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

Abstract

A: 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 C 2 H 2 F 4 , which is a greenhouse gas with a high environmental impact in the atmosphere. C 2 H 2 F 4 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 C 2 H 2 F 4 due to their similar chemical structures. This study is focused on the characterization of innovative gas mixtures with tetrafluoropropene HFO1234ze(E) (C 3 H 2 F 4 ) 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 CO 2 are extensively discussed in this paper as well as the role of i-C 4 H 10 and SF 6 in such mixtures.

Qualification of Eco-Friendly Gas Mixture for Avalanche Mode Operation of RPC

“…In section 5.2, the same observables have been calculated for the proposed gas mixture to study its efficacy for its application in the RPCs of INO-ICAL. These results have been compared to the performance of other potential eco-friendly mixtures [3,7] as well to envisage the figures of merit of the present gas mixture.…”

“…The gas mixtures compared with are given in the following table 1. In figure 8a [7]. Figure 8a, and 8b shows the comparison between experimental data with the simulated result for 5 mV and 1 mV threshold respectively.…”

“…It can be seen that the proposed mixture is a potential candidate as an eco-friendly solution for operating the RPCs in INO-ICAL adopting either of the two options. Finally, the proposed mixture has been compared for its performance with other potential eco-friendly mixtures proposed earlier by others [3,7] in figure 8. The gas mixtures compared with are given in the following table 1.…”

“…The problem has already been addressed with extensive studies on various gases and their properties in order to find suitable substitutes for operating RPCs in various high energy physics experiments [3][4][5][6][7][8][9]. According to these studies, one allotropic form of tetrafluoropropene, C 3 H 2 F 4 (commercially known as HFO1234ze) which is close to R134a in chemical structure, with very low GWP (∼ 6), can be regarded as a potential replacement.…”

“…A few promising mixtures based on HFO1234ze, i-C 4 H 10 and He or CO 2 could be identified with low GWP (< 150) [3,7] for efficient operation of RPC though the high voltage requirement of some of them [7] might not be compatible to ICAL High-Voltage supply system [10]. Moreover, these mixtures have shown presence of substantially large fraction of streamers [3,7] at higher efficiency which is well above the tolerable limit for safe and long-term operation. As a result, inclusion of small amount of SF 6 (∼ 1%) in the mixtures could not be ruled out for effective operation of the detectors which has led the effective GWP sometimes cross the limit of 150 [3,6,8,9].…”