An adjoint-based method for optimising MHD equilibria against the infinite-n, ideal ballooning mode

Gaur, Rahul; Buller, Stefan; Ruth, Maximilian E.; Landreman, Matt; Abel, Ian G.; Dorland, William D.

doi:10.1017/s0022377823000995

Title: An adjoint-based method for optimising MHD equilibria against the infinite-n, ideal ballooning mode

Journal Article · 30 October 2023 · Journal of Plasma Physics

DOI: https://doi.org/10.1017/s0022377823000995 · OSTI ID:2406035

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^[2]; Ruth, Maximilian E. ^[3];

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University of Maryland, College Park, MD (United States); University of Maryland
University of Maryland, College Park, MD (United States)
Cornell University, Ithaca, NY (United States)

We demonstrate a fast adjoint-based method to optimise tokamak and stellarator equilibria against a pressure-driven instability known as the infinite-n ideal ballooning mode. We present three finite-β (the ratio of thermal to magnetic pressure) equilibria: one tokamak equilibrium and two stellarator equilibria that are unstable against the ballooning mode. Using the self-adjoint property of ideal magnetohydrodynamics, we construct a technique to rapidly calculate the change in the eigenvalue, a measure of ideal ballooning instability. Using the SIMSOPT optimisation framework, we then implement our fast adjoint gradient-based optimiser to minimise the eigenvalue and find stable equilibria for each of the three originally unstable equilibria.

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Research Organization:: University of Maryland, College Park, MD (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES); National Science Foundation Graduate Research Fellowship

Grant/Contract Number:: FG02-93ER54197; SC0018429

OSTI ID:: 2406035

Journal Information:: Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 5 Vol. 89; ISSN 0022-3778

Publisher:: Cambridge University PressCopyright Statement

Country of Publication:: United States

Language:: English

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