抄録
The ballooning stability of high beta spherical tokamak(ST) was numerically investigated using 2-D magnetic field measurement of high beta ST in TS-3 ST merging experiment. Numerical analysis of experimental result indicates that the high beta ST produced by two merging STs locates in the boundary region of the first and the second stabilities. Effects of current and pressure profiles on the ballooning stability were studied by varying these profiles artificially around the experimental profiles. The broader pressure profile and the hollower current profiles cause the larger merginal beta value and the wider window region between the first- and the second-stable regions. On the basis of these results, a start-up scenario for ultra-high-beta and second-stable ST was proposed using two merging STs with additional RF heating.
