Quench protection for actively shielded magnets

摘要

This invention is concerned with actively shielded magnetic resonance (MR) devices and more particularly with protecting such systems in the event of a quench by preventing changes in the stray field outside the magnetic devices. The invention includes dividing the system's coils into groups each comprised of inner and outer coils and arranged so that the net dipole moment, and the contribution to stray field from each group is always close to zero. Each group is connected in parallel to a protective unit, for example a resistor, so that the excess current can flow through the protective unit in the event of a quench; thus avoiding the burnout of the system's coils.