Characterization of RPC detectors with LHC-like background radiation and new eco-friendly gas mixtures

Abstract

Resistive Plate Chamber (RPC) detectors are widely used at the CERN LHC experiments as muon trigger thanks to their excellent time resolution. They are operated with a gas mixture containing C2H2F4 and SF6, both greenhouse gases with a very high global warming potential. The search of new environmentally friendly gas mixtures is advised to reduce GHG emissions and costs as well as to optimize RPC performance. Several recently available gases with low GWP have been identified as possible replacements for C2H2F4 and SF6. In particular, HFO-1234ze has been studied as a possible replacement for C2H2F4 and several gases like Novec fluoroketones, C4F8O and CF3I were tested as a replacements of both C2H2F4 and SF6. The RPC detectors have been tested in laboratory conditions and few selected mixtures were tested 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 was studied at different gamma rates in a presence of muon beam by measuring efficiency, streamer probability, rate capability, induced charge and cluster size. The studies are being carried on by operating RPCs under gas recirculation with the selected 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.