Vacuum metrology for production
environments
M. BERGOGLIO
The European Metrology Research Programme (EMRP) is a metrologyfocused European programme of coordinated R&D that facilitates
closer integration of national research programmes. The EMRP is
supported by the European Commission and the participating
countries within the European Association of National Metrology
Institutes.
The EMRP is jointly funded by the EMRP participating countries
within EURAMET and the European Union
JRP start date and duration: September 1, 2011; 3 years
JRP-Coordinator: Dr. Karl Jousten, PTB
JRP-Partners:
PTB, Germany
CEM, Spain CMI, Czech Republic
IMT, Slovenia
INRIM, Italy LNE, France
TUBITAK UME, Turkey
Danfoss, Denmark INFICON AG, Liechtenstein
Lazzero, Italy
5Pascal, Italy
INFICON GmbH, Germany
VACOM, Germany
REG1: UNIGE, Italy
REG2: UTH University of Thessaly,
REG3: KIT Karlsruhe Institute of Technology
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Total eligible costs:
EURAMET contribution:
National contribution:
2.8 M€
1.3 M€ (45%)
1.5 M€
290 labour months
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Historically, vacuum has been an important tool in industry and has
been used in many applications, ranging from protecting light filaments
from chemical degradation to controlling the flow of current in
electronics.
The use of vacuum is still important today, in modern semiconductor
industry and fusion power research. However, vacuum is poorly
understood when used outside the laboratory, as traditional
measurements are unsuitable and based on the pressures of pure gases
in stable conditions.
This project will improve vacuum measurements in conditions
representative of those found in industry. The improved measurements
will lead to a more efficient use of vacuum and better end products.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
The existing vacuum measurement
standards in the EU provide
traceability from 10-9 Pa to 105 Pa for
pure gases under static or stationary
equilibrium conditions.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Some NMIs also operate standards for very low gas flows (10-15
mol/s to 10-8 mol/s) which are suitable to calibrate leak rates of
standard leaks for helium and some other pure gases.
Currently, no facility in the EU exists for calibrating vacuum
gauges for dynamic pressures or for calibrating quadrupole mass
spectrometers (QMS). Therefore, traceable outgassing rate
measurements with QMS are not possible. Furthermore, there is
no generally accepted way of converting leak rates from helium
to other gases or environmental conditions different from the
calibration.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
This JRP will go beyond the state of the art by:
• providing industry with a calibration facility to measure the response times of
vacuum gauges for fast dynamic pressure changes
• enabling users of calibrated leaks to predict leak rates under industrial
environmental conditions which are needed to meet regulations
• providing industry with a calibration facility to characterise and calibrate
QMS. This is needed to control processes more reliably
• providing traceability for outgassing rate measurements with QMS and also
with the use of reference materials for outgassing
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
WP1 Dynamic vacuum calibration facility
WP2 Leak measurement and testing
WP3 Partial pressure and outgassing rate
measurement
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
WP1 Dynamic vacuum calibration facility
Novel dynamic vacuum calibration facility :
Provision of a vacuum system with very fast pressure changes in rough vacuum
Enabling the detection of very fast pressure changes (the pressure will
decrease from 100 kPa to 100 Pa within 1 s or less) by suitable vacuum gauges
with simultaneous measurement of very fast temperature changes.
Data on the relaxation time of vacuum gauges for fast pressure changes.
Qualification of suitable gauges for dynamic vacuum pressure changes
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
PTB provides a calibration facility for the dynamic
response of vacuum gauges with the pressure
changing from 100 kPa to 100 Pa within 1 s. A
small and a large chamber separated by a well
defined conductance and a fast moving valve
were realized. The pressure decrease p(t) will be
generated by opening the valve causing the gas to
be expanded from the small into the large
chamber. The mass flow through the orifice is
calculated over the whole pressure range.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
High-pressure volume: V1  0,08745 L
Low-pressure volume: V2  185,4 L
Dead volume: V1'  0,03309L
Expansion ratio
f1 
V1
1

V1  V2 2121
Dead volume offset
poffs
p
V1
 p01
 01
V1  V2 5604
Final pressure
pf 
V1  V1'
V1  V1'  V2
p01 
p01
1539
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Fast opening valve
•VAT DN40 gate valve
•Opened pneumatically via an
actuation pressure of 9 bar
•Molecular conductance is
approximately 81 L/s
•Characterisation with a high
speed camera (10000 fps)
•Opening time: 5,7 ms
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Orifice
Orifice of conical geometry: diameter reduced from 8 mm to 3 mm, thickness of
2,6 mm.
Designed to have a conductance of about 1 L / s in the molecular regime.
Leads to an expansion into vacuum within 540 ms.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Orifice
The orifice geometry
is an important factor.
Orifice characterization in PTB.
Maximum deviation 1%,
average deviation <0,2%.
Measurement 30.07.12 (Front side): Area = 7,099 mm2
Measured radius = 1,503 mm, Nominal radius = 1,5 mm
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
INFICON Liechtenstein Tasks
Develop and donate a membrane sensor with associated signal
processing equipment that can measure
 pressure changes in the range 100 Pa to 100 kPa
 with an up-date time of < 1 ms
 for use in a pressure standards laboratory
2 CDG 1000 Torr and 2 CDG 10 Torr delivered
Time between measurement values approx. 700 μs < 1ms
Output at 21 bit resolution
Noise peak-peak < 0.5% F.S., typically 0.2 % F.S.
Improvements to system still possible (i.e. static calibration, noise reduction)
Patent application filed
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Pressure gauges
Inficon:
Capacitance
Diaphragm
Gauges (CDG)
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
VACOM:
piezo-resistive
gauges
Dynamic expansion
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Thermocouple
The gas expansion will be nonadiabatic so since gas pressure and
temperature are related, a
temperature sensor with very small
heat capacity has designed to
measure the gas temperature.
dfeedthrough =200 µm
dwire =25 µm
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
TC type K
Usage of very thin wires dWire = 25 µm
Type K: Ni Cr(10%), Ni Al(5%)
LN2
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Pressure distribution
t = 0.00012s
t = 0.01s
t = 0.02s
t = 0.2s
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Velocity distribution
t = 0.0001s
t = 0.00015s
t = 0.001s
t = 0.005s
t = 0.01s
t = 0.05s
t = 0.1s
t = 0.2s
Temperature distribution
t = 0.00012s
t = 0.2s
t = 0.0003s
t = 0.001s
t = 0.1s
Pressure measurement
Experimental conditions: p1 = 105 Pa, p2 = 0,05 Pa.
Conical orifice between the two volumes.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
First comparisons
• ANSYS CFX: Validation within the viscous regime, i.e the pressure
was decreased streamwise from 105 Pa to 5000, 2500 and 1000 Pa.
Experimental conditions: p1 = 105 Pa, p2 = 103 Pa.
Inficon CDGs, conical orifice between the two volumes.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
INRIM optical method for Dynamic vacuum
calibration facility
-the experiment is based on a homodyne
Michelson interferometer
- The heart of the system is the double mirror
multiplication set up ( angle between mirrors
of ~ 0.4 °)
- Sensitivity: ~ 2.6 nm/Pa
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
The laser source is a He–Ne frequency stabilized
laser linearly polarized (λ ≈ 632.8 nm).
The Faraday isolator (FI) prevents feedback-induced
instabilities and rotates the polarization by 45°.
The reference beam is sent to a fixed mirror M
through a λ/8 retarder. It has the effect of giving a
circular polarization to the beam returning to the BS.
Marco Pisani , “A homodyne Michelson
interferometer with sub-picometer resolution”,
Meas. Sci. Technol. 20 (2009)
The measurement beam is sent to the double
mirror multiplication setup.
The beam reflected back is summed to that coming from mirror M on the BS and is sent to the
detector assembly.
A polarizing beam splitter (PBS) is used to separate the vertical and the horizontal
components of the two beams and to address them towards photodetectors D1 and D2.
The vertical and the horizontal components of the linearly polarized measurement beam are
summed with the sine and cosine components of the circularly polarized reference beam
generating two quadrature interference signals, which are amplified and sent to the acquisition
system.
27
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
From 98 kPa to 100 Pa
L = 335 mm
dL = 86 µm
S = 0.88 nm/Pa
P /Pa
n
dn/n
dL/L
dL/mm @ L=1000 mm
98000
1.000259
0.000000
0.000000
0.0000
100
1.000000
0.000259
0.000259
0. 2585
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Base for interferometer
Base: ULE, diameter 160 mm, thickness
20mm
planarity better than l/10
Support for bonding of mirrors
Mirrors: ULE, 70x30x10 planarity better
than l/10 , orthogonal surface 10”
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
WP 2: Leak measurement and testing
Leak and small outflow measurements are very important in many
branches of industry (cold storage facilities, air conditioning
systems, etc). The most sensitive, versatile and accurate method
for leak measurement is the permanent gas (helium) throughput
measurement through the leak into vacuum. Nevertheless, the
leaks usually occur under conditions different from those at
measurement: different pressures, temperature, gas species and
mixtures. Research is needed to provide industry with traceability
under practical conditions.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
The aim of the WP2, is the improvement of the knowledge of
gas flow through nano/microchannels in terms of
predictability for different gas species and environmental
conditions with the focus on the industrial applications and
conditions. Several leak elements were realized with a well
known geometry in order to improve gas flow theory in the
narrow ducts, to increase the accuracy of conversion function
between different gases and to study metrological
characteristics of the leaks (temperature coefficient, gas flow
rate stability, influence of changing atmospheric pressure).
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Study of leak elements performance:
temperature coefficient, influence of
atmospheric pressure changes, influence of
the effects of gas mixture.
Development of a practical guide on
metrological performance of leak detectors:
either He leak detectors or infrared leak
analyzers.
Technical training course for
people working in leak
testing field.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
WP 3: Partial pressure and outgassing rate measurement
The aim of this workpackage is to provide dedicated calibration facilities for
quadrupole mass spectrometers (QMS) and to investigate factors influencing
metrological characteristics of QMS.
Another aim is to develop model systems for outgassing rate measurements
applying different methods, to compare them, and provide measurement
traceability of these methods. There are no "certified reference materials" for
outgassing rate available yet. Materials which exhibit reversible absorption of
different gasses may be used for such purpose. We will investigate the suitability
of different materials as e.g. high vacuum compatible polymers, nanostructures,
porous silicon, zeolite and choose the most suitable one as reference outgassing
material.
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Three glass capillaries as leak
elements operating in molecular
regime
2
Outgassing
sample chamber
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
QMS
Outgassing sample chamber
- load lock
- transportation system
Orifice having a
conductance of 1L/s
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
CDG
Variable
Leak
Valve
Calibration gas
BAG
QMS
IMT
SRG
Vacuum
pump
(turbo + rotary)
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Gas flow and “gas quantity”
calibration attachement
Bake-out oven to 400*C
CF
flange
CDG
N2
Ar
H2
He
CO
CO2
Ne
Kr
CH1
SRG3
calibration
gases
CH2
0.3 L
SRG2
QMS
BAG
SRG1
CCG
He leak
detector
ION
PUMP
TURBO
1
TURBO
2
IMT
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Calibrated leak
primary flowmeter
Gas inlet
RGA
IG
SRG
Auxiliary pump
Outgassing chamber
To pumping system
INRIM
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Study of stability over time of QMS sensitivity and
other properties
Evaluate following characteristics:
 sensitivity
 SEM gain
 mass number stability
 resolution
 fragmentation factor of N2
 minimum detectable partial pressure
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
- Determination of metrological characteristics of QMS
for calibration purposes and definition of reference
conditions to compare performance of instruments
from different manufacturers
ISO TS on the calibration of QMS
ISO TS on the outgassing rate measurements
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
Calibrated leak
primary flowmeter
Gas inlet
RGA
IG
SRG
Auxiliary pump
Outgassing chamber
To pumping system
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
S He / (A/Pa) (normalized to 1mA)
1.E-05
1.E-06
1.E-07
1.E-08
1.E-09
1.0E-06
1.0E-05
1.0E-04
1.0E-03
Pressure / Pa
PTB
CMI_1_1
IMT
UME_I
UME_II
UME_III
CMI_1_2
VACOM
INRIM 422
INRIM Transpector
LNE I
CEM
LNE II
LNE I'
CMI_2_F1
CMI_2_F2
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
S N2 (28) / (A/Pa) (normalized to 1mA)
1.E-05
1.E-06
1.E-07
1.E-08
1.E-09
1.0E-06
1.0E-05
1.0E-04
1.0E-03
Pressure / Pa
PTB
CMI_1_1
IMT
UME_I
UME_II
UME_III
CMI_1_2
VACOM
INRIM 422
INRIM Transpector
LNE I
CEM
LNE II
LNE I'
CMI_2_F1
CMI_2_F2
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013
0.25
cracking 14/18
0.20
0.15
0.10
0.05
0.00
1.0E-06
1.0E-05
1.0E-04
1.0E-03
Pressure / Pa
PTB
UME_I
CMI_1_2
INRIM Transpector
LNE II
CMI_2_F2
CMI_1_1
UME II
VACOM
LNE I
LNE I'
IMT
UME_III
INRIM 422
CEM
CMI_2_F1
Giornata di studio Metrologia del vuoto negli ambienti industriali - TORINO - 27 giugno 2013