Difficulties in obtaining an HPGe detector for low-level measurements

All low-level laboratories require HPGe detectors to meet certain technical specifications, some of which are not available from manufacturers prior to purchase. Ensuring an HPGe detector is fit for purpose requires the purchase and installation of a detector in the laboratory, incurring both financial risk and considerable time and effort. We show that the optimal HPGe crystal for low-level laboratories has a diameter matched to the source and a length providing 70% absorption of the gamma-rays of interest.