The influence of iron core on plasma equilibrium is considered as an action of the currents in the external coils. The problems is converted into solving the MHD equations for air-core transformer.

An air core spiral strip transformer, a kind of tesla transformers, which has been designd and manufactured.

This lack of static, DC offset current in the output transformer means that the core can be made smaller, because it requires no air gap to prevent core saturation from the static DC offset current.