Electronics System of the CMS GE1/1 Muon Upgrade and Lessons Learned From the Slice Test During the 2017-2018 LHC Runs

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 being installed into the CMS experiment during the present LHC long shutdown (LS2) in 2019-2020. We will also report on the lessons learned from the ten slice test detectors which have been installed in CMS since 2017 and represent the first time that such large triple-GEM detectors have been operated within the LHC environment, and on the first results from the slice test detectors equipped with v3 electronics that were added to the slice test in March 2018. We will also report on the performance of the GE1/1 production chambers recorded on a large cosmic ray test bench sitting outside the CMS environment. Ten slice test detectors were installed into the CMS muon endcap in January 2017. Data was recorded throughout the 2017-2018 runs, using both cosmic ray muons and LHC collisions. Lessons learned from this slice test allowed the development of the final GE1/1 electronics (hereafter referred to as "v3") for the production GE1/1 chambers which are now being installed during LS2. These new detectors are read out on the front end by 24 VFAT3 chips, which run at 320 MHz, four times higher than the frequency of the VFAT2 chip, as well as the v3 optohybrid (OH) board, which is equipped with a Xilinx Virtex6 FPGA and three CERN GBT chipsets. The VFAT3 chips communicate with the OH through a 1 meter-long set of PCBs, 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 nine 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, qualification, and installation of the final v3 GE1/1 detectors is currently ongoing.