High Performance Advanced Plasma in JT-60U without Using Central Solenoid Coils
Central solenoid coils (CS coils) are generally equipped in tokamak fusion devices to generate plasma and plasma current (Fig.1). In JT-60U, the research collaboration team (leader: Prof. Takase) among Univ. Tokyo, Kyoto Univ., Kyushu Univ., Kyushu Tokai Univ. and JAERI has succeeded (1) to generate plasma and plasma current with RF injection and using plasma position-control coils without using CS coils, and (2) to increase the bootstrap current and the beam driven current by the high power NBI heating, and (3) to create the high performance advanced plasma with high energy confinement (HHy2=1.6), and high bootstrap fraction (90% of total current) for the first time in the world (Fig. 2). The obtained performance has largely renewed the previous record without using CS coils (Fig. 3). The demonstration of the CS-less tokamak operation suggests the substantial simplification and the associated size reduction and increase in fusion power density of tokamak devices leading to the economical fusion power plant.
Such a research collaboration between universities and JAERI will effectively enhance the R&D of nuclear fusion, which further strengthens the solidarity for promoting the ITER project in Japan.
The total injected power of 3 MW was also maintained for 2.7 s, which allows the world highest level central electron temperature of about 26 keV for a reversed shear plasma.
Fig. 1 Central solenoid coils of tokamak
Fig. 2 Ip ramp-up without using CS coils
Fig. 3 Plasma performance without using CS coils