High sensitivity detection of 133gXe via delayed coincidence counting

Sensitive detection of Xe fission products is needed for monitoring the Comprehensive Test Ban Treaty. Pacific Northwest National Laboratory has developed an automated system for separating Xe from air which includes a beta-gamma counting system for ^131mXe, and ^133gXe, ^133mXe, and ^135gXe. Even greater sensitivity for ^133gXe can be achieved by use of the delayed coincidence between beta particles which feed the 81-keV state in ¹³³Cs and the in conversion electrons produced in the deexcitation of the 81-keV state (t_1/2=6.36 ns). Besides the ability to detect ^133gXe with 0 background, this technique distinguishes ^133gXe from ^131mXe and ^133m Xe