SUPERCONDUCTING SWITCH COOLED BY MEANS OF INTERNAL CAVITY FILLED WITH LIQUID OR GASEOUS COOLANT

When testing or powering up a magnet in a magnetic resonance imaging device, a switch is provided that switches a winding between resistive and superconductive modes. The switch includes a housing that contains a winding wound about a bobbin, and an internal coolant cavity that contains coolant that cools the winding, A baffle separates the internal coolant cavity from an external coolant reservoir. The baffle has small apertures that permit influx of liquid coolant into the internal cavity to cool the winding, At high temperatures, the coolant in the internal cavity vaporizes causing the winding to further increase its temperature and resistance, Upon reduction of heat to the winding, the winding cools sufficiently to permit influx of liquid coolant, thereby restoring a superconductive mode of operation to the winding.