Background Suppression in a Gas-Scintillation Proportional Detector for Exotic-Atom X-Rays

This is an update of the report on a gasscintillation detector with a 7-cm diameter Be window for the detection of the K X-ray lines of exotic atoms such as pp, pD and K p (Ref. 1). Additional insulation eliminated breakdown at 9 kV to allow an improvement in background suppression. Timing markers from two scintillation regions combined with energy information, signals from guard detectors, and offline analysis resulted in a background reduction factor of ≈300. Time and amplitude spectra are shown.