Test of freonless operation of resistive plate chambers with glass electrodes F 1 mm gas gap vs 2 mm gas gap

Non-freon gas mixtures (Ar/iso-C4H10) were tested as the chamber gas for 1 and 2 mm gas gap Resistive Plate Chambers (RPCs) with float glass as the resistive electrodes, operated in the streamer mode. With the narrower (1 mm) gas gap, streamer charge is reduced (B1=3), which reduces the dead time (and dead area), associated with each streamer, improving the detection efficiency. The best performance was obtained for two cases: Ar/iso-C4H10 1⁄4 50=50 and 60=40: For the 50=50 mixture, a detection efficiency of better than 98% was obtained for the 1 mm gap RPC, while the efficiency was 95% for the 2 mm gap RPC, each operated as a double-gap RPC. The measured time resolution (rms) was 1:4570:05 ð2:5270:09Þ ns for the 1 ð2Þ mm gap RPC for the 50=50 mixture. r 2002 Elsevier Science B.V. All rights reserved.