Abstract Details
| status: | file name: | submitted: | by: |
|---|---|---|---|
| approved | sherwood_ebrahimi2026__2_.pdf | 2026-02-27 18:02:26 | Fatima Ebrahimi |
Abstracts
Author: Fatima Ebrahimi
Requested Type: Consider for Invited
Submitted: 2026-02-27 18:01:40
Co-authors: J. King, T. Cote, A. O. Nelson, N. Leuthold, J. Dominguez-Palacios, K. E. Thome,C. Paz-Soldan, and F. Scotti
Contact Info:
Princeton Plasma Physics Laboratory
Stellarator RD
Princeton , 08540
USA
Abstract Text:
Recent DIII-D ELM-free strongly shaped NT plasmas have exhibited edge MHD dynamics with pronounced magnetic fluctuations [T. Cote et al. PPCF 2025]. Understanding and predicting the onset and saturation of these edge magnetic fluctuations within the MHD framework is crucial for assessing the viability of NT plasma shaping for fusion power plant (FPP). Here, we have carried out global extended MHD simulations of strongly shaped (with average triangularity delta = -0.54) plasmas at both low and high beta, as well as weakly shaped (delta =-0.01) NT DIII-D discharges. The NIMROD model includes two-fluid, electron inertia, ion gyroviscosity, and multispecies collisionality via Spitzer resistivity and heat conductivities from Braginskii closures. The multispecies corrections, in particular due to enhanced resistivity when carbon species are included, provide realistic diffusivities for the onset of edge instabilities. Here we obtain ELM-free NT states for strongly shaped discharges. Consistent with the experimental observations, we find pronounced global n=1 edge MHD mode activities in all these discharges. By performing a systematic Lundquist number (S) scaling and including multispecies collisionality, we first uncover a strong S scaling (~ S^{-0.6-0.7}) of tearing-like nature for strongly shaped NT plasmas while a rather weaker S scaling (~ S^{-0.4}) of interchange pressure-driven nature is obtained for the weakly shaped NT discharge. The strong S scaling of the reconnecting n = 1 edge mode in strongly shaped NT plasmas, at both high and low beta, indicates a favorable suppression of edge tearing mode activity as S increases, particularly toward the FPP projection. Second, our nonlinear simulations show a good agreement with experimental measurements obtained via electron cyclotron emission imaging (ECE-I) mode structure. Some highlights of nonlinear results, including relaxation of plasma current via a two-fluid dynamo effect will also be discussed.
Characterization: 2.0
Comments: