Effects of Gamma-Ray Damage on Energy Spectra and Polarization of a CdTe Detector With the Schottky Barrier for Imaging Equipment

Effects of gamma-ray radiation damage on energy spectra and polarization of the CdTe radiation detector with the Schottky barrier are demonstrated for application to the gamma-ray imaging equipment in diagnostic nuclear medicine. In particular, the polarization recovery mechanism by momentary bias-off (bias refreshment) is incorporated into the detector system, and the effect of radiation damage on the bias refreshment is quantitatively evaluated. The Schottky barrier is formed by using In as the anode of the CdTe detector. The gamma-ray irradiation source for the radiation damage test is ⁶⁰Co. Gamma-ray count rate in an energy window and leakage current between the cathode and the anode are not affected until irradiation at 6.83 kGy. Energy resolution is not affected until irradiation at 66.8 Gy, and there is significant deterioration when irradiation is more than 1.29 kGy. Polarization of the CdTe detector is hardly affected and can be recovered by the bias refreshment for irradiation at 66.8 Gy. However, complete recovery becomes impossible at more than 1.29 kGy irradiation. In conclusion, it is demonstrated that the CdTe detector can be used as the gamma-ray detector in SPECT (Single Photon Emission Computed Tomography) equipment for more than 20 years, and continuous SPECT examinations lasting more than 120 min become possible with the bias refreshment