Fourier Analysis of Parallel Block-jacobi Splitting with Transport Synthetic Acceleration in Two-dimensional Geometry

A Fourier analysis is conducted in two-dimensional (2D) Cartesian geometry for the discreteordinates (SN) approximation of the neutron transport problem solved with Richardson iteration (Source Iteration) and Richardson iteration preconditioned with Transport Synthetic Acceleration (TSA), using the Parallel Block-Jacobi (PBJ) algorithm. The results for the un-accelerated algorithm show that convergence of PBJ can degrade, leading in particular to stagnation of GMRES(m) in problems containing optically thin sub-domains. The results for the accelerated algorithm indicate that TSA can be used to efficiently precondition an iterative method in the optically thin case when implemented in the “modified” version MTSA, in which only the scattering in the low order equations is reduced by some non-negative factor β < 1.