Speaker
Description
The Resistive Plate Chambers (RPC) are gaseous detectors with excellent timing performance and are used for triggering on muons in the LHC experiments. They operate with the standard gas mixture, composed of C2H2F4/i -C4H10/SF6, because it allows the detector operation in avalanche mode, as required by the high-luminosity collider experiments. The gas density, the low current and the comfortable avalanche-streamer separation guarantee high detection efficiency, rate capability and longevity. This gas mixture has a high Global Warming Potential (GWP) of 1430 due to the presence of C2H2F4 (GWP~1450) and SF6 (GWP~22400). As these gases are progressively being phased out for industrial applications, their future availability is expected to decrease. Consequently, the development of alternative eco-friendly gas mixtures has become a priority for all experiments at CERN. The LHC experiments are meanwhile adopting an intermediate solution in order to reduce the C2H2F4 emissions, that consists of the addition of 30%CO2(GWP~1) in the standard gas, allowing the reduction of GWP. In this work, the performance of the ATLAS RPC detectors foreseen for the High-Luminosity LHC (HL-LHC) phase, with 1 mm gas gap thickness, is presented, using gas mixtures that fully replace the high-GWP components. In particular, mixtures with GWP below 10, based on C₃H₂F₄ / CO₂ / i-C₄H₁₀ / C₃H₂ClF₃, are tested. The tests are performed at the Gamma Irradiation Facility at CERN in presence of a muon beam, under conditions that closely reproduce the high-rate gamma irradiation background foreseen in the HL-LHC environment.