Studies of RPC detector operation with eco-friendly gas mixtures under irradiation at the CERN Gamma Irradiation Facility

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 Freon-based gas mixture containing $C_2 H_2 F_4$ and $SF_6$, both greenhouse gases (GHG) with a very high global warming potential (GWP). The search of new environmentally friendly gas mixtures is necessary 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 $C_2 H_2 F_4$ and $SF_6$. In particular, eco-friendly gas mixtures based on the HFO-1234ze have been investigated on 1.4 and 2 mm single-gap and double-gap RPCs. The RPC detectors have been tested at the CERN Gamma Irradiation Facility (GIF++), 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 ohmic and physics currents, fluorine radicals and HF production, rate capability and induced charge. Preliminary results on the long-term effects on the performance of the detectors are presented in this study.