Application of a Ge(Li) gamma detector-cadmium radiator arrangement for low level neutron flux measurements

Abstract

A neutron detection system is described which is based on the application of a Ge(Li) gamma detector to the observation of the 558-keV gamma radiation emitted following neutron capture in cadmium radiator foils placed around the detector housing. It is pointed out that the detection efficiency for such a system is essentially independent of the cadmium neutron capture cross section and the neutron spectrum shape for a flux having only a small epithermal component. Expressions are developed for calculating the efficiency of this type of system for several different radiator-foil geometries in an isotropic flux having a small but non-negligible epithermal component. Experimental evaluation of this system is carried out in an approximately isotropic flux situation for three radiator-foil arrangements including: 1) a circular disk perpendicular to and centered on the detector axis; 2) a cylindrical shell around the detector coaxial with the detector axis; 3) a rectangular foil along the side of the detector. Flux determinations for these three different geometries are in good agreement.