3D Equilibrium Effects Due to RMP Application on DIII-D
Authors: S. Lazerson, E. Lazarus, S. Hudson, N. Pablant and D. Gates
Abstract:
The mitigation and suppression of edge localized modes (ELMs) through application of resonant
magnetic perturbations (RMPs) in Tokamak plasmas is a well documented phenomenon
[1]. Vacuum calculations suggest the formation of edge islands and stochastic regions when
RMPs are applied to the axisymmetric equilibria. Self-consistent calculations of the plasma
equilibrium with the VMEC [2] and SPEC [3] codes have been performed for an up-down symmetric
shot (142603) in DIII-D. In these codes, a self-consistent calculation of the plasma response
due to the RMP coils is calculated. The VMEC code globally enforces the constraints of
ideal MHD; consequently, a continuously nested family of flux surfaces is enforced throughout
the plasma domain. This approach necessarily precludes the observation of islands or field-line
chaos. The SPEC code relaxes the constraints of ideal MHD locally, and allows for islands and
field line chaos at or near the rational surfaces. Equilibria with finite pressure gradients are approximated
by a set of discrete "ideal-interfaces" at the most irrational flux surfaces and where
the strongest pressure gradients are observed. Both the VMEC and SPEC calculations are initialized
from EFIT reconstructions of the plasma that are consistent with the experimental pressure
and current profiles. A 3D reconstruction using the STELLOPT code, which fits VMEC
equilibria to experimental measurements, has also been performed. Comparisons between the
equilibria generated by the 3D codes and between STELLOPT and EFIT are presented.
__________________________________________________
Submitted to: 39th European Physical Society Conference on Plasma Physics, Stockholm, Sweden (June 2012)
__________________________________________________
Download PPPL-4772 (pdf 732 KB 4 pp)
__________________________________________________