Cylindrical high pressure xenon spectrometer using scintillation light pulse correction

Abstract

Cylindrical high-pressure xenon detectors utilizing Frisch grid electrodes have been employed for many years. These detectors are limited to no better than 2% energy resolution at 662 keV, a factor of 3-4 above the intrinsic spectroscopic limit of xenon. This likely results from imperfections in the structure of the Frisch grid combined with the high capacitive load which increases amplifier noise substantially. Also, high sensitivity to microphonic noise of the sensitive grid severely limits field use. We propose a highly stable cylindrical structure consisting of concentric anode and cathode electrodes and use of scintillation light collected through a transparent end window. Measurement of the time interval between the prompt scintillation light from the interaction vertex and stimulated light produced by primary electrons arriving at the anode electrode provides determination of the radial deposited charge distribution, including effects of electron range and xenon fluorescence. In a 5 cm diameter detector employing a MgF/sub 2/ end window we have shown that anode signal levels can be corrected using the time digitized light output signal to achieve resolution superior to the Frisch grid systems and approaching the intrinsic xenon Fano limit. We anticipate employing the technique in arrays of kilogram scale detectors for high sensitivity high resolution field compatible gamma ray spectroscopy.