The phenomena of improved edge confinement due to ion cyclotron radio frequency boronization were observed with a fast reciprocating Langmuir probe in the HT-7 tokamak. A strong shear layer of radial electric field was produced in the plasma edge region, which resulted in the formation of an edge transport barrier. Consequently, the edge profiles of electron density were steepened, and both the absolute and relative fluctuation levels were suppressed by the shearing E×B flows. Concomitant reduction of the coherence between electron density and poloidal electric field fluctuations and the change of their cross-phase resulted in turbulent particle flux dropping by more than a half at the plasma edge. This demonstrates the de-correlation effect of turbulence and its contribution to edge transport. The results presented here suggest a link between wall conditions and boundary plasma physics, especially an interaction between atomic processes and turbulence through the formation of radial electric field shear at the plasma edge.
展开▼
