chiho wang atlas trt istanbul workshop duke university may, 2001 1 module gas leak chiho wang duke...

Chiho Wang ATLAS TRT Istanbul WorkshopDuke University May, 2001

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Module Gas Leak

Chiho Wang

Duke University



2

Gas leak requirements

Operating condition: 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: 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



3

Module leak test setup



4

Module leak test setup



5

Leak Measurement

Measurement procedure: 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 dP = pressure difference

Tank - Module (mBar) P = module pressure vs room (Bar) T = elapsed time (minute)



6

Module 2.07 mechanical

~42 hrs, Leak rate = -0.007 mB/B/min



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Measurement Accuracy

Affecting factors: 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.



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Module leak measurements

* measured at mechanical completion

Module Leak Rate module stage2.01 -0.017 done*2.02 -0.015 done*2.03 -0.080 done2.04 0.080 done2.05 -0.004 done2.06 0.024 mechanical2.07 -0.007 mechanical



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Summary

Modules built are leak tight Continue to improve leak

measurement and understand the measurement error 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.

chiho wang atlas trt istanbul workshop duke university may, 2001 1 module gas leak chiho wang duke...

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