Studies on RPC detectors operated with environmentally friendly gas mixtures in LHC-like conditions

Abstract

Resistive Plate Chambers (RPC) are gaseous detectors employed at CERN LHC experiments thanks to their trigger performance, timing capabilities and contained production costs. High Pressure Laminate RPCs are operated with a three-component gas mixture, made of 90%–95% of C2H2F4, around 5% of i-C4H10 and 0.3% of SF6. Due to the presence of leaks at detector level and to the greenhouse characteristics of C2H2F4 and SF6, RPCs in ATLAS and CMS were accounting for about 87% of CO2 equivalent emissions during LHC Run 2. The addition of some amount of CO2 into the RPCs gas mixture was explored as a possible short-to-medium term solution to lower the total greenhouse gases emissions and reduce the usage of C2H2F4. A dedicated data taking campaign was performed at the Gamma Irradiation Facility at CERN, where RPCs detectors performance were studied with muon beam and gamma background. The detectors were operated with the addition of 30% and 40% of CO2 to the standard gas mixture, together with an increased fraction of SF6. In addition, the performance with two different amount of i-C4H10 were evaluated in order to assess the compatibility of the gas mixture with the CMS and ATLAS requirements. Results on the muon beam performance of RPCs operated with the aforementioned gas mixtures are reported in this work.