Controlling Tokamak Geometry with 3D Magnetic Perturbations

TL;DR

This paper demonstrates that small 3D magnetic perturbations can effectively modify tokamak flux surface geometry, influencing turbulence and stability, with potential for controlled plasma performance improvements.

Contribution

It reveals that non-resonant 3D magnetic fields, combined with axisymmetric shaping, can control flux surface deformations impacting tokamak stability.

Findings

3D magnetic perturbations significantly alter flux surface geometry.

Non-resonant fields primarily induce dominant flux surface deformations.

Spectral control of 3D fields influences turbulence and stability.

Abstract

It is shown that small externally applied magnetic perturbations can significantly alter important geometric properties of magnetic flux surfaces in tokamaks. Through 3D shaping, experimentally relevant perturbation levels are large enough to influence turbulent transport and MHD stability in the pedestal region. It is shown that the dominant pitch-resonant flux surface deformations are primarily induced by non-resonant 3D fields, particularly in the presence of significant axisymmetric shaping. The spectral content of the applied 3D field can be used to control these effects.