Advanced Tokamak Research in JT-60U and JT-60SA

摘要

Results of experiment in JT-60U and design study in JT-60SA (Super Advanced) are described focusing on the development of advanced tokamak. In JT-60U, a high-integrated performance plasma with the normalized beta β_N = 2.6, confinement enhancement factor H_H98(y,2) = 1.0-1.1 and bootstrap current fraction f_BS = 0.4 has been sustained for 25 s (14 times current diffusion time (τ_R)). Neoclassical tearing mode (NTM) with the poloidal mode number m = 2 and the toroidal mode number n = 1 has been stabilized with modulated electron cyclotron current drive (ECCD) in synchronization with the mode frequency (～5 kHz). A high-beta plasma exceeding the ideal MHD limit without conducting wall has been sustained for 5 s (～3τ_R) by suppressing resistive wall mode (RWM). In addition, two new instabilities in the high-beta regime, Energetic particle driven Wall Mode (EWM) and RWM precursor, have been observed. In JT-60SA, exploration of full non-inductive steady-state operation with current drive by neutral beams and electron cyclotron waves is planned. In addition, NTM control with ECCD and RWM suppression with external coils are planned.