FRACTAL AND WADA EXIT BASIN BOUNDARIES IN TOKAMAKS

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The creation of an outer layer of chaotic magnetic field lines in a tokamak is useful to control
plasma-wall interactions. Chaotic field lines (in the Lagrangian sense) in this region eventually
hit the tokamak wall and are considered lost. Due to the underlying dynamical structure of this
chaotic region, namely a chaotic saddle formed by intersections of invariant stable and unstable
manifolds, the exit patterns are far from being uniform, rather presenting an involved fractal
structure. If three or more exit basins are considered, the respective basins exhibit an even
stronger Wada property, for which a boundary point is arbitrarily close to points belonging to
all exit basins. We describe such a structure for a tokamak with an ergodic limiter by means of
an analytical Poincar´e field line mapping.
http://www.escet.urjc.es/~fisica/investigacion/publications/Papers/2007/IJBC_17_4067_2007.pdf