Gamma-ray energy spectrum calculations for plane perpendicular incident source including annihilation and bremsstrahlung photons.

Abstract

The energy spectra of r-rays in water, concrete, iron and lead are calculated by PALLAS-PL, SP-Br code for the plane perpendicular incidence. The calculation takes into account both annihilation and bremsstrahlung photons as well as Compton scattered ones as the secondary source.Comparisons of energy spectra calculated by PALLAS were made with those of the moments method in water, iron and lead. In the PALLAS calculation the bremsstrahlung is neglected for the source energy of 6 MeV in iron because the influence of the bremsstrahlung on the energy spectrum is considered to increase for high energy photons. While for the case of inclusion of the bremsstrahlung source, a comparison of PALLAS calculations with experiments is made in transmitted dose through lead for a plane perpendicular 8-MeV source, resulting in good agreement.Several examples of the calculated energy spectra in each material are presented at penetration distances of 0.5-, 1.0-, 2.0-, 4.0-, 7.0-, 10.0-, 20.0-and 40.0-mfp in 43 mfp depth for source energies of 0.1~15.0 MeV.