUUM PUMPS 3 (Page 63 manual)

28 VACUUM SYSTEM USE 9 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 1 7 8 5 4 8 2 2 6 3 3a

29 Pump Construction (Page 66 manual)

30 How the Pump Works

31 How the Pump Works

32 Maximum Tolerable Foreline Pressure
(Page 73 manual)

33 LN2 reservoir with baffles
(Page 78 manual)

34 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 >760 350 760 <10 -10 (Page 79 manual)

35 Turbomolecular Pump (Page 81 manual) INLET FLANGE ROTOR BODY
STATOR BLADES HIGH PUMPING SPEED HIGH COMPRESSION BEARING EXHAUST HIGH FREQ. MOTOR BEARING (Page 81 manual)

36 Rotor - stator assembly
(Page 82 manual)

37 Pump Operation Molecule V Moving Wall with Speed V
Principle of the Turbomolecular Pump (Page 83 manual)

38 Pumping by Cryocondensation

39 Cryosorption in charcoal
(Page 98 manual)

40 Charcoal placement

41 Gauges 5 (Page 123 manual)

42 Gauge Operating Ranges
Ultra High Vacuum High Vacuum Rough Vacuum Bourdon Gauge Capacitance Manometer Thermocouple Gauge Pirani Gauge Hot Fil. Ion Gauge Cold Cathode Gauge Residual Gas Analyzer McLeod Gauge Spinning Rotor Gauge 10-12 10-10 10-8 10-6 10-4 10-2 1 10+2 P (mbar)

43 How the gauge works

44 Thermocouple gauge and Pirani Gauge
Heat Transfer Gauges Thermocouple gauge and Pirani Gauge

45 Thermocouple Gauge

46 How the gauge works

47 Ionization gauges

48 Ionization current is the measure of vacuum

49 Residual Gas Analyzer QUADRUPOLE HEAD CONTROL UNIT

50 How the RGA works

51 RGA SPECTRUM NORMAL (UNBAKED) SYSTEM RELATIVE INTENSITY H2O (A)
MASS NUMBER (A.M.U.) RELATIVE INTENSITY NORMAL (UNBAKED) SYSTEM H2 H2O N2,, CO CO2 (A)

52 RGA SPECTRUM N2 SYSTEM WITH AIR LEAK RELATIVE INTENSITY H2O (B) O2 H2
MASS NUMBER (A.M.U.) RELATIVE INTENSITY SYSTEM WITH AIR LEAK H2 H2O N2 CO2 (B) O2

53 LEAK DETECTION 9 (Page 249 manual)

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

55 Trapped Volumes

56 Vented Screw

57 PERMEATION LEAKS Permeation “leaks” are different than real leaks because the only way to stop them is to change to a less permeable material

58 Leak Rates over Time LEAK RATES 10 -1 STD CC/SEC --- 1 CC/10 SEC
10 -3 STD CC/SEC CC/HOUR 10 -5 STD CC/SEC CC/DAY 10 -6 STD CC/SEC CC/2 WEEKS 10 -7 STD CC/SEC CC/YEAR 10 -9 STD CC/SEC CC/30 YEARS

59 Why Helium is used

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

61 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 1 2 12 10 11 9 7 6 8 5 3 4

62 Ion Separation in Magnetic Field
Ion Gauge Ion Source 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

63 Tracer probe leak detection technique

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