INTERNAL TRANSPORT BARRIER ON Q=3 SURFACE AND POLOIDAL PLASMA SPIN-UP IN JT-60U HIGH-BETA(P) DISCHARGES

Spontaneous formation of an internal transport barrier was observed associated with improved confinement in the high-beta(p) discharges in the JT-60U tokamak. The radial location of the transport barrier was found to be on the q = 3 surface. A fast magnetohydrodynamic event localized at the transport barrier triggered the subsequent formation of an edge transport barrier that resulted in the further confinement improvement. In these discharges, a high poloidal plasma rotation velocity that significantly exceeded the prediction of the present neoclassical theory was also observed at r/a = 0.8.