A search for a freonless gas mixture for glass RPC

We have operated successfully glass resistive plate counters in the streamer mode at the BELLE experiment by using a nonflammable gas mixture of argon 30%, butane-silver 8%, and freon, HFC-134a 62%. This freon is non-ozone-depleting but has a high global warming potential (1300 times higher than that of CO/sub 2/). Thus freon gases might be unusable in the near future. We tested the performance of a glass resistive plate counter operated in the streamer mode with an alternative gas mixtures of argon, butane, CO/sub 2/, and/or O/sub 2/ gases and found an efficiency of about 90%.