The stochastic edge region of W7-X

The topology of stochastic magnetic fields in the edge region of Wendelstein 7-X (W7-X) is investigated. The Kolmogorov lengths of flux tubes are computed and compared with the corresponding connection lengths to the plasma-facing components (divertor elements and first wall). It is shown that the mean Kolmogorov length decreases with increasing β, and that stochastic layers exist in the considered cases. The field line diffusion coefficient in dependency of the Kolmogorov length is estimated from the radial displacements of flux tubes and the corresponding heat diffusion coefficients are also given.