Gamma spectroscopy with pixelated CdZnTe detectors

Excellent spectroscopy for higher energy gamma-rays is obtained with thick pixelated CdZnTe detectors, despite the large hole trapping inherent in the CdZnTe material. Our detector design was assisted by means of a theoretical Monte-Carlo code for optimizing the pixelated detector geometry for obtaining pad signals with minimum dependence on the depth of gamma interaction. We present spectra obtained for the 662-keV line of ¹³⁷Cs taken with a 1 cm×1 cm×1 cm CdZnTe detector with the anode segmented to a 4×4 array of pad electrodes. For each gamma interaction, signals for all 16 pad of the electrodes and for the common cathode electrode were digitized to enable further correction for the depth of gamma interaction and for the reconstruction of Compton scatter interactions. For single pixel events, the summed pad spectrum yields an energy resolution of 1.0% FWHM. For the reconstruction of Compton events with signals in two pad electrodes, we obtain a summed peak with an energy resolution of 1.4% FWHM.