Abstract
In DIII-D discharges with centrally enhanced confinement and peaked density profiles there is an accumulation and peaking of impurities in the core, as is predicted by neoclassical theory. In VH-mode discharges with an outer region of enhanced confinement and a broad density profile, the neoclassical thermal screening effect causes the impurities to accumulate near the edge. In discharges with anomalously high transport, the measured particle diffusivities are close to the measured thermal diffusivities and the density profiles are proportional to a fractional power of 1/q. When the plasma has regions of enhanced confinement, where the ion thermal transport is near neoclassical, then the particle transport also exhibits neoclassical transport behavior such as low diffusivities, neoclassical pinch effects and ion temperature gradient screening. Here we present experimental results of both impurity and electron transport in DIII-D discharges with large internal regions of enhanced confinement and discuss the relevance of these results to future tokamak designs.
