Development of a common gas analysis approach for the gas systems of all the experiments at the CERN Large Hadron Collider

Over the five experiments (ALICE, ATLAS, CMS, LHCb and TOTEM) taking data at the CERN Large Hadron Collider (LHC) more than 28 gas systems are delivering the proper gas mixture to the corresponding detectors. They are complex systems that extend over several hundred meters and have to ensure an extremely high reliability in terms of stability and quality of the gas mixture delivered to the detectors. In fact, the gas mixture is the sensitive media and a correct and stable composition is basic requirements for good and safe long term operation. In this context the monitoring of the gas mixture becomes of fundamental relevance. O₂ and H₂O analysis racks are already available on all the experimental sites. They provide a fast and simple quality check. Gas chromatographic stations are installed on two experiments and already in the past year they revealed to be very useful. In the present contribution, an overview of the analysis methods and few practical examples are described.