High Purity Germanium Detector Annealing

High purity germanium (HPGe) detectors are used to determine an objects output of gamma-ray radiation. This is done by counting charged particles released from the detectors inner materials when exposed to gamma-rays. As detectors age operational parameters change for the worse and detectors must be repaired. The damage that is received is due to both an accumulation of particulate matter and occasionally radiation damage (i.e. dislocation sites or trapping centers) to the germanium crystal. Liquid nitrogen operating temperatures expedites the collection of harmful particles. Crystal dislocations are created by the interaction between fast neutrons and the atoms of the crystal, these cause charge trapping, reduce amplitude of full-energy pulses and produce low-energy tails. All of which contribute to gamma-ray spectrum resolution degradation. Under these conditions the spectrum that the instrument produces is of much lower quality resolution which may cause confusion during spectra analysis. For this project, known damaged detectors will be used to take a spectrum before undergoing the repair process, called detector annealing. After which a second spectra of the same source will be gathered in order to compare quality of resolution. The procedure for detector annealing requires heating and a low pressure vacuum system. Application of high temperature dissociates particulate build up. The vacuum removes the particles and produces the necessary air free environment within the detector housing. The annealing process is able to restore the detector to operate within tolerance. Results indicate that it will be beneficial to continue development and refinement of a detector repair station and procedure.