Dependence of edge fluctuations on the disruption in tokamak plasmas

Summary form only given. Turbulence in magnetically confined plasmas continues to be one of the most important scientifically challenging research topics in controlled thermonuclear fusion research. Turbulence manifests itself as fluctuations in plasma parameters such as the density, temperature, magnetic field and electrostatic potential. The formation of the edge MHD modes may be caused by the fluctuations. In this work we investigated the dependency of magnetic and electrostatic fluctuations using Mirnov coils, a moveable limiter and Ha light emission in the normal and limiter biased discharges during formation of major disruption in the CT-6B Tokamak. The results shown that there is a close correlation in the fluctuation level and suppression of Ha emission and magnetic field at the core and edge of plasma. Also, it found that by applying positive bias voltages at different current regimes the sudden disruption may be controlled.