A metastable xenon isotope detector for treaty verification

A system to selectively detect and quantify the xenon metastable isotopes 131mXe, 133mXe, 133Xe, and 135Xe has been designed, fabricated, and tested. The system combines high-resolution electron and gamma-ray spectrometry with coincidence/anti-coincidence timing for signal selectivity and background rejection. By utilizing X-ray-fluorescence gating, backgrounds from other sources are expected to be reduced to the sub-becquerel level. Coincidence and anti-coincidence triggers are formed from the several individual detectors that comprise the system and used to identify K-shell conversion electrons and fluorescence X-rays from a 109Cd test source with good efficiencies and energy resolutions (20 keV for the low-energy electrons, ∼1.2 keV for the fluorescence X-rays, respectively).