Abstract Details
Abstracts
Author: Francisco J Saenz
Requested Type: Consider for Invited
Submitted: 2026-02-26 13:43:36
Co-authors: R. Gaur, D. Panici, E. Kolemen
Contact Info:
Princeton University
MAE
Princeton, 08540
USA
Abstract Text:
The surface-sheet-current representation on a winding surface for stellarator coils is often treated as a computational convenience that is later discretized into filaments. This type of coil design becomes an inverse magnetostatic problem posed on a winding surface: identifying discrete coil shapes that reproduce a target vacuum magnetic field on the plasma boundary. While widely used, discretization into coils introduces error and restricts the accessible solution space.
However, once one commits to a single-surface coil, the geometry of the coil stops being the primary design variable. Instead, the surface can be programmed by tuning a single parameter defined on the surface; one shapes the current distribution needed to generate a target magnetic field. Rather than searching for contours that define discrete coils, the design problem becomes one of prescribing how electricity flows on a continuous surface.
Favorable for coil design, the solutions for sheet currents to generate a target magnetic field are non-unique, which allows single-surface coils with imposed constraints without ruling out feasible engineering solutions. With this, several coil-design strategies emerge as different functional representations on the same surface: (1) variable conductivity distributions, (2) sources and sinks of electric current, (3) electric dipoles, (4) binary conductivity on the coil surface for current paths and (5) variable magnetic permeability surface. These representations provide a unifying mathematical structure for coil design rooted in surface programming rather than discrete coil geometry.
This work presents results demonstrating that multiple magnetic field configurations can be achieved with each of these sheet-current methods while satisfying Ohm’s law. This formulation connects stellarator optimization to a broader solution space for coils and opens a flexible pathway for rapidly and cheaply exploring stellarator equilibria in midsize experimental devices.
Characterization: 4.0
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