Ballooning Mode Stability of Bean-Shaped Cross Sections for High-β Tokamak Plasmas

Indentation of a tokamak plasma on its inner major radius side is shown to be strongly beneficial for achieving high-..beta.. stability against ballooning modes. Using a set of reasonable equilibrium profiles, it is found that moderate indentation provides accessibility to the second region of stability. Ohmic equilibrium configurations which exhibit the second stability region have not yet been found.