CROSS-FIELD PARTICLE-TRANSPORT IN THE EDGE PLASMA OF TOKAMAK TF-1

Edge plasma turbulence and DC-convection have been investigated in the small, ohmically-heated tokamak TF-1 using an array of radially moveable probes distributed poloidally in the vertical cross-section of the torus. The probes provided simultaneous measurements of both poloidal and radial components of cross-field particle fluxes. A 2D vector map of the particle fluxes due to both DC-convection and turbulence-driven drift demonstrates the complicated patterns of plasma flow in the tokamak boundary. Spatial zones characterized by an inward directed particle flux have been found to exist at the plasma edge. The contribution of DC-convection to the total cross-field particle transport generally exceeds that of the correlated fluctuation-induced drift. Radial and poloidal scans of the intermediate zone between the scrape-off and the main plasma edge provide evidence for small scale, quasi-stationary structure in the electron temperature distribution. The observed closed electron isotherm cells are localized near the limiter edge radius.