Monte Carlo simulation of the self-absorption corrections for natural samples in gamma-ray spectrometry

Gamma-ray self-attenuation corrections in the energy range 60-2000 keV were evaluated by means of Monte Carlo calculations for environmental samples in a cylindrical measuring geometry. The dependence of the full-energy peak efficiency on the sample density was obtained for some particular photon energies and, as a result, the corresponding self-attenuation correction factors were obtained. The calculations were performed by assuming that natural materials have mass attenuation coefficients very similar to those of water in the energy range studied. Three different HpGe coaxial detectors were considered: an n-type detector with 44.3% relative efficiency and two p-type detectors of relative efficiencies 20.0% and 30.5%. Our calculations were in very good agreement with the self-attenuation correction factors obtained experimentally by other workers for environmental samples of different densities. This work demonstrates the reliability of Monte Carlo calculations for correcting photon self-attenuation in natural samples. The results also show that the corresponding correction factors are essentially unaffected by the specific coaxial detector used.