EVENTS RECONSTRUCTION IN 3-D POSITION SENSITIVE CdZnTe GAMMA-RAY SPECTROMETERS

The wide band gap semiconductor material CdZnTe has long been of interest for gamma-ray spectroscopy at room temperature. Despite the resolution improvement using single-polarity charge sensing techniques, the variations in detector response, such as the peripheral asymmetry in coplanar grids and the material non-uniformity can still degrade the energy resolution of large volume CdZnTe detectors. A 3-D CdZnTe spectrometer employs a pixellated anode and a conventional planar cathode. The pixel position provides the interaction’s lateral coordinates, while the interaction depths for single-pixel events are derived from the cathode to anode signal ratio. For multiple-pixel events, individual electron drift times are recorded to obtain the depth for each interaction. The 3-D position sensitivity enables corrections of non-uniform detector response down to the limit of the position resolution over the whole detector volume. This work is the first successful demonstration of 3-D position sensing for multiple-pixel events, together with single-pixel events, all done through application specific integrated circuits (ASIC). Significant improvements in energy resolutions for both single-pixel and multiple-pixel events have been achieved. Variou