Effect of plasma-wall separation on the stability of resistive wall modes in the JT-60U tokamak

Matsunaga, Go; Takechi, Manabu; Kurita, Genichi; Ozeki, Takahisa; Kamada, Yutaka; JT-60 Team

Ideal MHD instabilities can become resistive wall modes (RWMs) which grows with the time sale of the skin time of the wall due to a finite wall resistivity. Since the RWM could limit the achievable beta-value, the understanding of the RWM physics and the stabilization mechanism is urgent issue for the steady-state high-beta plasma. For this reason, we have carried out the RWM experiment where the plasma-wall separation was systematically scanned in the JT-60U ohmic plasmas. These results show that the RWM growth rates become smaller with decreasing the plasma-wall separation. This means that the plasma-wall separation is effective for the stabilizing the RWM.