A hybrid method to compute accurate efficiencies for volume samples in gamma-ray spectrometry

In recent years, Monte Carlo (MC) methods have been increasingly applied to cope with variability in photopeak efficiencies due to matrix effects. But to obtain proper results only by numerical simulation, especially at low energies, sample bulk density and chemical composition must be well characterized. In this paper, we propose a method that combines both experimental measurements and MC simulations, being applicable to matrices of unknown composition. A transmission measurement of a 210Pb point source through the sample allows one to compute accurately its photopeak efficiencies at energies above 46.5 keV. The method is validated for several inorganic and organic matrices measured in Petri dishes geometry.