Speaker
John C. Schmitt
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1043.pdf
Status of Parametric Equilibrium Reconstructions for Wendelstein 7-X
J.C. Schmitt , S.A. Lazerson , J. Geiger , J. Schilling , and the W7-X Team
1 2 3 3
1
Auburn University, Auburn, AL, U.S.A
2
Princeton Plasma Physics Laboratory, Princeton, NJ, U.S.A.
3
Max-Planck-Institut für Plasmaphysik, Greifswald, Germany
The reconstruction of the plasma equilibrium is a vital tool for toroidal fusion
experiments to help understand plasma performance and interpret diagnostic signals. The
procedure involves solving the MHD equilibrium, computing synthetic diagnostic signals
based on that equilibrium, and comparing these signals to measured signals. The
parameters that describe the equilibrium are adjusted to find a best-fit of the measured and
synthetic signals. Information gained from the reconstruction includes details about the
shape of the plasma, the location of the plasma edge, and profile information regarding the
plasma pressure, current, and individual plasma species (e.g. T , N , T , N ). These inferred
e e i i
profiles are used to interpret diagnostic information and are used for further analyses.
The constraints for the reconstructions of plasmas at Wendelstein 7-X (W-7X)
include magnetic diagnostics (‘segmented’ and ‘complete’ Rogowski coils, diamagnetic
and compensated flux loops, saddle coils, field coil currents), Thomson Scattering,
interferometry, electron cyclotron emission, soft x-ray arrays and x-ray imaging crystal
spectroscopy. Treatments of edge constraints related to the edge rotational transform and
divertor location are also presented.
The MHD equilibrium solution is provided by VMEC, which assumes solution with
nested, closed flux surface. The contribution summarizes a benchmarking of the three
equilibrium reconstruction codes that use VMEC: V3FIT (approximate quasi-Newton with
1
SVD), STELLOPT (modified Levenberg-Marquardt, and others), and MINERVA (a 2
Bayesian modelling framework). Furthermore, the current status and future plans for
equilibrium reconstructions for W-7X are shown and discussed.
1
J. D. Hanson, S. P. Hirshman, S. F. Knowlton, L. L. Lao, E. A. Lazarus, and J. M. Shields, Nucl. Fusion 49,
075031 (2009).
2
J. Svensson and A. Werner, 2007 IEEE International Symposium on Intelligent Signal Processing, 2007, pp.
1-6.
