from the 9 &10 lecture, april 11th &14th: vacuum j...
TRANSCRIPT
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
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
SIHIdry - Pump
3-fold Cooling :1. Housing2. Internal Axis Cooling3. Direct Gas Cooling
Easy Service
variablepitch !
1 Rotor 2 Rotor Axis 3 Pump case4 Suction Channel 5 Water Ring 6 Outlet Channel
WaterWater Ring 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)
Ion Getter Pump (triode type)(better for noble gases)
Ion Getter Pump (triode type)(better for noble gases)
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
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