BASIC VACUUM PRACTICE

BASIC VACUUMPRACTICE

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?

Contamination(usually water)

Clean surface

Atmosphere (High)Vacuum

To provide a clean surface

HOW DO WE CREATE A VACUUM?

VACUUM PUMPING METHODS

Sliding VaneRotary Pump

MolecularDrag Pump

TurbomolecularPump

Fluid EntrainmentPump

VACUUM PUMPS(METHODS)

ReciprocatingDisplacement Pump

Gas TransferVacuum Pump

DragPump

EntrapmentVacuum Pump

Positive DisplacementVacuum Pump

KineticVacuum Pump

RotaryPump

DiaphragmPump

PistonPump

Liquid RingPump

RotaryPiston Pump

RotaryPlunger Pump

RootsPump

Multiple VaneRotary Pump

DryPump

AdsorptionPump

Cryopump

GetterPump

Getter IonPump

Sputter IonPump

EvaporationIon Pump

Bulk GetterPump

Cold TrapIon TransferPump

Gaseous Ring Pump

TurbinePump

Axial FlowPump

Radial FlowPump

EjectorPump

Liquid JetPump

Gas JetPump

Vapor JetPump

DiffusionPump

DiffusionEjector Pump

Self PurifyingDiffusion Pump

FractionatingDiffusion Pump

Condenser

SublimationPump

BAROMETER

WATER MERCURY

760mm

Mercury: 13.58 times heavier than water: Column is 13.58 x shorter :10321 mm/13.58=760 mm (= 760 Torr)

10.321mm

29,9in

(Page 12 manual)

PRESSURE OF 1 STANDARD ATMOSPHERE:

760 TORR, 1013 mbar

AT SEA LEVEL, 0O C AND 45O LATITUDE

Pressure Equivalents

Atmospheric Pressure (Standard) =

014.729.9760760760,000101,3251.0131013

gauge pressure (psig)pounds per square inch (psia)inches of mercurymillimeter of mercurytorrmillitorr or micronspascalbarmillibar

THE ATMOSPHERE IS A MIXTURE OF GASES

PARTIAL PRESSURES OF GASES CORRESPOND TO THEIR RELATIVE VOLUMES

GAS SYMBOLPERCENT BY

VOLUMEPARTIAL PRESSURE

TORR PASCAL

NitrogenOxygenArgonCarbon DioxideNeonHeliumKryptonHydrogenXenonWater

N2

O2

ACO2

NeHeKrH2

XH2O

7821

0.930.03

0.00180.00050.0001

0.000050.0000087Variable

5931587.1

0.251.4 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

79,00021,000

940331.8

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

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)

(Page 15 manual)

Vapor Pressure of some Solids

(Page 15 manual)

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)

GAS FLOWCONDUCTANCE

(Page 24 manual)

Viscous and Molecular Flow

Viscous Flow(momentum transferbetween molecules)

Molecular Flow(molecules moveindependently)

FLOW REGIMESViscous 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 betweenmolecules and wall dominate; flow through random motion;generally P smaller than 10 mbar-3

(Page 25 manual)

MEAN FREE PATH

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 in6.4 x 10-5 mm

2 inches5.1 cm

31 miles50 km

FLOW REGIMES

Mean Free PathCharacteristic Dimension

Viscous Flow: is less than 0.01

Mean Free PathCharacteristic Dimension

Molecular Flow: is greater than 1

Mean Free PathCharacteristic Dimension

Transition Flow: is between 0.01 and 1

Conductance in Viscous Flow

Under viscous flow conditions doubling thepipe diameter increases the conductance sixteen times.The conductance is INVERSELY related to the pipe length

(Page 28 manual)

Conductance in Molecular Flow

Under molecular flow conditions doublingthe pipe diameter increases the conductanceeight times.The conductance is INVERSELY related tothe pipe length.

SYSTEM

PUMP

C1

C2

Series Conductance

RT = R1 + R2

1 = 1 + 1C1 C2CT

1 = C1 + C2

C1 x C2CT

CT = C1 x C2

C1 + C2

(Page 29 manual)

GAS LOAD

Outgassing

Leaks

Virtual

Real

BackstreamingDiffusion

Permeation

GAS LOAD (Q) IS EXPRESSED IN:mbar liters per second

Pumpdown CurveP

ress

ure

(m

bar

)

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

Roughing Pumps

2(Page 39 manual)

VACUUM PUMPING METHODS

Sliding VaneRotary Pump

MolecularDrag Pump

TurbomolecularPump

Fluid EntrainmentPump

VACUUM PUMPS(METHODS)

ReciprocatingDisplacement Pump

Gas TransferVacuum Pump

DragPump

EntrapmentVacuum Pump

Positive DisplacementVacuum Pump

KineticVacuum Pump

RotaryPump

DiaphragmPump

PistonPump

Liquid RingPump

RotaryPiston Pump

RotaryPlunger Pump

RootsPump

Multiple VaneRotary Pump

DryPump

AdsorptionPump

Cryopump

GetterPump

Getter IonPump

Sputter IonPump

EvaporationIon Pump

Bulk GetterPump

Cold TrapIon TransferPump

Gaseous Ring Pump

TurbinePump

Axial FlowPump

Radial FlowPump

EjectorPump

Liquid JetPump

Gas JetPump

Vapor JetPump

DiffusionPump

DiffusionEjector Pump

Self PurifyingDiffusion Pump

FractionatingDiffusion Pump

Condenser

SublimationPump

PUMP OPERATING RANGES

10-12 10-10 10-8 10-6 10-4 10-2 1 10+2

P (mbar)

Rough VacuumHigh VacuumUltra High Vacuum

Venturi Pump

Rotary Vane Mechanical Pump

Rotary Piston Mechanical Pump

Sorption PumpDry Mechanical Pump

Blower/Booster Pump

High Vac. PumpsUltra-High Vac. Pumps

VACUUM SYSTEM USE

1

2

4

6

5

9

8

8

7

123

3a456789

ChamberHigh Vac. PumpRoughing PumpForeline PumpHi-Vac. ValveRoughing ValveForeline ValveVent ValveRoughing GaugeHigh Vac. Gauge

7

33a

(Page 44 manual)

Rotary Vane, Oil-Sealed Mechanical Pump

(Page 45 manual)

Pump Mechanism

How the Pump Works

(Page 46 manual)

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

123456789

101112

ChamberForelineRoughing ValveRoughing GaugeRoughing PumpForelineForeline ValveForeline GaugeHigh Vacuum ValveBooster/BlowerVent ValveHigh Vacuum Gauge

1

9

3

12

4

11

5

2

678

10

(Page 62 manual)

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

Sliding VaneRotary Pump

MolecularDrag Pump

TurbomolecularPump

Fluid EntrainmentPump

VACUUM PUMPS(METHODS)

ReciprocatingDisplacement Pump

Gas TransferVacuum Pump

DragPump

EntrapmentVacuum Pump

Positive DisplacementVacuum Pump

KineticVacuum Pump

RotaryPump

DiaphragmPump

PistonPump

Liquid RingPump

RotaryPiston Pump

RotaryPlunger Pump

RootsPump

Multiple VaneRotary Pump

DryPump

AdsorptionPump

Cryopump

GetterPump

Getter IonPump

Sputter IonPump

EvaporationIon Pump

Bulk GetterPump

Cold TrapIon TransferPump

Gaseous Ring Pump

TurbinePump

Axial FlowPump

Radial FlowPump

EjectorPump

Liquid JetPump

Gas JetPump

Vapor JetPump

DiffusionPump

DiffusionEjector Pump

Self PurifyingDiffusion Pump

FractionatingDiffusion Pump

Condenser

SublimationPump

PUMP OPERATING RANGES

10-12 10-10 10-8 10-6 10-4 10-2 1 10+2

P (Torr)

Rough VacuumHigh VacuumUltra High Vacuum

Roughing Pumps

Turbo Pump

Diffusion Pump

Cryo Pump

Ion Pump

Tit. Subl. Pump

Liquid Nitrogen Trap

VACUUM SYSTEM USE

1

4

6

5

9

8

8123

3a456789

ChamberHigh Vac. PumpRoughing PumpFore PumpHi-Vac. ValveRoughing ValveForeline ValveVent ValveRoughing GaugeHigh Vac. Gauge

7

33a

28

2

Oil Diffusion Pump

Pump Construction

(Page 66 manual)

How the Pump Works

How the Pump Works

First stage vapors are separated from others

Pumping Speed

10-10 10--3 10--1

Pu

mp

ing

Sp

eed

(A

ir)

1 2 3 4

Inlet Pressure (Torr)

Critical Point

1. Compression Ratio Limit2. Constant Speed3. 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

GasApproximate Vapor

Pressure (mbar)

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>760>760 350>760 760 <10 -10

(Page 79 manual)

Turbomolecular Pump

ROTOR BODY

HIGH PUMPING SPEED

HIGH COMPRESSION

EXHAUST

HIGH FREQ. MOTOR

INLET FLANGE

STATOR BLADES

BEARING

BEARING

(Page 81 manual)

Rotor - stator assembly

(Page 82 manual)

Pump OperationMolecule V

Moving Wall with Speed V

Principle of the Turbomolecular Pump

(Page 83 manual)

Roughing through the turbo

123456

ChamberTurbo PumpRoughing PumpVent ValveRoughing GaugeHigh Vac. Gauge

1

67

4

3

25

2

(Page 91 manual)

Pumping by Cryocondensation

Cryosorption in charcoal

(Page 98 manual)

Charcoal placement

Gauges

5

(Page 123 manual)

Gauge Operating Ranges

10-12 10-10 10-8 10-6 10-4 10-2 1 10+2

P (mbar)

Rough VacuumHigh VacuumUltra 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

Bourdon Gauge

How the gauge works

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

QUADRUPOLEHEAD

CONTROL UNIT

How the RGA works

MASS NUMBER (A.M.U.)

RE

LA

TIV

E I

NT

EN

SIT

Y

NORMAL (UNBAKED) SYSTEM

H2

H2O

N2,, CO

CO2

(A)

RGA SPECTRUM

MASS NUMBER (A.M.U.)

RE

LA

TIV

E I

NT

EN

SIT

Y

SYSTEM WITHAIR LEAK

H2

H2O

N2

CO2

(B)

O2

RGA SPECTRUM

LEAK DETECTION

9

(Page 249 manual)

Introduction

Problems that appear to be Leaks

Outgassing

Leaks

Virtual

Real

Backstreaming

DiffusionPermeation

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 SEC10 -3 STD CC/SEC --- 3 CC/HOUR10 -5 STD CC/SEC --- 1 CC/DAY10 -6 STD CC/SEC --- 1 CC/2 WEEKS10 -7 STD CC/SEC --- 3 CC/YEAR10 -9 STD CC/SEC --- 1 CC/30 YEARS

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

123456789

101112

Test PieceTest PortHigh Vac. PumpRoughing PumpFore PumpRoughingValveTest ValvePump ValveSpectrometer TubeCold TrapRoughing GaugeVent Valve

7 6

12

45

1

3

8

11

2

9 10

Ion Separation in Magnetic Field

Ion Source

To Pre-Amplifier

Collector

Magnetic FieldDeflects He Ions90O, other ions more or less than90O.

He ions passthrough slit andare collected

Lighter ions:more

Heavier ions:less

Ion Gauge

Tracer probe leak detection technique