required quality control of the experimental system. Gamma spectrometry system can be
used in a variety of different fields such as radiation and medical physics. In this paper the
absolute efficiency, peak to valley ratio, and energy resolution of a 3′′× 3′′ NaI (Tl)
detector were determined experimentally for 511, 662, 835, 1173, 1275, and 1332 keV
photon energies obtained from 22Na, 54Mn, 60Co, and 137Cs radioactive sources.