Resistive wall mode and neoclassical tearing mode coupling in rotating tokamak plasmas
Abstract
A model system of equations has been derived to describe a toroidally rotating tokamak plasma, unstable to Resistive Wall Modes (RWMs) and metastable to Neoclassical Tearing Modes (NTMs), using a linear RWM model and a nonlinear NTM model. If no wall is present, the NTM growth shows the typical threshold/saturation island widths, whereas a linearly unstable kink mode grows exponentially in this model plasma system. When a resistive wall is present, the growth of the linearly unstable RWM is accelerated by an unstable island: a form of coupled RWM-NTM mode. Crucially, this coupled system has no threshold island width, giving the impression of a triggerless NTM, observed in high beta tokamak discharges. Increasing plasma rotation at the island location can mitigate its growth, decoupling the modes to yield a conventional RWM with no threshold width.
Keywords
Cite
@article{arxiv.1302.4250,
title = {Resistive wall mode and neoclassical tearing mode coupling in rotating tokamak plasmas},
author = {Rachel McAdams and H R Wilson and I T Chapman},
journal= {arXiv preprint arXiv:1302.4250},
year = {2013}
}