Numerical studies on streamer probability in resistive plate chambers for eco-friendly gases

F-gas regulations foresee restrictions and bans of highly potent greenhouse gases such as R134a (C 2 H 2 F 4 ) and SF 6 used in RPCs. Current research is dedicated to finding an environmentally friendly gas mixture replacement for RPCs. Simulations of RPCs are crucial in supporting and extending the mostly experimental-based research of identifying suitable eco-friendly alternatives. To date, there is no comprehensive quantitative description of the avalanche-to-streamer transition in uniform electric fields. Particularly in the context of RPCs, this is essential for estimating the streamer probability of a particular mixture to predict the avalanche-streamer separation accurately. An improved form of the classical streamer inception criterion is introduced, predicting the transition phase to overcome this problem. The criterion is entirely based on the space-charge field of the many superimposed avalanches due to primary ionization. A rigorous simulation of the single-gap high-pressure laminated RPC (HPL-RPC) is developed to integrate and test the improved streamer criterion along with the capability to estimate other performance parameters, such as the detector’s efficiency. The simulation is based on Garfield++ and is extended for this study to include the axis-symmetric space-charge model originally developed by Christian Lippmann. A dedicated electrical signal transmission system is also modeled to replicate the experimental setup accurately. Validation of the simulation is achieved through comparison with acquired performance data of the experimental HPL-RPC setup at the GIF++ muon beam experiment for several eco-friendly gas mixtures. This contribution presents the detailed modeling of the RPC simulation and shows that for CO 2 -based standard mixtures (CO 2 /R134/i–C 4 H 10 /SF 6 ), the experimentally measured separation between the efficiency and streamer probability curves is accurately modeled by the improved streamer criteria.