Superconducting switch thermal interface for a cryogenless superconducting magnet

A superconducting magnet, comprising:

• a superconducting magnet coil for producing a magnetic field along a magnet axis;
• a structure supporting said coil to be substantially coaxial with said magnet axis;
• a refrigerated cold sink for cooling said magnet coil below a transition temperature at which said coil becomes superconducting;
• a superconducting switch for completing a closed superconducting electrical circuit including said coil;
• means supporting said superconducting switch on said structure, said supporting means including means for thermally insulating said switch from said structure;
• and
• a thermal bus bar connecting said switch and said cold sink, said thermal bus bar providing thermally conductive communication directly between said cold sink and said switch;
• wherein the thermal conductivity of the bus bar decreases as the temperature of the bus bar increases, thereby maintaining the rate of heat flow through the bus bar below a predetermined threshold during ramping of said coil and recovery of said switch to the persistent state according to Fourier's heat conduction equation.