Internal transport barrier onq=3 surface and poloidal plasma spin up in JT-60U high-βpdischarges

Spontaneous formation of an internal transport barrier was observed associated with improved confinement in the high-${\mathrm{\beta }}_{\mathit{p}}$ 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 rotation velocity that significantly exceeded the prediction of the present neoclassical theory was also observed at r/a=0.8.