Testing of GE2/1 & ME0 GEM detectors for CMS Phase-2 Muon System Upgrade*

The instantaneous luminosity of the Large Hadron Collider will be increased by half an order of magnitude as part of the High Luminosity upgrade. The endcap muon system of the Compact Muon Solenoid experiment (CMS) is being upgraded with new stations (called GE2/1 and ME0) of triple-gas electron multiplier (GEM) detectors to keep up with the expected higher Level-1 muon trigger rates. For prototypes of both subsystems, we will discuss the high and low voltage implementation, readout performance, and the optimization of grounding connections. The high and low voltages are supplied by a CAEN SY5527 power supply with logging software to monitor the voltages and currents over time to check for current leaks or sparks. The high light output of QSFP modules in the backend was identified as the root cause of a dropped data problem between the backend and the frontend, and long-term Forward Error Correction (FEC) tests proved this was indeed the issue. Several tests of the grounding configurations on ME0 with and without a detector cover gave 0.61 fC ENC and 0.36 fC ENC noise levels, respectively.