Flux-Limited Diffusion and Fokker-Planck Equations

A recently reported description of radiative transfer is generalized to the case of a linear transport equation containing a Fokker-Planck treatment of very peaked scattering. The resulting diffusion theory is naturally flux (current) limited; i.e., the magnitude of the current cannot exceed the scalar flux. It is shown that the effect of the Fokker-Planck terms is, within this theory, identical to treating the very peaked scattering via the classical transport correction to the scattering cross section. This description of linear transport has potential application in charged-particle and high-energy neutron transport calculations.