High-throughput full-f gyrokinetics of the tokamak boundary

TL;DR

This paper introduces a high-throughput, fully automated approach to global gyrokinetic simulations of tokamak boundaries, enabling systematic parameter scans and detailed analysis of plasma behavior.

Contribution

It demonstrates a paradigm shift by performing hundreds of concurrent, unsupervised full-f boundary gyrokinetic simulations, previously infeasible due to computational complexity.

Findings

Plasma shaping impacts confinement in a power-dependent manner.

Triangularity influences SOL ion temperature at low power and edge ion temperature gradient at high power.

The dataset can serve as a benchmark and training resource for fusion modeling.

Abstract

Full-f global gyrokinetic simulations of the plasma boundary have until now required heroic computational efforts and case-by-case expert intervention, precluding systematic parameter scans. Here we demonstrate a paradigm shift: hundreds of independent, concurrent, and unsupervised full-f boundary gyrokinetic simulations in a geometry inspired by the Tokamak \`a Configuration Variable (TCV), covering both the closed flux surface region and the open-field-line scrape-off layer (SOL) while scanning triangularity, elongation, and heating power. All simulations are evolved much longer than the turbulence relaxation time until the steady state is reached. Analysis of the steady-state profiles reveals that the impact of plasma shaping on confinement is strongly power dependent: at low power, triangularity primarily controls the SOL ion temperature, while at high power it mostly affects the edge ion temperature gradient. The low-power hot SOL observed for positive triangularity is explained by a neoclassical trapped-ion mechanism in which triangularity modifies the field-line arc length between banana turning points and the high-field-side limiter, altering the interaction with cold neutral-ionization regions. Fingerprint analysis of turbulent transport categorize the simulations in a regime dominated by ion temperature gradient (ITG) or trapped electron modes (TEMs), confirmed by dedicated local linear gyrokinetic calculations. The generated open data represents a previously unobtainable resource. It can serve both as a benchmark for boundary transport models, and as a training dataset for data-driven methods in fusion foundation and surrogate models.