Monte Carlo simulations of the SNM spectra for CZT and NaI spectrometers

The detector characteristics of CZT and NaI spectrometers that affect the choice of the nuclide analysis algorithm were analyzed with a general purpose Monte Carlo code to simulate the SNM spectra. The physical and geometric conditions strictly adhered to the IAEA series test requirements for a portable radionuclide identification device. The Hecht equation was used to describe the incompletion charge collection effect for the CZT detector, and a comparison calibration to determine the CZT spectrometer equivalent noise charge. The NaI spectrometer was calibrated by experiments. The calculated results agreed well with experiments.