Improved resolution for 3D position sensitive CdZnTe spectrometers

Two 3-dimensional position sensitive CdZnTe gamma-ray spectrometers based on VAS/TAT ASICs were developed and fully tested. The 1.5×1.5×1 cm³ CdZnTe detectors employ 11×11 pixellated anodes wire-bonded to the readout electronics The pixel number provides the interaction´s lateral coordinates, while the cathode/anode signal ratio and the electron drift time are used to obtain the interaction depth. Data-acquisition and processing software were developed to perform calibration and real-time spectroscopy. An energy resolution of 1.11% FWHM at 662 keV was obtained for single-pixel events from the 120 working pixels of one detector, and an energy resolution of 1.14% FWHM was obtained on the other detector. Significant progress in improving energy resolution for multiple pixel events has been realized. The energy resolution at 662 keV for two-pixel events and three-pixel events were 1.57% FWHM and 2.13% FWHM respectively.