Energy linearity of high-purity germanium detectors in the region of the Ge K-absorption edge: experimental results

Non-linearities in the energy response of gas detectors in the regions of the absorption edges of the detection medium are well documented. Monte Carlo calculations show that the non-linearity results from differences in efficiencies for converting absorbed radiation into ionisation for different atomic sub-shells. Energy non-linearity in germanium-based solid-state detectors in the region of the germanium 11.104-keV K-edge is not well documented, although a 1% non-linearity has been previously reported in a Ge(Li) detector. This relatively high value is of practical concern since high-purity germanium (HPGe) is often the detector of choice for alpha- and X-ray spectrometry down to a few keV. In this paper, we present the experimental results for the energy response of a HPGe detector in the 8-15-keV energy region of the germanium K-edge. Within the accuracy of our measurements, we conclude that there is no measurable non-linearity effect in germanium at the K-edge.