Study on discharge and short circuit generation in CMS GE1/1 triple-GEM detectors during Run 3

The installation of the new GE1/1 station of Gas Electron Multiplier (GEM) detectors in the Compact Muon Solenoid (CMS) experiment was completed during the Long Shutdown 2 (LS2) phase of the Large Hadron Collider (LHC). The GE1/1 station has been operational in the CMS detector since the beginning of the Run-3 data-taking phase, and for the first time the GEM technology was deployed on a large scale, comprised of 144 chambers and tested in running conditions as integral part of the CMS data acquisition, reconstruction, and analysis chain. The deployment of the GEM detector required careful planning throughout the years, posing several challenges of practical and conceptual nature in integrating an entirely new subsystem in the existing CMS frame. Operations on the other hand provided a unique opportunity to test the GEM technology in never-before seen conditions, and an occasion to study their behavior during data taking. In describing some of the solutions to the posed challenges and the findings during the data-taking, the article will focus on the aspects related to power system management, including high-voltage and current monitoring, which is intrinsically related to the response of the chamber due to the workings of the GEM foil charge flow. To this end, this article will illustrate the operations of GE1/1 detectors in the first two years of Run-3, with a particular focus on the analysis of discharge occurrences, on the generation of short circuits in GE1/1 GEM foils and on the adopted mitigation strategies. The applied layout of the GEM detectors is thoroughly described, and detailed operating conditions of the detectors are discussed, along with the actions taken to mitigate these events.