CMS GEM GE2/1 demonstrator chamber installation

The Gas Electron Multiplier (GEM) is one of the novel gaseous detectors that will be installed in the forward regions of the CMS muon endcaps and capable of handling high particle collision rates. There will be 2 stations of the GEM system, 1 and 2. The first one, GEM station (GE1/1) has already been completely installed during LS2. Of the second GEM station (GE2/1) only 2 chambers have been installed, but not the full station. Here, at the end of LS2, a few GEM (GE2/1) demonstrators, a kind of prototype chamber, have been installed in the forward region of the CMS experiment in order to be tested under real conditions in the CMS detector during Run 3. Meanwhile, the rest of the GE2/1 subsystem will be assembled and validated. The full second GEM station, GE2/1, will be installed for Run 4.