Analytical Formulae to Calculate the Total Efficiency of an Arbitrarily Positioned Point Source by an Elliptical Cylindrical Detector

In this paper, a direct analytical method is presented for calculating the absolute efficiency of an elliptical cylindrical detector in the case of an arbitrarily positioned (above the major axis a) point source. The absolute efficiency is required to determine the activity of an unknown radioactive source, taking into account the attenuation of the gamma-ray photons. The validity of the derived analytical expressions was successfully confirmed by the comparison with some published data.