Ion fluxes to the first wall of TEXTOR are modulated during application of a fast rotating resonant magnetic perturbation (RMP) field. The modulation in front of the RMP coils matches the magnetic topology modelled in vacuum approximation for low relative rotation of frel = −0.2 kHz between the RMP field and toroidal plasma rotation. With increasing relative rotation, the ion flux pattern is shifted linearly in counter-Bt direction. The shift is correlated to a displacement Δφ = π/2 of the electron density modulation at the outermost resonant flux surface caused by an internal plasma response. This indicates a competition between the near magnetic field of the RMP coils and the net magnetic field at the resonant flux surface.
Role of singular layers in the plasma response to resonant magnetic perturbations