Gas R&D on gas recirculation and recuperation for the Resistive Plate Chamber detectors

Abstract

Resistive Plate Chamber (RPC) detectors at the Large Hadron Collider (LHC) experiments are operated with a gas mixture containing C2H2F4 (R134a) and SF6. These gases are used because they allow to achieve specific detector performance. However, due to their high Global Warming Potential (GWP) they are currently subject to a phase down policy that started to affect the market with price increase and it may cause a decrease in their long-term availability. To minimize these risks, four different strategies have been identified for optimizing their usage. As immediate actions and where possible, during the LHC Long Shutdown 2 (LS2) the RPC gas systems will be upgraded to cope with new detector requirements and, in parallel, extensive campaigns for fixing leaks at detector level will be performed. Since R134a dominates the greenhouse gas consumption, the development of a R134a gas recuperation plant is going to be the next step and it might have an important positive impact on the overall optimization process. Recently a prototype system was tested with encouraging results. For future long-term detector operation, R&D studies are ongoing for finding “green” alternatives to the currently used gases. Unfortunately, new gases developed by industry as refrigerant fluids are not behaving as the R134a in particle detectors which makes the replacement for present experiments difficult. The last strategy consists in the possibility of using industrial plants for the disposal of greenhouse gases by decomposition in harmless compounds. This solution avoids the emission in the atmosphere but it does not optimize the gas usage and problems like gas availability and price for detector operation might become the challenge in the coming years due to the greenhouse phase down policy.