From the 9th & 10th lecture, April 11th & 14th: VACUUMJ. Wolfgang Hammer

Kaspar Schott, “Technica Curiosa” (1664), Otto von Guericke: Experiment in Regensburg and Magdeburg

Vacuum technology is needed in many different fields:

• All experiments with accelerators and particles

• Atomic physics with traps and spectrometers

• VUV spectroscopy

• Electron microscopy

• Plasma physics

• Low temperature experiments (insulation)

• Material research

• Space simulation

• Industrial processes as thin film production, glass coating

• Chemical industry

• Food processing

Very useful and comprehensive compendium andcollection offormulas (CD)

Vacuum Regimes(16 powers of ten!)

Rough Vacuum (RV) 1000 ..... 1 mbar

Medium Vacuum (MV) 1 ..... 10-3 mbar

High Vacuum (HV) 10-3 ..... 10-7 mbar

Ultrahigh Vacuum (UHV) 10-6 ..... 10-14 mbar

These regimes can be delineated from gas kinetics and the nature of

gas flow.

SI-unit: 1 pascal (Pa) ≡ 1 N·m−2 ≡ 1 J·m−3 ≡ 1 kg·m−1·s−2 ≡ 10-5 bar

usual : 1 mbar ≡ 1 hPa

Outline

• Gas laws, models and theory• Some Formula’s• Vacuum Generation• Vacuum connections, feedthrough’s• Vacuum Measurement, Control and Regulation• Mass spectroscopy• Leak Detection• Some Vacuum Applications

TkNTRVp =⋅⋅=⋅ ν

TRVp m ⋅=⋅

Gas equation for ideal gas:

Vm = Mol volume = 22.4 l at 0 oC and 1013 mbarNA = 6.022 · 1023 mol-1high pressures or near boiling point at use Van-der-Waals equation

p pressure [mbar]V volume [l]ν mol numberN particle numberR universal gas constant

[mbar·l / mol·K]k Boltzman constant [J/K]T absolute temperature [K]

Particle density:

at 1 bar (1013 mbar): n ≈ 3 · 1019 cm-3 (0 oC)

at 10-14 mbar: n ≈ 350 cm-3

Types of gas flow

Viscous flow λ∗ < d/100- laminar Re* < 2200- turbulent Re > 2200 p · d > 6 · 10-1 mbar·cm

* Reynold’s number *mean free path length λ

Knudsen flow d/100 < λ < d/26 · 10-1 > p · d > 1.3 · 10-2 mbar cm

Molecular λ > d/2p · d < 1.3 · 10-2 mbar cm

The “Zoo” of Vacuum PumpsThe “Zoo” of Vacuum Pumps

Rotary Vane PumpRotary Vane Pump

Rotary Plunger PumpRotary Plunger Pump

Diaphragm Pump

Neuberger Pump

Diaphragm PumpsVacuubrand

Diaphragm PumpsVacuubrand

Lederle Hermetic Pump (Screw Pump)Lederle Hermetic Pump (Screw Pump)

Lederle Hermetic Pump (Screw Pump)Lederle Hermetic Pump (Screw Pump)

SIHIdry - Pump

3-fold Cooling :1. Housing2. Internal Axis Cooling3. Direct Gas Cooling

Easy Service

variablepitch !

Claw PumpClaw Pump

Roots Blower (Pump)Roots Blower (Pump)

Roots Pump (Pfeiffer)Roots Pump (Pfeiffer)

Two StageRoots Pump(Pfeiffer)

Two StageRoots Pump(Pfeiffer)

1 Rotor 2 Rotor Axis 3 Pump case4 Suction Channel 5 Water Ring 6 Outlet Channel

WaterWater Ring Pump

Absorption PumpAbsorption Pump

Diffusion PumpDiffusion Pump

Diffusion PumpDiffusion Pump

Turbomolecular Pump with double Holweckstage and magnetic suspension of the rotor

Turbomolecular Pump with double Holweckstage and magnetic suspension of the rotor

Mini Turbomolecular Pumps with Holweck Stages (Alcatel-Adixen)Mini Turbomolecular Pumps with Holweck Stages (Alcatel-Adixen)

Sputter Ion Pump(diode type)

Sputter Ion Pump(diode type)

Ion Getter Pump (triode type)(better for noble gases)

Ion Getter Pump (triode type)(better for noble gases)

Why is steady pumping required ?Leaks (different types)Out-gassingVaporPocketsDiffusion

Desorption rates from clean surfaces [mbar l / s cm2]surface 1 h 10 h

Brass, cleaned 1.6 10-6 4 10-7

Copper, cleaned 3.5 10-7 5.5 10-8

Porcelain, glazed 8.7 10-7 2.8 10-7

Glass, cleaned 4.5 10-9 5.5 10-10

Acrylglass 1.6 10-6 4 10-7

Perbunan 4 10-6 1.3 10-6

Viton 1.2 10-6 2.2 10-7

Viton, baked 4 h at 150 oC 3.3 10-10 2.5 10-10

Teflon, degassed 2.3 10-7 1.5 10-7

Stainless steel, sanded, cleaned 2.7 10-7 2.7 10-8

Stainless steel, polished, cleaned 2.7 10-8 2.7 10-10

Stainless steel, pickled with acid 1h 1.4 10-9 1.4 10-10

Stainless steel, blasted with steel balls 3 10-10 4 10-11

Steel, Ni-plated, polished, cleaned 2 10-7 5 10-9

Steel, Cr-plated, polished, cleaned 1.3 10-8 1.2 10-9

Steel, rusty 6 10-7 1 10-7

Steel, bare, cleaned 5 10-7 5 10-8

Aluminum, cleaned 6 10-8 1.1 10-8

How to clean vacuum systems:

• degreasing by acetone or freon or tri to get rid of all oil, lubricant and grease rests

• or degreasing in a cooking pot with dishwasher detergent and boiling water for 2 hours

• alcohol doesn’t help much, but one can get rid of water• the last two procedures super-pure water and drying with

clean hot air• heating or baking to overcome the outgassing• use clean white cotton gloves for all procedures

Conductance and effective pumping speed

Only molecular flow considered here, different formula’s for different flow types

series of flow “resistors” (= ; C = conductance) :

...........+++++=Elbowtubetubetubeaptot CCCCCC111111

321

C1

Parallel setting of several conductances:

.........+++= 321 tubetubetubetot CCCC

Conductance of a tube, molecular flow:

Reduction of pumping speed by the use of tubes, elbows, apertures :

cminld,sl12

3

⎥⎦⎤

⎢⎣⎡⋅=

ldC mol

tube

⎥⎦⎤

⎢⎣⎡

+⋅

=+

=sl

111

nomtot

nomtot

nomtot

eff SCSC

SC

S

Two Examples → Whiteboard

ELEMENTS

Flange Systems

• Kleinflansch (KF)• Iso Norm (Pneurop)• Conflat (CF)

Special:• Goldwire• VCR• Cone edge• Aluminum (diamond profile)

ANGLE VALVES

GATE VALVES

Mechanical MembraneManometerMechanical MembraneManometer

Capacitive Membrane ManometerCapacitive Membrane Manometer

PiraniVacuum-MeterPiraniVacuum-Meter

Cold Cathode Ionization GaugeCold Cathode Ionization Gauge

Hot Cathode Ionization Vacuum Gauges

Partial Pressure Measurement: Quadrupole Mass Spectrometer

Example Mass SpectrumExample Mass Spectrum

Leak Testing

APPLICATIONSAPPLICATIONS

Differential Pumping Scheme of “Rhinoceros”

Differential Pumping Scheme of “Rhinoceros”

Proton Beam in Air WindowlessProton Beam in Air Windowless

Nuclear Pumped LaserNuclear Pumped Laser

He+ Beam in NeonHe+ Beam in Neon

Windowless Gas Target Facility “Rhinoceros”, extended versionWindowless Gas Target Facility “Rhinoceros”, extended version

Windowless Gas Target Facility RHINOCEROS with 4π Neutron DetectorWindowless Gas Target Facility RHINOCEROS with 4π Neutron Detector

Michael Jaeger