Greifswald 2024 – scientific programme

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P: Fachverband Plasmaphysik

P 5: Magnetic Confinement II/HEPP II

P 5.3: Talk

Monday, February 26, 2024, 17:20–17:45, ELP 6: HS 3

Direct Construction of Large Aspect Ratio Quasi-isodynamic Stellarators — •Katia Camacho Mata, Gabriel G. Plunk, and Alan G. Goodman — Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany

Quasi-isodynamic (QI) stellarators are attractive fusion reactor candidates due to their good confinement properties, inherent steady-state operation, low toroidal currents and favourable turbulence properties. However, optimisation methods traditionally used to find QI fields are highly dependent on the initial guess, often result in complicated geometries and do not offer physical insight into the solution space structure. The near-axis expansion (NAE) method, an expansion of the magnetohydrodynamic equations, can be used to construct exact QI equilibria in the vicinity of the magnetic axis, to first or second order. The NAE method is discussed, and it is shown that configurations with low neoclassical transport and simple boundary shapes can be constructed, even far from the axis, by carefully choosing the initial NAE parameters. The QI solution space structure is investigated using these parameters. The role the helicity of the magnetic axis plays in dividing the space into regions with different confinement properties is described and is used to construct NA QI solutions similar to existing optimised stellarators. The strengths of the NAE are discussed, namely its suitability to provide initial points for traditional optimization, and the ability to perform a systematic and exhaustive search of the QI solution space, aiding in the search of the next generation stellarator designs.

Keywords: Stellarator; Quasi-isodynamic; Near-axis expansion; Optimization