Simulation of neoclassical tearing modes in the DIII-D tokamak. II. Suppression by radially localized electron cyclotron current drive

摘要

The problem of neoclassical tearing mode (NTM) suppression by a radially localized toroidal current from electron cyclotron current drive (ECCD) is considered. Simulation of NTM stabilization by ECCD is performed with the Nonlinear Fully Toroidal Code (NFTC) [Phys. Plasmas 8, 3605 (2001)] for DIII-D discharges. The optimal parameters are determined for the radially localized ECCD current required to reduce the NTM instability. The time response and nonlinear evolution of the magnetic island width for ECCD and the required modulation phasing, the current drive location with respect to the rational surface, and the width of the spatial distribution are determined for both monotonic q-profile and negative central shear discharges. (C) 2002 American Institute of Physics. [References: 9]