Plasma rotation and electric field effects in H-mode in DIII-D

Poloidal rotation has been observed near the separatrix of H-mode discharges in the DIII-D tokamak. This rotation persists thoughout the entire time of the H-phase and is a general characteristic of all H-mode discharges studied to date. The force balance equation for a single ion species shows unambiguously that the poloidal rotation is produced by a negative radial electric field. Field strengths of at least 200-300 V/cm have been inferred 1-3 cm inside the separatrix, and the electric field may extend across the separatrix into the scrape-off layer. This paper discusses the techniques used to measure poloidal rotation and the salient features of the rotation. (author) 6 refs., 2 figs