Abstract Details
Abstracts
Author: Rahul Gaur
Requested Type: Poster
Submitted: 2023-03-31 12:02:36
Co-authors: Rahul Gaur, David Dickinson, Noah R. Mandell, Matt Landreman, Stefan Buller, Ian G. Abel, William D. Dorland
Contact Info:
University of Maryland, College Park
8815 Patricia Court
College Park, Maryland 20740
United States
Abstract Text:
We present a framework to optimize the high-beta tokamak and stellarator equilibria against ideal MHD and kinetic instabilities. We integrate the SIMSOPT optimization suite with the microstability code GS2 and an infinite-n ideal ballooning solver to optimize an axisymmetric equilibrium. We start with high-$beta$ tokamak and quasisymmetric stellarator(beta_{axis} = 14%) equilibria that are unstable to various electromagnetic instabilities such as the Kinetic Ballooning Mode (KBM), Electromagnetic Electron Temperature Gradient (EM-ETG) mode, and Micro-tearing Mode (MTM). To stabilize these equilibria, we define an objective function F in SIMSOPT that is a function of the maximum linear growth rate gamma_{max} = gamma_{max}(psi, k_x, k_y), obtained by running the aforementioned linear stability codes on multiple flux surfaces labeled by the normalized radius psi for various values of perpendicular wavenumbers k_x, k_y. Using a nonlinear least-squares optimizer in SIMSOPT, we minimize F by varying the initial equilibrium's boundary shape and safety factor profile. The optimizer finds several new equilibria with a lower gamma_{max} than the original equilibrium throughout the inner core region of the plasma. To ensure that a reduction in growth rate corresponds to a reduction in the non-linear heat flux, we calculate the heat and particle fluxes of the stabilized equilibria using the fully electromagnetic code GX.
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