title: An improved photo-absorption cross section model for the physics models regime in MCNPX.
abstract: The photo-nuclear physics model capabilities utilising the CEM2k model implemented in the MCNPX code were improved > 100 MeV photon energy by basing the photon transport on experimental photo-absorption cross sections of nuclides rather than on free nucleon cross sections. Below 100 MeV, the photo-nuclear physics model now uses isotope-specific giant dipole resonance (GDR) photo-absorption cross sections that are provided to the code in a parameterised form on a data file. Adjustments of the photo-fission cross sections were implemented to match the BOFOD evaluated data through a CEM2k internal parameter. The physics models with these improvements are better equipped to supplement the tabulated data based photo-nuclear MCNPX capability for isotopes with missing tabulated data evaluations especially in the GDR region, and has improved its predictive power at energies above the GDR resonances.
authors.affiliation: Oak Ridge National Laboratory, P.O. Box 2008, MS 6474, Oak Ridge, TV 37831, USA. fzgallmeier@ornl.gov
authors.forename: Franz X
authors.initials: FX
authors.lastname: Gallmeier
mesh_terms: D000042:Absorption; D003198:Computer Simulation; D018499:Linear Energy Transfer; D015233:Models, Statistical; D009010:Monte Carlo Method; D009686:Nuclear Physics / Q000379:methods*; D017785:Photons; D011835:Radiation Protection / Q000379:methods*; D011868:Radioisotopes / Q000032:analysis*; D011874:Radiometry / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012984:Software
chemical_list: D011868:Radioisotopes