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Transport barriers and bifurcation characteristics in stellarators

Transport barriers in the present stellarators are reviewed in comparison with those in tokamaks. Peculiarities of stellarator plasma structures are introduced in order to obtain a unified view of the barrier formation mechanism. Particular attention is paid to neoclassical (-driven) internal transport barriers that are commonly observed in stellarators. Discussion is made about important aspects of structural formation; e.g. the formation or bifurcation mechanism of radial electric field and its causal link with the transport barrier, and effects of magnetic field configuration on the barrier formation.