PNNL

Abstract

This work addresses the energy spectrum correction due to increased charge carrier collection times in larger HPGe spectrometers. The energy of the radiation interaction is expected to be proportional to the total collected charge. This is increasingly not true with larger HPGe spectrometers. Some charge is lost as the total charge travels from the interaction location to the collection electrode. This path dependent loss of charge results in decreased energy resolution. In HPGe spectrometers, this process is characterized by the charge carrier lifetime constant and is given as an exponential function of the charge carrier collection time divided by this constant. Thus large detectors can experience exponential decrease in energy resolution as charge carrier collection time increases. We study the effect of charge carrier lifetime on energy resolution for a large diameter p-type coaxial and p-type point contact HPGe spectrometers using pulse shape analysis. We present a method to measure the charge carrier lifetime for a given HPGe spectrometer.