Studies of Read-Out Electronics and Trigger for Muon Drift Tube Detectors at High Luminosities

The Large Hadron Collider (LHC) at the European Centre for Particle Physics, CERN, collides protons with an unprecedentedly high centre-of-mass energy and luminosity. The collision products are recorded and analysed by four big experiments, one of which is the ATLAS detector. For precise measurements of the properties of the Higgs-Boson and searches for new phenomena beyond the Standard Model, the LHC luminosity of $L=10^{34}cm^{-2}s^{-1}$ is planned to be increased by a factor of ten leading to the High Luminosity LHC (HL-LHC). In order to cope with the higher background and data rates, the LHC experiments need to be upgraded. In this thesis, studies for the upgrade of the ATLAS Muon Spectrometer are presented with respect to the read-out electronics of the Monitored Drift Tube (MDT) and the small-diameter Muon Drift Tube (sMDT) chambers and the Level-1 muon trigger. Due to the reduced tube diameter of sMDT chambers, background occupancy and space charge effects are suppressed by an order of magnitude compared to the MDT chambers. The rate capability of the sMDT chambers is limited by signal pile-up effects of the MDT read-out electronics using bipolar signal shaping. In order to profit from the full potential of sMDT chambers, prototype read-out electronics with improved signal shaping and baseline restoration has been developed. Measurement and simulation of the sMDT drift-tubes with the new read-out electronics show that the high-rate performance of the sMDT chambers is substantially increased. At HL-LHC, muon trigger rates are expected to be about 10 times higher than at the LHC design luminosity. In order to fully exploit the physics potential of the HL-LHC, the selectivity of the ATLAS Muon Trigger system has to be improved. This is achieved by using the MDT chambers of the ATLAS Muon Spectrometer in the muon trigger to obtain the optimum achievable muon momentum resolution in the trigger. Simulations and measurements with a demonstrator of the MDT based trigger at the CERN Gamma Irradiation Facility demonstrate the feasibility of this concept.