The role of neoclassical convection in the confinement improvement of plasmas with impurity injection in DIII-D

Abstract

A series of three otherwise identical DIII-D ͓J. L. Luxon, F. Batty, C. B. Baxi et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 ͑International Atomic Energy Agency, Vienna, 1987͒, Vol. I, p. 159͔ L-mode ͑low confinement mode͒ plasma experiments with and without neon injection was analyzed with neoclassical theory. The measured increases in momentum and energy confinement times, central rotation speed, and EϫB with increasing neon injection are predicted quantitatively by neoclassical theory, in particular by the predicted increase in the inward neoclassical convective momentum and energy fluxes with neon injection. This agreement between theory and experiment suggests that the physical mechanism by means of which neon injection improves the confinement of these L-mode DIII-D plasmas is to increase the inward neoclassical particle flux, and hence increase the inward convective momentum and energy fluxes.