Formation of an advanced tokamak plasma without the use of Ohmic heating solenoid in JT-60U

An integrated scenario consisting of (1) a novel plasma start-up method using the vertical field and shaping coils, (2) an intermediate noninductive ramp-up stage, and (3) controlled transition to a high-density, bootstrap-dominated, high-confinement plasma has been demonstrated for the first time on the JT-60U tokamak. It was shown that plasma current can be ramped up even with a negative vertical field (in the direction opposite to that required for toroidal equilibrium) provided that there is a strong source of plasma. The plasma created by this technique had both internal and edge transport barriers, and had βp = 3.6 (εβp =1), βN = 1.6 (marginally stable to the n =1 kink-ballooning mode), HH98y2 = 1.6 and fBS≥ 90% at Ip = 0.6 MA and n-bare = 0.5nGW. In these experiments, inboard turns of the shaping coil supplied about 20% of the total poloidal flux input, but further improvement is possible. This result opens up the possibility of OH-less operation, which is a requirement for ST reactors, and can also make a substantial improvement in the economic competitiveness of conventional aspect ratio tokamak reactors. (author)