Study of discharges in the CMS GEM GE1/1 station with LHC beam

Abstract

Abstract The Large Hadron Collider (LHC) and the experiments installed there are being upgraded for the High Luminosity LHC project that will provide a greatly enlarged data sample in the search for physics beyond the Standard Model. During Long Shutdown 2, from 2018 to the first months of 2022, some of these upgrades were completed. In particular, the muon spectrometer of the CMS experiment was upgraded with installation of the GE1/1 detector station, based on Gas Electron Multiplier (GEM) technology. This station is positioned in the endcap region of the CMS muon system and covers the pseudorapidity range 1.55 < |η| < 2.18. On the 5th of July, 2022, Run 3 of the LHC began with collision energy of 13.6 TeV. The newly installed GEM detectors experienced high-voltage discharges when the beams were colliding inside CMS. To monitor these events and to understand how to safely operate the detectors, a study of these phenomena became necessary. The intensity of discharge current and the discharge rate were recorded in different detectors as a function of luminosity and time. It was observed that some chambers have a significantly higher discharge rate than the modal value of rate over the entire chamber population. The reasons responsible for this behavior are currently under investigation. In this contribution, an analysis of discharges will be presented, illustrating the dependence of discharge rate on different LHC beam configurations and the high voltage working point of the chambers.