Electromagnetic Field of the Dynamic Ergodic Divertor

Dynamic Ergodic Divertors (DED) had been proposed by the Torus Experiment for Technology Oriented Research (TEXTOR) group in order to obtain better control on the plasma recycling process and, at the same time, to reduce the heat load at the outer wall of a tokamak. In the concept of DED, external perturbation coils create at the edge a rotating helical field whose frequency can be changed from dc to a few kilohertz depending on the operational regime. When the corresponding wave propagation into the finite temperature plasma is studied, kinetic effects are important, in particular if the resonant magnetic surface (the local helical magnetic field lines are parallel to the external DED coils) is located inside the core plasma, where the plasma is essentially collisionless.