Evaluation of stochastic layer near separatrix in toroidal divertor

Stochasticity of magnetic field lines near the separatrix in the Toroidal Divertor Tokamak is investigated by the island overlapping model and the separatrix mapping method. Both results indicate that the undisturbed confinement core region can exist, and the width of stochastic region is found to be controllable by the x-point position and poloidal magnetic field. The width of stochastic layer obtained by the more reliable separatrix mapping method was larger than that determined by the island overlapping model. 3 refs., 2 figs