Modelling the effects of electrical traps in radiation detectors

We describe a method, for deriving the shape and position of the photopeak as functions of the electrical parameters of the traps, from first principles, without using empirical factors, but assuming a knowledge of detector geometry, bias, temperature and radiation conditions. The paper deals only with the charge loss in the detector for photo electric events with the emphasis on physical principles and methods. Methods for calculating the true local trap occupancy factor and the trapping rates of drifting carriers as functions of the electric field are described. Recombination effects as well as emission of either type of carrier are fully taken into account. We present examples of the results obtained with a simulator for a uniform intensity of 1.33 MeV gamma rays in a large cylindrical germanium (Ge) detector. These are in good agreement with published experimental results.