不純物輸送研究の現状

摘要: Present status of impurity transport study in tokamaks is reviewed. Ohmically-heated and neutral-beam heated L-mode discharges exhibit anomalous impurity transport. The values of particle diffusivity range from 0.5 to 2m 2/s. With improved energy confinement such as in H-mode, impurity transport is suppressed, which results in a radiation collapse of H-mode state in the absence of edge-localized mode (ELM). With high power neutral beam heating, frequent ELMs expel particles and heat out of the separatrix surface, which results in long (-5seconds), quasi-stationary H-mode.