Magnetic fields with precise quasisymmetry for plasma confinement

TL;DR

This paper demonstrates that high-precision quasisymmetry in toroidal magnetic fields can significantly improve plasma confinement, with symmetry-breaking modes reduced to geomagnetic field levels over substantial volumes.

Contribution

It shows that both quasi-axisymmetry and quasi-helical symmetry can be achieved with unprecedented precision in large-volume magnetic fields, enhancing plasma confinement capabilities.

Findings

Symmetry-breaking modes can be minimized to ~50 μT levels.

High-precision quasisymmetry is achievable over large aspect ratios.

Enhanced confinement due to reduced symmetry-breaking modes.

Abstract

Quasisymmetry is an unusual symmetry that can be present in toroidal magnetic fields, enabling confinement of charged particles and plasma. Here it is shown that both quasi-axisymmetry and quasi-helical symmetry can be achieved to a much higher precision than previously thought over a significant volume, resulting in exceptional confinement. For a 1 Tesla mean field far from axisymmetry (vacuum rotational transform $>$ 0.4), symmetry-breaking mode amplitudes throughout a volume of aspect ratio 6 can be made as small as the typical $\sim 50$ $\mu$T geomagnetic field.