A Parallel Plate Imaging Proportional Counter with High Background Rejection Capability

We present the results of studies of the scintillation produced by avalanches in a parallel plate proportional counter. It is shown, that for applications in X-ray astronomy, background rejection of greater than 90% may be achieved by risetime discrimination using the light pulse. We also present images of individual avalanches obtained by coupling an image intensifier to the counter with fibre optics. Electronic centroid analysis using such an intensifier is discussed. Measurements are also presented of the scintillation emission spectrum and position resolution with various gas mixtures.