High energy γ-ray detection using CZT detectors with virtual Frisch grid

Abstract

The spectroscopic performance of two Frisch collar CdZnTe (CZT) detectors with different dimensions has been tested and evaluated after exposing to high energy gamma rays. The dimensions of one of the detectors, detector A, were 4.2×6.2×6.5 mm 3 and that of detector B were 3.0×4.0×9.0 mm 3 . Detector grade CZT crystals were grown from zone refined Cd, Zn, and Te (~7N) precursor materials, using the tellurium solvent method. Detectors with virtual Frisch grid configuration were fabricated from these crystals. I-V measurements revealed low leakage currents at room-temperature, ~ 11 nA at 1100V for detector A and 14.5 nA at 1800V for detector B. For the spectroscopic measurements, the detectors were irradiated using a 137 Cs source. Detector A showed an impressive energy resolution of 1.4% and detector B showed an energy resolution of ~5.9 % for 662 keV from Cs-137 radioisotope. A digital technique based biparametric correlation study showed that the performance of detector B was limited by the operating bias voltage. Further, a digital correction scheme has been described and was applied to recover the effect of charge (electron) -loss.