Three-dimensional tokamak equilibria in the presence of resonant field errors

Numerical solutions are described for three-dimensional MHD equilibria in the presence of resonant magnetic field perturbations. The effects of a realistic spectrum of resonant field errors are calculated for a range of current profiles in cylindrical geometry, and the results are benchmarked against toroidal calculations for two different current profiles. It is found that field errors of the magnitude existing in present day devices, and contemplated for future devices, can produce a set of magnetic islands occupying a significant fraction of the plasma cross-section. The calculations are applicable to those situations where flow effects are unimportant. The conditions under which this is the case are discussed, and implications for several cases of interest are considered