Spatial variation of energy resolution in 3-D position sensitive CZT Gamma-Ray spectrometers

This paper reports the energy resolutions obtained from two 3-D CZT γ-ray spectrometers. Each device is a 1 cm³ cube CZT crystal with an 11×11 pixellated anode. For single-interaction events in the detector, the gamma ray interaction location can be determined in 3-D. With the volume of each detector conceptually divided into 11×11×18 voxels, the spectra of single-interaction events from each of the voxels were collected. The energy resolutions at 662 keV from a single voxel are typically 9.3 keV and 9.9 keV for the two detectors, with electronic noise contributing ~7 keV and ~6 keV respectively a spatially-varying energy resolution has been observed for both detectors, which accounts for the degradation of energy resolution of the overall spectrum combined from all the voxels. The causes for the variations have been analyzed, and the impact of a spatially-varying energy resolution on a CZT gamma-ray spectrometer has been investigated