Modelling of JT-60U Detached Divertor Plasma using SONIC code

The characteristics of the JT-60U detached divertor plasma in the SONIC simulation are investigated. With increasing mid-plane density, the electron temperature at the divertor decreases and the ion flux to the divertor plate increases. At higher densities, the temperature becomes less than 1 eV. However, rollover of the ion flux at the divertor plate, which is a characteristic of the detachment, is not observed. In order to improve the modelling of the detachment, the effects of some assumptions in the model on the divertor plasma characteristics are investigated. In the case with the wall pumping effect and low chemical sputtering, rollover of the ion flux appears. The low recycling and low sputtering yield prevent radiation cooling near the X-point. The appearance of rollover is possibly explained by the decrease in the ionization and the increase in the volume recombination associated with the high upstream density without the large radiation cooling near the X-point.