Optimizing the Spectral Response from Coplanar-Grid Sensors

The coplanar-grid (CPG) technique applied to CdZnTe (CZT) crystals resulted in efficient and large volume room-temperature gamma-ray detectors. In order to achieve a good spectral response with CPG sensors, some correction of the electron trapping effect must be applied. This is typically done either by reducing the gain of one of the two co-planar grid signals, or by using for each event one additional measurement from the cathode signal. In this work a comparison between four different techniques for electron trapping correction is presented. In addition to the relative gain and the use of the cathode signal, the availability of an application specific integrated circuit (ASIC) developed for CPG-CZT sensors allowed the implementation of two other techniques based on the use of the two grids signals only. The experimental results from the four techniques will be presented and briefly discussed.