Feasibility Studies for Optimising Spheromak Equilibria. Part I: Sphex

With reference to both the spheromak experiments SPHEX and FACT, we initiate an investigation into the extent to which a realistic equilibrium parameter-set can be determined by a measured magnetic data-set that is ultimately expected to be non-intrusive. Compared to the tokamak, it is pointed out that the spheromak suffers from both theoretical and practical difficulties in attaining this goal, with the result that a feasibility study utilizing interior SPHEX data is first attempted. As a consequence, we hope to indicate the type of global, and otherwise, data that must be measured (within the engineering constraints represented by the spheromak configuration) in the more difficult, but diagnostically more relevant, non-intrusive case.