Observation of an energetic-particle-driven instability in the wall-stabilized high- plasmas in the JT-60U tokamak

Matsunaga, Go; Aiba, Nobuyuki; Shinohara, Koji; Sakamoto, Yoshiteru; Isayama, Akihiko; Takechi, Manabu; Suzuki, Takahiro; Oyama, Naoyuki; Asakura, Nobuyuki; Kamada, Yutaka; Ozeki, Takahisa; JT-60 Team

We have observed bursting modes driven by trapped energetic particles in the high- plasmas where the resistive wall mode (RWM) is marginally stable by plasma rotation. This mode can directly trigger the RWM despite enough plasma rotation for RWM stabilization. Mode structure is radially extended and mode frequency corresponds to the precession frequency of the trapped particle from the perpendicular neutral beams. We have concluded that the mode is the energetic particle branch as the results of the interaction between the energetic particle and a marginally stable RWM, and then, it is named as "energetic particle driven wall mode (EWM)".