Superconducting magnet assembly

A superconducting magnet arrangement comprises a field coil assembly with coil windings that when in operation are electrically superconducting. The field coil assembly is circuited between connection ports for a voltage supply. A switching module switches a sub-section of the field coil assembly's coil windings between its electrical superconducting and electrical resistive states, said sub-section forming a switching coil circuited between the connection ports. In the operational state where both the switching coil and the field coil(s) are superconducting and carry a permanent electrical current, the field coil(s) and the switching coil together generate a stationary magnetic field. According to the invention the switch windings give a significant contribution to the magnetic field. The field coil assembly's coil windings that may be switched between it electrically superconducting and resistive states form the switching coil. That is, the switching coil forms part of the field coil assembly and contributes significantly to the magnetic field generated by the field coil assembly.