A Position Sensitive Gas Scintillation Proportional Counter for X-Ray Astronomy

A position sensitive gas scintillation proportional counter is presented for use as a broad band spectrometer in the focal plane of an imaging X-ray telescope. The 7 cm diameter detector has an on-axis position of ~ 2.5 mm and an energy resolution of ~ 10% for 6 keV X-rays. Design improvements are outlined which should provide a position resolution below ~ 1 mm at 6 keV over a useful aperture of ~ 8 cm. Such a detector, can, in conjunction with a suitable telescope, perform a spectral mapping in the range 0.1 - 6 keV of extended objects such as clusters of galaxies and supernova remnants with medium spatial resolution.