Sherwood 2015

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The nonlinear plasma response in the continuously nested flux surface limit

Author: Samuel A. Lazerson
Requested Type: Poster Only
Submitted: 2015-01-06 06:53:55

Co-authors: J. Loizu, S. Hudson, A. Cerfon, G. McFadden, J. King, Z. Wang, S. Hirshman

Contact Info:
Princeton Plasma Physics Laboratory
Princeton Plasma Physics Labor
Princeton, NJ   08543
United States

Abstract Text:
The question of the three dimensional plasma response at rational surfaces in the limit of continuously nested flux surfaces is examined. A simple model problem and one with realistic tokamak geometry are utilized to examine the response. In the simple model, a large aspect ratio circular cross section tokamak equilibrium is computed with external perturbation. The perturbation is resonant with a q=2 surface in the plasma volume. This model is examined with the VMEC code, which assumes continuously nested flux surfaces. It is found that VMEC predicts a peaked non-axisymmetric current centered on the q=2 surface. The localization and amplitude of this current scales with radial resolution and local shear. Improved radial differencing in the calculations of current densities is described. Comparisons with the linear ideal MHD code MARS-F and non-linear ideal MHD code NSTAB are made. A more realistic case is evaluated where DIII-D equilibria with applied n=3 field is examined. Here the newly installed 3D magnetic diagnostics may shed some light on the presence of such currents.

If possible placement of poster next to contributions by S. Hudson or J. Loizu is desired.

March 16-18, 2015
The Courant Institute, New York University