Mitigating Teleportation Error in Frequency Dependent Hybrid Implicit Monte Carlo Diffusion Methods

This work investigates teleportation error in frequency-dependent Hybrid Implicit Monte Carlo Diffusion (HIMCD). HIMCD dynamically applies Implicit Monte Carlo Diffusion (Gentile, 2001; Cleveland et al., 2010) to regions of a problem that are opaque and diffusive while applying standard Implicit Monte Carlo (IMC) (Fleck and Cummings, 1971) to regions where the diffusion approximation is invalid. Teleportation error arises in Monte Carlo simulations when a source is represented with the wrong spatial distribution causing radiation energy to propagate unphysically fast through a material (McKinley et al., 2003). Both frequency-dependent HIMCD and Hybrid IMC/Discrete Diffusion Monte Carlo (Densmore et al., 2012) suffer from a new source of teleportation error that is intrinsic to these methods. This teleportation error arises from sampling a new spatial location of a Monte Carlo particle when it scatters from a diffusive opaque group to a moderately opaque transport group. In this work we show that sampling ...