Analytical method for calculating the efficiency and solid angle of an NaI(Tl) detector

Highlights: • The calculation of photons flux balance through the detector surface is used to determine the detector efficiency. • The detector's solid angle value is obtained by calculating the flux of photons entering the detector. • The method adaptable to calculating the efficiency of a detector irradiated with a source in form of a disk, ring, rectangle. An approach for calculating the detection efficiency of gamma-ray detectors, based on the calculation of the influx/outflux balance of the photons through the detector, is presented. This method can be applied to several simple geometrical configurations. The method is also used to estimate the solid angle of a detector.