Interaction Reconstruction in Digital 3-D CdZnTe Under Various Circumstances

Abstract

Cadmium zinc telluride (CdZnTe) is a semiconductor material that has attracted wide attention in the field of radiation detector in recent years. With the improvements in crystal growth, electrode design and readout electronics, the performance of CdZnTe detectors has been improving and approaching HPGe detectors without the requirements of cryogenic cooling. This work attempts to extend the application of CdZnTe detectors in multiple dimensions by addressing different challenges.

The advancements in digital readout systems enables more accurate information extraction from the CdZnTe detectors. Improvements were made on the measurement of electron mobility-lifetime product in 3-D CdZnTe detectors using more suitable filtering methods.

Though CdZnTe detectors can be operated at room temperature, the front-end devices still need to be temperature-regulated because the electronic gain as well as the electron transport property changes with temperature. The regulation requires extra power consumption, and impedes development of hand-held CdZnTe detector devices. In this work, the effect of temperature change on digital CdZnTe systems was studied in detail. In addition, practical algorithms were developed to correct for the systematic changes with varying temperature in both material and electronics.

Fast neutron damage in high-performance, 3-D sensitive CdZnTe detectors were studied. 3-D CdZnTe detectors showed significant performance degradation after neutron damage. The annealing process of neutron damage was studied both at room temperature and 80 $^o$C. The annealing was significantly accelerated at higher temperatures. The detectors' performance was recoverable after annealing.

The usage of digital CdZnTe detector systems was extended to measurement of gamma rays in the above-3 MeV range. Pair-production double-escape event peaks were clearly resolved. Resolution degradation mechanisms in 3-D CdZnTe for gamma-ray interactions in this energy range were studied.

An algorithm was developed that estimates the distribution of electron cloud from gamma-ray interactions in digital readout, 3-D CdZnTe detector. Promising results were acquired for muon events which have high signal-to-noise ratio.