Low aspect-ratio MHD toroidal equilibria

In this paper a new approach to the approximate solution of the MHD equilibrium equation is described. The axisymmetric equilibrium equation is first transformed to a time-independent Schrödinger equation and then solved by the Ritz method in a suitable rotational co-ordinate system, the validity of the solution being not limited to large aspect-ratio configurations. The zeroth-order approximation is analytically computed and the relationship between the poloidal beta and the shift of the magnetic axis is derived. To the same order, the adiabatic compression of the plasma ring is studied and a non-dimensional compression chart is obtained. Results of numerical computations of the higher orders are also reported.