Peak efficiency calibration for attenuation corrected cylindrical sources in gamma ray spectrometry by the use of a point source

A theoretical method of determining the gamma-ray peak efficiency for a cylindrical source, based on a modified expression for point sources is derived. A term for the photon self-attenuation is included in the calculation. The method is valid for any source material as long as the source activity concentration is considered to be homogeneous. Results of this expression are checked against experimental data obtained with 241Am, 57Co, 137Cs, and 60Co sources.