Abstract
Experiments on edge localized magnetohydrodynamic (ELMy) H-modes and reversed shear modes in JT-60U are presented. In ELMy H-mode discharges in conjunction with a W-shaped pumped divertor, efficient helium exhaust is demonstrated by inner divertor pumping when particle recycling is high in the inner divertor. Despite suppression of the backflow of neutrals, degradation of global energy confinement with the W-shaped divertor is similar to that with an open divertor. In recent reversed shear experiments, the nominal DT fusion power gain reached 1.25. By modulated helium gas puffing to a reversed shear plasma with an internal transport barrier, an inward particle pinch was confirmed in the internal transport barrier (ITB) region. In central ion cyclotron resonance frequency (ICRF) heating of a strongly reversed shear plasma, a hollow heating profile was found while the heating profile in normal (positive) shear peaked at the centre. The measured shine through of a 350 keV hydrogen beam agrees well with theoretical prediction.
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