Bochum 2015 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 2: Magnetic Confinement I
P 2.1: Hauptvortrag
Montag, 2. März 2015, 10:30–11:00, HZO 30
Impact of magnetic perturbation fields on tokamak plasmas — •Sina Fietz1, Ivo Classen2, Marc Maraschek1, Wolfgang Suttrop1, Hartmut Zohm1, and the ASDEX Upgrade Team1 — 1Max-Planck-Institut für Plasmaphysik, Garching, Deutschland — 2FOM-Institute DIFFER, Nieuwegein, The Netherlands
Non-axisymmetric external magnetic perturbation (MP) fields arise in every tokamak e.g. due to not perfectly positioned external coils. Additionally many tokamaks, like ASDEX Upgrade (AUG), are equipped with a set of external coils, which produce a 3D MP field in addition to the equilibrium field. This field is used to either compensate for the intrinsic MP field or to influence MHD instabilities such as Edge Localised Modes (ELMs) or Neoclassical Tearing Modes (NTMs).
But these MP fields can also give rise to a more global plasma response. The resonant components can penetrate the plasma and influence the stability of existing NTMs or even lead to their formation via magnetic reconnection. In addition they exert a local torque on the plasma. These effects are less pronounced at high plasma rotation where the resonant field components are screened. The non-resonant components do not influence NTMs directly but slow down the plasma rotation globally via the neoclassical toroidal viscous torque.
The island formation caused by the MP field as well as the interaction of pre-existing islands with the MP field at AUG is presented. It is shown that these effects can be modelled using a simple forced reconnection theory. Also the effect of resonant and non-resonant MPs on the plasma rotation at AUG is discussed.