A STUDY OF NON-FLAMMABLE GAS-MIXTURE FOR RESISTIVE PLATE COUNTER

The RPC(resistive plate counter) has good time and position resolution . These factors make it an attractive candidate for trigger system at collider experiment. The standard gas mixtures (Ar+iso-C4H10+Freon) us ed in RPC are very flammable when leaked into air. In view of safety i ssue,we have studied non-flammable gas of Ar+CO2+iso-C4H10+Freon as a function of ratio Ar:CO2 allowed in non-flammable gas mixtures for the RPC with ABS electrodes. The basic performance of the various mixture s have been measured; singles(untriggerd) count rate, detection effici ency and charge spectra versus operating voltage. We have found a set of non-flammable mixtures of the kind of Ar+CO2+Freon contained less t han similar to 8.4% of iso-C4H10 for. K-L/muon counter of KEK B-factor y at KEK.