Deposition of energy from low-energy neutrons in the ICRU tissue sphere.


This work has investigated the characteristics of the energy deposition throughout the spherical volume of tissue as a result of being bombarded with neutron beams of varying energies, all the way from 0.3 MeV down to thermal. Absorbed dose and dose equivalent values have been obtained throughout the spherical phantom having the ICRU-prescribed 4-element tissue composition. The basic studies involved broad, parallel beams; but the data were easily used to provide information on isotropic beam conditions also. Average dose values were easily determined. Except for the thermal neutron source case, all the beams studied were monoenergetic in character. The thermal neutron source had a Maxwellian distribution appropriate for room temperature (20 sub 0 C). The analyses were done by Monte Carlo on the CYBER 175 computer of the University of Illinois. Cross sections used were those in the latest ENDF/B files of Brookhaven National Laboratory. Point cross-sectional data were used except for the energy groups with group-averaged values for the cross sections. This work was supported by a grant from the US National Science Foundation. Shiue,-Y.L.