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Gas-Flow Measurements Chiho Wang Duke University

Gas-Flow Measurements Chiho Wang Duke University. Gas-flow Measurement. Method Monitor gas gain at 2 fixed locations ( X) along the straws. Change gas composition (gas gain), and measure the time (  T) it takes for the change to propagate from one location to the other.

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Gas-Flow Measurements Chiho Wang Duke University

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  1. Gas-Flow Measurements Chiho Wang Duke University

  2. Gas-flow Measurement • Method • Monitor gas gain at 2 fixed locations (X) along the straws. • Change gas composition (gas gain), and measure the time (T) it takes for the change to propagate from one location to the other. • Flow speed = X/ T

  3. Previous Measurements • Module 1.-1 in 1998 (see X-ray paper from Duke) • Flow variation ~<30% with single gas inlet & single gas outlet

  4. Module 2.11 Measurements • Use 2 gas inlets at acute corners. • Use 2 gas outlets at acute corners. • X = 20cm (~10, 30 cm from end of module) • Gain measured every100 sec @each location • Gas composition: Ar-CO2, 140 cc/min • 70%-30% at T = -0 • 73%-27% at T ~ 150 sec • 70%-30% at T ~ 500 sec

  5. Module 2.11 measurements Gas Inlet Gas Inlet  ~ 9%

  6. Module 2.11 Measurements • Sample ~160 straw for higher & lower flow rate. 180cc/min 110cc/min • Peak is broader with lower flow rate

  7. Module 2.11 Measurements • Average flow speed measurement • Measured > expected • Lower flow rate shows higher discrepancy • Diffusion enhancement?

  8. Summary • Ionization gas flow rate uniformity was measured with module 2.11 with 2 gas inlets and 2 gas outlets located at the same corners (worse scenario). • Gas flow rate variation among straws are within ~20% at the standard 1 volume exchange / hour rate • The flow speed measured is higher than expected, possibly due to diffusion effect.

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