Studies of RPC detector operation with eco-friendly gas mixtures under irradiation at the CERN Gamma Irradiation Facility

Abstract

Since 2019 a collaboration between researchers from various institutes and experiments (i.e. ATLAS, CMS, ALICE, LHCb/SHiP and the CERN EP-DT group), has been operating several RPCs with diverse electronics, gas gap thicknesses and detector layouts at the CERN Gamma Irradiation Facility (GIF++). The studies aim at assessing the performance of RPCs when filled with new eco-friendly gas mixtures in avalanche mode and in view of evaluating possible ageing effects after long high background irradiation periods, e.g. High-Luminosity LHC phase. This challenging research is also part of a task of the European AidaInnova project. A promising eco-friendly gas identified for RPC operation is the tetrafluoruropropene (C3H2F4, commercially known as HFO-1234ze) that has been studied at the CERN GIF++ in combination with different percentages of CO2. Between the end of 2021 and 2022 several beam tests have been carried out to establish the performance of RPCs operated with such mixtures before starting the irradiation campaign for the ageing study. Results of these tests for different RPCs layouts and different gas mixtures, under increasing background rates are presented here, together with the preliminary outcome of the detector ageing tests.

Environment-friendly gas mixtures for Resistive Plate Chambers: an experimental and simulation study

“…On the contrary, the electron avalanche growth can occur at ∼290 Td in pure C 3 H 2 F 4 . When C 3 H 2 F 4 is diluted with CO 2 , the growth of electron avalanches occurs at lower values of the electric field, as reported by experimental studies [11][12][13][14]18]. This observation is also supported by MATOQ simulations.…”

“…Although there are no European regulations restricting the use of C 2 H 2 F 4 for scientific applications, some research teams [8][9][10][11] have explored the possibility of replacing C 2 H 2 F 4 with more environmentally friendly gases. Many experimental studies are currently focused on measuring the performance of RPCs by replacing the current C 2 H 2 F 4based gas mixture with environmental-friendly alternatives [11][12][13][14]. Recently, some encouraging results have been obtained by replacing the C 2 H 2 F 4 with tetrafluoropropene.…”

“…This would result in too high operating voltages for RPCs that are not compatible with the already existing power supply systems. Instead of replacing C 2 H 2 F 4 with only C 3 H 2 F 4 , binary mixtures of C 3 H 2 F 4 and CO 2 may be a feasible alternative [11][12][13][14]. However, purely experimental studies require a large number of trials to identify gas mixtures that yield satisfactory performance of RPCs.…”

Eco-friendly gas mixtures for future RPC detectors

“…Performance and aging tests are continuously performed on several gas mixtures at the CERN Gamma Irradiation Facility (GIF++) [2] under strong photon irradiation and in presence of a muon beam (100 GeV/c). Currently, the collaboration is testing the performance of RPCs operating with the following three gas mixtures: ECO1: CO The first mixture under study was ECO1, which showed a significant increase of the detector currents after few months of operation under irradiation [3]. Therefore, the collaboration adopted a new strategy testing gas mixtures with lower HFO content [4].…”

Longevity studies for the CMS Muon System towards HL-LHC

“…3b) at the expected HL-LHC rates. Very challenging are instead the ecogas studies, handled by a joint collaboration between CMS and other CERN experiments [6]. Three potential mixtures, combining different amount of CO 2 , HFO, iso-C 4 H 10 , and SF 6 , are under study: 50/45/4/1, 60/35/4/1, and 69/25/5/1.…”