Speaker
Michio Okabayashi
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1051.pdf
Locked-Tearing Mode Control by 3D Magnetic Field Entrainment
in the presence of Static Error Fields
1
M. Okabayashi, 2S. Inoue, 3E. Strait, 3N.Z. Taylor, 1N. Ferraro, 3J. de Grassie, 4J. Hanson, 3R.
La Haye, 1S. Jardin and 1N. Logan
1
Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543-0451, USA
2
National Institutes for Quantum and Radiological Science and Technology, 801-1
Mukoyama, Naka, Ibaraki 311-0193, Japan
3
General Atomics, PO Box 85608, San Diego, CA 92186-5608, USA
4
Columbia University, 2960 Broadway, New York, NY 10027-6900, USA
DIII-D experiments on control of locked tearing modes using applied 3D fields are in
good qualitative agreement with predictions of a non-linear reduced MHD code (AEOLUS-
IT) [1]. The plasma condition was the ITER base line scenario target with low safety factor
discharges. The simulation is nonlinear, but highlights fundamental processes by simplifying
the physics to isolate a single helicity with m/n=2/1, using only the vorticity equation and
Ohm’s law without any additional transport properties. In the experiment, internal mode
structures were monitored by the perturbed rotation and ion temperature profiles measured by
Charge Exchange Recombination (CER) in this very low mode frequency (zero-100 Hz)
regime. Experiments have illuminated several critical physical processes that are qualitatively
consistent with non-linear reduced MHD simulations. One example is the consistency of
external kink- and tearing- mode structure in the partial / full applied 3D field penetration.
This shows that the possible non-linear process of kink-tearing mode coupling during tearing
mode locking can be well represented by a relatively simplified model. Another example is
the qualitative agreement of the formation of second-harmonic-type rotational structure very
near q=2 surface with very little fundamental component. On the other hand, the magnetic
structure remains fundamental. This implies a possible second harmonic effect for non-linear
self-stabilization. Predictive understanding of mode time-evolution is crucial to designing a
feedback scheme that will help to avoid disruptions in present and future devices. This work
was supported in part by the US Department of Energy under DE-AC02-09CH11466, DE-FC02-
04ER54698, DE-FG02-04ER54761
(1) S. Inoue et al., NF 2017 57, 116020-10, S. Inoue et al., PPCF 2018 online
