THE WIDE-GAP RESISTIVE PLATE CHAMBER

The resistive plate chamber (RPC) has good time and position resolutio n; these factors (coupled to its simple construction) make it an attra ctive candidate for muon trigger systems at future colliders. However, operated in spark mode, the RPC has severe rate problems that make it unusable above 10 Hz/cm(2). We have previously published our results concerning the operation of the RPC in spark and in avalanche mode; we have shown that the rate limit can be increased to 150 Hz/cm(2) if th e RPC is operated in avalanche mode. Here, we discuss the performance of chambers with 6 and 8 mm gas gaps (compared to the more usual 2 mm gap). We outline the reasons for this choice, and also discuss anode v ersus cathode strip readout. We have measured the efficiency versus fl ux, and also show that an enhanced rate limit can be obtained if only a small region of the chamber is exposed to the beam (spot illuminatio n). Finally we have tested the performance of chambers constructed wit h other materials for the resistive plate and compare it to chambers c onstructed with our preferred plastic, melamine laminate.