Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Xe-CO2 Stability

Chiho Wang

Duke University

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Setup

X-ray aperture limits active region ~ 6-7cm on straw.

0.002” Cu foil reduced X-ray intensity to ~0.1uA/cm

Only 1 pair of ASD sockets are active to draw current.

Scan along straw at 8cm intervals.

At each location, raise HV from 1550V to 1750V at 25V step, 20 sec interval.

Record current & # of Trips.

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09 ASD #1

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09 ASD #2

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #3

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #4

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #5

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #6

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #10

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #11

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #15

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #16

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #21

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #22

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #27

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #28

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #30

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #31

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #32

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD #33

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Observation

Most ASD HV trip at mid wire support location. Some ASD HV trip at end wire support. After several hours of “burning” at the wire

support, it gets more stable and less likely to trip ASD 28-33 were scanned many times with Ar-CO2 before

taking Xe data. They are obviously more stable. In the case of Ar-CO2, X-ray also triggers a self-sustained

current draw that lasts for several hours even after X-ray is turned off. This contributes to an increase of current draw when X-ray passes through mid wire support. This current, however, also dies out after burning.

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Module 2.09, ASD 30, Ar-CO2

Chiho Wang ATLAS TRT Duke University Hampton, May. 2002

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Summary

Xe-CO2 is stable at 1750V with 0.3uA/cm local rate Mid wire support tends to be unstable in the

beginning of the chamber operation, but can be improved with “burning”.

Some end wire supports also show the same instability but not as often as mid wire support.