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The work presents analysis of the correlation existing between the spectrometric performance of commercially produced hemispherical detectors of volume 500 mm 3 and the quality of starting CdZnTe material. More then 100 detectors made from CdZnTe crystals grown by eV Products, Saint-Gobain and Yinnel Tech. were studied. For the incoming inspection of the material an infrared (IR) transmission microscope was used. The presence of structural defects such as grain boundaries, twins, inclusions and cavities was checked and their shapes, sizes and spatial distributions were examined; the values of electron mobility-lifetime product (µτ) e were measured. The hemispherical detectors were made by a technology elaborated at the RITEC. Spectrometric performance of the detectors was verified by measuring the energy resolution and the peak-to-Compton ratio at the 662 keV line. It was found that all tested detectors had numerous structure defects, whose shapes, sizes, numbers and spatial distributions varied from sample to sample. Were found that hemispherical detectors made from samples containing inclusions of irregular shape had a poor spectrometric performance, while the detectors from samples containing large inclusions (>50 µm) of regular shape (triangular, hexagonal) as a rule performed well. It was also found that a highly non-uniform spatial distribution of structural defects usually leads to a poor spectrometric performance.

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Presently room-temperature CdZnTe (CZT) nuclear radiation detectors of various designs and sizes are widely used for spectrometric measurements of X and gamma-radiations. In most cases the spectrometric detectors with highest efficiency are requiredl. But there are tasks where good spectrometric detectors with a low efficiency should be applied. Those are tasks connected with spectrometric measurements in strong radiation fields where small size quasi-hemispherical CZT detectors can be used. Now the quasi-hemispherical CZT detectors with a very small volume of about 0.5 mm3 are available. These detectors have energy resolution (FWHM) from 1% to 2% at a 662 keV.The possibilities and limitations of the miniature detection probes with CZT detectors for application in strong radiation fields are discussed in the report. Some results of these probes application for irradiated nuclear spent fuel and other high-level objects spectra measurements under water in a NPP cooling pond are presented.