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Gas Flow Rate Measurements with Dual Inlets and Outlets at Acute Corners

This study by Chiho Wang from Duke University explores gas flow measurements using dual inlets and outlets at acute corners. The method monitors gas gain at fixed locations along straws to determine flow speed and gas composition changes. Previous and recent measurements reveal variations in flow rate and diffusion effects, suggesting ionization gas flow rate uniformity. The study indicates flow rate variations within straws and higher-than-expected flow speeds due to diffusion effects.

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Gas Flow Rate Measurements with Dual Inlets and Outlets at Acute Corners

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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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