Cadmium Sulfide Neutron Detectors: Annealing of Radiation Damage

A new method for measuring fast-neutron fluences using CdS has recently been developed. The technique consists of detecting induced conductivity resulting from the beta decay of radioisotopes which are produced by the neutron irradiation. In previous studies of radioactive decay effects in these detectors it was necessary to correct the conductivity data for effects associated with radiation damage (defects). In this study, electrical changes associated with neutron-induced defects have been minimized by annealing the detectors at 300°C before measuring electrical changes resulting from radioactive decay. The measured conductivity following annealing is just the induced conductivity from beta decay, and no further corrections for radiation damage are required. These results also (1) confirm the accuracy of the previous correction procedure, and (2) show that differences in the radioactive decay rate constants and the rate constants determined from the associated electrical changes, which have been observed for some detectors, are not necessarily due to errors introduced by that correction procedure. Given in this paper is a brief discussion of some of the general characteristics of CdS neutron detectors as well as a detailed description of the annealing experiments.