introduction to vacuum technology - univapfree path to minimize collisions clean environment to run...
TRANSCRIPT
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Rafael M. Seraphim ([email protected])
LNLS Vacuum Group
Introduction to Vacuum
Technology
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Contents
- Vacuum basics
- Vacuum system:
- Valves
- Pumps
- Gauges
- Examples of vacuum systems
- Final remarks
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Vacuum basicsRafael Seraphim
Why vacuum?
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Vacuum basicsRafael Seraphim
Why vacuum?
Free path to minimize collisions
Particle
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Vacuum basicsRafael Seraphim
Why vacuum?
Free path to minimize collisions Clean environment to run an experiment
or
simulate a specific environment
sample
Particle
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Vacuum basicsRafael Seraphim
Why vacuum?
What is the target pressure (P) or tolerable molecular
density (n)?
Free path to minimize collisions Clean environment to run an experiment
or
simulate a specific environment
sample
Particle
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Vacuum basicsRafael Seraphim
Classification of vacuum ranges
Pressure range
[mbar]
Molecular Density n
at 293 K [cm-3]
Low Vacuum LV 103-1 1019-1016
Medium Vacuum MV 1-10-3 1016-1013
High Vacuum HV 10-3-10-9 1013-107
Ultra High vacuum UHV 10-9-10-12 107-104
Extreme High Vacuum XHV <10-12 <104
According to Ideal Gas Law P = n K TPressure P [Pa]
Gas density n [molecules/m3]
Boltzman constant k [J/K] = 1.38 10-23
Temperature T [K]
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Vacuum basics:Flow regimes in vacuum
Rafael Seraphim
Vacuum Technology Know How. Pfeiffer book
��=λ
�Knudsen number:
d is vacuum chamber diameter
�[��] =�����
�[���]Mean free path:
Pressure
rabge [mbar]
Mean free
path λ [cm]
103-1 <10-2
1-10-3 10-2-10
10-3-10-9 10-106
10-9-10-12 106-108
<10-12 >108
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Vacuum basics:Gas Flow
Rafael Seraphim
Gas flow in vacuum can be described by the simple equation:
CP1 P2
Q = C (P1-P2)
ThroughputConductance Pressure difference
Pressure P [mbar]
Conductance C [l/s]
Throughput Q [mbar*l/s]P1 > P2P1 > P2
Q
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Vacuum basics:Gas Flow
Rafael Seraphim
Gas flow in vacuum can be described by the simple equation:
CP1 P2
Q = C (P1-P2)
ThroughputConductance Pressure difference
Pressure P [mbar]
Conductance C [l/s]
Throughput Q [mbar*l/s]P1 > P2P1 > P2
Q
ParallelSeries
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Vacuum basics:Conductance calculation in molecular regime
Rafael Seraphim
Conductance C [l/s]
Orifice area A [cm2] For an orifice:
For a tube:
For exemple, the conductance of an orifice of 4 cm is: 146 l/s
���,��°�= ��. ��
Conductance C [l/s]
Tube diameter d [cm]
Tube length L [cm]
For exemple, the conductance of a tube with diameter of 4 cm
and length of 10 cm is: 77.5 l/s
For simple geometry the conductance can be calculated by simple eqs.:
���,��°�= ��. ���
�
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Rafael Seraphim
For complex geometry the conductance can be calculated by:
http://cern.ch/test-molflow
Based on Test-Particle Monte Carlo
method (TPMC), which calculates a
large number of molecular
trajectories to have a picture of a
rarefied gas flow.
R. Kersevan and J.-L. Pons, JVST A 27(4) 2009, p1017
Vacuum basics:Conductance calculation in molecular regime
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Vacuum basics:Calculating the pressure in vacuum chambers
Rafael Seraphim
The pressure in a vacuum chamber can be described by
using the following equations:
Pressure in the chamber P1 [mbar]
Pressure in the pump P2 [mbar]
Conductance C [ls]
Gas load/throughput Q [mbar*l/s]
Pump nominal pumping speed S [l/s]
Pump effective pumping speed Seff [l/s]
1
�� =1
S+1
#
Q = C (P1-P2)
Q = S P2
Q = Seff P1C
P1
P2
S
Qchamber
pump
Seff
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Vacuum basics:Calculating the pressure in vacuum chambers
Rafael Seraphim
The pressure in a vacuum chamber can be described by
using the following equations:
Pressure in the chamber P1 [mbar]
Pressure in the pump P2 [mbar]
Conductance C [ls]
Gas load/throughput Q [mbar*l/s]
Pump nominal pumping speed S [l/s]
Pump effective pumping speed Seff [l/s]
1
�� =1
S+1
#
Q = C (P1-P2)
Q = S P2
Q = Seff P1C
P1
P2
S
Qchamber
pump
Seff
To lower the pressure in the chamber
there are only two approaches:
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Vacuum basics:Calculating the pressure in vacuum chambers
Rafael Seraphim
The pressure in a vacuum chamber can be described by
using the following equations:
Pressure in the chamber P1 [mbar]
Pressure in the pump P2 [mbar]
Conductance C [ls]
Gas load/throughput Q [mbar*l/s]
Pump nominal pumping speed S [l/s]
Pump effective pumping speed Seff [l/s]
1
�� =1
S+1
#
Q = C (P1-P2)
Q = S P2
Q = Seff P1C
P1
P2
S
Qchamber
pump
Seff
To lower the pressure in the chamber
there are only two approaches:
↓ Q
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Vacuum basics:Gas load
Rafael Seraphim
Permeation
Outgassing
DiffusionBackstreaming
Real
Virtual
QT = Qout + Qdiff + Qperm + Qleak
[mbar l/s)]
Leaks
Pump
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Vacuum basics:Calculating the pressure in vacuum chambers
Rafael Seraphim
The pressure in a vacuum chamber can be described by
using the following equations:
Pressure in the chamber P1 [mbar]
Pressure in the pump P2 [mbar]
Conductance C [ls]
Gas load/throughput Q [mbar*l/s]
Pump nominal pumping speed S [l/s]
Pump effective pumping speed Seff [l/s]
1
�� =1
S+1
#
Q = C (P1-P2)
Q = S P2
Q = Seff P1C
P1
P2
S
Qchamber
pump
Seff
To lower the pressure in the chamber
there are only two approaches:
↓ Qor
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Vacuum basics:Calculating the pressure in vacuum chambers
Rafael Seraphim
The pressure in a vacuum chamber can be described by
using the following equations:
Pressure in the chamber P1 [mbar]
Pressure in the pump P2 [mbar]
Conductance C [ls]
Gas load/throughput Q [mbar*l/s]
Pump nominal pumping speed S [l/s]
Pump effective pumping speed Seff [l/s]
1
�� =1
S+1
#
Q = C (P1-P2)
Q = S P2
Q = Seff P1C
P1
P2
S
Qchamber
pump
Seff
To lower the pressure in the chamber
there are only two approaches:
or↓ Q
↑ SeffISWA 2016, July, 3-8, Campinas
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Adapted from Chiaggiato; CAS-CERN, Vacuum Techniques
for Superconducting Devices, 2013.
Example: Vessel and pump connected by a 100 mm diameter tube; N2 ,
S=250 l/s and 1000 l/s.
Se
ffa
nd
C [
l/s]
L/D
1
�� =1
�+1
#
The design of the chamber, how the pumps will be connected and the size of pumps are a
compromise that must be analyzed.
Vacuum basics:Conductance between the pump and the chamber
C
P1
P2
S
Qchamber
pump
Seff
�$� ≫ &:&($$ ≈ &
�$� ≪ &:&($$ ≈ �
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�$� ≫ &:&($$ ≈ &
�$� ≪ &:&($$ ≈ �
Adapted from Chiaggiato; CAS-CERN, Vacuum Techniques for Superconducting Devices, 2013.
Example: Vessel and pump connected by a 100 mm diameter tube; N2 ,
S=250 l/s and 1000 l/s.
Se
ffa
nd
C [
l/s]
L/D
+ = &($$��
1
�� =1
�+1
#
The design of the chamber, how the pumps will be connected and the size of pumps are a
compromise that must be analyzed.
Vacuum basics:Conductance between the pump and the chamber
C
P1
P2
S
Qchamber
pump
Seff
Do you think this design is effective???
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Vacuum systemRafael Seraphim
Vacuum chamber
H/UHV
pump
Primary pump
Safety
shut-off
valve
Valve
Sputter ion
pump
Ti sublimation
pump
RGA
Gauge
Valve
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Vacuum systemRafael Seraphim
Vacuum chamberVacuum chamber
H/UHV
pump
Primary pump
Safety
shut-off
valve
Valve
Sputter ion
pump
Ti sublimation
pump
RGA
Gauge
Valve
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Vacuum system:
valves
Rafael Seraphim
All metal right angle valves:
Sealing concept: hard-hard
Sealing concept: hard-soft
Gate valves:
Metal sealed O-ring sealed
Safety shut-off valves:
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Vacuum systemRafael Seraphim
Vacuum chamber
H/UHV
pump
Primary pump
Safety
shut-off
valve
Valve
Sputter ion
pump
Ti sublimation
pump
RGA
Gauge
Valve
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Vacuum systemRafael Seraphim
Vacuum chamberVacuum chamber
H/UHV
pump
Primary pump
Safety
shut-off
valve
Valve
Sputter ion
pump
Ti sublimation
pump
RGA
Gauge
Valve
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Vacuum system:
pumps
Rafael Seraphim
10-12 10-10 10-8 10-6 10-4 10-2 1 10+2
Mechanical pumps
Turbomolecular
Cryogenic pump
Sputter ion pump
Titanium sublimation pump
Diffusion pump
mbar
Ultrahigh vacuum High vacuum Rough and Medium Vacuum
Mu
st b
e c
om
bin
ed
wit
h
me
cha
nic
al p
um
ps
On
ly s
tart
ed
aft
er
pu
mp
ed
by t
he
com
bin
ati
on
of
pu
mp
s a
bo
ve
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Vacuum systemRafael Seraphim
Vacuum chamber
H/UHV
pump
Primary pump
Safety
shut-off
valve
Valve
Sputter ion
pump
Ti sublimation
pump
RGA
Gauge
Valve
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Vacuum systemRafael Seraphim
Vacuum chamberVacuum chamber
H/UHV
pump
Primary pump
Safety
shut-off
valve
Valve
Sputter ion
pump
Ti sublimation
pump
RGA
Gauge
Valve
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Vacuum system:
gauges
Rafael Seraphim
10-12 10-10 10-8 10-6 10-4 10-2 1 10+2
Rough and Medium VacuumHigh vacuumUltrahigh vacuum
Bourdon manometer
Cold cathode
Hot cathode
Residual Gas Analyzer (RGA)
Convection enhanced Pirani gauge
Penning gauge
mbar
Extractor gauge
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Examples of vacuum systemsRafael Seraphim
UHV chamber – beamline monochromator UHV chamber – Infrared mirrors
UHV chamber – surface analysis
HV chamber – Furnace for brazing process
Mechanisms inside
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Final remarks
• Vacuum technology is interdisciplinary and correlates with other areas;
• A vacuum system must fabricated following a well defined flow:
Define vacuum requirements (working pressure; residual atmosphere; etc…)
Mechanical and vacuum design(materials selection; chamber design; vacuum, mech. and thermal calculations/simulations; etc…)
Vacuum equipment specification(pumps and instrumentation selection; feedthroughs; etc…)
Fabrication(adequate fab. process; inspections; cleaning; etc…)
Assembly and tests(integration of equipaments and components; leak tests; etc…)
Conditioning and commissioning(bake-out; final pressure validation; etc…) Ready for use!
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Thank you for your attention!
Questions???
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