Improved energy confinement with nonlinear isotope effects in magnetically confined plasmas

TL;DR

This paper demonstrates through gyrokinetic simulations that nonlinear isotope effects significantly influence energy confinement in magnetically confined plasmas, impacting future nuclear fusion reactor designs.

Contribution

It reveals the nonlinear multiscale microturbulence effects involving isotope mass, zonal flows, and electromagnetic interactions that explain isotope-dependent confinement.

Findings

Plasma microturbulence depends on isotope mass via nonlinear effects.

Nonlinear interactions involve zonal flows and electromagnetic effects.

Implications for designing multi-ion species fusion reactors.

Abstract

The efficient production of electricity from nuclear fusion in magnetically confined plasmas relies on a good confinement of the thermal energy. For more than thirty years, the observation that such confinement depends on the mass of the plasma isotope and its interaction with apparently unrelated plasma conditions has remained largely unexplained and it has become one of the main unsolved issues. By means of numerical studies based on the gyrokinetic theory, we quantitatively show how the plasma microturbulence depends on the isotope mass through nonlinear multiscale microturbulence effects involving the interplay between zonal flows, electromagnetic effects and the torque applied. This finding has crucial consequences for the design of future reactors since, in spite of the fact that they will be composed by multiple ion species, their extrapolation from present day experiments heavily relies on the knowledge obtained from a long experimental tradition based in single isotope plasmas.