Speaker
Description
Cathode Strip Chambers (CSC) are used for precise measurements of muon track coordinates in the CMS endcap region. CMS CSCs operate with 40%Ar+50%CO2+10%CF4 as a working gas mixture, where the CF4 component provides reliable protection against anode wire aging sufficient for operation during the HL-LHC period. However, CF4 has a Global Warming Potential (GWP) of 6630 over 100 years, and is subject to the European Union F-gas regulation which aims reduction of the F-gas emission by two-thirds by 2030 compared with 2014 levels. So, either lowering the fraction of CF4 or excluding it entirely from the CSC gas mixture is well-motivated.
Measurements of the performance and longevity capability of various gas mixtures are primarily done with small CSC prototypes constructed of the original CSC materials strictly following the production technology. Dedicated material analysis of irradiated electrodes provides additional information on possible aging processes during the prototype irradiation. The role of CF4 in preventing anode wire aging is clearly seen and searches for its safe reduction or replacement in the CSC working gas mixture are ongoing.
