Nonresonant Diffusion in Alpha Channeling

TL;DR

This paper develops a theory of alpha channeling in fusion reactors, showing how nonresonant diffusion can suppress rotation drive but enhance fusion reactions through wave-particle interactions.

Contribution

It introduces a coupled linear-quasilinear theory of alpha channeling that explains the role of nonresonant diffusion in fusion plasma dynamics.

Findings

Nonresonant diffusion cancels the resonant alpha current.

Wave growth can fuel the fusion reaction.

Rotation drive is prevented by nonresonant effects.

Abstract

The gradient of fusion-born alpha particles that arises in a fusion reactor can be exploited to amplify waves, which cool the alpha particles while diffusively extracting them from the reactor. The corresponding extraction of the resonant alpha particle charge has been suggested as a mechanism to drive rotation. By deriving a coupled linear-quasilinear theory of alpha channeling, we show that, for a time-growing wave with a purely poloidal wavevector, a current in the nonresonant ions cancels the resonant alpha particle current, preventing the rotation drive but fueling the fusion reaction.