Properties of an Imaging Gas Scintillation Proportional Counter

We have mated a parallel-grid gas scintillation proportional counter (GSPC) to a multiwire proportional counter (MWPC) through a UV transparent window to produce a new instrument that combines the good energy resolution of the GSPC with the imaging capabilities of the MWPC. The imaging gas scintillation proportional counter (IGSPC) operates on the principle of detecting the centroid of the UV light excited by X-ray photons interacting in the noble gas of the GSPC with a UV sensitive gas [e.g. Tetrakis (dimethylamino) ethylene (TMAE)] in the MWPC. A prototype version of the counter has been built which yields a measured performance of 9% (FWHM) energy resolution and 0.9 mm (FWHM) spatial resolution at 6 keV. Further refinements of this counter and a new counter, designed for flight on a sounding rocket, should permit us to achieve 18% (FWHM) energy resolution and 0.6 mm (FWHM) spatial resolution at 1 keV.