Study on relaxation phenomenon of CdZnTe photon counting detectors in X-ray imaging

During X-ray scanning imaging, the X-ray dose received by CdZnTe photon counting detectors varies dynamically because of the different absorption coefficients that occur at different locations in the object being imaged. This paper explores the phenomenon of count rate relaxation in CdZnTe detectors during X-ray dose mutations and studies the intrinsic relationship of this phenomenon with the polarization effect. The characterization of the count rate relaxation processes of CdZnTe detectors at three typical X-ray doses are studied in detail. It is concluded that the count rate relaxation process of the CdZnTe detectors correspond to the polarization process, which can be divided into three stages according to the accumulation rate of space charges, and the relaxation time depends on the settling time of the polarizing electric field. In addition, the effects of temperature and bias voltage on the relaxation phenomenon of CdZnTe detectors are studied. The results show the relaxation process of the count rate can be regulated by adjusting the temperature and bias voltage of the CdZnTe detectors. Changes in temperature and bias mainly act on the trapping and de-trapping processes of deep-level traps, thereby affecting the establishment of the polarization electric field, which further proves the close relationship between the count rate relaxation phenomenon and the polarization effect. Finally, the effects of count rate relaxation on DR image quality are discussed based on self-built DR imaging system.