Plasma Confinement Modification in IR-T1 Tokamak by Velocity Shear Stabilization

摘要

E × B velocity shear effects on the plasma confinement were investigated in the IR-T1 tokamak. The investigations have been done at the presence of external applied electric and Resonant Helical magnetic Fields (RHF). In this work, experimental data have been measured by using two arrays of the Langmuir probes in both the radial and poloidal directions. A velocity shear stabilization mechanism has also been proposed to be responsible for an improvement in plasma confinement. The results show that E_r × B drift velocity (V_(E×B)) reduces about 90 % due to applied biasing and RHF at edge plasma. We have also observed that positive biasing and RHF lead to a significant decrease (＞80 %) for radial turbulent transport (Γ_(E×B)) at edge plasma. In this paper, the electrostatic Reynolds stress (Rs) and the shearing rate γ_(E×B) have been calculated. We have also compared the Rs and γ(E×B) at presence of the biasing and RHF and without biasing and RHF. A good correlation between confinement modifications and E_r × B velocity shear has been found suggesting that confinement enhancement originates at the edge plasma as a consequence of the formation of a particle transport barrier just inside the limiter.