Radioxenon Measurements With a Coincidence Silicon Detector System

by , , , , | Sep 10, 2012 | Papers

The radioxenon detectors currently used in applications related to nuclear explosion monitoring have a very high sensitivity to detect very small amounts of radioxenon. However, to better distinguish the radioxenon background created by nuclear power plants and medical isotope facilities from a nuclear explosion, an improved discrimination of Xe isotopes is desirable. Silicon detectors have a number of advantages over the existing detectors (high resolution, low background, sensitivity to both photons and electrons, and no memory effect) and thus have the potential to outperform them in isotope discrimination.

In the work reported here, a radioxenon detector based on silicon PIN diodes has been designed, assembled, and tested. In Si-Si coincidence measurements with various Xe isotopes, resolutions were ~0.7 keV for 30 keV X-rays and 1.3-2.5 keV for conversion electrons at 129-232 keV. The presence of metastable Xe isotopes can easily be detected by observing conversion electron peaks in the energy spectra. The efficiency for detecting higher energy gamma rays is low, but backgrounds are practically zero so that overall the minimum detectable concentration is estimated to be well below 1 mBq/m3 for a Si detector system with 100 mm2 active area on each of the six sides of a cubic Xe cell.

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