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

Abstract. H-modes operated at higher li with the current ramp down have shown higher energy confinement with higher density in JT-60U. The H-factor evaluated for the core plasma depends strongly on li with the relation of H89core ∝ li 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. The enhanced energy confinement in high li H-modes is attributed to the core improvement with the peaked profiles of electron density and electron temperature while no explicit difference in pedestal profile is observed. The electron heat diffusivity is reduced at the plasma core in high li case, resulting in the center peaked Te profile while the Ti profiles are approximately unchanged. In addition, the characteristics of the spatial width Δped of the H-mode pedestal are investigated in hydrogen and deuterium plasmas in JT-60U. Similar edge profiles of the ion temperature are obtained for both cases while ρ*pol is not fixed but differs by a factor of ~1.4 (which is the square root of the mass ratio). This result suggests a weak dependence of Δped on ρ*pol. Based on these dimensionless parameter scans, the scaling was evaluated as Δped ∝ aρ*pol βpol.