Traces of stable and unstable manifolds in heat flux patterns

Experimental observations of heat fluxes on divertor plates of tokamaks show typical structures (boomerang wings) for varying edge safety factors. The heat flux patterns follow from general principles of nonlinear dynamics. The pattern selection is due to the unstable and stable manifolds of the hyperbolic fixed points of the last intact island chain. Based on the manifold analysis, the experimental observations can be explained in full detail. Quantitative results are presented in terms of the penetration depths of field lines.