Seminare de DPNC
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Mercredi, 22. jan. 1997

17.00 - Auditoire Stuckelberg

Universite de Geneve
Departement de physique
nucleaire et corpusculaire
24, quai Ernest-Ansermet
1211 Geneva 4

Tel. 022 702 6273
Fax. 022 781 2192

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Sujet:		Ageing and Gain Limits of Microstrip Gas Chambers at High Rates

Par:		Prof. A. Sharma, Universite de Haute Alsace and CERN 

Resume:

	MSGCs are one of the key detection elements for high luminosity
tracking at LHC in the CMS experiment at CERN. Long term ageing tests
performed on prototype open "banana" modules envisaged to be arranged
around the interaction region in the forward part of the tracker show no
evidence of gain drop up to equivalent ~ 10 years of LHC operation. A
comparison is made between argon and neon gas mixtures with DME in equal
proportions by investigating long term irradiation effects on chamber
operation by introducing controlled and reproducible pollution in the gas
lines. In addition to the high dose rate of 10 mC/year per cm of strip,
these detectors have to survive the hostile presence of highly ionizing
particles, neutrons low energy gammas and hadrons. The results of
systematic short and long term tests on maximum safe operational gain
limits in MSGCs before the discharge show that these devices are marginal
in operation.

	New ideas on the possible solutions for stable operation at high
rates will be discussed and in particular the development and application
of the Gas Electron Multiplier (GEM) structure will be discussed.