Study of Detection Deficiency of 3D Position-Sensitive Pixellated CdZnTe Detectors

Three dimensional position-sensitive Cadmium Zinc Telluride (CdZnTe) detectors can provide positions and corresponding energy depositions of each individual gamma-ray interaction within the detector. For single-interaction events, the interaction depth is obtained by calculating the cathode to anode ratio. For multi-interaction events, the individual interaction depth is obtained by measuring the timing difference between the cathode and anode signals. It had been observed that some of the measured events were lost during the event reconstruction process. It was discovered recently that the discrepancy on total efficiency is due to the triggering threshold of the system, because some interactions cannot trigger the cathode or the anode readout channel. As a result, the detection efficiency is lowered for multi-interaction events if timing trigger is always required on all channels. In this study, we analyze the effect of triggering threshold on the detection efficiency, and present a method of recovering events lacking certain timing triggers.