Abstract:
Gas Electron Multiplier (GEM) based chambers are used in the most forward
and inner most layers of the Compact Muon Solenoid (CMS) detector to
enhance the trigger performance during the High Luminosity phase of the
Large Hadron Collider (HL-LHC). This phase of the experiment will be used
to collect data for the physics program beyond the discovery of the Higgs
Boson. The new GEM system has been designed to improve the triggering and
tracking capability of CMS in this particularly harsh region during HL-LHC.
To reach those objectives, each detector must be operated at acceptable
electronics thresholds to ensure high detection efficiency of minimum ionizing
particles (MIPs) (> 97%), while limiting the noise to maintain the Level-1
muon trigger rate at acceptable levels. This work aimed to study the noise at
different stages of the final assembly of the chambers and to come up with a
proper grounding scheme to keep the noise rates at a minimum level. The noise
rates were measured against the threshold in each of the readout sectors using
an Application Specific Integrated Circuit (ASIC). The measurement was
repeated after the introduction of additional components, or whenever a
variation was done on the grounding scheme with the intention of bringing
down the already observed noise levels. The developed methods and
techniques through this study, allowed the chambers with the final grounding
scheme to be operated at thresholds of a maximum of 8𝑓𝐶, which is favorable
for data collection at CMS.
