Global gyrokinetic simulations of ASDEX Upgrade up to the transport time-scale with GENE-Tango

TL;DR

This paper introduces GENE-Tango, a coupled gyrokinetic and transport solver, enabling high-fidelity, long-time plasma profile simulations that incorporate complex physics and significantly reduce computational costs, advancing fusion research.

Contribution

The paper presents the first coupling of GENE with Tango, allowing accurate transport-scale simulations with kinetic electrons, electromagnetic effects, and realistic geometries, overcoming previous limitations.

Findings

GENE-Tango accurately reproduces ion temperature peaking in ASDEX Upgrade discharges.

Electromagnetic effects of submarginal MHD instability influence ion temperature profiles.

Expected speedup for ITER scenarios exceeds two orders of magnitude.

Abstract

An accurate description of turbulence up to the transport time scale is essential for predicting core plasma profiles and enabling reliable calculations for designing advanced scenarios and future devices. Here, we exploit the gap separation between turbulence and transport time scales and couple the global gyrokinetic code GENE to the transport-solver Tango, including kinetic electrons, collisions, realistic geometries, toroidal rotation and electromagnetic effects for the first time. This approach overcomes gyrokinetic codes' limitations and enables high-fidelity profile calculations in experimentally relevant plasma conditions, significantly reducing the computational cost. We present numerical results of GENE-Tango for two ASDEX Upgrade discharges, one of which exhibits a pronounced peaking of the ion temperature profile not reproduced by TGLF-ASTRA. We show that GENE-Tango can correctly capture the ion temperature peaking observed in the experiment. By retaining different physical effects in the GENE simulations, e.g., collisions, toroidal rotation and electromagnetic effects, we demonstrate that the ion temperature profile's peaking is due to electromagnetic effects of submarginal MHD instability. Based on these results, the expected GENE-Tango speedup for the ITER standard scenario is larger than two orders of magnitude compared to a single gyrokinetic simulation up to the transport time scale, possibly making first-principles ITER simulations feasible on current computing resources.