Investigation of the Imaging Polarization Effect Based on a Pixellated CdZnTe Detector

Abstract

A pixel array CdZnTe imaging system, employing a 40 × 40 × 5 mm 3 pixellated CdZnTe detector, is established. The imaging polarization effect in the CdZnTe pixellated detector for a collimated Cs 137 Gamma source is investigated in detail. The experimental results for different irradiated fluxes indicate that excessive irradiated flux indeed causes central pixels to be shut off completely. The imaging performance of the polarized detector is severely degraded. Polarized detector counts are simultaneously reduced to one-third of the non-polarized detector counts. A theoretical model of potential distribution is also proposed by solving the Poisson equation and, in turn, the electric potential distortion for high irradiated flux is discussed by comparison with the experimental results.

X-ray micro-beam characterization of a small pixel spectroscopic CdTe detector

“…have been shown to lead to localised build up of space charge and modification of the electric field in Cd(Zn)Te detectors [30][31][32] which can have an adverse effect on the detector spectroscopy.…”

Further process of polarization within a pixellated CdZnTe detector under intense x-ray irradiation

“…This behavior is consistent with the buildup of positive space charge caused by photo-generated holes which are strongly trapped in deep levels in the material. At high flux, the rate of charge injection into the CdZnTe is sufficiently high that charge trapping dominates over thermal emission and recombination processes, and a significant net space charge accumulates in the bulk [15,16]. Furthermore, strong hole trapping causes a buildup of a dynamic space charge region under a higher flux irradiated area.…”

Performance of common-grid pixelated CZT detector with different array geometries

“…Among all the single charge carrier sensing detectors, pixelated CZT detectors not only show good energy resolution, but also are motivated for two-dimensional position sensitive imaging applications, coupled with high efficiency and no cryogenic cooling requirement, making them as good candidates for medical and astronomic imaging. To improve the spectroscopic and imaging performance of pixelated CZT detectors, more and more researches were focused on the study of the small pixel effect [10,11], charge sharing effect [12,13], polarization effect [14][15][16], etc.…”