Potassium Iodide Fast Neutron Detector

A fast neutron detector has been developed consisting of powdered thallium activated potassium iodide dispersed in polystyrene. Recoil protons from the polystyrene are detected by potassium iodide. The detection efficiency of the potassium iodide detector for radium-beryllium neutrons is comparable to that of zinc sulphide dispersed in polystyrene. Potassium iodide has a longer decay time than zinc sulfide, permitting ``phoswich'' coincidence arrangements. The energy response of the potassium iodide detector is closer to the energy response of a thick hydrogenous radiator than that of a zinc sulfide detector.