ASYMMETRIC MULTIWIRE PROPORTIONAL COUNTER WITH THIN QUARTZ FIBER SPACERS

Using thin quartz fibres as insulating spacers, a simple way to reduce the anode-cathode gap is presented for a higher rate capability for a multiwire proportional counter. For a prototype counter using Phi 12- mu m anode wires and Phi 250-mu m quartz fibre spacers, we measured a gas gain of 1000 at an anode voltage of 700 V and a drift voltage of - 300 V with an energy resolution of 22% FWHM in an Ar-CH4 (90/10) gas m ixture. The gas gain remained stable up to a rate of 4 x 10(4) Hz/mm(2 ), which is a much higher rate than that obtained with a conventional MWPC.