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Author: Meng Li
Requested Type: Pre-Selected Invited
Submitted: 2018-03-01 16:29:22

Co-authors: D.P.Brennan, A.J.Cole, J.M.Finn

Contact Info:
Princeton University
100 Stellarator Rd
Princeton, New Jersey   08540
United States

Abstract Text:
This work focuses on modeling of disruptive 2/1 magnetohydrodynamic (MHD) instabilities, which onset as high beta is approached with low qmin >= 1 in DIII-D discharges. We present both our theoretical and computational analysis for this problem. In a reduced model of energetic ion interaction with the resistive MHD mode, energetic ions are found to affect the mode stability signi ficantly [M. Halfmoon and D. Brennan, Phys. Plasmas 24, 062501 (2017)]. Yet, plasma rotation and nite frequency response in the tearing layer are ignored in this work, which are known to be crucial for the resistive MHD instabilities, especially the resistive plasma - resistive wall modes [J. Finn, A. Cole, and D. Brennan, Phys. Plasmas 22, 120701 (2015)]. Therefore, we applied a theoretical framework which includes energetic particle effects, resistive wall and plasma rotation. The theoretical work supports our numerical study using the NIMROD code [C. Sovinec et al., J. Comp. Phys. 195, 355(2004)]. Based on experimental reconstructions from DIII-D, we generate a set of realistic equilibria characterized by different magnetic shear and beta for our simulation. We examine the linear stability map using the delta f module [C. Kim and the NIMROD team, Phys. Plasmas 15, 072507 (2008)] in NIMROD, with flow and resistive wall and compare to our theoretical results. We are also initiating nonlinear simulations to interpret the experimental data.

Plasma Properties, Equilibrium, Stability, and Transport