The design study of the JT-60SU device (No.2). The physical design and diagnostic system of JT-60SU

The JT-60 Super Upgrade (JT-60SU) is a highly upgraded tokamak device of JT-60U for developing the steady-state fusion reactor and advanced tokamak operation in ITER. The device is planned to utilize the JT-60 facility fully and to minimize the necessary modification. The major radius is 4.8 m and the maximum plasma current is 10 MA. Neutral beam injection with 750 keV beam energy is the primary heating method. The machine is capable of steady-state operation with high density up to 8.8 x 1019 m-3 at 5 MA plasma current. The high operating density, around the Greenwald-limit, is critically important in order to achieve high bootstrap current fraction. Ballooning modes and low-n ideal modes were analyzed for steady-state operation including the bootstrap current. The current profile must be optimized to get high normalized beta up to 3. The plasma configuration with high triangularity was adopted in order to get good MHD stability and high energy confinement. A compact divertor was designed in order to get high space availability. The JT-60SU diagnostic system consists of main plasma and peripheral plasma diagnostics, which are basically composed of the existing diagnostics for JT-60U. YAG Thomson scattering system will be specially improved to provide electron density and temperature profiles for various plasma equilibria at a good spatial resolution and a high repetition rate (50 Hz). The diagnostic system also introduces magnetic probes for steady-state magnetic field measurements, micro-fission chambers and Penning gauges as new diagnostic tools. The field of view of each diagnostic and its basic requirements were determined. (author)