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/anticoincidence 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 low-energy electrons, ∼1.2 keV for the fluorescence X-rays, respectively).