Studies on tetrafluoropropene-based gas mixtures with low environmental impact for Resistive Plate Chambers

Gaseous detectors are widely used in high-energy physics experiments, and in particular at the CERN Large Hadron Collider (LHC), to provide tracking and triggering over large volumes. It has been recently estimated that Resistive Plate Chambers (RPC), used for muon detection, have the highest contribution on the overall greenhouse gas (GHG) emissions at the LHC experiments. Gas mixtures for RPCs are mainly made of C2H2F4, which is a greenhouse gas with a high environmental impact in the atmosphere. C2H2F4 is already phasing out of production, due to recent European Union (EU) regulations, and its cost is expected to increase in the near future. Therefore, finding alternative gas mixtures made of gas components with a low Global Warming Potential (GWP) has become extremely important for limiting the GHG emissions as well as for economic reasons. The novel hydrofluoroolefins are likely appropriate candidates to replace C2H2F4 due to their similar chemical structures. This study is focused on the characterization of innovative gas mixtures with tetrafluoropropene HFO1234ze(E) (C3H2F4) that is one of the most eco-friendly hydrofluoroolefins, thanks to its very low GWP. HFO1234ze(E)-based gas mixtures with the addition of Ar, N-2, O-2 and CO2 are extensively discussed in this paper as well as the role of i-C4H10 and SF6 in such mixtures.