| pubmed-article:3972584 | pubmed:abstractText | For isotropic point photon sources above an air-ground interface, the spectral energy fluences at the ground have been calculated by the Monte Carlo method for source energies in the range 50 keV-10 MeV. The source heights and the horizontal source-detector distances varied from 0.05 to 5 mean free paths in air. Air-ground interface correction factors have been calculated and then analytically approximated. The greatest deviations from unity were found for 100-keV sources located on the ground. Near the source, kerma free in air is enhanced by 30%, and far from the source it is reduced by a factor of 3. | lld:pubmed |
