A geometric approach to constructing quasi-isodynamic fields

Fuente: arXiv
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Main Authors: Plunk, G. G., Rodríguez, E.
Format: Preprint
Published: 2025
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author Plunk, G. G.
Rodríguez, E.
author_facet Plunk, G. G.
Rodríguez, E.
contents The near-axis theory for quasi-isodynamic stellarator equilibria is reformulated in terms of geometric inputs, to allow greater control of the ``direct construction'' of quasi-isodynamic configurations, and to facilitate understanding of the space of such equilibria. This includes a method to construct suitable magnetic axis curves by solving Frenet-Serret equations, and an approach to controlling magnetic surface shaping at first order (plasma elongation), which previously has required careful parameter selection or additional optimization steps. The approach is suitable for studying different classes of quasi-isodynamic stellarators including different axis ``helicities'' and topologies (e.g. knotted solutions), and as the basis for future systematic surveys using higher order near-axis theory. As an example application, we explore a family of configurations with per-field-period axis helicity equal to one half, demonstrating an approximate scaling symmetry relating different field period numbers.
format Preprint
id arxiv_https___arxiv_org_abs_2508_12820
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A geometric approach to constructing quasi-isodynamic fields
Plunk, G. G.
Rodríguez, E.
Plasma Physics
The near-axis theory for quasi-isodynamic stellarator equilibria is reformulated in terms of geometric inputs, to allow greater control of the ``direct construction'' of quasi-isodynamic configurations, and to facilitate understanding of the space of such equilibria. This includes a method to construct suitable magnetic axis curves by solving Frenet-Serret equations, and an approach to controlling magnetic surface shaping at first order (plasma elongation), which previously has required careful parameter selection or additional optimization steps. The approach is suitable for studying different classes of quasi-isodynamic stellarators including different axis ``helicities'' and topologies (e.g. knotted solutions), and as the basis for future systematic surveys using higher order near-axis theory. As an example application, we explore a family of configurations with per-field-period axis helicity equal to one half, demonstrating an approximate scaling symmetry relating different field period numbers.
title A geometric approach to constructing quasi-isodynamic fields
topic Plasma Physics
url https://arxiv.org/abs/2508.12820