A study of aging effects in gas proportional detectors at the BAC calorimeter of the ZEUS experiment

Abstract The multicell proportional chambers at the backing calorimeter of the ZEUS experiment at the storage ring HERA are supplied with a gas mixture of Ar/CO 2 by an open gas system. Flow proportional counters with the build-up 55 Fe sources are used as gas system monitoring detectors. The ZEUS experiment is planned to collect data for about 10 years. Therefore, the lifetime of the Ar/CO 2 mixture should be known. In this paper, the results of laboratory tests and preliminary measurements of the aging effects for monitoring counters are presented.