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Abstract

The Large Hadron Collider (LHC) is the world’s largest and most powerful proton-proton collider at the present moment. In the future, a new project, called High-Luminosity LHC (HL-LHC), will upgrade the LHC. This upgrade aims to increase the instantaneous luminosity by a factor of 5 to 7.5, leading to a higher probability of observing rare processes. In addition, after this upgrade, the next project, the Future Circular Collider (FCC), is already planned, which will provide p-p col- lisions at a center of mass energy of 100 TeV. The ATLAS muon spectrometer is currently upgraded for the upcoming operation at the HL-LHC. The Monitored Drift Tube (MDT) cham- bers in the barrel inner region will be replaced entirely by the small Monitored Drift Tube (sMDT) chambers for precise muon track recon- struction. Newly developed readout electronics will be installed on all MDT and sMDT chambers and used for signal processing instead of the current readout electronics. The new on-chamber readout electronic system contains new Amplifier-Shaper-Discriminator chips (ASD-6) and Time-to-Digital-Converter (TDC) chips that improve the spatial resolu- tion of the chambers in the presence of the challenging environment. It is known that the pile-up of background and muon hits deteri- orates the spatial resolution of a drift tube. The influence of signal pile-up on the performance of muon drift tube chambers was studied in this bachelor thesis. A pulse generator was connected to three ASD-6 chips and one TDC chip and produced different input signals that were then processed by the readout chips. The signals from the pulse gen- erator are a simulation of signals generated by sMDT drift tubes. One pulse from the input signal represents the signal from the background radiation, and the other represents the signal caused by muon hits. By varying each pulse’s amplitude and the temporal distance between the two pulses and implementing three different thresholds, it could be inves- tigated how strongly the pile-up effect deteriorates the time resolution and the pulse detection efficiency. Timewalk corrections were carried out and led to an improvement in time resolution. The new sMDT tubes with new readout chips were tested at the Gamma Irradiation Facility (GIF++) at CERN by exposing them to high radi- ation rates generated by the radioactive probe, 137Cs and muon beams. The spatial resolution for different γ-counting rates was determined. By applying the timewalk corrections, a better spatial resolution was deter- mined for every background rate.