Development of Gas Systems for Gaseous Detector Operation at HL-LHC

After the highly remarkable results achieved in the first decades of operation of the CERN Large Hadron Collider (LHC), the accelerator complex is currently facing major upgrades, and the substantial increase in luminosity will pose major technical challenges also for the Experiments. A long consolidation and upgrade program is being realized during the Long Shutdown 2, concerning among others the Muon systems, composed of gaseous detectors for which a correct and stable gas mixture composition is a key requirement to guarantee good and stable long-term performance. As Greenhouse gases (GHGs) are widely used as gas mixture components in LHC gaseous detectors, their operation shall keep into account the latest CERN requirements in terms of reduction of GHGs emission and gas systems cost. This work delineates the development and upgrades of two different research lines put in place to contribute to the CERN strategies to minimize GHGs consumption. The first is the operation of gas systems with gas recirculation, in particular for the Triple-GEM detectors case, which performance was validated in a HL-LHC-like radiation environment, in terms of long-term stability, Muon detection efficiency and CF4-based impurities production. A possible strategy to further limit GHG emission is the recuperation of valuable gas components after their usage in the detectors, with the aim of reinjecting them in the gas system. This thesis focuses in particular on the recuperation of two GHGs used in LHC Experiments gaseous detectors, CF4 and C2H2F4. The design and operation of CF4 recuperation plants on the LHCb RICH2 and CMS CSC gas systems is discussed, showing how good recuperation efficiencies can be reached with a good purity of the recuperated CF4. Furthermore, the development of a C2H2F4 recuperation prototype plant is presented, which characterization proves a very high separation efficiency (80%-95%) and an extremely good quality of the recuperated C2H2F4.