Suppression of electric and magnetic fluctuations and improvement of confinement due to current profile modification by biased electrode in Saha Institute of Nuclear Physics tokamak

Improvement of plasma confinement is achieved in normal qa discharges of SINP-tokamak by introducing a biased electrode inside the last closed flux surface. All the important features of high confinement mode are observed biasing the electrode negatively with respect to the vacuum vessel. Arrays of electric and magnetic probes introduced in the edge plasma region reveal suppression of electric and magnetic fluctuations over distinct frequency ranges as well as modification of the toroidal current profile due to biasing. Further analysis identifies the electrostatic fluctuations to be due to drift mode and the magnetic fluctuations may be of slow compressional Alfven waves. Both get suppressed due to current profile modification during biasing, hence leading to the improvement of plasma confinement.