Feasibility of second stable spherical torus reactor

Equilibrium and MHD stability of spherical torus (ST) are numerically examined using computer codes named 'j-solver', 'balloon' and 'camino'. It is found that the path between the first and the second stable regions in the s-α diagram is wider when the aspect ratio of tokamak is lower. Thus, ST has a good accessibility to the second stable region. It is found that the absolute minimum B is created in the bad curvature region. This result suggests that the second stable ST may be free from the anomalous transport. The feasibility of ST reactor is studied using a mechanical analysis of the center post and the ITER93H scaling. Second stable spherical torus with R0 10 m has a potential to be an advanced fuel reactor. (author)