FW/CADIS-$Ω$: An angle-informed hybrid method for deep-penetration radiation transport

A new method for generating variance reduction parameters for strongly anisotropic, deep-penetration radiation shielding studies is presented. This method generates an alternate form of the adjoint scalar flux quantity, $φ^{\dagger}_Ω$, which is used by both CADIS and FW-CADIS to generate variance reduction parameters for local and global response functions, respectively. The new method, called CADIS-$Ω$, was implemented in the Denovo/ADVANTG software suite, and results are presented for a concrete labyrinth test problem. Results indicate that the flux generated by CADIS-$Ω$ incorporates localized angular anisotropies in the flux effectively. CADIS-$Ω$ outperformed CADIS in the test problem while obtaining accurate results. This initial work indicates that CADIS-$Ω$ may be highly useful for shielding problems with strong angular anisotropies. A future test plan to fully characterize the new method is proposed, which should reveal more about the types of realistic problems for which the CADIS-$Ω$ will be suited.