Stabilizing effects of a width of externally applied current on Neoclassical Tearing Mode
T. OZEKI, S. TOKUDA, K. HAMAMATSU
Naka Fusion Research Establishment, Japan Atomic Energy Research Institute
Abstract.
Investigations of neoclassical tearing mode (NTM) are considered to be important since it may softly limit and degrade the beta value. An externally applied local current is effective to stabilize the NTM. The local current inside a magnetic island stabilizes the NTM, however, the local current outside the island can stabilize or destabilize the NTM through the change of current profile in the equilibrium. Therefor we reconsider effects of the ratio of the width of the externally applied local current and the island width on the stability of NTM for the case that the external current does not synchronize to an rotating island. To evaluate the island width due to the NTM, a calculation of D' is important. Here, we evaluate D' by the cylinder model as well as the more accurate method using the two-dimensional Newcom equation [1]. Effects of width of external current on the NTM stability for various current profiles are discussed.
[1] S. Tokuda, T. Watanabe, Phys. Plasmas 6 (1999) 3012.