The characteristics of ohmically and high power neutral beam heated (PNBI ∼ 20 MW) hydrogen divertor plasmas in JT-60 are analysed on the basis of a plasma fluid model. The calculated radiation loss of the divertor plasma and the density dependence of the neutral pressure in the divertor chamber are qualitatively in good agreement with the experimental results. The divertor radiation loss in ohmically heated discharges can be explained by hydrogen line radiation and impurity radiation. The higher neutral pressure in neutral beam heated discharges can be explained by the decrease of the global particle confinement time in comparison with that in ohmically heated discharges.
Characteristics of the divertor plasma in neutral-beam-heated ASDEX discharges