Internal transport barrier with improved confinement in the JT-60U tokamak

Characteristics of the internal transport barrier (ITB) were studied. The region of steep and , i.e. the ITB front, propagated from the core outwards. The thickness of the ITB front was about 3 cm. The ITB worked as a particle transport barrier as well as a thermal transport barrier for ions. The threshold heating power for ITB formation strongly increased with electron density and was independent of the toroidal magnetic field. ITB with was sustained for twice the global energy confinement time . A repetitive relaxation phenomenon at ITB was observed, which induced spikes like ELMs but had a different poloidal distribution.