Measurements of dust movement in main chamber and divertor on JT-60U

Asakura, Nobuyuki; Kawashima, Hisato; Ono, Noriyasu*; Nakano, Tomohide; Takamura, Shuichi*; Uesugi, Yoshihiko*

Measurement of visible image emitted during its ablation started since 2006, using a fast TV camera located at tangential port in the JT-60U tokamak. Typical frame rate of the TV camera was between 2 kHz and 8 kHz. Trajectory and velocity of emission during dust ablation were measured in ELMy H-mode plasmas. Trajectory of the ablating dust corresponded to a few meter (near-poloidal case) to several meters (near-toroidal case), and toroidal or poloidal velocity was evaluated to be 0.2-0.5 km/s. In divertor, many dusts were observed in inner divertor just after ELM events, in particular, for the inner strike-point located above the normal operations. Toroidal movement of the dusts (ion drift side) was seen frequently and velocity was 0.2-0.4 km/s, which was similar to those at main chamber. Specific movement of dusts was sometimes seen in outer divertor when ELM occurred: dust moved towards separatrix (inboard), then the direction changed away from separatrix (outboard).