Nonlinear stabilization of tokamak microturbulence by fast ions

TL;DR

This paper demonstrates that nonlinear electromagnetic effects from fast ions significantly stabilize tokamak microturbulence, reducing ion heat flux and stiffness, based on gyrokinetic simulations aligned with JET experiments.

Contribution

It reveals the crucial role of suprathermal pressure gradients in nonlinear electromagnetic stabilization, enhancing understanding of turbulence control in tokamaks.

Findings

Nonlinear electromagnetic stabilization reduces ion heat flux.

Fast ions significantly augment turbulence suppression.

Results align with experimental observations on JET.

Abstract

Nonlinear electromagnetic stabilization by suprathermal pressure gradients found in specific regimes is shown to be a key factor in reducing tokamak microturbulence, augmenting significantly the thermal pressure electromagnetic stabilization. Based on nonlinear gyrokinetic simulations investigating a set of ion heat transport experiments on the JET tokamak, described by Mantica et al. [Phys. Rev. Lett. 107 135004 (2011)], this result explains the experimentally observed ion heat flux and stiffness reduction. These findings are expected to improve the extrapolation of advanced tokamak scenarios to reactor relevant regimes.