Results from the Compact Muon Solenoid GE1/1 Slice Test and Status of the Installation and Commissioning of the GE1/1 Detectors

The GE1/1 system is the newest subdetector to be added to the CMS (Compact Muon Solenoid) endcap muon system. It consists of a series of 144 triple-GEM (gas electron multiplier) detectors, installed as 36 two-detector superchambers in each endcap. Due to the existing mechanical restrictions of CMS, these are further broken down into 18 short (1.61 <; |η|<; 2.18) and 18 long (1.55 <; |η|<; 2.18) superchambers in each endcap. These detectors are placed in front of the already-existing CSCs (cathode strip chambers) and will interface with them, allowing for added redundancy in a difficult region, better tracking in a high rate environment, and measurement of the bending angle at the trigger level to decrease the number of mismeasured muons. During the 2017-2018 run, ten slice test detectors were installed in order to serve as a proof of concept and to act as a trial run for the full system. Data was recorded during these runs using both cosmic ray muons and LHC collisions. During this time, a loss of VFAT2 channels was observed, with two detectors exhibiting rapidly-increasing channel loss beginning mid-2018. Investigations as to the cause of this loss were launched, and the lessons learned from these investigations allowed for the improvement of the design of the VFAT3 readout chip in time for the production and installation of the final GE1/1 detectors. In this contribution, we will present the status of the production, installation, and commissioning of the GE1/1 detectors and on the lessons learned throughout the process.