Speaker: Dr. Nate Ferraro, Princeton Plasma Physics Laboratory
Title: Extended-MHD Stellarator Modeling with M3D-C1
Abstract:
The nonlinear extended-magnetohydrodynamics (MHD) code M3D-C1 has been adapted to enable simulations of strongly-shaped stellarators [1]. This capability has been applied to W7-X, LHD, NCSX, and other novel configurations to explore beta limits, nonlinear stability, and self-consistent profiles in the presence of sources, anisotropic transport, and nonintegrable magnetic geometry. M3D-C1 simulations of W7-X scenarios were able to reproduce the sawtooth-like behavior observed in W7-X driven by electron cyclotron current drive, yielding insight into the cause of the observed double-crashes [2]. Additional W7-X simulations provide a consistent explanation for the robustness of standard W7-X operating scenarios at high-beta, finding that ballooning modes, which tend to be radially localized and to saturate at low amplitude, drive significantly less transport than low-n interchange modes that may be present in some low-shear configurations, even at low-beta [3]. M3D-C1 simulations in LHD configurations explored soft beta limits by simulating the heating of the plasma from vacuum fields, showing the formation of islands and chaotic regions as MHD stability thresholds were crossed [4]. In addition to these recent studies, new capabilities are now under development or being tested to calculate resistive linear stability; to calculate fast-ion transport self-consistently with MHD evolution; to interface calculated equilibria (with potentially nonintegrable magnetic geometry) with neoclassical codes; and to include a bootstrap current model in quasisymmetric configurations. The numerical methods used by M3D-C1 that set it apart from other nonlinear extended-MHD codes will be discussed. Interfaces to neoclassical codes are done using Fusion-IO, an application programming interface that provides a code-independent interface to data from a variety of MHD and equilibrium codes. These developments provide a useful set of tools for high-fidelity stellarator design validation and MHD analysis.
[1] Y. Zhou, N.M. Ferraro, S.C. Jardin, and H.R. Strauss, Nucl. Fusion 61 086015 (2021)
[2] Y. Zhou, K. Aleynikova, and N.M. Ferraro, Phys. Plasmas 30, 032503 (2023)
[3] Y. Zhou, K. Aleynikova, C. Liu, and N.M. Ferraro, Phys. Rev. Lett. 133, 135102 (2024)
[4] A. Wright, N.M. Ferraro, Phys. Plasmas 31, 102509 (2024)
Bio: Nate Ferraro is a research scientist at the Princeton Plasma Physics Laboratory, focusing on computational magnetohydrodynamics. His research has included modeling disruptions and edge localized modes in tokamaks, the plasma response to error fields, and stability limits in stellarators. Dr. Ferraro presently serves as the Deputy Head of the PPPL Theory department. Prior to joining PPPL, he was a member of the Theory and Computational Science group at General Atomics.