Trimming Tokamak No-insulation Toroidal Field Coils by Current Bypasses

A magnet system and method of operating may be used in connection with operating a superconducting electromagnet, for example in a tokamak. The magnet system includes a coil having windings retained within a non-insulated structure, so that current can pass both along the windings to generate a magnetic field, and between the windings. The amount of current passing through the coil is trimmed using a bypass circuit, coupled in parallel to the coil terminals. The bypass circuit is controlled on the basis of measurements of the field components to divert current from passing through the field coil. In this way, the magnetic fields of each of multiple field coils can be brought into mutual uniformity.