A Method of Improving Photon Detection Efficiency of High Purity Germanium Cameras by including Double-Interaction Photopeak Events

We propose a method to utilize double-interaction photopeak events in high purity Germanium cameras to improve sensitivity with no apparent degradation in spatial resolution. This procedure is based on an energy comparison between the energy deposited at two interaction sites for photons of up to 255 keV. To determine the sensitivity improvement quantitatively, we simulated the photon transport process for 140 keV photons in detail for Ge detectors having thicknesses of 1.00 to 2.00 cm in 0.25 cm steps. Discrete HPGe cameras were modeled using pixel sizes of (1.0 mm)2, (1.5 mm)2, and (2.0 mm)2. Our results indicate sensitivity improvements of 29-42%, depending on detector thickness and pixel size.