Searching for alternative gases in RPC detectors: performance studies of eco-friendly gas mixture

Abstract Resistive Plate Chamber (RPC) detectors used in CERN's LHC experiments traditionally operate with a gas mixture containing C 2 H 2 F 4 (R134a) and SF 6 , both of which are greenhouse gases with high Global Warming Potential (GWP). In Europe, the production of these fluorinated gases is being phased out, making the identification of environmentally friendly alternatives increasingly urgent. This study evaluates the performance of RPC detectors when R134a or SF 6 are replaced with candidate gases featuring a lower GWP. Detector tests are first conducted in a controlled laboratory environment using cosmic muons, followed by beam tests at the CERN Gamma Irradiation Facility. There, a muon beam is combined with background irradiation from a 12TBq 137Cs source to emulate LHC-like conditions. Key detector parameters under investigation include efficiency, dark current, streamer probability, mean prompt charge, cluster size, and time resolution. The results aim to provide an initial selection of promising eco-friendly gas mixtures, paving the way for future long-term ageing tests to assess their durability and operational stability. This work presents the results obtained with these alternative gas mixtures.