Quality Control and Production Status of Large-area GEM Detectors for the CMS Muon Endcap Upgrade*

Gas Electron Multiplier (GEM) detectors will be installed in the high-eta region of the CMS muon system by the year 2020. GEM detectors were selected for their superior spatial resolution and high-rate capability because the particle rate will increase in the high-eta region of CMS after a second long shut-down of the LHC. The use of GEM detectors in the endcaps will improve the CMS muon triggering, identification, and track reconstruction. Seven sites across the globe are engaged in an international effort to construct 161 detectors (81 long and 80 short) and to perform rigorous quality control (QC) testing. We will discuss the detector assembly and the QC tests in detail. Some of the most important quality controls concern: current leakage across GEM foils, chamber gas leakage, gas gain measurements, high voltage stability, and response uniformity. We will also present a comparison of effective gains of the detectors produced at various sites. An overall production summary will conclude our discussion.