GEM

A Gas Electron Multiplier is a type of gaseous ionization detector used in nuclear and particle physics and radiation detection. GEM detectors represent a muon system in CMS. CMS GEM detectors are made of three layers, each of which is a 50 micron thick copper-cladded polyimide foil. The ESA section performed the fiducialisation of the 216 GEM chambers of CMS and is in charge of their position measurement after installation in the experiment in the cavern.

Gas Electron Multiplier