FURTHER-STUDIES OF AVALANCHE MODE-OPERATION OF RESISTIVE PARALLEL-PLATE CHAMBERS

We have investigated the high rate operation of the resistive plate chamber and have discovered that melamine-phenolic laminates are good candidates for a plate material. We have previously shown that avalanche mode (rather than spark mode) gives a substantial improvement in the rate capability. There are two new encouraging results; the timing spectra are not affected by the rate; and particles at non normal incidence have a higher detection efficiency; these substantially increase the rate capability of this device. However there are two results that show that further R & D is needed. These are: the change in resistivity of the plate material with time; and the fall off of the efficiency with increasing high voltage. Our goal is to produce a cheap large area detector that has good spatial and time resolution and has a raft capability suitable for the muon system at a future collider. We believe that these results show that this detector is already promising and should satisfy these requirements with further R & D.