Module Gas Leak
Chiho Wang
Duke University
1
Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001
Gas leak requirements
 Operating condition:
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ionization gas at 1 atm with 70% Xe
purging gas at 1 atm with 100% CO2
allow 10 volume / year of Xe loss
 Measurement simulates Xe loss with:
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Same gas (or different gases assuming both
are ideal gas) in each gas volume
Slight over pressure of ionization gas
volume
monitoring pressure change over time
(indifference of composition change)
 Present requirement at Duke/IU:
< 0.1 mBar/Bar/minute
2
Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001
Module leak test setup
3
Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001
Module leak test setup
4
Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001
Leak Measurement
 Measurement procedure:
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pressurize/equalize module and
reference tank pressure to ~ 20mB
above room atm
isolate module from reference tank
monitor pressure change between
reference tank and module over time
 Leak rate is calculated = dP/P/T
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dP = pressure difference
Tank - Module (mBar)
P = module pressure vs room (Bar)
T = elapsed time (minute)
5
Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001
Module 2.07 mechanical
~42 hrs, Leak rate = -0.007 mB/B/min
6
Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001
Measurement Accuracy
 Affecting factors:
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
Temperature may swing 2ºC during
measurement.
 The measurement assumes module and
reference tank responds to temperature
change equally.
 Suppose there’s a 10% mismatch in their
responses, the error in dP measurement
would be
~ 10% * 2/300*1013 ~ 0.68 mB
 To wash out temperature effect with time to
0.05mB/B/min would be:
0.05 = 0.68(mB) / 0.02(Bar) / T (minute)
T ~ 675 minutes = 11.3 hours
Room pressure may swing 10s of mBar and
affect module P used in calculating leak rate
 This, however, can be corrected by taking
average P or integrating P over time.
7
Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001
Module leak measurements
Module Leak Rate module stage
2.01
-0.017 done*
2.02
-0.015 done*
2.03
-0.080 done
2.04
0.080 done
2.05
-0.004 done
2.06
0.024 mechanical
2.07
-0.007 mechanical
* measured at mechanical completion
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Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001
Summary
 Modules built are leak tight
 Continue to improve leak
measurement and understand the
measurement error
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Added barometer to obtain absolute
module pressure
Try to understand temperature
dependence of dP between module
and tank
Try different method of leak rate
calculation, e.g. using P/T = nR/V
without using reference tank.
9
Chiho Wang
Duke University
ATLAS TRT Istanbul Workshop
May, 2001