An extensive aging study of bakelite Resistive Plate Chambers

We present recent results of an extensive aging test, performed at the CERN Gamma Irradiation Facility, on two bakelite Resistive Plate Chambers (RPC) detectors. With a method based on a model describing the behavior of an RPC exposed to a large particle flux, we have periodically measured the electrode resistivity ρ of the two detectors over 3 years. We observed a large increase of ρ with time, from initial values of about 1010 Ω cm to more than 200×1010 Ω cm. A corresponding degradation of the RPC rate capability, from about 3 kHz/cm2 to less than 200 Hz/cm2, was observed. The reversibility of the process, using a humid gas mixture, has also been studied.