Study of Particle Behavior for Steady-State Operation in JT-60U

Abstract

This paper summarizes recent studies of particle balance in long pulse discharges, long-term erosion/deposition and hydrogen retention for carbon divertor tiles, and particle behavior in SOL and divertor plasmas related to the two foregoing topics in JT-60U. Global saturation of the particle inventory appeared in the later phase of an ELMy H-mode plasma after several long pulse discharges. As for carbon divertor tiles, erosion was dominant in the outer divertor, and deposition was dominant in the inner divertor. Hydrogen isotope concentration (H+D)/C in the deposition layer was estimated to be ∼0.032. The SOL plasma flow towards the inner divertor was observed at the low-field-side midplane, and influence of the Er × B drift flow from the outer divertor to the inner divertor via the private region on the divertor particle flux was evaluated to be large in the attached divertor plasmas. The preferential deposition in the inner divertor can be a consequence of these flows. For direct observation of the hydrogen molecular behavior in the divertor plasmas, hydrogen molecular line emission was measured and the fall in the emission intensity with distance from the divertor plates was reproduced by calculation with a neutral transport code and a collisional radiative modeling code.