Validating modeling assumptions of alpha particles in electrostatic turbulence
Journal article, 2015

To rigorously model fast ions in fusion plasmas, a non-Maxwellian equilibrium distribution must be used. In this work, the response of high-energy alpha particles to electrostatic turbulence has been analyzed for several different tokamak parameters. Our results are consistent with known scalings and experimental evidence that alpha particles are generally well confined: on the order of several seconds. It is also confirmed that the effect of alphas on the turbulence is negligible at realistically low concentrations, consistent with linear theory. It is demonstrated that the usual practice of using a high-temperature Maxwellian, while previously shown to give an adequate order-of-magnitude estimate of the diffusion coefficient, gives incorrect estimates for the radial alpha particle flux, and a method of correcting it in general is provided. Furthermore, we see that the timescales associated with collisions and transport compete at moderate energies, calling into question the assumption that alpha particles remain confined to a flux surface that is used in the derivation of the slowing-down distribution.

Author

George Wilkie

Chalmers, Applied Physics, Nuclear Engineering

E.G. Highcock

W. Dorland

Journal of Plasma Physics

0022-3778 (ISSN) 1469-7807 (eISSN)

Vol. 81 3

Areas of Advance

Energy

Roots

Basic sciences

Subject Categories

Fusion, Plasma and Space Physics

DOI

10.1017/S002237781400124X

More information

Created

1/8/2018 3