A RICH DETECTOR WITH 2-STAGE GAS AMPLIFICATION AT ATMOSPHERIC-PRESSURE

A prototype of a Ring Imaging Cherenkov detector (RICH) with two-stage gas amplification has been developed. The detector consists of a time projection chamber (TPC) with a sensitive volume of 19 X 20 X 6 cm3 f ollowed by a parallel plate avalanche counter (sensitive volume 20 X 5 X 0.4 cm3) and a multiwire proportional chamber (MWPC) with 96 wires 2 mm apart. The gas used was an argon/methane/isobutane mixture (ratio 60/20/20) at atmospheric pressure. TMAE at 15-degrees-C served as the photosensitive component. The measurements were done with a calibrate d VUV photon source. The following results were obtained: spatial reso lution of the MWPC 1.2 mm, spatial resolution of the TPC 800 mum, atta chment length (13.0 +/- 1.6) cm and photon detection efficiency 4.2% c orresponding to N0 = 25 cm - 1.