First principles of modelling the stabilization of microturbulence by fast ions
Journal article, 2018

The observation that fast ions stabilize ion-temperature-gradient-driven microturbulence has profound implications for future fusion reactors. It is also important in optimizing the performance of present-day devices. In this work, we examine in detail the phenomenology of fast ion stabilization and present a reduced model which describes this effect. This model is derived from the high-energy limit of the gyrokinetic equation and extends the existing 'dilution' model to account for nontrivial fast ion kinetics. Our model provides a physically-transparent explanation for the observed stabilization and makes several key qualitative predictions. Firstly, that different classes of fast ions, depending on their radial density or temperature variation, have different stabilizing properties. Secondly, that zonal flows are an important ingredient in this effect precisely because the fast ion zonal response is negligible. Finally, that in the limit of highly-energetic fast ions, their response approaches that of the 'dilution' model; in particular, alpha particles are expected to have little, if any, stabilizing effect on plasma turbulence. We support these conclusions through detailed linear and nonlinear gyrokinetic simulations.

fast ions

simulation

microturbulence

stabilization

gyrokinetics

turbulence

Author

George Wilkie

Chalmers, Physics, Subatomic and Plasma Physics

Aylwin Iantchenko

Chalmers, Physics, Subatomic and Plasma Physics

Ecole Polytechnique Federale De Lausanne

Ian Abel

Chalmers, Physics, Subatomic and Plasma Physics

Edmund Hood Highcock

Chalmers, Physics, Subatomic and Plasma Physics

Istvan Pusztai

Chalmers, Physics, Subatomic and Plasma Physics

Nuclear Fusion

0029-5515 (ISSN)

Vol. 58 8 082024

Implementation of activities described in the Roadmap to Fusion during Horizon 2020 through a Joint programme of the members of the EUROfusion consortium (EUROfusion)

European Commission (EC), 2014-01-01 -- 2019-01-01.

Research for future fusion reactors: using or avoiding impurities

Swedish Research Council (VR), 2015-01-01 -- 2018-12-31.

Subject Categories

Applied Mechanics

Other Physics Topics

Fusion, Plasma and Space Physics

DOI

10.1088/1741-4326/aab727

More information

Latest update

9/19/2018