New numerical simulation approach to calibrate the NaI(Tl) detectors array using non-axial extended spherical sources

The aim of the current study was to utilize the efficiency transfer technique (ET) to obtain the full-energy peak efficiency (FEPE) applying a new numerical simulation approach. The approach was implemented on a detection system array composed of two [NaI (Tl)] detectors. The simulation approach included a derivative of the effective solid angles subtended by an arbitrarily located source and the active volume of the detectors. The attenuation of the source matrix, the source container and the end-caps of the detector materials were considered. Resulting outcomes have been compared with those measured by the NaI(Tl) detector array comprising different volumes as (3 '' x 3 '' & 2 '' x 2 '') and resolutions (FWHM) of 7.5% and 8.5% at 662 keV respectively. Eu-152 aqueous radioactive spherical sources were employed during the measurements, covering the energy range from 121.78 keV up to 1408.03 keV. A remarkable agreement was observed between the measured and the calculated efficiencies employing the new numerical approach. These conclusions were consistent for a variety of source-to-detector lateral distances, providing solid evidence for the stability of the developing method.