Turbulence and Transport in Spectrally Accelerated full-f Gyrokinetic Simulations

TL;DR

This paper demonstrates that the spectrally accelerated full-f gyrokinetic code GENE-X accurately reproduces edge and SOL turbulence features, including TEM-driven transport, and offers a robust, first-principles tool for plasma turbulence prediction.

Contribution

The study extends the spectral full-f gyrokinetic approach to edge and SOL turbulence, showing it matches grid-based results and captures key turbulence features.

Findings

Accurately reproduces turbulence profiles and spectra.

Captures key features of TEM-driven turbulence.

Remains robust with increased spectral resolution.

Abstract

We investigate edge and scrape-off layer (SOL) turbulence and transport using the spectrally accelerated full-f gyrokinetic (GK) code GENE-X, recently introduced in [B. J. Frei et al., arXiv:2411.09232 (2024)]. Extending previous work on the TCV-X21 scenario, we show that the velocity-space spectral approach not only reproduces outboard midplane profiles but also captures key features of trapped electron mode (TEM)-driven turbulence and transport, including fluctuation spectra, turbulent fluxes, phase shifts, and power crossing the separatrix, in close agreement with grid-based results. This agreement remains robust when increasing spectral resolutions. We further analyze the radial force balance (accurately satisfied) and the structure of the radial electric fields and poloidal flows in the edge and SOL. Finally, we contrast our results with Braginskii-like fluid models, which inherently neglect TEMs. These results confirm the spectral full-f GENE-X approach as an efficient and first-principles tool for predicting edge and SOL turbulence.