1. Chiho Wang ATLAS TRT Duke University CERN, Feb. 2002 1 Gas-Flow Measurements Chiho Wang Duke University

2. Chiho Wang ATLAS TRT Duke University CERN, Feb. 2002 2 Gas-flow Measurement  Method u Monitor gas gain at 2 fixed locations (  X) along the straws. u Change gas composition (gas gain), and measure the time (  T) it takes for the change to propagate from one location to the other. u Flow speed =  X/  T

3. Chiho Wang ATLAS TRT Duke University CERN, Feb. 2002 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. Chiho Wang ATLAS TRT Duke University CERN, Feb. 2002 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 u 70%-30% at T = -0 u 73%-27% at T ~ 150 sec u 70%-30% at T ~ 500 sec

5. Chiho Wang ATLAS TRT Duke University CERN, Feb. 2002 5 Module 2.11 measurements Gas Inlet  ~ 9%

6. Chiho Wang ATLAS TRT Duke University CERN, Feb. 2002 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. Chiho Wang ATLAS TRT Duke University CERN, Feb. 2002 7 Module 2.11 Measurements  Average flow speed measurement u Measured > expected u Lower flow rate shows higher discrepancy u Diffusion enhancement?

8. Chiho Wang ATLAS TRT Duke University CERN, Feb. 2002 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.