Modification of edge current profile and improved confinement induced by biased electrode in the very low qa (VLQ) discharges of SINP ? tokamak

A better energy-confined state with modified current density profile is achieved by fast biasing (applied voltage rise time ~ the ion?ion collision time) an electrode placed inside the limiter in very low qa discharges of the Saha Institute of Nuclear Physics?tokamak (SINP?Tokamak) (Lahiri et al 1996 Nucl. Fusion 36 254). The plasma current increases and lasts for an extended period. Profile modification of the radial electric field (Er) in the edge region is also observed in the better-confined state. However, j?-profile modification as well as energy confinement time improvement occurs prior to Er-profile modification.