Speaker
Qiming Hu
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1060.pdf
45 EPS Conference on Plasma Physics 13474
Nonlinear modeling of the effect of multi-locked modes on heat transport
Q.M. Hu1, X.D. Du2, Q. Yu3, E. Kolemen4, N. Logan1, R. Nazikian1
1
Princeton Plasma Physics Laboratory, Princeton NJ 08543-0451, USA
2
University of California Irvine, Irvine CA 92697, USA
3
Max-Plank-Institut für Plasmaphysik, 85748 Garching, Germany
4
Mechanical and Aerospace Engineering, Princeton University, Princeton NJ, USA
Experimental evidence of the formation of multiple helicity island chains during the locked
[1]
mode phase preceding plasma disruption is observed on DIII-D . To understand the
experimental results, nonlinear numerical modeling of multi-components (m/n = 2/1, 3/1,
4/1 etc) resonant magnetic perturbations (RMPs) penetration has been studied based on
reduced MHD equations. It is found that after field penetration, the non-rotating magnetic
islands, having helicity of 2/1, 3/1 and 4/1, flatten the temperature at the corresponding
rational surfaces, and the co-existence these islands significantly enhances the plasma heat
transport from q = 2 rational surface to plasma edge. As a result, the core temperature is
decreased by more than 50% in a time scale of 100 ms. In addition, the temperature profile
from 2/1 to 4/1 rational surface can be nearly flattened even if there is no island overlap,
and the temperature inside the islands are determined by outboard separatrix of the island.
The mild increase of RMP amplitude leads to an island overlap between 3/1 and 4/1, and
further induces the rapid cooling the temperature inside 2/1 rational surface. The results
indicate that by the presence of error field of application of RMPs, the plasma is susceptible
to multi-helicity locked modes. These island chains further deteriorate plasma thermal
confinement, which may be responsible for the fast thermal quench proceeding plasma in
major disruption.
Fig. Time evolution of Te
profile and 2D profile of
Te together with magnetic
flux surface.
Acknowledgement: The experimental target plasma described here were performed on the DIII-D
National User Facility operated by General Atomics in San Diego, CA for the U.S. Department of
Energy under contract number DE-AC02-09CH11466, early career research program
DE-FOA-0001386, and award number DE-SC0015878 and DE-FC02-04ER54698.
[1] Du X.D., et al, A Key Role of Multiple, High-order, Small Locked Island Chains in Triggering
Plasma Major Disruption in DIII-D tokamak, to be submitted.
