Convergence history of the four components of the source vector for x = 0 and μ = 0.025 calculated with the core-wing method. Same model as in Fig. 3. The dotted lines show the initial solutions (ϵB for , and zero for all other components). Since the slab is symmetric about the mid-plane, the results are shown only for a half-slab, τ ∈  [0,T/2] .