Year: 2026
Type: article
Abstract: We develop a systematic configuration-search methodology for the Heliotron J helical-axis heliotron, combining a Bayesian exploration approach with field-line tracing and evaluation of magnetic field structural parameters. The methodology enables efficient exploration of an enormous coil current parameter space ( ∼ 10 11 possible combinations) and is consistent to VMEC equilibrium calculations. As a demonstration, the methodology is applied to search three magnetic configurations: σ = + 1 (uniform ripple bottom), σ = − 1 (uniform ripple top), and quasi-omnigenous configurations. The σ = + 1 exploration successfully identifies configurations with a factor-of-two reduction in ε eff 3 / 2 , associated with an increase in the bumpiness (toroidal mirror) component. The σ = − 1 exploration yields configurations with worse ε eff 3 / 2 ,as expected, providing as a contrasting reference to the σ = + 1 case. A practical omnigenous configuration was not found, suggesting that the inherent toroidicity cannot be overcome through coil current optimization alone. The developed framework provides a practical methodology for systematic magnetic configuration search within a single device, providing the way for element-wise experimental studies of how individual magnetic field components affect confinement in stellarator/heliotron devices.
Institutions: Kyoto University, National Institute for Fusion Science
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W7203780141