Gamma spectroscopy with pixelated CdZnTe detectors

Excellent spectroscopy for higher energy gamma-rays are obtained with thick pixelated CdZnTe detectors, despite the large hole trapping inherent in the CdZnTe material. Our detector design was assisted with the help 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 1cm×1cm×1cm CdZnTe detector where the anode is segmented to a 4×4 array of pad electrodes. For each gamma interaction, signals for all the 16 pad electrodes and 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 the full energy peak, the summed pad spectra yields energy resolution of 1.0 % FWHM. For the reconstruction of Compton events with signals in two pad electrodes, we obtain a summed peak with energy resolution of 1.4 % FWHM.