Carlo Transport Code MCNPX Research Articles

A Monte Carlo model of sea-level neutron background: Directionality, spectra, and intensity

We are developing a model of the cosmic ray-induced neutron backgroundat sea-level using the high-energy/Monte Carlo transport code MCNPX. The modelaccounts for and records anisotropy in neutron production from cosmic rayinteractions, as well as the known “ground effect” neutron albedo.Initial results with an isothermal, constant density atmosphere in slab geometryshow good agreement with experimental data on neutron intensity and low-energydirectionality predicted previously. Our model also indicates significantnet downward directionality above the energy range 0.1–1.0 MeV dependingon the sea-level material composition.