Method of evaluating the effect of HPGe design on the sensitivity of physics experiments

Abstract

Motivated by planned double beta decay experiments in 76Ge I describe a computational model for the electric fields of solid state diode detectors and the subsequent charge transport. Aspects of detector performance determined by the impurity charge concentration are explored in a series of measurements of comparable point contact" p-type germanium detectors and compared to our computational model. In particular, we measure the capacitance of the germanium detector as a function of the bias voltage to determine the free parameters in a three parameter model of the impurity charge density, selectively mapping out the density at all points within the detector volume. We then use our impurity charge density map to determine the sensitivity of pulse shape analysis applied to various classes of physics events detected in the crystal. When possible, the impact of our refinements on a figure-of-merit for double-beta decay experiments is described.