Optimization criteria for coplanar-grid detectors

The coplanar-grid charge-sensing technique is a powerful method to achieve excellent spectroscopic performance with large-volume, CdZnTe-based, gamma-ray detectors despite the poor charge transport characteristics of the CdZnTe material. Critical to the success of the technique are the charge induction characteristics of the sensing-grid electrodes as governed by the detector geometry and the grid design. In this paper we demonstrate through numerical calculations of the detector response that the criteria for optimizing the grid design depend on the particular method in which the coplanar-grid technique is implemented. We present the fundamental design criteria in terms of the desired charge induction on the grid electrodes for the commonly used coplanar-grid implementations.