Aging and materials: lessons for detectors and gas systems

Aging of gaseous detectors is known as the degradation of their performance under the exposure to ionizing radiation. It is a complex phenomenon that depends on many parameters. Among others, aging depends on the gas mixture and may be enhanced by the presence of pollutants in the gas. The origin of the impurities is diverse and includes outgassing from assembly materials, contamination of the detector during the assembly process and the gas system itself. Systematic studies on this topic have been carried out. The methods used to ascertain the outgassing properties of materials are described and compared. Materials that might be used for assembling gaseous detectors and associated gas systems are catalogued according to their outgassing rate. Some factors affecting the aging rate of some fast gases are presented. Finally, a set of recommendations to build and operate gaseous detectors in high-luminosity experiments is given.