Gas Mixture Monitoring Techniques for the LHC Detector Muon Systems

Abstract

At the LHC experiments the Muon Systems are equipped with different types of gaseous detectors that will need to assure high performance until the end of the LHC run. One of the key parameters for good and safe long-term detector operation is the gas mixture composition and quality. Indeed a wrong gas mixture composition can decrease the detector performance or cause aging effects and irremediable damages. It is therefore a fundamental requirement to verify and monitor the detector gas mixture quality.

In the last years several gas monitoring techniques have been studied and developed at CERN to automatically monitor the detector gas mixture composition as well as the impact of gas quality on detector performance. In all LHC experiments, a gas analysis module allows continuous monitoring of O₂ and H₂O concentrations in several zones of the gas systems for all muon detectors. More sophisticated and precise gas analyses are performed with gas chromatograph and mass spectrometer devices, which have sensitivity at the level of ppm and allow to verify the correctness of the gas mixture composition. In parallel to standard gas analysis techniques, a gas monitoring system based on single wire proportional chamber has been implemented: these detectors are very suitable to detect any possible aging contaminants thanks to their high sensitivity.