Aging tests and chemical analysis of Resistive Plate Chambers for the trigger of the ALICE dimuon arm

Resistive Plate Chambers operated in streamer mode have been chosen as trigger detectors for the forward dimuon spectrometer of the ALICE experiment. During tests performed at CERN PS, small size prototypes with low-resistivity bakelite electrodes and with a strongly quenched gas mixture have shown the required rate capability, tracking and timing properties. Present efforts are devoted to the study of the detector performance after long irradiation periods. In this paper, a summary of the results of aging tests performed at the Gamma Irradiation Facility at CERN will be presented. Detectors show quite stable performance up to about 50 mC / cm 2 , as the requirements for 10 years operation program at LHC including a safety factor of 2. Afterwards, we observed an increase of the dark current not associated with an increase of the counting rate. We also report results of chemical analysis carried out by different CERN teams on exhaust gases and electrode surfaces of the detectors after aging.