Calibration of NaI (Tl) cylindrical detector using axially shifted radioactive cylindrical sources

In this article, the full energy peak efficiency of NaI detector using non-axial cylindrical sources is calculated by using a new efficient theoretical approach. This approach depends on using the efficiency transfer method and analytical calculations of the average path length of a gamma photon inside the source to the detector system. Measured efficiencies made by using 152Eu aqueous radioactive cylindrical sources with volumes 25 ml and 400 ml. Comparing calculated efficiencies to the measured one showed good agreement enabling the validation of this approach.