Plasma turbulence simulations with X-points using the flux-coordinate independent approach

TL;DR

This paper develops and demonstrates the Flux-Coordinate Independent (FCI) approach for simulating plasma turbulence in complex magnetic fields, including X-points and stochastic lines, showing its effectiveness in various turbulent regimes.

Contribution

The paper formulates the FCI method for static magnetic fields with X-points and stochastic lines, and applies it to nonlinear turbulence simulations with reduced resolution.

Findings

Standard ITG features are recovered with reduced toroidal resolution.

The FCI approach is applicable to turbulence with static magnetic islands.

Simulations demonstrate the method's wide applicability to ITER-like parameters.

Abstract

In this work, the Flux-Coordinate Independent (FCI) approach to plasma turbulence simulations is formulated for the case of generic, static magnetic fields, including those possessing stochastic field lines. It is then demonstrated that FCI is applicable to nonlinear turbulent problems with and without X-point geometry. In particular, by means of simulations with the FENICIA code, it is shown that the standard features of ITG modes are recovered with reduced toroidal resolution. Finally, ITG turbulence under the influence of a static island is studied on the transport timescale with ITER-like parameters, showing the wide range of applicability of the method.