A Bayesian method for pulse shape and energy estimation for gamma spectrometry measurements using semiconductor detectors

Abstract. The gamma spectroscopy principle is to evaluate a gamma ray energy by measuring the quantity of free charges generated by the gamma-ray absorption. Semiconductors like CdTe and CdZnTe are promising materials for this application. However, they encounter a major drawback: due to imperfections in their charge transport properties, the transient signal induced by a gamma ray has a varying shape. This phenomenon severely degrades energy resolution. The measured pulse amplitude depends not only on the gamma-ray energy but also on the interaction location. The aim of this paper is to present a new approach based on the Bayesian probabilistic inference, to estimate jointly the pulse shape and the energy. It brings a methodology for founding a relevant estimation of gamma-ray energy associated with a pulse. The pulse shape variability is modeled by assigning a prior probability law on his dispersion around its nominal shape. Then, using this prior knowledge and the observations, we tried to estimate jointly the pulse shape and its amplitude that correspond to the associated energy of the gamma-ray energy.