In this contribution, we will present the status of the readout electronics system for the triple-GEM detectors of the GE1/1 system, an upgrade which is planned for installation into the CMS experiment during the next LHC long shutdown (LS2) in 2019-2020. We will also report on the performance of the ten slice test detectors which have been present in the CMS muon endcap since the 2017 LHC run, which represent the first time that such large triple-GEM detectors have been operated within the LHC environment, and on the first results from the v3 slice test detectors that were added to the slice test in March 2018.

Ten slice test detectors were installed into the CMS muon endcap in January 2017. Data was recorded throughout the 2017-2018 run, using both cosmic ray muons and LHC collisions. Using the lessons learnt from this slice test allowed for the development of the final GE1/1 v3 electronics which will be used on the production chambers to be installed during LS2. These new detectors will be read out on the front-end by 24 VFAT3 chips, which runs at 320 MHz, four times higher than the frequency of the VFAT2 chip, as well as the v3 optohybrid (OH) board. The VFAT3 chips communicate with the OH through a 1m-long PCB, called the GEM electronics board (GEB), which has been re-designed to accommodate the faster VFAT3 digital signals. The on-detector electronics are powered via ten FEAST DC-DC converters. Optical communication to the back-end, which includes a microTCA crate containing CTP7 and AMC13 boards, is based on the CERN Versatile link, including GBT and SCA chips as well as VTRx and VTTx optical modules. Production and qualification of the v3 GE1/1 detectors is currently ongoing.