BASIC VACUUM PRACTICE

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)

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

HOW DO WE CREATE A VACUUM?

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

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

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

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

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 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)

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)

(Page 15 manual)

Vapor Pressure of some Solids (Page 15 manual)

PRESSURE RANGES RANGE ROUGH (LOW) VACUUM HIGH VACUUM ULTRA HIGH VACUUM 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)

GAS FLOW CONDUCTANCE (Page 24 manual)

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

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)

MOLECULAR DENSITY AND MEAN FREE PATH 1013 mbar (atm) 1 x 10-3 mbar 1 x 10-9 mbar # mol/cm3 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

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

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)

Viscous Flow (Long Round Tube; air) C = 1.38 x 102 x d4 x P1 + P2 (l/sec) 2 l d = diameter of tube in cm l = length of tube in cm P1 = inlet pressure in torr P2 = exit pressure in torr

Viscous Flow (Long Round Tube; nitrogen) EXAMPLE: d = 4 cm P1 = 2 torr l = 100 cm P2 = 1 torr C = 138 x d4 x P1 + P2 (liter/sec) 2 l C = 138 x 256 x 3 (liter/sec) 100 C = 530 (liter/sec)

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.

Conductance in Molecular Flow (Long Round Tube) C = 3.81 x d3 x T M l (l/sec) d = diameter of tube in cm l = length of tube in cm T = temperature (K) M = A.M.U.

Conductance in Molecular Flow (Long Round Tube) EXAMPLE: T = 295 K (22 OC) M = 28 (nitrogen) C = 3.81 x d3 x T M l (l/sec) = 3.81 x d3 x 295 28 = 12.36 x d3

EXAMPLE: T = 295 K (22 OC) d = 4 cm M = 28 (nitrogen) l = 100 cm C = 3.81 x d3 x T M l (l/sec) = 3.81 x d3 x 295 28 = 12.36 x d3 = 12.36 x 0.64 = 7.9 (l/sec)

Series Conductance RT = R1 + R2 1 = 1 + 1 1 = C1 + C2 CT C1 C2 C1 CT SYSTEM 1 = 1 + 1 CT C1 C2 C1 1 = C1 + C2 CT C1 x C2 C2 CT = C1 x C2 C1 + C2 PUMP (Page 29 manual)

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

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)

Roughing Pumps 2 (Page 39 manual)

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

PUMP OPERATING RANGES Ultra High Vacuum High Vacuum Rough Vacuum Rotary Vane Mechanical Pump Rotary Piston Mechanical Pump Dry Mechanical Pump Sorption Pump Blower/Booster Pump Venturi Pump High Vac. Pumps Ultra-High Vac. Pumps 10-12 10-10 10-8 10-6 10-4 10-2 1 10+2 P (mbar)

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)

Rotary Vane, Oil-Sealed Mechanical Pump (Page 45 manual)

Pump Mechanism

How the Pump Works (Page 46 manual)

Pump Down Curves

OIL BACKSTREAMING 2 PRESSURE LEVELS: LESS THAN 0.2 mbar

The Molecular Sieve/Zeolite Trap (Page 48 manual)

Dry Vacuum Pumps

Blower/Booster Pump (Page 61 manual)

One Stage Roots Blower Pump Assembly

VACUUM SYSTEM USE 12 11 1 4 3 2 9 10 7 6 8 5 1 Chamber 2 Foreline 3 Roughing Valve Roughing Gauge Roughing Pump 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)

Piston Type Pump (Page 51 manual)

Piston design (Page 50 manual)

Sorption Pump

Sorption Pump Components (Page 54 manual)

Vapor Pressure (Page 56 manual)

Cryo-condensation

Cryo-sorption (Page 55 manual)

HIGH VACUUM PUMPS 3 (Page 63 manual)

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

PUMP OPERATING RANGES Ultra High Vacuum High Vacuum Rough 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 10+2 P (Torr)

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

Oil Diffusion Pump

Pump Construction (Page 66 manual)

How the Pump Works

How the Pump Works

Release of Vapors (Page 67 manual)

First stage vapors are separated from others

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

Maximum Tolerable Foreline Pressure (Page 73 manual)

LN2 reservoir with baffles (Page 78 manual)

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)

VACUUM SYSTEM USE LN2 COLD TRAP (Page 80 manual)

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)

Rotor - stator assembly (Page 82 manual)

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

Roughing through the turbo 1 6 7 4 3 2 5 1 2 3 4 5 6 Chamber Turbo Pump Roughing Pump Vent Valve Roughing Gauge High Vac. Gauge (Page 91 manual)

Pumping by Cryocondensation

Cryosorption in charcoal (Page 98 manual)

Charcoal placement

Gauges 5 (Page 123 manual)

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)

Bourdon Gauge

How the gauge works

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

Thermocouple Gauge

How the gauge works

Ionization gauges

Ionization current is the measure of vacuum

Residual Gas Analyzer QUADRUPOLE HEAD CONTROL UNIT

How the RGA works

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)

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

LEAK DETECTION 9 (Page 249 manual)

Introduction

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

Trapped Volumes

Vented Screw

Double O ring sealed shafts Atmosphere (760 torr) Vacuum

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

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

One standard cubic centimeter/sec (std. cc/sec)

Leak rate of 1 x 10-1 std cc/sec

Leak rate of 1 x 10-3 std cc/sec

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

Permeation may occur <1X10-8 std cc/sec

Why Helium is used

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

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

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

Tracer probe leak detection technique

Leak detectors are calibrated with the “permeation leak”