Three-Dimensional Position Sensitive CdZnTe Detector Array for PNNL

A new CdZnTe gamma-ray spectrometer system that employs two layers of modular detector arrays is being developed under the collaboration between the University of Michigan and PNNL. Each layer can accommodate up to three by three 3-dimensional position sensitive CdZnTe gamma-ray spectrometers. This array system is based on the newly developed VAS_UM/TAT4 ASIC readout electronics. Each of the nine detector modules consists of a pixellated CdZnTe detector and a VAS_UM/TAT4 ASIC front-end board. Each 1.5times1.5times1.0 cm³ CdZnTe detector employs an array of 11 by 11 pixellated anodes and a planar cathode. The energy depositions and 3-dimensional positions of individual interactions of each incident gamma ray can be obtained from pulse amplitude, location of each pixel anode and the drift time of electrons. This is the first system that multiple 3D CdZnTe detector modules can be tiled together to achieve detection volume greater than 40 cm³. This configuration allows the expansion of detector area to achieve higher detection efficiency while maintaining the excellent energy resolution. Experimental results of individual detectors and the array system are presented and discussed.