Soft X-ray energy resolution and background rejection in a driftless gas scintillation proportional counter

Abstract

Energy resolution measurements are presented for a driftless xenon-filled parallel plane gas scintillation proportional counter in the X-ray energy range 0.1–25 keV. Due to the high electric field near the entrance window of the detector, the degrading influence of primary electron loss to this window on the energy resolution, particularly below ∼ 2 keV, has been made negligible. This has resulted in an excellent soft X-ray energy response, e.g. an energy resolution of 31% full width at half maximum (FWHM) has been measured for C K X-rays (0.28 keV). Further, the background rejection capability of a gas scintillation proportional counter has been significantly increased by using the driftless concept. The large difference in pulse shape between X-ray events and extended tracks of ionization enables the use of a very efficient background rejection technique. High rejection efficiencies have been achieved, e.g. 99.3% in the energy range 0.4–15 keV for an X-ray acceptance of 85% at 5.9 keV.