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DOE OSTI · 2406035

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.
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Abstract

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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70 PLASMA PHYSICS AND FUSION TECHNOLOGYfusion plasmaplasma confinementplasma instabilities

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Gaur, Rahul, Buller, Stefan, Ruth, Maximilian E., Landreman, Matt, Abel, Ian G., Dorland, William D.. 2023-10-31. An adjoint-based method for optimising MHD equilibria against the infinite- n , ideal ballooning mode. https://doi.org/10.1017/s0022377823000995

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