Analysis of transmitted gamma-rays by the multiple scattering method, (2)

Dose buildup factors and number spectra of γ-rays transmitted through stratified slabs have been estimated by the multiple scattering method, taking scattering into consideration up to the fourth order and including back scattering. Further, the method proposed in the previous paper for estimating the contribution to the total dose buildup factor by γ-rays of the fifth and higher orders of scattering was applied to the present case of stratified slabs made up of different materials. The calculations covered the range of source energy from 1 to 10 MeV, and various arrangements of strata made up of combinations of two of the three materials water, iron and lead, making up slabs of total thicknesses up to 6 mfp. Calculations were also performed for 60Co γ-rays normally incident on stratified slabs of water-lead-water. The results of the above calculations were found to be in good agreement with those of other calculations, such as by Monte Carlo method and by numerical integration of the photon transport equation. The present results were also found to agree well with the dose buildup factors calculated by our own empirical formula. Comparisons with experimental results too have proved good.