Reduced turbulent transport in the quasi-isodynamic stellarator configuration CIEMAT-QI4

TL;DR

This paper demonstrates that the CIEMAT-QI4 quasi-isodynamic stellarator configuration exhibits reduced turbulent transport, supported by nonlinear gyrokinetic simulations, and relates this to its approximate maximum-J property, enhancing stellarator performance understanding.

Contribution

It shows that CIEMAT-QI4 has reduced turbulent transport due to its near maximum-J property, combining good confinement, stability, and low neoclassical transport.

Findings

Reduced turbulent transport observed in simulations.

Correlation between maximum-J property and turbulence reduction.

Supports stellarator optimization for better confinement.

Abstract

CIEMAT-QI4 is a quasi-isodynamic stellarator configuration that simultaneously features very good fast-ion confinement in a broad range of $\beta$ values, low neoclassical transport and bootstrap current, and ideal magnetohydrodynamic stability up to $\beta=5\%$. In this paper it is shown that CIEMAT-QI4 also exhibits reduced turbulent transport. This is demonstrated through nonlinear electrostatic simulations with the gyrokinetic code stella, including kinetic ions and electrons. The relation between reduced turbulent transport and the fact that CIEMAT-QI4 very approximately satisfies the so-called maximum-J property is discussed.