Stability of toroidal plasma with non-circular cross-section

Under the cap-cyclide coordinate system, the marginal stability of a sharp boundary toroidal plasma whose cross section is not circular is examined using the energy principle. The analytical results are valid for arbitrary values of β, aspect ratio, and elougation of the plasma. There exists a maximum elougation for a given aspect ratio. The critical βc is computed for several aspect ratios and elongations. For a given aspect ratio, βc increases as long as the elongation increases. (author)