Performance of a resistive plate chamber operated in avalanche mode under Cs-137 irradiation

A 2 mm gas gap Resistive Plate Chamber with bakelite plates has been operated in avalanche mode with a Cs-137 source. We report measurements of the efficiency for a cosmic ray detection and the charge developed in the gap, performed for two different gas mixtures: the first containing a high percentage of environmental friendly ''freon'' C2H2F4; the second one having a high percentage of argon. We show that the freon-based mixture exhibits a wide full-efficiency plateau with low streamer probability, while the argon-based mixture allows a reduction in the detector power consumption