A superconducting magnet assembly comprising a plurality of superconducting magnet coil portions forming a coil series circuit to provide a magnetic field, a power supply to supply power to the plurality of superconducting magnet coil portions during a magnet ramp mode of operation, and a ramp switch coupled to the superconducting magnet coil portions, wherein the ramp switch is configured to be open during a magnet ramp mode and closed during a persistent mode. A dump resistor is disposed externally to the vessel and is connectable by the ramp switch to the superconducting magnet coil portions. Further, a controller is coupled to at least one superconducting magnet coil portion and the ramp switch and is configured to detect a quench onset condition in the at least one superconducting magnet coil portion and to open the ramp switch upon detection of the quench onset condition in order to dump magnet energy.