Particle control in long-pulse H-mode discharges of JT-60U

Abstract

An H-mode plasma was successfully maintained for∼30 s at a constant density of by using divertor pumping even under the outgassing condition. At a high density of , an H-mode plasma was maintained for ∼25 s with a continuous fuel retention, which was ascribed to low outgassing, high co-deposition of deuterium with carbon and the dynamically changed fuel retention process. It was found that the third process worked with the change in edge plasma parameters, in particular particle flux, so as to maintain the electron density against the density control: the outgassing dominated when the divertor pumping was on and the fuel retention dominated when the divertor pumping was off.