Momentum confinement in DIII-D shots with impurities

A neoclassical momentum transport model, consisting of gyroviscous and convective components, is applied to the analysis of momentum confinement in DIII-D [Luxon, Anderson, Batty et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (IAEA, Vienna, 1987), Vol. 1, p. 159] experiments with significant impurity content. Good agreement between predicted and measured central rotation speeds and momentum confinement times is obtained, for L-mode (low-mode) discharges with and without neon injection and for an ELMing (edge-localized modes) H-mode (high-mode) discharge. The observed improvement in momentum confinement time with increasing neon impurity content in the L-mode shots can be accounted for by a neoclassical inward convective momentum flux that increases with impurity content.