Feasibility of a Flexible, Hybrid Tokamak-Stellarator Experiment using an Axisymmetric Dipole Coil Array
Abstract
We demonstrate the design of a flexible, university-scale hybrid tokamak-stellarator experiment based on an axisymmetric array of planar HTS dipole coils. Because the coil array has few geometric degrees of freedom, we use single-stage optimization of the coil currents initialized from two-stage solutions to obtain mutually consistent equilibria and coil sets within realistic engineering limits. We find that the field error and coil current thresholds set minimum and maximum coil-plasma distances that confine the boundary to a roughly fixed axisymmetric envelope, within which rotational transform, volume, coil current, and quasi-symmetry (QS) error trade off against one another. Tighter current limits delocalize the non-axisymmetric shaping and raise QS error at fixed transform. From this single coil array we obtain a broad range of equilibria-quasi-axisymmetric vacuum stellarators with ι up to 0.2, finite-β hybrids with realistic profiles reaching on-axis ι ≈ 1 and vacuum transform relevant for MHD stabilization, and strongly shaped tokamaks with elongation κ = 1.7 and triangularity δ = ±0.6, all at peak pointwise coil forces well below the HTS tolerance. We show the same array can additionally correct toroidal field (TF) coil ripple, reducing the number of TF coils required compared to the equivalent tokamak. These results establish the design as a promising platform for hybrid tokamak-stellarator research.
Versions
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BibTeX
@misc{halpern2026feasibility,
title = {{Feasibility of a Flexible, Hybrid Tokamak-Stellarator Experiment using an Axisymmetric Dipole Coil Array}},
author = {Jacob Halpern and Mohammed Haque and Elizabeth Paul and Carlos Paz-Soldan and Rithik Banerjee and Talia Angles and Frederick Sheehan and Ian Stewart and Alan Kaptanoglu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.13326},
eprint = {2606.13326},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.13326},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Feasibility of a Flexible, Hybrid Tokamak-Stellarator Experiment using an Axisymmetric Dipole Coil Array
AU - Jacob Halpern
AU - Mohammed Haque
AU - Elizabeth Paul
AU - Carlos Paz-Soldan
AU - Rithik Banerjee
AU - Talia Angles
AU - Frederick Sheehan
AU - Ian Stewart
AU - Alan Kaptanoglu
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2606.13326
UR - https://arxiv.org/abs/2606.13326
AB - We demonstrate the design of a flexible, university-scale hybrid tokamak-stellarator experiment based on an axisymmetric array of planar HTS dipole coils. Because the coil array has few geometric degrees of freedom, we use single-stage optimization of the coil currents initialized from two-stage solutions to obtain mutually consistent equilibria and coil sets within realistic engineering limits. We find that the field error and coil current thresholds set minimum and maximum coil-plasma distances that confine the boundary to a roughly fixed axisymmetric envelope, within which rotational transform, volume, coil current, and quasi-symmetry (QS) error trade off against one another. Tighter current limits delocalize the non-axisymmetric shaping and raise QS error at fixed transform. From this single coil array we obtain a broad range of equilibria-quasi-axisymmetric vacuum stellarators with ι up to 0.2, finite-β hybrids with realistic profiles reaching on-axis ι ≈ 1 and vacuum transform relevant for MHD stabilization, and strongly shaped tokamaks with elongation κ = 1.7 and triangularity δ = ±0.6, all at peak pointwise coil forces well below the HTS tolerance. We show the same array can additionally correct toroidal field (TF) coil ripple, reducing the number of TF coils required compared to the equivalent tokamak. These results establish the design as a promising platform for hybrid tokamak-stellarator research.
ER -