Ahmed M El-Khatib - Physics Department, Faculty of Science, Alexandria University, Alexandria ۲۱۵۱۱, Egypt
Mohamed S Badawi - Physics Department, Faculty of Science, Alexandria University, Alexandria ۲۱۵۱۱, Egypt
Mohamed A Elzaher - Department of Basic and Applied Sciences, Faculty of Engineering, Arab Academy for Science, Technology andMaritime Transport, Alexandria, Egypt
Abouzeid A Thabet - Department of Medical Equipment Technology, Pharos University in Alexandria, Alexandria, Egypt

The full-energy peak efficiency (FEPE) curvesof the (2 x 2 and 3 x 3 ) NaI (Tl) detectors weremeasured at seven different axial positions from theirsurfaces. The calibration process was done using radioactivepoint sources, which produce a wide energy rangefrom 59.53 up to 1,408.01 keV. This work has beenundertaken to explain the effects of source energy andsourcE-to-detector distance on the detector efficiencycalculations. The study provides an empirical formula tocalculate FEPE based on the efficiency transfer method fordifferent detectors using the effective solid angle ratio atvery large distances and for higher energies. A remarkableagreement between the measured and calculated efficienciesfor the detectors at the sourcE-to-detector distances<35 cm and above that slight difference was observed.

Scintillation detectors Full-energy peak efficiency (FEPE) Efficiency transfer method Effective solid angle