Performance studies of RPC detectors with new environmentally friendly gas mixtures in presence of LHC-like radiation background

RPC detectors are widely used at the CERN LHC experiments as muon trigger thanks to their excellent time resolution. They are operated with a Freon-based gas mixture containing C2H2F4 as well as some amount of SF6. Both C2H2F4 and SF6 are greenhouse gases with a very high global warming potential. The search of new environmentally friendly gas mixtures is necessary to reduce greenhouse gas emissions and costs as well as to optimize the RPC performance. Several recently available gases with low global warming potential have been identified as possible replacements for C2H2F4 and SF6. More than 60 environmentally friendly gas mixtures have been investigated on 2 mm single-gap RPCs. The RPC detectors have been tested in laboratory conditions and at the CERN Gamma Irradiation Facility, which provides a high energy muon beam combined with an intense gamma source allowing to simulate the background expected at HL-LHC. The performance of RPCs were studied at different gamma rates with the new environmentally friendly gases by measuring efficiency, streamer probability, rate capability, induced charge, cluster size and time resolution. To finalize the studies, the RPCs are now operated under gas recirculation with the selected new gas mixture and exposed to the intense gamma radiation of GIF++ for evaluating possible long-term aging effects, gas damage due to radiation and compatibility of LHC gas system with new gases.