Characterization of Cd_(0.9)Zn_(0.1)Te based virtual Frisch grid detectors for high energy gamma ray detection

摘要

Detector grade CZT single crystals have been grown from zone refined Cd, Zn, and Te (～7 N) precursor materials using a tellurium solvent method. Infrared transmission imaging has shown an average tellurium inclusion size of ～8 μm in the as-grown crystal. Radiation detectors were fabricated in planar and virtual Frisch grid geometry and characterized for their spectroscopic performance. Charge transport properties revealed a high drift mobility of ～1200 cm~2/V s and a mobility-lifetime product of ～2.8 × 10~(-3) cm~2/V. A detector with planar configuration (dimensions 6.9 × 6.9 × 4.8 mm~3) showed an energy resolution of 4.7% for 59.5 keV gamma rays. The detector in a Frisch grid configuration (dimensions 4.2 × 6.2 × 6.5 mm~3) exhibited an energy resolution of 1.4% for 662 keV gamma rays. Digital spectroscopic measurements were carried out using a high-resolution digitizer card. A biparametric correlation scheme was employed to study the effect of charge loss on energy resolution of the planar detector. Based on this correlation scheme, a digital correction method was applied and improved pulse-height spectrum was obtained for 662 keV gamma rays using the planar detector with spectral features comparable to those of the virtual Frisch grid detector.