Conduction cooling structure for superconducting magnets

Abstract

The present disclosure provides a conduction cooling structure for a superconducting magnet, and relates to the technical field of superconducting magnets. The conduction cooling structure for the superconducting magnet comprises: a plurality of cooling belts extending along the axial direction of the superconducting magnet and laid in the circumferential direction of each layer of coils of the superconducting magnet; a cooling ring unit radially wound on a predetermined position of each layer of cooling belts; and a cooling plate unit arranged at both ends and a middle region of the superconducting magnet and configured to transfer received cooling capacity to the cooling belts and the cooling ring unit.

Description

Technical Field

[0001] This disclosure relates to the field of superconducting magnet technology, and more specifically, to conductive cooling structures for superconducting magnets. Background Technology

[0002] With the increasingly widespread application of superconducting magnets in various fields, traditional liquid helium immersion cooling methods are no longer sufficient to meet cooling requirements under specific operating conditions, such as rotational operation. During rapid pulsed operation, the AC and eddy current losses generated by the superconducting magnet can lead to heat accumulation, temperature rise, and ultimately, quench failure, especially in environments without liquid helium. Therefore, an effective conductive cooling structure is needed to reduce temperature and ensure the stable operation of the superconducting magnet. Summary of the Invention

[0003] In view of this, the present disclosure provides a conductive cooling structure for superconducting magnets, which at least partially solves the above-mentioned technical problems.

[0004] This disclosure provides a conductive cooling structure for a superconducting magnet, comprising: a plurality of cooling strips extending along the axial direction of the superconducting magnet and laid in the circumferential direction of each layer of coils of the superconducting magnet; cooling ring units radially wound around predetermined positions of each layer of cooling strips; and cooling plate units disposed at both ends and the middle region of the superconducting magnet, configured to transfer received cooling energy to the cooling strips and cooling ring units.

[0005] According to embodiments of this disclosure, the coverage of the cooling strip on each layer of coil is not less than 90%.

[0006] According to an embodiment of this disclosure, the cooling ring unit includes two cooling rings that are radially symmetrical along the superconducting magnet, with both ends of each cooling ring bent and inserted into a groove in the cooling plate unit; wherein the two symmetrical cooling rings form a complete circumference around a predetermined position of each cooling strip.

[0007] According to an embodiment of this disclosure, the cold-conducting plate unit includes: an end-face cold-conducting plate disposed at both ends of the superconducting magnet and in contact with the cold-conducting strip; and a middle cold-conducting plate disposed in the middle region of the superconducting magnet and embedded in the groove of the superconducting magnet, in contact with each layer of cold-conducting ring unit.

[0008] According to an embodiment of this disclosure, the central cooling plate includes two central sub-cooling plates that are radially symmetrical along the superconducting magnet, wherein the two central sub-cooling plates divide the cooling ring unit into two symmetrical cooling rings.

[0009] According to embodiments of this disclosure, each central sub-cooling plate is divided into no less than three oxygen-free copper plates along the beam direction, and adjacent oxygen-free copper plates are electrically isolated by a polyimide film.

[0010] According to embodiments of this disclosure, the conductive cooling structure for a superconducting magnet further includes: a glass fiber cloth layer for applying a preload to the cooling strip to regulate the thermal resistance contact between the cooling strip and the coil.

[0011] According to embodiments of this disclosure, the conductive cooling structure for the superconducting magnet further includes an indium sheet disposed at the connection between the cooling ring and the central cooling plate.

[0012] According to embodiments of this disclosure, the material of the cooling ring includes oxygen-free copper, and the diameter of the cooling ring is less than or equal to 0.5 mm.

[0013] According to embodiments of this disclosure, the material of the cooling strip includes oxygen-free copper, and the diameter of the cooling strip is less than or equal to 1 mm.

[0014] The conductive cooling structure for superconducting magnets provided according to the embodiments of this disclosure has at least the following beneficial effects:

[0015] This disclosure utilizes a cooling plate to introduce the cooling energy of the refrigerator into the magnet. By using circumferential cooling of the cooling ring and axial cooling of the cooling strip, it effectively solves the problem of coordinated circumferential and axial thermal diffusion in fast pulsed superconducting magnets in a liquid helium-free environment, reduces the risk of excessive local temperature rise of the superconducting magnet, and ensures its stable operation in a liquid helium-free environment. Attached Figure Description

[0016] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic diagram of a conductive cooling structure according to an embodiment of the present disclosure is shown;

[0018] Figure 2 This schematic diagram illustrates the structure of the connection between the cold-conducting ring unit and the cold-conducting plate unit according to an embodiment of the present disclosure;

[0019] Figure 3 A schematic diagram of the structure of the central sub-cooling plate according to an embodiment of the present disclosure is shown.

[0020] Figure 4 A schematic diagram of the structure of the cooling strip according to an embodiment of the present disclosure is shown.

[0021] Figure 5 This schematic diagram illustrates a comparison of the thermal conductivity of different materials according to embodiments of the present disclosure.

[0022] Figure 6 This schematic diagram illustrates the relationship between the material and width of the cooling strip according to an embodiment of the present disclosure and eddy current loss.

[0023] Figure 7 The diagram illustrates the relationship between the width of the cooling ring and eddy current losses according to an embodiment of the present disclosure.

[0024] Figure 8 The diagram illustrates the relationship between the thickness of the cooling plate and eddy current loss according to an embodiment of the present disclosure.

[0025] Figure 9 A schematic diagram illustrating a thermal simulation of a non-conductive cooling structure is shown.

[0026] Figure 10 A schematic diagram of a thermal simulation of a conductive cooling structure according to an embodiment of the present disclosure is shown. Detailed Implementation

[0027] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known systems and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0029] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0030] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0031] Figure 1 A schematic diagram of a conductive cooling structure according to an embodiment of the present disclosure is shown.

[0032] like Figure 1As shown, this embodiment provides a conductive cooling structure for a superconducting magnet, including: multiple cooling strips 101, a cooling ring unit 102, and a cooling plate unit 103.

[0033] Multiple cooling strips 101 extend along the axial direction of the superconducting magnet and are laid circumferentially on each layer of coils of the superconducting magnet.

[0034] The cooling ring unit 102 is radially wound around a predetermined position on each layer of cooling strip 101.

[0035] And cold-conducting plate units 103 and 104, located at both ends and the middle region of the superconducting magnet, are configured to transfer the received cold energy to the cold-conducting strip 101 and the cold-conducting ring unit 102.

[0036] In the embodiments of this disclosure, the cold-conducting plate units 103 and 104 are connected to the cold head 106 of the refrigerator via a flexible copper braided strip 105, for receiving the cooling energy transferred from the cold head 106. The cold-conducting strip 101 axially transfers the cooling energy from the refrigerator to the far end region of the magnet, while simultaneously absorbing heat generated by AC and eddy current losses in the superconducting wire. The cold-conducting ring unit 102 directs heat to the cold-conducting plate connected to the cold head, achieving heat exchange and homogenizing the circumferential temperature distribution of the coil through circumferential heat conduction, eliminating local hot spots. Furthermore, the cold-conducting ring unit 102 is in direct contact with the cold-conducting plate 103 and the cold-conducting strip 101, enabling interconnection of radial-circumferential-axial cooling paths. The cold-conducting plate unit 103 efficiently guides the cooling energy from the refrigerator into the interior of the magnet, optimizing the cooling energy distribution through the cold-conducting plates at different locations.

[0037] The multi-layered cooling system, composed of cooling strips 101, cooling ring units 102, and cooling plate units 103, forms a highly efficient heat conduction network, ensuring that heat can be rapidly transferred from the coil to the external cooling medium, greatly improving cooling efficiency. By extending along the axial direction of the superconducting magnet and laying it circumferentially on each layer of the coil, multiple cooling strips can cover the entire coil surface, ensuring that heat is uniformly carried away from all directions. This effectively avoids local overheating that may occur in traditional cooling methods, improving overall cooling efficiency. Simultaneously, under helium-free conditions, the synergistic cooling effect of the cooling plate combined with the cooling strips and cooling plate rings significantly improves the cold transfer efficiency of the refrigerator's cold head, keeping the overall magnet temperature fluctuation within 1 K, effectively avoiding the risk of quenching due to localized temperature rise. To address the AC losses of superconducting wires and the eddy current losses of metal structures under fast pulse conditions (dB / dt>0.6T / s), the axial cooling path of the cooling strip and the circumferential cooling path of the cooling ring work together to reduce the maximum temperature rise of the magnet from 107 K in the traditional liquid helium scheme to 4.8 K, without relying on the latent heat of phase change of liquid helium.

[0038] Based on the above embodiments, the coverage of the cooling strip on each layer of coil is not less than 90%.

[0039] In the embodiments of this disclosure, the cooling strip employs an axially layered laying strategy, with copper wires arranged in a close-packed manner and oriented axially along the magnet. Each layer of cooling strip covers ≥90% of each coil layer. This configuration ensures an axial heat flux density ≥500 W / m²·K, satisfying the temperature drop gradient from a 4.2K cold source to each coil layer.

[0040] Figure 2 The diagram illustrates the structure of the connection between the cold-conducting ring unit and the cold-conducting plate unit according to an embodiment of the present disclosure.

[0041] like Figure 2 As shown, the cooling ring unit disclosed in this embodiment includes two cooling rings that are radially symmetrical along the superconducting magnet. The two ends of each cooling ring are bent and inserted into the groove in the cooling plate unit. The two symmetrical cooling rings form a complete circumference around a predetermined position of each cooling strip.

[0042] In the embodiments of this disclosure, the cooling ring unit is wound in a spring shape on the surface of the superconducting magnet. The number of turns and the winding position can be set as needed. The cooling ring unit is laser-cut at the corresponding slot, and the cut end is bent 90° and embedded into the mounting hole of the skeleton cooling plate by a cold bending forming process. To ensure strength, indium sheets can be used for padding at the bend.

[0043] Based on the above embodiments, such as Figure 1 As shown, the coolant plate unit includes: end coolant plates 104, disposed at both ends of the superconducting magnet and in contact with the coolant strips of each layer; and a middle coolant plate 103, disposed in the middle region of the superconducting magnet and embedded in the groove of the superconducting magnet, in contact with each layer of coolant ring unit. The end coolant plates 104 are located at a distance of N mm from the end, where N needs to be further calculated based on the structure of different superconducting magnets.

[0044] In this embodiment, the central cold-conducting plate 103 is in direct contact with the cold-conducting ring unit 102, achieving radial cold transfer. Simultaneously, a non-contact thermal coupling design is employed between the cold-conducting plate 103 and the cold-conducting strip 101, with the cold-conducting ring acting as the cold-transfer medium between them, and the cold-conducting strip enabling axial cold transfer. This design ensures effective cold conduction while avoiding mechanical problems that might arise from direct contact, thus improving the system's stability and efficiency.

[0045] Furthermore, the central cold-conducting plate 103 adopts a wedge-shaped tenon structure, and after being assembled with liquid nitrogen at low temperature, it forms an interference fit with the cold-conducting ring unit to ensure that there is a certain pressure on the contact surface and achieve efficient cold transfer. Among them, the taper ratio of the central cold-conducting plate is 1:50, and the surface roughness Ra≤0.8μm.

[0046] like Figure 1 As shown, the central cooling plate 103 of this embodiment includes two central sub-cooling plates 103-1 and 103-2 that are radially symmetrical along the superconducting magnet, wherein the two central sub-cooling plates 103-1 and 103-2 divide the cooling ring unit into two symmetrical cooling rings.

[0047] In the embodiments of this disclosure, the two ends of one cooling ring are bent and inserted into the middle sub-cooling plates 103-1 and 103-2 respectively, and the two ends of the other cooling ring are also bent and inserted into the middle sub-cooling plates 103-1 and 103-2 respectively.

[0048] Figure 3 A schematic diagram of the structure of the central sub-cooling plate according to an embodiment of the present disclosure is shown.

[0049] like Figure 3 As shown, in this embodiment, each central sub-cooling plate is divided into no less than 3 oxygen-free copper plates along the beam direction. Adjacent oxygen-free copper plates are electrically isolated by a 0.1mm thick polyimide film, which can maintain the continuity of axial heat flow.

[0050] In the embodiments of this disclosure, to reduce eddy current losses caused by the alternating magnetic field (AC magnetic field) and to simplify the manufacturing process, the central sub-cooling plate is constructed using a stacking method of ≥3 plates, with each stack insulated from the others. The number of oxygen-free copper plates can be adjusted as needed.

[0051] Figure 4 A schematic diagram of the structure of the cooling strip according to an embodiment of the present disclosure is shown.

[0052] like Figure 4 As shown, the conductive cooling structure for superconducting magnets in this embodiment further includes a glass fiber cloth layer 201, which is used to apply a pre-tightening force to the cooling strip in order to regulate the thermal resistance contact between the cooling strip and the coil.

[0053] In the embodiments of this disclosure, each layer of cooling conductive tape is fixed to the surface of the superconducting coil by wrapping it with high-strength glass fiber cloth, ensuring uniform pressure at the contact surface and achieving low thermal resistance contact between the cooling conductive tape and the superconducting coil. Simultaneously, thermal grease is coated on the contact surface between the cooling conductive ring and the cooling conductive tape, which effectively reduces interfacial thermal resistance.

[0054] According to embodiments of this disclosure, the material of the cooling ring includes oxygen-free copper, and the diameter of the cooling ring is less than or equal to 0.5 mm.

[0055] In the embodiments of this disclosure, the cooling ring is made of high-purity oxygen-free copper enameled wire, with each individual copper wire insulated from the others. By controlling the diameter of the cooling ring to ≤0.5mm, the feasibility of the winding process can be ensured, and eddy current losses under alternating magnetic field conditions can be minimized.

[0056] According to embodiments of this disclosure, the material of the cooling strip includes oxygen-free copper, and the diameter of the cooling strip is less than or equal to 1 mm.

[0057] In the embodiments of this disclosure, the cooling strip is made of high-purity oxygen-free copper with insulation and a core wire diameter ≤1mm, which can minimize eddy current losses under alternating magnetic field conditions. Simultaneously, the copper wires are arranged parallel to the axis of the superconducting magnet to ensure structural integrity is maintained under low-temperature contraction conditions.

[0058] According to embodiments of this disclosure, since oxygen-free copper, a material with high thermal conductivity, also has high electrical conductivity, the higher the electrical conductivity of the material, the higher the eddy current loss will be generated in a fast-pulse magnetic field, resulting in a worse heat conduction effect. That is, the higher the thermal conductivity, the better the cooling effect, but the larger the introduced eddy current. Therefore, it is necessary to perform insulating segmentation on the cooling structure to cut off the eddy current, find the balance point between eddy current loss and thermal conductivity efficiency, and determine the cooling material and size.

[0059] This embodiment effectively cuts off eddy currents, reduces eddy current losses, and improves heat conduction efficiency by controlling the core wire diameter of the cooling strip and cooling ring, as well as controlling the number of cuts in the cooling plate.

[0060] Figure 5 The diagram illustrates a comparison of the thermal conductivity of different materials according to embodiments of the present disclosure.

[0061] like Figure 5 As shown, in a liquid helium-free fast-pulse superconducting magnet system, the selection of cooling materials must comprehensively consider the balance between thermal conductivity and electromagnetic performance. To rapidly dissipate the heat generated by the superconducting coil during excitation, materials with high thermal conductivity are required. Currently, metals with relatively high thermal conductivity include 6-series aluminum, 1-series aluminum, high-purity oxygen-free copper (RRR=30), and high-purity oxygen-free copper (RRR=100). The RRR value is the ratio of the material's resistivity at room temperature to its resistivity at low temperatures. Specific material selection requires calculation of the thermo-electric-magnetic equilibrium point through multiphysics coupling simulation to determine the optimal material and geometric parameters.

[0062] Ignoring the effects of eddy currents, the temperature rise of the magnet shows a significant decreasing trend as the material changes from I-series aluminum to oxygen-free copper (RRR=30) and then to oxygen-free copper (RRR=100). This indicates that selecting appropriate materials is crucial for controlling the temperature rise of superconducting magnets when designing their cooling structures. Oxygen-free copper (especially RRR=100) performs exceptionally well in reducing magnet temperature rise due to its excellent thermal conductivity.

[0063] Figure 6 The diagram illustrates the relationship between the material and width of the cooling strip according to an embodiment of the present disclosure and eddy current loss.

[0064] Figure 7The diagram illustrates the relationship between the width of the cooling ring and eddy current loss according to an embodiment of the present disclosure.

[0065] Figure 8 The diagram illustrates the relationship between the thickness of the cooling plate and eddy current loss according to an embodiment of the present disclosure.

[0066] like Figure 6 As shown, for the same width of the cooling strip, although Al1100 has the lowest eddy current loss, its cooling conductivity is far inferior to that of copper. Furthermore, when the cooling strip width is 1 mm, the difference in eddy current loss between Al1100 and oxygen-free copper (RRR=100) is only about 1 W, a relatively small difference. Therefore, considering the overall cooling conductivity of the cooling strip, oxygen-free copper (RRR=100) is the preferred material.

[0067] As shown in Figure 7, the material of the cooling ring is oxygen-free copper (RRR=100). As the width of the cooling ring decreases, the eddy current loss decreases rapidly, and when the width is 0.3 mm, the eddy current loss can be reduced to 0.15 W.

[0068] like Figure 8 As shown, the material of the cold conductive plate is oxygen-free copper. As the thickness of the cold conductive plate decreases, the eddy current loss decreases accordingly. The material of the cold conductive plate can be selected as oxygen-free copper (RRR=30) or oxygen-free copper (RRR=100) as needed.

[0069] Depend on Figures 6-8 It can be seen that cooling materials can be selected according to actual design needs, which can effectively suppress eddy current losses.

[0070] Figure 9 A schematic diagram illustrating a thermal simulation of a non-conductive cooling structure is shown.

[0071] Figure 10 A schematic diagram of a thermal simulation of a conductive cooling structure according to an embodiment of the present disclosure is shown.

[0072] like Figures 9-10 As shown in the Ansys Workbench simulation, the boundary conditions refer to the 4.2 K chiller cold head and fast pulse condition (dB / dt > 0.6 T / s). Without a conductive cooling structure, the local temperature of the superconducting coil reaches as high as 107 K under the fast pulse condition, making it impossible for the magnet to operate stably. After adopting the three-dimensional heat conduction network disclosed in this paper, the overall temperature distribution of the magnet is uniform, the highest temperature drops to 4.88 K, and the axial temperature gradient is less than 1 K / m, verifying the synergistic heat dissipation effect of the multi-dimensional heat conduction path.

[0073] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0074] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A conductive cooling structure for superconducting magnets, characterized in that, include: Multiple cooling strips extend along the axial direction of the superconducting magnet and are laid circumferentially on each layer of coil of the superconducting magnet; A cooling ring unit is radially wound around predetermined positions on each layer of the cooling strip; and The cooling plate unit includes end-face cooling plates disposed at both ends of the superconducting magnet and a central cooling plate in the middle region, and is configured to transfer the received cold energy to the cooling strip and the cooling ring unit. The cooling ring unit includes two cooling rings that are radially symmetrical about the superconducting magnet. The two ends of each cooling ring are bent and inserted into the grooves in the cooling plate unit. The two symmetrical cooling rings form a complete circumference that radially surrounds a predetermined position on each layer of the cooling strip. The end face cooling plate contacts the cooling strip, and the middle cooling plate is embedded in the groove of the superconducting magnet and contacts each layer of the cooling ring unit. The central cooling plate includes two central sub-cooling plates symmetrically arranged radially along the superconducting magnet. The two central sub-cooling plates divide the cooling ring unit into two symmetrical cooling rings. Each central sub-cooling plate is divided into no less than three oxygen-free copper plates along the beam direction. Adjacent oxygen-free copper plates are electrically isolated by a polyimide film. The material of the cooling strip includes oxygen-free copper, and the diameter of the cooling strip is less than or equal to 1 mm. The material of the cooling ring includes oxygen-free copper, and the diameter of the cooling ring is less than or equal to 0.5 mm, thereby effectively cutting off eddy currents and reducing eddy current losses.

2. The conductive cooling structure for superconducting magnets according to claim 1, characterized in that, The cooling strip has a coverage of no less than 90% on each layer of coil.

3. The conductive cooling structure for superconducting magnets according to claim 1, characterized in that, Also includes: A fiberglass cloth layer is used to apply preload to the cooling strip in order to regulate the thermal resistance contact between the cooling strip and the coil.

4. The conductive cooling structure for superconducting magnets according to claim 1, characterized in that, Also includes: An indium sheet is disposed at the connection between the cooling ring and the central cooling plate.

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