Ohmic and H-mode particle transport in the CCT tokamak edge plasma

Measurements of equilibrium and turbulent plasma parameters in the far edge and scrape-off layer region of CCT H-mode discharges are presented. The results indicate a large reduction in cross-field particle transport rates during the transition from Ohmic to H-mode confinement. The reduced transport is due in part to changes in saturated fluctuation amplitudes as well as changes in the nature of the edge turbulence. In H-mode, the peak cross-field particle flux is reduced by a factor of 3-6 over the flux in an Ohmic discharge. These changes in edge transport rates are similar to changes in global particle confinement time. Analysis of the radial profiles indicates that poloidal and/or toroidal variations in transport play an important role in the overall particle transport. This paper presents measurements of equilibrium and fluctuating plasma parameters made during a CCT H-mode transition. (author) 3 refs., 2 figs