Production and quality control of the new chambers with GEM technology in the CMS muon system

The CMS Collaboration has approved the installation of an additional set of muon detectors based on triple-GEM technology in the first endcap muon station known as GE1/1. The chambers are currently under construction and will be installed in 2019 during the second Long Shutdown (LS2) planned by LHC. About half of the required 144 chambers have been already built by different production sites in Europe, Asia and the United States. Systematic inspections and strict quality controls, scheduled for the GE1/1 chambers approval by the central site (CERN), were carried out successfully in Bari and Frascati (Italy). The results of the quality control procedures concerning the effective gain and the response uniformity of the delivered detectors will be shown together with the results on other relevant parameters like internal pressure drop and maximum spurious signal rate