MODIFICATIONS OF PLASMA EDGE ELECTRIC-FIELD AND CONFINEMENT PROPERTIES BY LIMITER BIASING ON THE KT-SC TOKAMAK

Experiments using a biased multiblock limiter in the KT-5C tokamak sho w that positive biasing is more effective than negative biasing in mod ifying the edge electric field, suppressing fluctuations and improving plasma confinement. The biasing effect varies With the limiter area, the toroidal magnetic field and the biasing voltage. By positive biasi ng, the edge profiles of the plasma potential, the electron temperatur e and the density become steeper, resulting in a reduced edge particle flux, an increased global particle confinement time and lower fluctua tion levels of the edge plasma.