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

Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 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

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

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

Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 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)

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

Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 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.

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

Chiho Wang ATLAS TRT Istanbul Workshop Duke University May, 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.