Physical Interpretation of Current Start-Up by rf in WT-2 Tokamak

In order to reveal the physical mechanism of the plasma current start-up experiment by rf in WT-2 tokamak, a two dimensional Fokker-Planck equation, which includes quasilinear diffusion terms of electron cyclotron wave (ECW) and lower hybrid wave (LHW), particle and energy losses, is solved computationally. The calculations show the following results; In the initial electron cyclotron heating plasma, the applied vertical field B V cancels the toroidal drift for some electrons which generate a current to produce the poloidal field and the electrons are confined in an equilibrium position. The dependence of generated currents on B V qualitatively agrees with experimental results. Further, the electrons, which are accelerated in the perpendicular direction by ECW, are pitch-angle scattered by Coulomb collision to the parallel direction and quasilinearly interact with LHW having high phase velocity, resulting in a toroidal current start-up.