Computation of parallel flow and concomitant electric field in the collision dominated edge of tokamak plasmas

Finite Larmor radius effects and inertia become important in the edge region, where the scale lengths of the plasmaparameters are intermediate between the ion Larmor radius and the connection length. Since standard neoclassical theory is not valid in this case, the ambipolarity constraint and the parallel momentum equation of the revisited neoclassical theory [Phys. Plasmas 1, 619 (1994)] are applied to predict the normalized parallel and poloidal speed g = B(theta)/B(phi) upsilon(parallel to)/upsilon(T), and h = upsilon(theta)/upsilon(T), respectively, and therefore the radial electric field E(r) via the usual radial momentum balance equation. The equations also account for the friction with the neutral gas due to recycling and for neutral beam injection. The equations are solved numerically (1) to benchmark with a simplified analytical theory and (2) to explore the parameter space in regions where the simplified analytical theory is not valid.