An Imaging Gas Scintillation Proportional Counter for the Detection of Subkiloelectron-Volt X-Rays

A large area imaging gas scintillation proportional counter (IGSPC) has been constructed for use in X-ray astronomy. The IGSPC consists of a gas scintillation proportional counter (GSPC) with a 1 µm polypropylene window coupled to a multiwire proportional counter (MWPC) via a calcium fluoride window. The MWPC, filled with a mixture of argon, methane, and tetrakis (dimethylamino) ethylene, detects the UV photons emitted by the xenon gas in the GSPC. Over a sensitive area of 21 cm2 the instrument has a measured energy resolution of 17.5% (FWHM) and 1.9 mm (FWHM) spatial resolution at 1.5 keV.