Direct Microstability Optimization of Stellarator Devices

TL;DR

This paper introduces a method to optimize stellarator designs by coupling stellarator optimization with linear gyrokinetic simulations to reduce turbulent heat flux, balancing neoclassical and turbulent transport.

Contribution

It presents a novel approach that integrates gyrokinetic simulations into the stellarator optimization process to directly minimize microstability-related turbulence proxies.

Findings

Significant reduction in quasilinear heat flux achieved.

Effective coupling of optimization with gyrokinetic simulations.

Balanced reduction of neoclassical and turbulent transport.

Abstract

Turbulent transport is regarded as one of the key issues in magnetic confinement nuclear fusion, both for tokamaks in stellarators. In this work, we show that a significant decrease in a microstability-based proxy, as opposed to a geometric one, for the turbulent heat flux, namely the quasilinear heat flux, can be obtained in an efficient manner by coupling stellarator optimization with linear gyrokinetic simulations. This is accomplished by computing the quasi-linear heat flux at each step of the optimization process, as well as the deviation from quasisymmetry, and minimizing their sum, leading to a balance between neoclassical and turbulent transport proxy.