Heat transport and pedestal structure of H-mode in the variation of current density profiles in JT-60U

H-modes operated at higher li with the current ramp down have shown higher energy confinement with higher density. The H-factor evaluated for the core plasma depends strongly on li, with the relation of H89core ∼ li0.74 for the case without sawtooth activities. Center peaked profiles of electron density and electron temperature are obtained in high li H-modes. While the peripheral current density profiles are largely modified by the current ramp, the pedestal pressure is not significantly changed. Thus, the increased density in high li H-modes is attributed to the peaked density profile with no explicit difference in pedestal profiles. It was found for the first time that the electron heat diffusivity is reduced at the centre in high li case, resulting in the centre peaked Te profile while the Ti profiles are approximately stiff. (author)