Installation of first full set of GEM chambers within the CMS muon system at the CERN LHC


The Physics Institute IIIA at RWTH-Aachen University is proud to announce the completion of the installation of the first full set of Gas Electron Multiplier (GEM) chambers within the CMS muon system at the CERN LHC. This represents an important milestone for the CMS collaboration, for which the GEM group here in Physics Institute IIIA played a significant role.

  positive and negative endcaps © Brendan Regnery

This installation is the first LHC Phase-II detector upgrade that utilizes a new detector technology and it includes one full circular station of GEM chambers (GE1/1) in each endcap of CMS. GEMs are a relatively new technology in high energy physics experiments, of which the CMS variant represents the largest size, as well as highest number of detectors used to date. GEMs have been shown to operate resiliently in harsh radiation environments, necessary to cope with the increasing energy and luminosity of the LHC in the upcoming data taking periods. These detectors also provide precise tracking information and excellent time resolution. They will improve the muon momentum resolution measurement by exploiting the bending angle of muons passing through the system, and will keep the endcap muon trigger rate under control.

Prior to installation, the GE1/1 chambers were produced by the collaboration member universities situated in seven different countries spread around the world. These detectors then underwent eight stages of quality control (QC) tests, three of which were also performed here in the IIIA GEM lab. After all of the chambers passed the rigorous QC stages, they were finalized at CERN and then installed in the CMS detector. The next chapter in the GEM story is commissioning within the experiment to confirm and maximize their performance, in symphony with the rest of CMS.

  negative endcap © Giovanni Mocellin