The role of secondary defects in the loss of energy resolution of fast-neutron-irradiated HPGe gamma-ray detectors

The resolution characteristics of high-purity germanium gamma-ray detectors irradiated with fast neutrons are studied in detail. The influence of the neutron fluence on the energy resolution as well as the annealing temperature of irradiated detectors is investigated. Similarities are observed between the annealing behavior of the defects created by fast neutron irradiation in high-purity germanium and the changes in the energy resolution of the detectors when they are annealed. The energy resolution of the detectors measured by means of a resolution factor which takes into account tailing effects has been investigated. Its behavior has been illustratively explained by the differences between the respective roles of the stable defects at low temperature (<100 K) and those formed by a thermal treatment up to room temperature.<>