development of micro-pattern gaseous detectors – gem - LMU

2
Figure 2: Schematics of the whole ATLAS detector [ATLA 10].
field of 2 T. The hadronic (“Tile Calorimeter”) and electromagnetic (“Liquid Argon”) calorimeters
are responsible for measuring the energy deposited by the corresponding particle in the material.
In the outer region the muon chambers surround the detector in three layers. Only muons reach
this area as all other particle are supposed to be absorbed in the inner layers. The muon system
consists of cathode strip chambers (CSC) and Ar/CO2 filled drift tube chambers placed in a toroidal
magnetic field of 0.4 T for measuring the momentum of the traversing charged muons by their radius
of curvature. Resistive plate chambers and thin gap chambers provide the trigger.
Figure 3: Expected background rates in Hz
cm2
at five times LHC luminosity [Loeb 10].
Additionally to the primary collision products from the proton-proton collision, background radiation
is produced, mostly by interactions in the collimator. For the planned luminosity upgrade to
5 · 10 34 cm −2 s −1 for SuperLHC the proportionally increased background rate will decrease the performance
of specific detector regions.
Fig. 3 shows the expected background rate in the muon spectrometer. Mostly affected are the CSC
and the muon chambers sitting close by. Estimated background rates in the detector reach here values
of 8500Hz/cm 2 . Due to their intrinsic insensitivity to space charge effects, large area GEM detectors
are considered as replacement candidates.
To study the influence of high radiation background on ATLAS MDT chambers our working group