Upgrades of the ATLAS Muon Spectrometer Front-end Electronics for the High-Luminosity LHC

Abstract

The Large Hadron Collider (LHC) is the world’s largest and most powerful particle accelerator. The High-Luminosity LHC (HL-LHC) is an upgraded version of the LHC that will further increase the instantaneous luminosity by a factor of 5-7.5 and the integrated luminosity by a factor of 10. The ATLAS detector is one of the two general-purpose detectors at the LHC. It offers unique opportunities to study properties of fundamental particles and explore physics beyond the Standard Model. The current detector needs to be upgraded to maintain or improve its performance to profit from the HL-LHC operation. Two major upgrades, the Phase-I upgrade and the Phase-II upgrade, have been planned and they are both 10-year-long projects.

The integration and commissioning of the Phase-I upgrade happened during the period between 2019 and 2021. The innermost endcap station of the ATLAS Muon Spectrometer was replaced by a New Small Wheel (NSW) detector to reduce fake muon triggers and to improve offline muon track measurements for future HL-LHC runs. The small-strip Thin Gap Chamber (sTGC) is the primary trigger detector for the NSW. It utilizes the sTGC pad detector to form a coarse region of interest (ROI) and read out the charge information from the sTGC strip detector underneath the ROI. The charge information is further used to generate trigger primitives for the first-level trigger. This dissertation presents the design of a mobile data acquisition system and its application to the sTGC trigger chain integration and commissioning. This dissertation also presents cosmic ray studies with an sTGC chamber, which provides first insights into the performance of the sTGC detector in the trigger chain with final front-end electronics. For the first time, the sTGC strip charges from the detector were read out through the trigger chain data path.

The integration and commissioning of the Phase-II upgrade will happen during the period between 2025 and 2027. The primary muon tracking detector, Monitored Drift Tube (MDT), will also be used as a trigger device at the first trigger level to improve the trigger muon momentum resolution. The present MDT electronic system can not offer enough bandwidth for the increased event rate (by about an order of magnitude) at the HL-LHC. As a result, all MDT front-end and back-end electronics need to be replaced. This dissertation presents the development of a Time-to-Digital Converter (TDC) Application-Specific Integrated Circuit (ASIC) for the new MDT front-end electronics. The TDC provides digitization of the rising and falling edges of the earliest arrival signal, which is the basis for all subsequent trigger and readout processing. Detailed performance studies have been performed on the produced prototype chips.