Modelling of improved confinements in tokamak

Recently various improved modes have been found other than H-mode in tokamaks. In H-mode the steep gradient is established only near the edge region. Other improved modes are characterized by the peaked density/ion temperature profiles. In this paper, a model of peaked density profile in the core associated with sheared rotation due to E'r and the extended model of H-mode based on the bifurcation of E'r at the edge are presented. Both confinements are related to the plasma rotations due to Er(E'r) in edge and core regions. If the plasma radius is large, combined structure can exist. (author) 4 refs., 3 figs