Characterization of a 500 mm3 CdZnTe Detector for U and Pu Isotopic Composition Determination Tasks in Safeguards

High-purity Germanium (HpGe) detectors have traditionally been the detectors of choice for quantitative gamma-ray spectroscopy in safeguards applications. They benefit from the best resolution achievable nowadays yielding in the possibility to distinguish closely positioned peaks in complex spectra such as those of Pu or mixed materials. Their response has been very well characterized and a variety of existing software algorithms is available for isotopic composition determination tasks of U and Pu materials in safeguards applications. However, HpGe detectors require cooling either via the means of liquid nitrogen or thermoelectric cooling making the equipment heavy, bulky and thus inconvenient to use for hand held devices for nuclear inspectors, limited space locations or unattended nuclear installations. CdZnTe (CZT) room temperature semiconductor detectors have been proposed as a viable alternative. These detectors exhibit usually an asymmetrical peak shape and worse resolution in comparison to HpGe detectors; therefore, their application to isotopic composition determination tasks in safeguards is not straightforward. CZT detectors have now been optimized in their design yielding resolution of 1.5% at 661 keV for a 10 mm x 10 mm x 5 mm device. Such detectors are also used in the framework of the Inter-Comparison Exercise on U and Pu Isotopic Measurements with Medium Resolution Gamma-Ray Spectrometers organized by the IAEA in cooperation with the ESARDA NDA Working Group and the International Working Group on Gamma-Spectrometry Techniques (IWG-GST). The response