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EP-4367693-B1 - ELECTRICAL CONNECTION FOR USE IN CRYOGENIC APPLICATIONS

EP4367693B1EP 4367693 B1EP4367693 B1EP 4367693B1EP-4367693-B1

Inventors

  • PYNE, Alexander, James
  • GRACE, Kevin

Dates

Publication Date
20260513
Application Date
20220620

Claims (15)

  1. An apparatus (200, 300, 400, 500, 600) for making an electrical connection between a superconducting component disposed in a cryogenic chamber (302, 402) and an electrical device disposed outside the cryogenic chamber, the apparatus comprising: a coil providing an electrical path from the external electrical device to the superconducting component, the coil comprising a plurality of helical loops (206, 506, 606) and disposed in the cryogenic chamber; and an actuator (304, 404) disposed in the cryogenic chamber and comprising a linear motor or a translational mechanism configured to be actuated to apply a force to compress and expand the coil between a first state and a second state, wherein in the first state the coil has a first electrical resistance and a first thermal conductance and in the second state the coil has a second electrical resistance and a second thermal conductance.
  2. The apparatus of claim 1, wherein the first electrical resistance is less than the second electrical resistance.
  3. The apparatus of claim 1, wherein the first thermal conductance is greater than the second thermal conductance.
  4. The apparatus of claim 1, wherein the apparatus has a first cross-sectional area in the first state and a second cross-sectional area in the second state, and the second cross-sectional area is less than the first cross-sectional area.
  5. The apparatus of claim 4, wherein when the apparatus is in the first state, the helical loops are compressed against each other, and the first cross-sectional area is an area of a ring.
  6. The apparatus of claim 4, wherein when the apparatus is in the second state, the helical loops are separated from each other, and the second cross-sectional area is an area of a rectangle.
  7. The apparatus of claim 5, wherein when the apparatus is in the first state, electrical current of a first magnitude is transmitted through the apparatus.
  8. The apparatus of claim 7, wherein when the apparatus is in the second state substantially no electrical current is transmitted through the apparatus.
  9. A method (800) of providing electrical current to a superconductor component disposed in a cryogenic chamber, the method comprising: providing an apparatus (801), which comprises a coil providing an electrical path from an electrical device external to the cryogenic chamber to the superconducting component, the coil comprising a plurality of helical loops and disposed in the cryogenic chamber; the apparatus further comprises an actuator (304, 404) disposed in the cryogenic chamber and comprising a linear motor or a translational mechanism configured to be actuated to apply a force to compress and expand the coil; compressing the coil to a first state (802), wherein in the first state the coil has a first electrical resistance and a first thermal conductance; and expanding the coil to a second state (803), wherein in the second state the coil has a second electrical resistance and a second thermal conductance.
  10. The method of claim 9, wherein the first electrical resistance is less than the second electrical resistance.
  11. The method of claim 9, wherein the first thermal conductance is greater than the second thermal conductance.
  12. The method of claim 9, wherein the apparatus has a first cross-sectional area in the first state and a second cross-sectional area in the second state, wherein the second cross-sectional area is less than the first cross-sectional area.
  13. The method of claim 12, wherein when the apparatus is in the first state, the helical loops are compressed against each other, and the first cross-sectional area is an area of a ring.
  14. The method of claim 12, wherein when the apparatus is in the second state, the helical loops are separated from each other, and the second cross-sectional area is an area of a rectangle.
  15. A magnetic resonance imaging system (100), comprising: a magnet system (101) comprising a superconducting magnet disposed in a cryogenic chamber; and an apparatus (200,300,400, 500, 600) according to one of claims 1 to 8.

Description

BACKGROUND Superconducting devices, including superconducting magnets, are generally maintained at very low temperatures (e.g., close to absolute zero) by placing the superconducting magnet into a chamber, which is maintained at very low pressure and including a cooling agent. These superconducting devices are ubiquitous in applications, with one common application being in magnetic resonance imaging (MRI) systems commonly used in healthcare. Maintaining the temperature at a constant low temperature in these so-called cryogenic chambers is very important to the proper operation of the superconductor that makes up the superconducting magnet. As such, maintaining the seal of the cryogenic chamber is very important to ensure heat from outside the cryogenic chamber does not significantly adversely impact the internal temperature of the cryogenic chamber. However, electrical connections must be made from room-temperature equipment to superconducting components (e.g., a superconducting magnet). For example, current must be applied from an external a power supply to the superconducting components for their operation. However, in making the electrical connections between the external devices and the superconducting components inside the cryogenic chamber, pathways for heat conduction may be created, and as a result unacceptable levels of heat may pass from the ambient into the cryogenic chamber that can compromise the desired superconducting properties of the superconducting components in the cryogenic chamber. Typical superconducting components (e.g., magnets) use liquid helium baths to maintain cryogenic temperature of superconducting coils and ancillaries housed within a cryogenic chamber. In certain known systems, electrical connections to these types of magnetic coils is often provided by removable electrical leads that penetrate the pressure vessel, relying on the constant vaporization of included liquid helium to temporarily remove heat conducted along, and generated by, these leads. As such, during ramp-up operation of the superconducting components, these electrical leads are inserted through the cryogenic chamber, and once steady-state operation is achieved, these leads are removed to reduce the heat load to the refrigeration system. Specifically, and as is known to those ordinarily skilled in the art, after ramping up the magnet to full current, a superconducting switch is closed to create a loop. However, some superconducting magnets include a sealed cooling system within a vacuum space of the cryogenic chamber that directly cools the superconducting components. In such applications, an electrical path for making electrical connections from an electrical device (e.g., power supply) located outside the cryogenic chamber to the superconducting components is required. Known connections result in an unacceptable degree of thermal conductivity along the electrical connections. As such, the performance of the superconducting components can be deleteriously compromised using known electrical connections. What is needed, therefore, is an electrical connection between a superconducting component disposed in a cryogenic chamber and an electrical device disposed outside the cryogenic chamber that overcomes at least the drawbacks of known electrical connections described above. JP 2007 250972 A describes a low-heat invasion current lead device which reduces electric resistance when an electrification current is large or suppresses heat invasion when there is no electrification, wherein when there is no energization or when the energization current is small, a turn (spiral or meander) shaped current lead conductor having a positive coefficient of linear expansion does not generate heat, so the temperature is low, and a material with a negative linear expansion coefficient that is connected through a heat conducting connection to the current lead conductor expands, creating a gap between the turns of the current lead conductor acting as one long conductor, and the cross-sectional area of the current lead conductor is also small, so the heat transfer distance is that of a long and thin conductor, and heat penetration can be suppressed; while when the energization current is large, current flows through the current lead conductor, and the current lead conductor generates heat and the temperature rises because the cross section of the current lead conductor is small and the resistance value is large, wherein as the temperature rises, the current lead conductor expands, and the material with a negative coefficient of linear expansion contracts, such that a current lead conductor having a large cylindrical or rectangular cross-sectional area and a short length is formed in which the electrical resistance is reduced, and heat generation due to electrical resistance is suppressed. JP H07 283023 A describes a superconducting oxide current lead which can exhibit highly reliable current conducting function constantly by enhanc