Optimisation of confinement in a fusion reactor using a nonlinear turbulence model

TL;DR

This paper presents a novel multidimensional optimization of fusion reactor confinement, employing first-principles nonlinear turbulence simulations to enhance plasma power output by adjusting flux surface geometry.

Contribution

It introduces a first-principles turbulence model integrated into an optimization algorithm for the first time in fusion confinement studies.

Findings

Two-fold increase in plasma power per unit volume.

Optimal confinement achieved with higher elongation and negative triangularity.

Use of gyrofluid and gyrokinetic models for turbulence simulation.

Abstract

The confinement of heat in the core of a magnetic fusion reactor is optimised using a multidimensional optimisation algorithm. For the first time in such a study, the loss of heat due to turbulence is modelled at every stage using first-principles nonlinear simulations which accurately capture the turbulent cascade and large-scale zonal flows. The simulations utilise a novel approach, with gyrofluid treatment of the small-scale drift waves and gyrokinetic treatment of the large-scale zonal flows. A simple near-circular equilibrium with standard parameters is chosen as the initial condition. The figure of merit, fusion power per unit volume, is calculated, and then two control parameters, the elongation and triangularity of the outer flux surface, are varied, with the algorithm seeking to optimise the chosen figure of merit. A two-fold increase in the plasma power per unit volume is achieved by moving to higher elongation and strongly negative triangularity.