The interaction of the DED magnetic field with a tokamak plasma

The penetration of the rotating magnetic field of the dynamic ergodic divertor (DED) into the TEXTOR tokamak plasma has been investigated, using a two-dimensional reduced magnetohydrodynamics model and taking into account the effects of plasma-neutral interaction and neoclassical viscosity. The real three-dimensional structure of the DED coils design results in a mixture of several spatial Fourier modes which rotate at different phase velocities. It is shown that the field penetration is accompanied by poloidal acceleration of the plasma, which plays a crucial role in the process. For the DED TEXTOR parameters, the plasma-neutral interaction and the neoclassical viscosity allow for a distribution of the perturbed magnetic field close to vacuum one. If the mixture of harmonics is taken into account, the acceleration of the plasma in poloidal direction does not provide a complete penetration of the perturbation.