Observation of spontaneous neoclassical tearing modes

Plasma rotation effects on neoclassical tearing modes

The effect of an equilibrium sheared ow on the nonlinear evolution of a neoclassical tearing mode is investigated by estimating the inuence it has on the inner and outer layer dynamics of the mode. Two complementary approaches are adopted. A generalized Rutherford model calculation is carried out to estimate the ow contributions to the polarization current term in the inner layer. For the ou...

Control of Neoclassical Tearing Modes for Improved Performance in Iter

Introduction to Neoclassical Tearing Modes and the Role of Rotation

It is now well established from theoretical considerations and from several experimental observations of long pulse high β tokomak discharges that the limit on plasma pressure is not set by the ideal MHD modes but is rather due to the onset of low (m, n) resistive modes. These instabilities, which produce magnetic islands at the low order rational surfaces, appear to be well described by the ne...

Theoretical Studies on Neoclassical Tearing Modes and Their Stabilization

Numerical simulation results for the nonlinear evolution of neoclassical tearing modes (NTMs) and the stabilization of NTMs by localized RF current drive are presented. It is shown that the saturated island width does not increase linearly with the local bootstrap current density fraction. The NTMs are found to be stabilized by a localized RF current drive, if a sufficiently large RF current is...

On modeling the interaction of neoclassical and classical tearing modes with rf waves

A model which incorporates the effects of electron cyclotron current drive (ECCD) into the magnetohydrodynamic (MHD) equations is implemented in the NIMROD code [C. R. Sovinec et al., J. Comp. Phys. 195, 355 (2004)] and used to investigate the effect of ECCD injection on the stability, growth, and dynamical behavior of magnetic islands associated with resistive tearing modes. Predictions of the...