Conduction cooling structure for superconducting magnet

Abstract

The invention 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 conduction cooling belts which extend in the axial direction of the superconducting magnet and are laid in the circumferential direction of each layer of coil of the superconducting magnet; the cold conduction ring unit is radially wound on a preset position of each layer of cold conduction belt; and the cold conduction plate units are arranged at the two ends and the middle area of the superconducting magnet and are configured to transmit the received cold energy to the cold conduction belt and the cold conduction ring units.

Description

Technical Field

[0001] The present disclosure relates to the technical field of superconducting magnets, and more particularly, to a conduction cooling structure for superconducting magnets. Background Art

[0002] With the increasingly wide application of superconducting magnets in various fields, the traditional liquid helium immersion cooling method cannot meet the cooling requirements under specific working conditions, such as rotational operation. In the fast pulse operation state, the AC losses and eddy current losses generated by the superconducting magnet may cause heat accumulation and temperature rise, which may further lead to the quench phenomenon, especially in the liquid helium-free environment. Therefore, an effective conduction cooling structure is needed to reduce the temperature and ensure the stable operation of the superconducting magnet. Summary of the Invention

[0003] In view of this, the present disclosure provides a conduction cooling structure for superconducting magnets to at least partially solve the above technical problems.

[0004] The present disclosure provides a conduction cooling structure for superconducting magnets, including: a plurality of cold conduction bands extending along the axial direction of the superconducting magnet and laid circumferentially on each layer of the coils of the superconducting magnet; a cold conduction ring unit radially wound around a predetermined position of each layer of the cold conduction bands; and a cold conduction plate unit disposed at both ends and the middle region of the superconducting magnet, configured to transfer the received cold quantity to the cold conduction bands and the cold conduction ring unit.

[0005] According to an embodiment of the present disclosure, the coverage rate of the cold conduction bands on each layer of the coils is not less than 90%.

[0006] According to an embodiment of the present disclosure, the cold conduction ring unit includes two cold conduction rings that are radially symmetric along the superconducting magnet, and both ends of each cold conduction ring are bent and inserted into the grooves in the cold conduction plate unit; wherein, the two symmetric cold conduction rings form a complete circumference around a predetermined position of each layer of the cold conduction bands.

[0007] According to an embodiment of the present disclosure, the cold conduction plate unit includes: an end face cold conduction plate disposed at both ends of the superconducting magnet and in contact with the cold conduction bands; a middle cold conduction 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 the cold conduction ring unit.

[0008] According to an embodiment of the present disclosure, the middle cold conduction plate includes two middle sub-cold conduction plates that are radially symmetric along the superconducting magnet, wherein the two middle sub-cold conduction plates divide the cold conduction ring unit into two symmetric cold conduction rings.

[0009] According to an embodiment of the present disclosure, each middle sub-cold conduction plate is divided into at least 3 oxygen-free copper plates along the beam direction, and adjacent oxygen-free copper plates are electrically isolated by polyimide films.

[0010] According to an embodiment of the present disclosure, the conduction cooling structure for a superconducting magnet further includes: a fiberglass cloth layer for applying a pre-tightening force to the cold conduction strip to regulate the thermal resistance contact between the cold conduction strip and the coil.

[0011] According to an embodiment of the present disclosure, the conduction cooling structure for a superconducting magnet further includes: an indium sheet disposed at the connection between the cold conduction ring and the middle cold conduction plate.

[0012] According to an embodiment of the present disclosure, the material of the cold conduction ring includes oxygen-free copper, and the diameter of the cold conduction ring is less than or equal to 0.5 mm.

[0013] According to an embodiment of the present disclosure, the material of the cold conduction strip includes oxygen-free copper, and the diameter of the cold conduction strip is less than or equal to 1 mm.

[0014] The conduction cooling structure for a superconducting magnet provided according to an embodiment of the present disclosure has at least the following beneficial effects:

[0015] The present disclosure introduces the cold quantity of the refrigerator into the magnet interior by means of the cold conduction plate, and effectively solves the problem of the cooperation of circumferential and axial heat diffusion of a rapid pulse superconducting magnet in a liquid-helium-free environment through the circumferential cold conduction of the cold conduction ring and the axial cold conduction of the cold conduction strip, reduces the risk of excessive local temperature rise of the superconducting magnet, and ensures its stable operation in a liquid-helium-free environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Through the following description of the embodiments of the present disclosure with reference to the drawings, the above and other objects, features, and advantages of the present disclosure will become clearer. In the drawings:

[0017] Figure 1 Schematically shows a schematic diagram of the conduction cooling structure according to an embodiment of the present disclosure;

[0018] Figure 2 Schematically shows a schematic diagram of the structure at the connection between the cold conduction ring unit and the cold conduction plate unit according to an embodiment of the present disclosure;

[0019] Figure 3 Schematically shows a schematic diagram of the middle sub-cold conduction plate according to an embodiment of the present disclosure;

[0020] Figure 4 Schematically shows a schematic diagram of the cold conduction strip according to an embodiment of the present disclosure;

[0021] Figure 5 Schematically shows a schematic diagram of the comparison of the heat conduction effects of different materials according to an embodiment of the present disclosure;

[0022] Figure 6 Schematically shows a schematic diagram of the relationship between the material and width of the cold conduction strip and the eddy current loss according to an embodiment of the present disclosure;

[0023] Figure 7 Schematically shows a schematic diagram of the relationship between the width of the conduction cooling ring and the eddy current loss according to an embodiment of the present disclosure;

[0024] Figure 8 Schematically shows a schematic diagram of the relationship between the thickness of the conduction cooling plate and the eddy current loss according to an embodiment of the present disclosure;

[0025] Figure 9 Schematically shows a thermal simulation schematic diagram of a conductionless cooling structure according to an embodiment;

[0026] Figure 10 Schematically shows a thermal simulation schematic diagram of a conduction cooling structure according to an embodiment of the present disclosure. Detailed implementation manners

[0027] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known systems and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0028] The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. 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 should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0030] In the case of using expressions such as "at least one of A, B, and C", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include, but is not limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0031] Figure 1 Schematically shows a schematic diagram of a conduction cooling structure according to an embodiment of the present disclosure.

[0032] As Figure 1As shown, this embodiment provides a conduction cooling structure for a superconducting magnet, including: a plurality of cold conduction bands 101, a cold conduction ring unit 102, and a cold conduction plate unit 103.

[0033] The plurality of cold conduction bands 101 extend along the axial direction of the superconducting magnet and are laid on the circumferences of each layer of coils of the superconducting magnet.

[0034] The cold conduction ring unit 102 is radially wound around a predetermined position of each layer of cold conduction bands 101.

[0035] And the cold conduction plate units 103 and 104 are arranged at both ends and the middle region of the superconducting magnet, and are configured to transfer the received cold quantity to the cold conduction bands 101 and the cold conduction ring unit 102.

[0036] In the embodiment of the present disclosure, the cold conduction plate units 103 and 104 are connected to the cold head 106 of the refrigerator through the flexible copper braided belt 105 for receiving the cold quantity transmitted from the cold head 106 of the refrigerator. Among them, the cold conduction band 101 axially transfers the cold quantity of the refrigerator to the distal region of the magnet, and at the same time absorbs the heat generated by the ac loss and eddy current loss of the superconducting wire. The cold conduction ring unit 102 conducts the heat into the cold conduction plate connected to the cold head and realizes heat exchange, and homogenizes the circumferential temperature distribution of the coil through circumferential heat conduction to eliminate local hot spots; and the cold conduction ring unit 102 is in direct contact with the cold conduction plate 103 and the cold conduction band 101, and can realize the interconnection of the radial-circumferential-axial cold conduction paths. The cold conduction plate unit 103 efficiently conducts the cold quantity of the refrigerator into the magnet and optimizes the cold quantity distribution through the cold conduction plates at different positions.

[0037] The multi-level cooling system composed of the cold conduction band 101, the cold conduction ring unit 102, and the cold conduction plate unit 103 forms an efficient heat conduction network, ensuring that heat can be quickly transferred from the coil to the external cooling medium, greatly improving the cooling efficiency. By extending along the axial direction of the superconducting magnet and being laid on the circumferences of each layer of coils, the plurality of cold conduction bands can cover the entire coil surface, ensuring that heat is evenly taken away from all directions. This effectively avoids the local overheating phenomenon that may occur in the traditional cooling method and improves the overall cooling efficiency. At the same time, under the condition of no liquid helium, the combined cooling effect of the cold conduction plate, the cold conduction band, and the cold conduction plate ring significantly improves the cold quantity transfer efficiency of the cold head of the refrigerator, and the overall temperature fluctuation of the magnet is controlled within 1 K, effectively avoiding the risk of quench caused by local temperature rise. For the ac loss of the superconducting wire and the eddy current loss of the metal structure under the fast pulse working condition (dB / dt>0.6T / s), the axial cold conduction path of the cold conduction band and the circumferential cold conduction path of the cold conduction ring act together, reducing the maximum temperature rise of the magnet from 107 K of the traditional liquid helium scheme to 4.8 K, and without relying on the latent heat of phase change of liquid helium.

[0038] On the basis of the above embodiment, the coverage rate of the cold conduction band on each layer of coil is not less than 90%.

[0039] In an embodiment of the present disclosure, the heat conduction belt adopts an axial layered laying strategy, and the copper wires are axially oriented along the magnet in a closely arranged manner. The coverage rate of each layer of the heat conduction belt covering each layer of the coil is ≥90%, and this configuration ensures that the axial heat flux density is ≥500 W / m²·K, meeting the temperature drop gradient from the 4.2K cold source to each layer of the coil.

[0040] Figure 2 A schematic structural diagram of the connection between the heat conduction ring unit and the heat conduction plate unit according to an embodiment of the present disclosure is schematically shown.

[0041] As Figure 2 shown, the heat conduction ring unit disclosed in this embodiment includes two heat conduction rings that are radially symmetric along the superconducting magnet, and both ends of each heat conduction ring are bent and inserted into the grooves in the heat conduction plate unit; wherein, the two symmetric heat conduction rings form a complete circumference and surround a predetermined position of each layer of the heat conduction belt.

[0042] In an embodiment of the present disclosure, the heat conduction ring unit is wound around the surface of the superconducting magnet in a spring shape, and the number of turns and the winding position can be set as needed. The heat conduction ring unit is subjected to laser cutting treatment at the corresponding slot positions, and the broken ends are bent by 90° through a cold bending forming process and embedded into the mounting holes of the skeleton heat conduction plate. To ensure strength, indium sheets can be used to pad the folded corners.

[0043] Based on the above embodiment, as Figure 1 shown, the heat conduction plate unit includes: an end face heat conduction plate 104, which is arranged at both ends of the superconducting magnet and is in contact connection with each layer of the heat conduction belt. A middle heat conduction plate 103, which is arranged in the middle region of the superconducting magnet and is embedded in the groove of the superconducting magnet and is in contact with each layer of the heat conduction ring unit. Among them, the end face heat conduction plate 104 is arranged at a distance of N mm from the end, and N needs to be further calculated and determined according to the structures of different superconducting magnets.

[0044] In this embodiment, the middle heat conduction plate 103 is in direct contact with the heat conduction ring unit 102, realizing radial heat transfer. At the same time, a non-contact thermal coupling design is adopted between the heat conduction plate 103 and the heat conduction belt 101. Among them, the heat conduction ring acts as a heat transfer medium between the two, and axial heat transfer is realized by means of the heat conduction belt. Such a design not only ensures the effective conduction of heat, but also avoids mechanical problems that may be caused by direct contact, improving the stability and efficiency of the system.

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

[0046] AsFigure 1 As shown, the middle heat conduction plate 103 of this embodiment includes two middle sub-heat conduction plates 103-1 and 103-2 that are radially symmetric along the superconducting magnet. Among them, the two middle sub-heat conduction plates 103-1 and 103-2 divide the heat conduction ring unit into two symmetric heat conduction rings.

[0047] In the embodiment of the present disclosure, the two ends of one heat conduction ring are respectively bent and inserted into the middle sub-heat conduction plates 103-1 and 103-2 correspondingly, and the two ends of the other heat conduction ring are also respectively bent and inserted into the middle sub-heat conduction plates 103-1 and 103-2 correspondingly.

[0048] Figure 3 Schematically shows a structural schematic diagram of the middle sub-heat conduction plate according to an embodiment of the present disclosure.

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

[0050] In the embodiment of the present disclosure, to reduce the eddy current loss caused by the alternating magnetic field (AC magnetic field) and reduce the process installation difficulty, the middle sub-heat conduction plate adopts a stacking method of ≥3 sheets, and each stack is insulated from each other. Among them, the number of oxygen-free copper plates can be set as required.

[0051] Figure 4 Schematically shows a structural schematic diagram of the heat conduction belt according to an embodiment of the present disclosure.

[0052] As Figure 4 shown, the conduction cooling structure for the superconducting magnet in this embodiment further includes: a fiberglass cloth layer 201 for applying a pre-tightening force to the heat conduction belt to regulate the thermal resistance contact between the heat conduction belt and the coil.

[0053] In the embodiment of the present disclosure, each layer of the heat conduction belt is wound and fixed on the surface of the superconducting coil by a high-strength fiberglass cloth to ensure uniform contact surface pressure and achieve low thermal resistance contact between the heat conduction belt and the superconducting coil. At the same time, a heat-conducting grease is coated on the contact surface between the heat conduction ring and the heat conduction belt, which can effectively reduce the interface thermal resistance.

[0054] According to the embodiment of the present disclosure, the material of the heat conduction ring includes oxygen-free copper, and the diameter of the heat conduction ring is less than or equal to 0.5 mm.

[0055] In the embodiment of the present disclosure, the heat conduction ring is made of high-purity oxygen-free copper enameled wire, and the single copper wires are insulated from each other. By controlling the diameter of the heat conduction ring ≤0.5 mm, the feasibility of process winding can be ensured, and the eddy current loss in the alternating magnetic field environment can be minimized.

[0056] According to an embodiment of the present disclosure, the material of the heat conduction belt includes oxygen-free copper, and the diameter of the heat conduction belt is less than or equal to 1 mm.

[0057] In an embodiment of the present disclosure, the heat conduction belt uses high-purity oxygen-free copper with insulation and a core wire diameter ≤ 1 mm, which can minimize the eddy current loss in an alternating magnetic field environment. At the same time, the copper wires are arranged parallel to the axis of the superconducting magnet to ensure structural integrity even under cryogenic shrinkage conditions.

[0058] According to an embodiment of the present disclosure, since the high thermal conductivity material oxygen-free copper is accompanied by 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, and the larger the introduced eddy current. Therefore, it is necessary to perform insulation segmentation on the heat conduction structure to cut off the eddy current and find the balance point between eddy current loss and heat conduction efficiency to determine the heat conduction material and size.

[0059] In this embodiment, by controlling the core wire diameter of the heat conduction belt and the heat conduction ring, and controlling the cutting number of the heat conduction plate, the eddy current can be effectively cut off, the eddy current loss can be reduced, and the heat conduction efficiency can be improved.

[0060] Figure 5 Schematically shows a comparison diagram of the heat conduction effects of different materials according to an embodiment of the present disclosure.

[0061] As Figure 5 shown, in a liquid-helium-free fast-pulse superconducting magnet system, the selection of the heat conduction material needs to comprehensively consider the balance between thermal conductivity and electromagnetic performance. To quickly conduct the heat generated by the superconducting coil during the excitation process, a material with high thermal conductivity needs to be selected. Currently, the metal materials with relatively high thermal conductivity are 6-series aluminum, 1-series aluminum, high-purity oxygen-free copper (RRR = 30), and high-purity oxygen-free copper (RRR = 100). Among them, the RRR value is the resistance ratio of the material at room temperature and low temperature. The specific material selection needs to calculate the thermal-electric-magnetic balance point through multi-physical field coupling simulation to determine the optimal material and geometric parameters.

[0062] Without considering the influence of eddy currents, as the material changes from 1-series aluminum to oxygen-free copper (RRR = 30), and then to oxygen-free copper (RRR = 100), the temperature rise of the magnet shows an obvious downward trend. This shows that when designing the cooling structure of a superconducting magnet, choosing the appropriate material is crucial for controlling the temperature rise of the magnet. And oxygen-free copper (especially RRR = 100) performs excellently in reducing the temperature rise of the magnet due to its excellent heat conduction performance.

[0063] Figure 6 Schematically shows a relationship diagram between the material and width of the heat conduction belt and the eddy current loss according to an embodiment of the present disclosure.

[0064] Figure 7Schematically shows a schematic diagram of the relationship between the width of the conduction cooling ring and the eddy current loss according to an embodiment of the present disclosure.

[0065] Figure 8 Schematically shows a schematic diagram of the relationship between the thickness of the conduction cooling plate and the eddy current loss according to an embodiment of the present disclosure.

[0066] As Figure 6 shown, in the case of the same conduction cooling belt width, although the eddy current loss of Al1100 is the smallest. However, the heat conduction effect of Al is much worse than that of copper, and when the width of the conduction cooling belt is 1 mm, the difference in eddy current loss between Al1100 and oxygen-free copper RRR = 100 is about 1 W, and the difference is small. Therefore, considering the heat conduction ability of the conduction cooling belt comprehensively, the material of the conduction cooling belt is preferably oxygen-free copper RRR = 100.

[0067] As shown in 7, the material of the conduction cooling ring is oxygen-free copper (RRR = 100). As the width of the conduction 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] As Figure 8 shown, the material of the conduction cooling plate is oxygen-free copper. As the thickness of the conduction cooling plate decreases, the eddy current loss decreases accordingly. The material of the corresponding conduction cooling plate can be selected as oxygen-free copper (RRR = 30) or oxygen-free copper (RRR = 100) according to needs.

[0069] From Figures 6 - 8 it can be seen that the conduction cooling material can be selected according to the actual design needs, which can effectively suppress its eddy current loss.

[0070] Figure 9 Schematically shows a thermal simulation schematic diagram of a non-conductive cooling structure of an embodiment.

[0071] Figure 10 Schematically shows a thermal simulation schematic diagram of a conduction cooling structure according to an embodiment of the present disclosure.

[0072] As Figures 9 - 10 it can be seen that based on the simulation of Ansys Workbench software, the boundary conditions refer to the cold head of a 4.2 K refrigerator and the fast pulse condition (dB / dt > 0.6 T / s). In the case of no conduction cooling structure, the local temperature of the superconducting coil under the fast pulse condition is as high as 107 K, and the magnet cannot operate stably. After adopting the three-dimensional conduction cooling network of the present disclosure, the overall temperature distribution of the magnet is uniform, the highest temperature rises to 4.88 K, and the axial temperature gradient is lower than 1 K / m, verifying the collaborative heat dissipation effect of the multi-dimensional conduction cooling path.

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

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

Claims

1. A conduction cooling structure for a superconducting magnet, characterized in that, Comprising: A plurality of heat conduction bands, extending along the axial direction of the superconducting magnet and laid on the circumference of each layer of coils of the superconducting magnet; A heat conduction ring unit, radially wound around a predetermined position of each layer of the heat conduction bands; and A heat conduction plate unit, disposed at both ends and the middle region of the superconducting magnet, configured to transfer the received cooling capacity to the heat conduction bands and the heat conduction ring unit.

2. The conduction cooling structure for a superconducting magnet according to claim 1, wherein The coverage rate of the heat conduction bands on each layer of coils is not less than 90%.

3. The conduction cooling structure for a superconducting magnet according to claim 1, wherein The heat conduction ring unit includes two heat conduction rings symmetrically arranged along the radial direction of the superconducting magnet, and both ends of each heat conduction ring are bent and inserted into the grooves in the heat conduction plate unit; wherein, the two symmetric heat conduction rings form a complete circumference around a predetermined position of each layer of the heat conduction bands.

4. The conduction cooling structure for a superconducting magnet according to claim 3, characterized in that, The heat conduction plate unit includes: An end face heat conduction plate, disposed at both ends of the superconducting magnet and in contact with the heat conduction bands; A middle heat conduction 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 the heat conduction ring unit.

5. The conduction cooling structure for a superconducting magnet according to claim 4, wherein The middle heat conduction plate includes two middle sub-heat conduction plates symmetrically arranged along the radial direction of the superconducting magnet, wherein, the two middle sub-heat conduction plates divide the heat conduction ring unit into the two symmetric heat conduction rings.

6. The conduction cooling structure for a superconducting magnet according to claim 5, characterized in that, Each middle sub-heat conduction plate is divided into not less than 3 oxygen-free copper plates along the beam direction, and adjacent oxygen-free copper plates are electrically isolated by polyimide films.

7. The conduction cooling structure for a superconducting magnet according to claim 1, wherein Further comprising: A glass fiber cloth layer, used to apply a pre-tightening force to the heat conduction bands to regulate the thermal resistance contact between the heat conduction bands and the coils.

8. The conduction cooling structure for a superconducting magnet according to claim 3, wherein, Further comprising: An indium sheet, disposed at the connection between the heat conduction ring and the middle heat conduction plate.

9. The conduction cooling structure for a superconducting magnet according to claim 1, characterized in that, The material of the heat conduction ring includes oxygen-free copper, and the diameter of the heat conduction ring is less than or equal to 0.5 mm.

10. The conduction cooling structure for a superconducting magnet according to claim 5, characterized in that, The material of the heat conduction band includes oxygen-free copper, and the diameter of the heat conduction band is less than or equal to 1 mm.

Images