Study of environment-friendly gas mixtures for Resistive Plate Chambers in view of future applications

The purpose of this thesis is the search of an environment-friendly gas mixture for the Resistive Plate Chambers (RPC) for present and future applications. The standard gas mixture, composed of C2H2F4/i-C4H10/SF6, is currently used in the RPCs at the Large Hadron Collider (LHC) experiments because it ensures good rate capability and long-term operation in a high-radiation background environment. This gas mixture has a high Global Warming Potential(GWP) ∼ 1430 due to the pres- ence of C2H2F4 and SF6. European Union regulations have imposed a progressive phase down in the production and use of the F-gases in industry, thus reducing their avail-ability and increasing their price. For this reason, the search for an environment-friendly gas mixture that can maintain the excellent performance of the standard one is crucial for the usage of RPCs in present and future experiments. In this thesis alternative gases to both C2H2F4 and SF6 have been studied, with an ATLAS RPC already in operation during Run-2 and with a new RPC (thinner gas gap) foreseen the High-Luminosity phase of the LHC. The C2H2F4 has been substituted with a proper mixture of CO2 (GWP = 1) and Tetrafluoropropene (C3H2F4, GWP∼6), while the Chloro-Trifluoropropene (C3H2ClF3, GWP ∼ 5), never tested before in the RPC detectors, has been chosen to substitute the SF6. The tests have been performed both using cosmic rays and under strong photon irradiation. This thesis also include an analysis work concerning the measurement of muon isolation efficiency and scale factors in a busy environment using tt events, , to give a complementary approach to extract these quantities to the one currently used in the analysis.