Correction of small error fields at high BetaN in ASDEX Upgrade

Tokamak plasmas are able to amplify even very small error fields when operating close to the MHD limits. As a result of this process, ideal kink modes and/or a tearing modes can become unstable and limit the plasma performance. In our experiments, in ASDEX Upgrade, the plasma is close to the pressure limit. The plasma has ?N values around the "no-wall" boundary. In this situation, the ideal kink becomes the main limiting factor. Previous experiments demonstrate that the dominant error field comes from the feedthroughs for the poloidal field coils [1, 2]. Although the error field itself is very small (Berr Btor