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Archived Messages for CLAS_DRIFT_CHAMBERS_1997@cebaf.gov: drift chamber gas choice
drift chamber gas choice
MAC MESTAYER (MESTAYER@CEBAF.GOV)
Tue, 21 Jan 1997 14:15:45 -0500 (EST)
Hello Drifters;
An update on choice of gas for the chambers: Larry Weinstein, Liming Qin
and Gail Dodge report that they have been looking at cosmic ray/ noise
signals from their prototype chamber running on Ar/C02 (85/15? or 90/10?)
and they report that about 10% of the signals are accompanied by
``afterpulses" (my wording) delayed by 500 ns. This is probably evidence
of inadequate quenching and would seriously degrade our chambers' performance.
because 10% of the hits would have the wrong time (delayed by 500 ns).
This is presumably why other experiments have used 1% methane as a quenching
additive. The open question is this: would about 1% isopropanol vapor
work as well in quenching as well as providing aging protection?
regards, Mac