1. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 1 Module Gas Leak Chiho Wang Duke University

2. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 2 Gas leak requirements  Operating condition: u ionization gas at 1 atm with 70% Xe u purging gas at 1 atm with 100% CO2 u allow 10 volume / year of Xe loss  Measurement simulates Xe loss with: u Same gas (or different gases assuming both are ideal gas) in each gas volume u Slight over pressure of ionization gas volume u monitoring pressure change over time (indifference of composition change)  Present requirement at Duke/IU: < 0.1 mBar/Bar/minute

3. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 3 Module leak test setup

4. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 4 Module leak test setup

5. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 5 Leak Measurement  Measurement procedure: u pressurize/equalize module and reference tank pressure to ~ 20mB above room atm u isolate module from reference tank u monitor pressure change between reference tank and module over time  Leak rate is calculated = dP/P/T u dP = pressure difference Tank - Module (mBar) u P = module pressure vs room (Bar) u T = elapsed time (minute)

6. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 6 Module 2.07 mechanical ~42 hrs, Leak rate = -0.007 mB/B/min

7. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 7 Measurement Accuracy  Affecting factors: u 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 u 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.

8. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 8 Module leak measurements * measured at mechanical completion

9. Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 2001 9 Summary  Modules built are leak tight  Continue to improve leak measurement and understand the measurement error u Added barometer to obtain absolute module pressure u Try to understand temperature dependence of dP between module and tank u Try different method of leak rate calculation, e.g. using P/T = nR/V without using reference tank.