Evaluation of a semiconductor-based atmospheric radioxenon detection system

Abstract

Abstract A prototype radioxenon detection system for beta–gamma coincidence measurements has been designed using a PIPSBox and a pair of coplanar CdZnTe (CZT) detectors. Coincidence events are identified in real-time using a Field-Programmable Gate Array (FPGA). The measurement of 131m Xe and studies on electron backscatter and memory effect in the PIPSBox have been presented previously; this paper details the measurement of 133∕133m Xe, 135Xe, and background. Absolute efficiencies were determined, regions of interest were defined, and Minimum Detectable Concentrations (MDC) for all four radioxenon isotopes were calculated. When neglecting interferences between the radioxenons, the prototype system has an estimated MDC of 0.61 ± 0.15 mBq/m3 for 133Xe when using gas processing parameters associated with Xenon International, satisfying the CTBTO requirement for sensitivity of ≤ 1 mBq/m3 for 133Xe. Simulation suggests that by increasing number of CZT detectors used by a factor of 16, the MDCs of the system can be improved by a factor of 2-3. The design shows great promise for future improvement and expansion due to its exceptional energy resolution, high background rejection rate, room temperature operation, minimal memory effect, and simple readout electronics.