A novel technique for the characterization of a HPGe detector response based on pulse shape comparison

A novel technique for measuring the HPGe detector pulse shape as a function of the γ-ray interaction position inside the detector volume is presented. This technique is based on a specific pulse shape comparison procedure. Its main feature is that it allows to characterize the 3D position response of a HPGe segmented detector in a much shorter time as compared with the standard coincidence techniques. The method was first validated using a GEANT simulation of a 36-fold HPGe AGATA detector realized taking into account the effects of the electronic chain response and electrical noise on the calculated signal shape. This procedure was then applied to extract experimentally the position response of a non-segmented coaxial HPGe detector along the radial direction, using a 438 MBq 137Cs collimated γ-source. The results of this measurement show a dependence of the pulse shape as a function of γ-ray interaction radial coordinate consistent with that obtained with calculations. The signal acquisition rate reached using this characterization technique allows to realize a full scan of a large volume highly segmented HPGe detector in less than a week.