Attainment of high fusion reactivity under high bootstrap current fraction in JT-60U

Abstract

The fusion performance of high β_p plasmas with significant D-D neutron production up to (5.6 ± 0.6) × 10¹⁶ n/s, has been investigated. The attainment of a high fusion triple product, n_d(0) τ_E^totalT_i(0), up to (1.1 ± 0.3) × 10²¹ m^-3.s.keV is confirmed by both time dependent and time slice analysis. The highly enhanced confinement of up to 3.6 times ITER-89P scaling is dominated by the improved thermal confinement, and one half of the D-D neutrons come from the thermal reactions. The highest equivalent Q_DT of approximately 0.56 was obtained. The ratio Q_DT/Q_DD is in the range 133-151. More importantly, a high bootstrap current of up to approximately 1 MA (~50% of the total current) was obtained simultaneously with the high fusion performance. These results are quite encouraging as far as the realization of a steady state tokamak reactor is concerned