Dependence of Neoclassical Toroidal Viscosity on the 
Poloidal Spectrum of Applied Nonaxisymmetric
 Fields

Authors:  Nikolas C. Logan, Jong-Kyu Park, Carlos Paz-Soldan,
Matthew J. Lanctot, Sterling P. Smith, K. H. Burrell

Abstract:  This paper presents a single mode model that accurately predicts the coupling of applied nonaxisymmetric fields to the plasma response that induces neoclassical toroidal viscosity (NTV) torque in DIII-D H-mode plasmas. The torque is measured and modeled to have a sinusoidal dependence on the relative phase of multiple error field sources, including a minimum in which large amounts of nonaxisymmetric drive is decoupled from the NTV torque. This corresponds to the coupling and decoupling of the applied field to a NTV-driving mode spectrum. Fully nonlinear modeling using the Perturbed Equilibrium Nonambipolar Transport (PENT) code confirms a single mode coupling between the applied field and the resultant torque. The coupling to the NTV mode is shown to have a similar dependence on the relative phasing as that of the IPEC dominant mode, providing a physical basis for the efficacy of this linear metric in predicting error field correction optima in NTV dominated regimes.
_________________________________________________________________________________________________

Submitted to: Nuclear Fusion
_________________________________________________________________________________________________

Download PPPL-5135 (pdf 7 MB 21pp)
_________________________________________________________________________________________________