Calculation of total efficiencies of extended samples for HPGe detectors

Calculation of coincidence summing correction factors in gamma-ray spectrometry can be carried out by making use of full-energy-peak and total efficiencies for a given sample geometry and detector setup. In the case of extended samples, the contribution of gamma-rays that scatter in the sample itself to the total efficiency needs to be taken into account. A method is described for calculating this contribution based on calibration measurements with point sources positioned on the detector housing. The approach is aimed at environmental gamma-ray spectrometry analysis of cylindrical samples on p-type HPGe detectors and is verified against full Monte Carlo calculations of total efficiencies with the GEANT code.