Studies on fluorine-based impurity production in Triple-GEM detectors operated with CF4-based gas mixture

Abstract One of the primary elements influencing gaseous detector operation is the purity of the gas mixture. Its quality can be undermined by the presence of impurities, already present in the supply gas bottles or that could be created in the gas system or from the detector itself. Gaseous detectors operated with Freon-based gas mixtures are subject to the formation of the products of gas molecules break up, occurring when the gas is exposed to high-rate radiation, and enhanced by the presence of high electric field. The release of highly reactive products could be critical as they could either create polymerized deposits or cause material etching, that could compromise detector performance and accelerate aging processes. Moreover, the operation of gas systems with gas recirculation, nowadays common in many gas systems, could worsen the risk of damage due to possible impurities accumulation. This work focuses on the production of fluorine-based impurities in Triple-GEMs detectors operated with C F 4 -based gas mixture. Detectors are operated in a LHC-like gas system and exposed to high-rate gamma irradiation thanks to the intense 137Cs source provided by the CERN Gamma Irradiation Facility (GIF++). Impurity production is characterized for different detector operation conditions such as gas mixture, working voltage, input flow rate, and irradiation rates. Furthermore, purifier module operation is validated proving its efficiency in removing Fluoride impurities.