Neoclassical radial electric field and transport with finite orbits - art.no. 055002

Neoclassical transport in a toroidal plasma with finite ion orbits is studi ed, including for the first time the self-consistent radial electric field. Using a low-noise deltaf particle simulation, we demonstrate that a deep e lectric-field well develops in a region with a steep density gradient, beca use of the self-collision-driven ion flux. We find that the electric field agrees with the standard neoclassical expression, when the toroidal rotatio n is zero, even for a steep density gradient. Ion thermal transport is modi fied by the electric-field well in a way which is consistent with the orbit squeezing effect, but smoothed by the finite orbits.