The edge fluctuations and transport in the HT-7 tokamak are investigated using a Langmuir probe array in ohmic and IBW heated discharges. The normalized fluctuation levels are in the range 15-60% and 5-20% for electron density and temperature, respectively, and have the non-Boltzmann relation ef/Te > ñe/ne > e/Tein the SOL of the ohmically heated plasmas. The fluctuation spectra show typical broadband features as observed in other tokamaks. In IBW heated plasmas, the particle confinement is greatly improved and the poloidal velocity shear in the SOL is strongly modified in a manner that is equivalent to an additional poloidal velocity in theelectron diamagnetic direction produced by the IBW. A decorrelation in the fluctuations and the suppression of turbulent transport by the effect of the poloidal shear are found to be common mechanisms that are observed from the radial profiles of the fluctuating quantities in all these discharges. Electrostatically driven turbulent transport can account for a significant part of global particle losses in both ohmic and IBW heated plasmas.
Effect of poloidal velocity shear on the edge fluctuations in the SINP tokamak