Variable thermal conductance link for superconducting persistent current switch for fast magnet ramping

A system for rapid ramping of an MRI magnet, the system comprising:

• a cooling source for the MRI magnet;
• a persistent current switch in a circuit with coils of the MRI magnet;
• and
• a thermal link having a first end thermally coupled to the persistent current switch and a second end thermally coupled to the cooling source;
• wherein the thermal link is configured to provide a low thermal conductance connection between the cooling source and the persistent current switch while the MRI magnet is ramping;
• and
• wherein the thermal link is configured to provide a high thermal conductance connection between the cooling source and the persistent current switch when the MRI magnet reaches a target current corresponding to a target magnetic field to rapidly cool the persistent current switch;
• wherein the thermal link comprises at least one variable thermal conductivity material component configured to change thermal conductivity thereof between:
• (i) a low thermal conductivity state providing the low thermal conductance connection during magnet ramping;
• and
• (ii) a high thermal conductivity state providing the high thermal conductance connection after magnet ramping.

A method for rapid ramping of an MRI magnet, the method comprising:

• providing a cooling source for the MRI magnet and a persistent current switch in a circuit with coils of the MRI magnet;
• while the MRI magnet is ramping, configuring a thermal link to provide a low thermal conductance connection between the cooling source and the persistent current switch;
• when the MRI magnet reaches a target current corresponding to a target magnetic field, configuring the thermal link to provide a high thermal conductance connection between the cooling source and the persistent current switch to rapidly cool the persistent current switch;
• wherein configuring the thermal link between the low thermal conductance connection and the high thermal conductance connection comprises at least one of:
• (a) changing a contact force between mating surfaces of a variable thermal conductance interface using an actuator to selectively configure the interface between a first pressed state providing the high thermal conductance connection and a second low-force state providing the low thermal conductance connection;
• and
• (b) changing thermal conductivity of at least one material component of the thermal link between a low thermal conductivity state providing the low thermal conductance connection and a high thermal conductivity state providing the high thermal conductance connection.