Longevity studies and searches for eco-friendly gas mixture for CMS Cathode Strip Chambers

Cathode Strip Chambers (CSC) provide precise measurements of muon track coordinates in the CMS endcap region. CSC uses 40%Ar+50%CO₂+10%CF₄ as a working gas mixture, where CF₄ provides reliable protection against anode wire aging sufficient for CSC operation during the HL-LHC era. However, CF₄ has a Global Warming Potential (GWP) of 6630 over 100 years, so the CMS CSC community is searching for a way of either lowering the fraction of CF₄ in or excluding it entirely from the CSC gas mixture.

Measurements of the performance and longevity capability of various gas mixtures are primarily done with small CSC prototypes constructed with the original CSC materials strictly following the production technology. Long-term irradiation tests are ongoing at the Gamma Irradiation Facility at CERN with large original CSC chambers.