Current state of nuclear fusion plasma research. Tokamak system: history and current state of tokamak research

This paper reviewed the research and development of tokamak in the past 30 years, with a focus on the performances required for tokamak core plasma. As the performances of core plasma, there are high confinement efficiency, fully non-inductive current drive, high output density, and low first-wall thermal load. As for core plasma, all of these plasma performances must be satisfied at the same time. For this purpose, sufficiently high values are required for the following seven elements: energy confinement improvement index, plasma pressure index, spontaneous current ratio, non-inductive current drive ratio, electron density index, fuel purity, and radiation power ratio against heating power. It is JT-60SA that aims at the above conditions. The JT-60SA project is a joint research project between Japan and Europe aiming at the following: (1) to reform JT-60 equipment to superconducting equipment, (2) to conduct research to support ITER and research to complement ITER aiming at tokamak type prototype reactor, and (3) to cultivate human resources who lead the development of ITER and prototype reactor. The manufacture and assembly of JT-60 SA is progressing toward the start of operation in 2020. The key point of future tokamak core plasma research toward the prototype reactor is the comprehension of the plasma that can sufficiently predict the prototype reactor. (A.O.)