Internal transport barrier on<i>q</i>=3 surface and poloidal plasma spin up in JT-60U high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">β</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">p</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>discharges

Spontaneous formation of an internal transport barrier was observed associated with improved confinement in the high-${\mathrm{\ensuremath{\beta}}}_{\mathit{p}}$ 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.