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EP-4740228-A1 - ELECTROMAGNETIC COIL

EP4740228A1EP 4740228 A1EP4740228 A1EP 4740228A1EP-4740228-A1

Abstract

The present inventive concept relates to an electromagnetic coil (10) having a transversal cross-section (11) comprising a channel (20) for a cooling fluid, wherein said electromagnetic coil (10) comprises a plurality of cross-connections (26) for said cooling fluid, each cross-connection (26) of said plurality of cross-connections (26) running between the channels (20) of two windings (12) of said electromagnetic coil (10), wherein said plurality of cross-connections (26) are circumferentially displaced with respect to each other so as to form a staircase-shaped flow path (30) for said cooling fluid between the windings (12) of said electromagnetic coil (10).

Inventors

  • Jäderberg, Jan

Assignees

  • Novatron Fusion Group AB

Dates

Publication Date
20260513
Application Date
20240614

Claims (15)

  1. 1. An electromagnetic coil (10) having a transversal cross-section (11) comprising a channel (20) for a cooling fluid, wherein said electromagnetic coil (10) comprises a plurality of cross-connections (26) for said cooling fluid, each cross-connection (26) of said plurality of cross-connections (26) running between the channels (20) of two windings (12) of said electromagnetic coil (10), wherein said plurality of cross-connections (26) are circumferentially displaced with respect to each other so as to form a staircase-shaped flow path (30) for said cooling fluid between the windings (12) of said electromagnetic coil (10).
  2. 2. The electromagnetic coil (10) of claim 1, wherein a cross-connection (26) of said plurality of cross-connections (26) runs between the channels (20) of two adjacent windings (12) of said electromagnetic coil (10).
  3. 3. The electromagnetic coil (10) of any one of claims 1-2, wherein a cross-connection (26) of said plurality of cross-connections (26) departs from and/or joins a channel (20) at an acute angle (a).
  4. 4. The electromagnetic coil (10) of claim 3, wherein said acute angle (a) is between 10 and 50 degrees, preferably between 20 and 40 degrees, and even more preferably between 25 and 35 degrees.
  5. 5. The electromagnetic coil (10) of any one of claims 1-2, wherein a cross-connection (26) of said plurality of cross-connections (26) departs from or joins a channel (20) at a right angle.
  6. 6. The electromagnetic coil (10) of any one of claims 1-5, wherein a channel (20) from which a cross-connection (26) of said plurality of cross- connections (26) depart is sealed at a location adjacent to and past said cross-connection (26), said channel (20) preferably being sealed by means of a plug.
  7. 7. The electromagnetic coil (10) of any one of claims 1-4, wherein a plurality of inlets (22) of a first winding (12) of the electromagnetic coil (10) are configured to receive the cooling fluid from a fluid reservoir in fluid contact with the plurality of inlets (22) of the first winding (12).
  8. 8. The electromagnetic coil (10) of any one of claims 1-7, wherein the cooling fluid is a cooling liquid.
  9. 9. The electromagnetic coil (10) of any one of claims 1-8, wherein the electromagnetic coil (10) is a resistive coil.
  10. 10. The electromagnetic coil (10) of any one of claims 1-9, wherein a first cross-connection (26) between a first winding (12) and a second winding (12) is aligned with a second cross-connection (26) between said second winding (12) and a third winding (12).
  11. 11. The electromagnetic coil (10) of any one of claims 1-10, wherein at least a subset of cross-connections (26) in said plurality of cross-connections (26) are circumferentially evenly distributed along said electromagnetic coil (10).
  12. 12. The electromagnetic coil (10) of any one of claims 1-11, said electromagnetic coil (10) being an extruded profile.
  13. 13. The electromagnetic coil (10) of any one of claims 1-12, wherein said channel (20) is internal to said electromagnetic coil (10).
  14. 14. A plasma confinement device (100) comprising the electromagnetic coil (10) of any one of claims 1-13.
  15. 15. A method of cooling an electromagnetic coil (10), comprising running (1000) a cooling fluid through said electromagnetic coil (10), said electromagnetic coil (10) having a transversal cross-section (11) comprising a channel (20) for a cooling fluid, wherein said electromagnetic coil (10) comprises a plurality of cross-connections (26) for said cooling fluid, each cross-connection (26) of said plurality of cross-connections (26) running between the channels (20) of two windings (12) of said electromagnetic coil (10), wherein said plurality of cross-connections (26) are circumferentially displaced with respect to each other so as to form a staircase-shaped flow path (30) for said cooling fluid between the windings (12) of said electromagnetic coil (10).

Description

ELECTROMAGNETIC COIL Field of technology The present disclosure relates an electromagnetic coil, to a plasma confinement device comprising an electromagnetic coil, and to a method of cooling an electromagnetic coil. Background Great efforts are being made to design a reactor for controlled fusion on earth. The most promising fusion process is between the hydrogen isotopes deuterium (2H) and tritium (3H). In the deuterium-tritium fusion prosses, a 4He alpha particle, having a kinetic energy of about 3.5 MeV and a neutron, having a kinetic energy of about 14.1 MeV, are created. For fusion to occur, nuclei must be in the form of a plasma having a temperature in the order of 150 million kelvins. Providing confinement for such a plasma remains a major challenge. Plasma confinement involves confining the charged particles of the plasma. There are several different known magnetic configurations for plasma confinement. A well-known design is the magnetic mirror, or magnetic mirror machine. Therein, particles follow magnetic field lines, typically running substantially longitudinally through the magnetic mirror machine, and are reflected in areas of increasing magnetic flux density at the respective ends of the device. Other examples of plasma confinement devices are the tokamak, and the biconic cusp. Further examples of plasma confinement devices are disclosed in published patent application WO 2021/094372. Common to most plasma confinement devices is the generation of strong electromagnetic fields using electromagnetic coils. During the operation of such devices, and other systems comprising electromagnetic coils, the coils generate heat due to the flow of electric current, which may overheat the coils and limit their performance. Therefore, there is a need for an efficient cooling system that can maintain the temperature of the coils within a safe operating range. The use of superconducting coils may allow for higher current densities, and thus stronger magnetic fields, than what is possible using conventional, resistive, conductors. However, a disadvantage of superconductor coils, and superconductor materials in general, is the need of low temperatures for the materials to become superconducting. In particular, temperatures close to the absolute zero may be needed, which results in high operating costs. In practice, while superconductor materials used in fusion experiments may intrinsically allow for current densities in the order of 50 A/mm2, engineering considerations may limit the practically achievable current density, taking the whole cable area into account, to the order of 10-20 A/mm2. Such engineering considerations may be that conventional cooling systems take up a lot of space, e.g. due to heat shields, and that superconducting components must be surrounded by copper layers to cope with breakdown of the superconducting property due to material defects, high temperatures, high magnetic fields, etc. Meanwhile, traditional copper and/or aluminium windings in electromagnetic coils may have current densities up to 3 A/mm2 without any active cooling, up to 5 A/mm2 when using conventional air cooling methods, and up to 10 A/mm2 when using conventional liquid-based cooling methods. Thus, using superconductors may only marginally provide higher current densities than conventional, resistive, conductors. Conventional electromagnetic coils being subject to a cooling process may have a duct running helically through the electromagnetic coil along a centre of each winding, thereby forming a channel for cooling fluid to flow in, wherein a first winding has an inlet and a last winding has an outlet. However, the cooling fluid may heat up, boil, and/or lose its cooling capabilities before reaching said outlet. Thus, there is a need to improve the cooling methods of non-superconductor electromagnetic coils in order to obtain greater current densities running through the windings in electromagnetic coils that may approach current densities practically achievable using superconductors. It is an object of the present disclosure to solve, or at least mitigate, the above problems. To this end, according to a first aspect, there is provided an electromagnetic coil having a transversal cross-section comprising a channel for a cooling fluid, wherein said electromagnetic coil comprises a plurality of cross-connections for said cooling fluid, each cross-connection of said plurality of cross-connections running between the channels of two windings of said electromagnetic coil, wherein said plurality of cross-connections are circumferentially displaced with respect to each other so as to form a staircase-shaped flow path for said cooling fluid between the windings of said electromagnetic coil. Thus, a plurality of such staircase-shaped flow paths may be formed in the electromagnetic coil. Hereby, the flow capacity for the cooling fluid is multiplied as compared to a conventional coil providing only a single flow path for the