Validation of analytical formulae for the efficiency calibration of gamma detectors used in laboratory and in-situ measurements.

Direct analytical formulae for the efficiency calibration of gamma (scintillation and semiconductor) detectors using an arbitrarily positioned radiating point source are extended to include sources with volumetric shapes. The attenuation of photons by the source itself (self-absorption) is determined by calculating the photon path length through the source material. The theoretical and the published experimental efficiency values are in good agreement.