Speaker
Stefan Koenig
(Uni Freiburg)
Description
The Monitored Drift Tube chambers (MDT) of the ATLAS muon system have
been constructed and partly installed in the ATLAS cavern at CERN with the
required mechanical precision and spatial resolution. The main challenge at
LHC will be the high dose of radiation. Therefore it is essential to avoid any
pollution, since it can cause severe ageing effects in a short period of time.
Despite the use of safe construction materials and care taken during
production, impurities of tiny amounts of silicone compounds remain a
serious concern due to the large number of commercial components in the
system. Detailed ageing studies carried out in Freiburg confirm this worry.
Therefore a gas filter based on a zeolite has been developed which removes
these pollutions effectively. The performance of the filters have been studied
with a calibrated silicone source which can inject silicone pollutions of
different levels into the drift tubes. The high absorption capacity of a single
filter ensures a reliable the operation of the ATLAS Muon spectrometer for
many years assuming typical pollutions as expected from greased O-rings or
gas valves. Measurements of temperature effects on the filter adsorption
show that no measurable distortions in the drift time spectra are expected
during ATLAS operation. These zeolite filter can be used for other gas
detectors in order to avoid chamber ageing at high radiation.
Author
Stefan Koenig
(Uni Freiburg)
