Monte Carlo calculations of escape fractions in the determination of Fricke G-values for monochromatic soft X-rays

Calculations of percentages escaped from incident energy fluence for soft X-rays were undertaken using a Monte carlo code which simulates the photon transport exactly. The calculations were improved by taking into account correction factors for photon angular distributions and multiple scattering processes. A reduction of coherent backscatter and enhancement of fluorescence backscatter for lower energies were observed for 3 mm thick Si slab which was comparable to the previous analytical calculations by Greening and Randle. The total escape percentages of incident energy lost from the Fricke solution (2 x 2 cm area and 1 cm thick) were determined to be 0.61% for 8.856 keV and 12.3% for 13.55 keV. Using this calculated percentage of the measured energy fluence as a correction factor, absorbed dose in the Fricke solution, accordingly ferrous sulphate G-values too, were determined with a high accuracy. (author)