We present the results from testing the performance of CdZnTe (CZT) position-sensitive virtual Frisch-grid (VFG) detectors for gamma-ray imaging. Large-volume CZT detectors with dimensions up to 10x10x30 mm3 recently became available from CZT crystal vendors. Such devices improve detection efficiency and position resolution when integrated into position-sensitive photon counting cameras proposed for nonproliferation, nuclear security, and gamma-ray astronomy. It is important to evaluate the factors affecting the response uniformity and limiting the performance of these detectors. In general, the response non-uniformities could be caused by detector geometries, materials inhomogeneity, and crystal defects. Several techniques have been developed to correct response non-uniformities and improve detector performance. Among them are the high-granularity position-sensitive detectors, which provide the most accurate and robust corrections. Position sensitivity can also be used to reveal response non-uniformities and understand their causes during the detector development or fabrication stages. Here, we describe a technique that we developed for position-sensitive virtual Frisch-grid detectors employing CdZnTe (CZT) and other semiconductors. To illustrate our experimental technique, we measured responses from the selected detectors of different qualities acquired from different vendors and grown by different methods.
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