An empirical formula to calculate the full energy peak efficiency of scintillation detectors

This work provides an empirical formula to calculate the FEPE for different detectors using the effective solid angle ratio derived from experimental measurements. The full energy peak efficiency (FEPE) curves of the (2″*2″) NaI(Tl) detector at different seven axial distances from the detector were depicted in a wide energy range from 59.53 to 1408 keV using standard point sources. The distinction was based on the effects of the source energy and the source-to-detector distance. A good agreement was noticed between the measured and calculated efficiency values for the source-to-detector distances at 20, 25, 30, 35, 40, 45 and 50 cm.

► A new empirical formula for calculation of the FEPE is deduced.
► The method depends on the calculation of the effective solid angle ratio.
► Radioactive point sources covering energy range from 59 up to 1408 keV were used.
► A comparison between measured and calculated efficiencies was carried out.