On the invariability of the total-to-peak ratio in gamma-ray spectrometry

It is demonstrated that the assumption on the independence of the total-to-peak ratio of the source position in gamma-ray spectrometry holds for coaxial detectors with sufficient accuracy to make it applicable to the determination of the full energy peak efficiencies in environmental measurements via the so-called efficiency transfer method. The calculations show that for planar detectors the assumption breaks down at higher gamma-ray energies and that for such detectors the use of the efficiency transfer method is only warranted for gamma-ray energies up to 200 keV.