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Module Gas Leak Chiho Wang Duke University

Module Gas Leak Chiho Wang Duke University. 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:

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Module Gas Leak Chiho Wang Duke University

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  1. 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 Reference Volume

  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

  7. 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.

  8. Module leak measurements * measured at mechanical completion

  9. 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.

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