A superconducting wire

Abstract

This invention provides a superconducting wire, belonging to the field of superconducting material processing and application. The superconducting wire, from the outside in, consists of a magnetic buffer assembly, a copper substrate, a superconducting core wire, and a thermal buffer assembly. The thermal buffer assembly is composed of multiple high-specific-heat core wires and is located at the center of the copper substrate. The magnetic buffer assembly covers the outer surface of the reference superconducting strand. The high-specific-heat core wires absorb Joule heat generated by magnetic flux movement at low temperatures, while the magnetic buffer assembly reduces the local actual magnetic field of the superconducting core wire in low-field regions. Together, they achieve full-condition magnetic flux jump suppression. This invention constructs an electromagnetic-thermal coupling numerical model, using the radial position of the high-specific-heat core wire, the mass ratio of high-specific-heat material to copper, and the thickness of the magnetic buffer assembly as design variables for parametric simulation. The parameter combination with the fewest magnetic flux jumps is selected as the optimal structural parameters, and the optimal superconducting strand is fabricated accordingly. This invention can significantly improve the magnetocaloric stability of high-field superconducting strands.

Description

Technical Field

[0001] This invention belongs to the field of superconducting material processing and application, and specifically relates to a superconducting wire. Background Technology

[0002] Superconducting materials, especially Nb3Sn superconducting wires, are widely used in high-field magnets, nuclear fusion devices, and particle accelerators due to their superior properties such as high critical current density and high upper critical magnetic field. However, Nb3Sn superconducting wires are highly susceptible to flux jumping during changes in external magnetic fields. Flux jumping refers to the rapid influx of a large number of magnetic flux lines into the superconducting wire within a very short period of time, causing localized temperature rises and a sharp drop in current-carrying capacity. In severe cases, it can lead to quenching failure or even irreversible microcracks, greatly threatening the mechanical and magnetothermal stability of superconducting devices. Therefore, suppressing flux jumping has become a key technical problem for improving the practical application of Nb3Sn superconducting wires.

[0003] Currently, technical solutions for suppressing flux jump in superconducting wires mainly fall into two categories. The first category is passive shielding, such as the superconducting wire disclosed in Chinese patent application CN202310518348. This solution involves setting an insulating layer made of ferromagnetic material on the outside of the wire and / or the core wire. The high permeability of the ferromagnetic material under low field conditions is used to shield or guide the external magnetic field, reducing the amount of magnetic flux entering the wire and thus suppressing flux jump. The second category is active temperature control, such as the superconducting wire, superconducting coil, superconducting magnet, and flux jump suppression method disclosed in Chinese patent application CN202410619833. This solution involves setting an insulating layer and a heating component inside the superconducting wire or between the layers of the superconducting coil. By adjusting the current of the heating component, the temperature of the wire or coil is actively controlled, keeping it within a preset magnetothermal stability range, thereby preventing flux jump.

[0004] However, the aforementioned existing technical solutions still have significant shortcomings. For ferromagnetic shielding, it can only passively shield the external magnetic field, failing to address the internal heat accumulation caused by flux movement during flux jumps. Its suppression effect is limited under low magnetic field and high sweep speed conditions, and it lacks synergistic design with high specific heat materials. For active heating, it requires real-time temperature detection and current control, resulting in a complex system with limited response speed, making it difficult to handle millisecond-level transient flux jump events. Furthermore, the heating components introduce additional heat load, affecting cryogenic cooling efficiency. More critically, both types of solutions lead to unstable or insufficient flux jump suppression effects under low field (less than 1T) and high sweep speed (greater than or equal to 10mT / s) conditions.

[0005] Therefore, there is an urgent need to provide a superconducting wire structure that can effectively suppress flux jumps at low field and high sweep speed, retain the current carrying capacity of the wire to the greatest extent, and does not require a complex active control system. Summary of the Invention

[0006] To address the aforementioned problems, the present invention provides a superconducting wire, comprising a reference superconducting strand 100, a thermal buffer assembly 200, and a magnetic buffer assembly 300.

[0007] The thermal buffer assembly 200 is axially positioned at the center of the reference superconducting strand 100; the thermal buffer assembly 200 is composed of multiple high specific heat core wires, each of which is a hexagonal core wire structure; the magnetic buffer assembly 300 is circumferentially positioned outside the reference superconducting strand 100, and the magnetic buffer assembly 300 is made of ferromagnetic material.

[0008] Preferably, the high specific heat core wire is made by mixing rare earth compounds and copper powder in a preset ratio.

[0009] Preferably, the high specific heat core wire is obtained by uniformly mixing high specific heat powder with copper powder and pressing it into a precursor rod, then filling the precursor rod into a copper billet, and then sequentially undergoing initial drawing, cutting, secondary tube loading, and then drawing again.

[0010] Preferably, the thickness of the ferromagnetic material in the magnetic buffer assembly 300 is in the range of [0.0mm, 1.0mm].

[0011] Preferably, the magnetic buffer assembly 300 is manufactured using electroplating or winding processes, and is disposed outside the reference superconducting strand 100.

[0012] Preferably, the reference superconducting strand 100 includes a superconducting core wire 110 and a copper substrate 120, wherein the superconducting core wire 110 is embedded in the copper substrate 120.

[0013] Preferably, the heat buffer assembly 200 is composed of seven high specific heat core wires.

[0014] Preferably, the rare earth compound is Gd₂O₃, GdAlO₃, Gd₂O₂S, PrCu₂, PrB₆, NdSn₃, or Nd₂O₂S. 0.9 Pr 0.1 Any one of Sn3, HoCu2, HoCu5, CeCu6, and CeAl2.

[0015] Preferably, the internal thermal buffer assembly 200 is used to absorb the Joule heat generated by the magnetic flux movement and delay the temperature rise of the superconducting core wire 110; the external magnetic buffer assembly 300 is used to reduce the actual magnetic field borne by the superconducting core wire 110; the internal high specific heat core wire and the external magnetic buffer assembly 300 work together to achieve full-condition magnetic flux jump suppression.

[0016] The superconducting wire provided by this invention has the following beneficial effects: Through the synergistic design of an internal thermal buffer component and an external magnetic buffer component, this superconducting wire breaks through the traditional trial-and-error empirical design. The internal high-specific-heat core wire has extremely high specific heat capacity at low temperatures, which can absorb the Joule heat generated by magnetic flux movement, thus playing a thermal buffering role. The external ferromagnetic material layer has high permeability in the low-field region, which can reduce the local actual magnetic field of the superconducting core wire and delay the triggering of magnetic flux jump. The synergistic effect of these two components achieves magnetic flux jump suppression across all operating conditions, from low field to high field and from low speed to high speed scanning, significantly improving the thermomagnetic stability of the superconducting strand under dynamic magnetic fields. Attached Figure Description

[0017] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a structural diagram of a superconducting wire according to an embodiment of the present invention; Figure 2 This is a comparison chart of experimental and simulation calculation results of embodiments of the present invention; Figure 3 This is a diagram showing the arrangement of different numbers of high specific heat core wires according to an embodiment of the present invention; Figure 4 This is a graph showing the number of magnetic flux jumps corresponding to different numbers of high specific heat core wires in an embodiment of the present invention. Figure 5 This is a diagram showing the positions of different high specific heat core wires in an embodiment of the present invention; Figure 6 This is a graph showing the number of magnetic flux jumps corresponding to different high specific heat core wire positions in an embodiment of the present invention. Figure 7 This is a schematic diagram of the core wire arrangement for evaluating the effect of high specific heat powder mass fraction in an embodiment of the present invention; Figure 8 This is a graph showing the number of magnetic flux jumps corresponding to different mass fractions of high specific heat powders in embodiments of the present invention. Figure 9 These are thickness diagrams of different magnetic buffer components according to embodiments of the present invention; Figure 10 This is a graph showing the number of magnetic flux jumps corresponding to different thicknesses of the magnetic buffer components in this embodiment of the invention. Figure 1 The labeling is as follows: 100 - reference superconducting strand, 110 - superconducting core wire, 120 - copper matrix, 200 - thermal buffer assembly, 300 - magnetic buffer assembly. Detailed Implementation

[0019] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0020] This invention addresses the problem that existing Nb3Sn superconducting wires are prone to flux jumps under low magnetic fields, and that existing enthalpy stabilization schemes (introducing high specific heat materials) lack structural optimization and composition design for dynamic electromagnetic conditions, resulting in limited improvement in thermomagnetic stability under low fields and high sweep rates. It provides a high thermomagnetic stability Nb3Sn superconducting strand structure using an internal tin method. Combined with the synergistic effect of a magnetic buffer component 300, it achieves efficient suppression of flux jumps while ensuring that the engineering critical current density meets practical application requirements.

[0021] Based on this, the present invention provides a superconducting wire, such as... Figure 1 As shown, from the outside in, a magnetic buffer assembly 300, a copper substrate 120, a superconducting core wire 110, and a thermal buffer assembly 200 are arranged closely together. The magnetic buffer assembly 300 tightly covers the superconducting strand 100 and is composed of ferromagnetic materials. The thermal buffer assembly 200 is located at the center of the copper substrate 120 and is composed of seven high specific heat core wires evenly arranged; the preparation process of the high specific heat core wires is compatible with that of the superconducting core wire 110. The high specific heat core wires are made of powder materials with high specific heat characteristics in the low temperature range (4K~10K). In this invention, PrCu2 powder material and copper powder are mixed at a mass ratio of 3:1 to prepare the high specific heat materials. High specific heat materials are mostly rare earth compounds, and the available materials include Gd2O3, GdAlO3, Gd2O2S, PrCu2, PrB6, NdSn3, and Nd2O2S. 0.9 Pr 0.1 Sn3, HoCu2, HoCu5, CeCu6, CeAl2, etc. The high specific heat core wire is hexagonal, and its preparation method includes: first, uniformly mixing high specific heat powder with copper (Cu) powder and pressing it into a precursor rod, which is then filled into a copper billet. This composite billet undergoes initial drawing, segmentation, secondary tube loading, and final drawing. During the forming process, constrained by the arrangement of the precursor rod and the compression of the matrix, the high specific heat core wire ultimately evolves into a hexagonal cross-sectional morphology consistent with superconducting core wires. The preparation process is simple and compatible with existing manufacturing processes.

[0022] The thermal buffer layer of this superconducting wire uses a material with extremely high specific heat at low temperatures. Its function is to improve the thermal effect of the strands and enhance stability. The high specific heat core wire is made into a hexagon because its manufacturing process is the same as that of superconducting core wire 110: first, high specific heat powder and copper powder are mixed to form a precursor rod which is embedded in a copper billet. Then, through processes such as drawing, cutting, tube assembly, and redrawing, its shape is determined to be hexagonal, just like other superconducting core wires 110. Regarding the placement of the high specific heat core wires, seven high specific heat core wires are introduced in the middle of the strands. This is because simulation calculations show that the placement of the high specific heat core wires has no direct impact on the magnetic flux jump phenomenon, possibly because heat diffuses sufficiently quickly within the cross-sectional area. Therefore, they are placed in the middle of the copper substrate 120. This approach can improve the overall thermal performance of the strands without affecting the superconducting current-carrying capacity.

[0023] This invention proposes a composite structure Nb3Sn superconducting strand. This structure significantly increases the overall heat capacity by integrating a high specific heat material (such as PrCu2) internally, and uses a ferromagnetic material (such as 1J22) on the periphery to achieve low-field magnetic shielding by utilizing its high magnetic permeability. This synergistic internal and external design effectively suppresses low-field magnetic flux jumps and significantly improves the magnetothermal stability of the strand. The specific implementation scheme is as follows:

[0024] First, high specific heat material powder and copper powder are uniformly mixed, and then cold-worked through tubing encapsulation, rotary forging, and drawing to prepare a high specific heat composite precursor rod with good density and processing performance. Subsequently, the high specific heat composite precursor rod is assembled with niobium rods, tin sources, and copper spacers to complete the sub-unit assembly, followed by integral drawing and reaction heat treatment to prepare Nb3Sn superconducting strands containing high specific heat units. Based on this, after the Nb3Sn superconducting strands are formed and reaction heat treated, a continuous magnetic buffer assembly 300 is introduced outside the strands. The magnetic buffer assembly 300 is set on the outside of the strands in a composite structure formed by electroplating or winding. The magnetic buffer assembly 300 does not participate in the Nb3Sn phase formation process, but its strong magnetic cohesion under low field can synergistically work with the high specific heat core wire inside the strands to suppress magnetic flux jumps, thereby improving the conductor's operational stability.

[0025] This invention establishes a two-dimensional electromagnetic-thermal coupling numerical simulation model based on the structure and material properties of superconducting strands. The number, position, mass fraction of high specific heat core wires, and thickness of the ferromagnetic buffer layer are used as variables to be optimized. Under various background magnetic field conditions, the hysteresis loops of the superconducting strands are calculated for different variable values, and the number and amplitude of magnetic flux jumps are recorded. The objective function is to minimize the number and amplitude of magnetic flux jumps and minimize the impact on the overall current carrying capacity of the strands. The simulation results under different variables are compared to determine the optimal configuration for suppressing magnetic flux jumps.

[0026] An electromagnetic-thermal coupling numerical model of Nb3Sn superconducting wire was established using the finite element software COMSOL Multiphysics, and systematic calculations were performed on the wire structure. The distribution characteristics (quantity, location, and proportion) of the high specific heat material and the thickness of the external magnetic buffer component 300 were studied parametrically to analyze its suppression effect on magnetic flux jumps under different magnetic field sweep velocities. Based on the calculation results, the optimal wire structure was determined.

[0027] Geometric structure data, material physical parameters, and dynamic magnetic field scanning conditions of the reference superconducting strand 100 were obtained. Based on the geometric structure data, material physical parameters, and dynamic magnetic field scanning conditions, an electromagnetic-thermal coupling numerical model of the reference superconducting strand 100 was constructed. This model includes constitutive relations describing the macroscopic electromagnetic properties of the reference superconducting strand 100 and thermal diffusion equations describing the dynamic evolution of internal heat. A three-dimensional parameter space set was constructed using the radial position of the high specific heat core wire to be introduced within the cross-section of the reference superconducting strand 100, the mass fraction of high specific heat material in the high specific heat core wire to be prepared, and the thickness of the outer magnetic buffer component 300 to be added as design variables. The parameter combinations of the three-dimensional parameter space set were input into the electromagnetic-thermal coupling numerical model for dynamic magnetic field scanning to obtain the hysteresis loop data and the temperature rise data corresponding to the occurrence of magnetic flux jumps for each parameter combination. Based on temperature evolution data and hysteresis loop data, the occurrence of flux jumps under various parameter combinations is determined, and the flux jump behavior generated during the occurrence process is recorded. The parameter combination with the fewest flux jumps and the smallest amplitude is selected as the optimal structural parameters. Based on the optimal structural parameters, the optimal superconducting strand that can suppress flux jumps is fabricated.

[0028] The reference superconducting strand 100 is an Nb3Sn superconducting strand without the introduction of the internal thermal buffer component 200 and the peripheral magnetic buffer component 300; the geometric data includes the outer diameter of the strand, the number and diameter of the Nb3Sn superconducting core wire 110, the cross-sectional area of ​​the copper substrate 120, the diameter of the central non-reactive region and the radial position range; the material physical parameters include the specific heat capacity, thermal conductivity, and resistivity of Nb3Sn, the density, specific heat capacity, thermal conductivity and resistivity of copper, the density, specific heat capacity and thermal conductivity of high specific heat materials, and the specific heat capacity, thermal conductivity, magnetic permeability and saturation magnetic field of ferromagnetic materials; the dynamic magnetic field scanning conditions include the external magnetic field scanning range, scanning rate and operating temperature.

[0029] The electromagnetic behavior of the multi-core superconducting conductor was analyzed using the finite element software COMSOL Multiphysics. A completely decoupled two-dimensional model was used instead of the actual three-dimensional twisted model. To simulate the electromagnetic properties of the composite multi-core superconducting conductor, the H-method differential equation with H as the state variable was derived from Maxwell's equations and the EJ constitutive relation. The constitutive relation between the electric field intensity E and the current density J inside the superconductor can be expressed as: ;

[0030] Where ρ is the effective resistivity and J is the current density, a complex function of temperature T and local magnetic field B. To smoothly describe the EJ constitutive relation of superconductivity from the flux creep region (FC) to the normal state (N), the effective resistivity ρ is expressed as:

[0031] ; Where, ρ n ρ represents the equivalent resistivity of the Nb3Sn superconductor in its normal state. s This represents the resistivity of the Nb3Sn superconductor in the flux creep region.

[0032] ρ s Represented using a power-law model: ; Among them, E c The critical electric field strength is usually taken as E. c =10 -4 V / m, where n is the flux creep coefficient, and its expression is: Where n0 is taken as 18.51, and Jc is the critical current density, which is a function related to temperature and magnetic field, using a generalized... expression: ; in, In the formula T c The critical transition temperature is set to 18.2 K, T0 is the operating temperature set to 4.2 K, b, A, p, and q are material-related fitting parameters, and H... c2 The upper critical magnetic field is a function of temperature. Where H c2 (0) is the upper critical magnetic field at 0K; The re-motion of magnetic flux vortices generates heat, causing changes in the macroscopic temperature of the superconductor. However, the heat transfer in the superconductor still follows Fourier's law: ; In the formula, q is the heat flux density, and λ is the thermal conductivity of the material. The temperature control equation for superconducting materials is as follows, where the heat source term is the Joule heat generated by magnetic flux motion. .

[0033] ; In practical applications of Nb3Sn superconducting wires, liquid helium cooling is generally used. The heat exchange between the superconducting material and liquid helium satisfies the following boundary conditions: ; In the formula, This represents the normal heat flux density at the boundary per unit time. For the general case, It can be represented as:

[0034] ; In the formula, h is the heat transfer coefficient, which is generally considered to be proportional to the cube of the temperature, and T0 is the ambient temperature.

[0035] The magnetic flux motion equation and the temperature-induced thermal diffusion equation are bidirectionally coupled in real time through the temperature-dependent critical current density Jc(T) and the Joule heating of magnetic flux motion in the heat source term Q. The macroscopic thermophysical parameters of the high-specific-heat core wire (including equivalent volumetric specific heat capacity Ceff and equivalent thermal conductivity Keff) are calculated based on the inherent properties of each component material using the composite material mixing rule.

[0036] Volume fraction V of component j j Calculation formula: ; The equivalent thermal conductivity and equivalent volumetric specific heat are: ; ; Among them, M j ρ j K j C j denoted as the mass fraction, density, thermal conductivity, and specific heat at constant pressure of the j-th component, respectively.

[0037] The radial position r of the high specific heat core wire to be introduced within the cross section of the reference superconducting strand 100 ranges from [0, Rcore], where Rcore is the radius of the non-reactive region at the center of the reference superconducting strand 100; the mass fraction of the high specific heat material in the high specific heat core wire to be prepared ranges from [0%, 100%]; and the thickness δ of the peripheral magnetic buffer assembly 300 to be added ranges from [0.0 mm, 1.0 mm].

[0038] The three-dimensional parameter space set is generated by uniform grid discretization or Latin hypercube sampling; each parameter combination is input into the electromagnetic-thermal coupling numerical model for dynamic magnetic field scanning at a scanning rate of 10 mT / s to 100 mT / s, and a scanning range of -3 T to 3 T.

[0039] Determining the occurrence of magnetic flux jumps under various parameter combinations includes: monitoring the rate and magnitude of temperature rise in temperature evolution data; when the rate of temperature rise at a certain time point or region far exceeds the normal thermal conduction temperature rise, and the temperature rise amplitude instantaneously approaches the critical transition temperature Tc, it can be determined that a magnetic flux jump has occurred. Correspondingly, when the temperature evolution remains stable and there is no sudden temperature rise in a short period of time, it is determined that the magnetic flux jump is suppressed. Extracting the change of magnetization M in the entire superconducting region with the external field H; if the originally smooth envelope suddenly drops almost vertically, it can be determined that a magnetic flux jump has occurred. Correspondingly, when the envelope of the magnetization M in the superconducting region changes with the external field H without abrupt change, it is determined that the magnetic flux jump is suppressed.

[0040] The optimal superconducting strand that can suppress magnetic flux jump is fabricated based on the optimal structural parameters as follows: high specific heat material powder and copper powder are mixed in the optimal mass ratio, and a high specific heat composite precursor rod is prepared by sleeve encapsulation, rotary forging, and drawing; the high specific heat composite precursor rod is placed at the optimal radial position and assembled with Nb rod, tin source, and copper spacer rod to complete the sub-unit assembly, and Nb3Sn superconducting core wire 110 is formed by integral drawing and reaction heat treatment; and a magnetic buffer component 300 of optimal thickness is composited around the strand to obtain the optimal superconducting strand.

[0041] This embodiment uses an 11.7T high-field human MRI magnet as an example. The inner coil of this magnet is wound with the superconducting wire described in this invention. The superconducting wire includes: a copper substrate, multiple Nb3Sn superconducting core wires embedded in the copper substrate, a high-heat-density core wire (a mixture of PrCu2 and copper powder, volume ratio 3:1) located in the non-reactive region at the center of the copper substrate, and a ferromagnetic layer (1J22 alloy, 0.3mm thick) covering the outside of the wire. During magnet excitation, the magnetic field scans from 0T to 11.7T at a rate of 10mT / s. When the magnetic field is in the 0~0.4T range, the outer ferromagnetic layer uses its high permeability to concentrate the magnetic flux outside the wire, reducing the amount of magnetic flux entering the wire; at the same time, the high-heat-density core wire absorbs the heat generated by the magnetic flux movement, suppressing local temperature rise. Simulation and experimental results show that the superconducting wire with the structure of this invention does not experience any magnetic flux jumps in the 0-1T low-field range, while the comparative sample with the traditional structure experienced 7 magnetic flux jumps in this range. Ultimately, the magnet reached a stable operating state in a single excitation process, reducing the number of training cycles from more than 30 in the traditional structure to once, and reducing liquid helium consumption by more than 90%.

[0042] To verify the accuracy of the numerical algorithm on the two-dimensional model, this embodiment of the invention compared the hysteresis loop measured under a transverse magnetic field from short samples made of WST and OST wires with the hysteresis loop calculated by simulation. Figure 2The red dashed line represents the experimental results, and the blue solid line represents the two-dimensional simulation results. It can be seen that the simulated hysteresis loop matches the experimental results well, which establishes a reliable benchmark model for subsequent structural optimization schemes that introduce thermal buffer layers and magnetic buffer layers.

[0043] Example 1: Implementation and Verification of High Specific Heat Core Wire Center Layout Structure This embodiment provides a Nb3Sn superconducting wire structure with a high specific heat material placed in the central region of a Cu matrix. To verify the superiority of this placement, this embodiment considers multiple distribution models, such as... Figure 5 As shown, with other parameters remaining constant, the magnetic flux jump of different wire structure schemes in the magnetic field scanning range of [-3T, 3T] was investigated. Figure 6 As shown. Figure 5 Five different radial distribution schemes (center, middle, edge, and random distribution) of high specific heat core wires in copper substrate 120 are shown. Figure 6 The corresponding simulation results show that the number of magnetic flux jumps under different position schemes is basically consistent, and is much lower than that of the reference wire without the introduction of a high specific heat core wire. This indicates that the suppression effect of magnetic flux jumps is mainly related to the total heat capacity of the introduced high specific heat material, and is not sensitive to the radial position of the core wire. Based on this result, the central layout scheme is selected in this embodiment. The significant technical advantage of this structure is that by using the non-reactive zone space in the center of the inner tin wire to set the high specific heat core wire, the magnetocaloric stability of the wire is significantly improved without reducing the number of Nb3Sn superconducting core wires 110 or the theoretical current carrying capacity of the wire.

[0044] Furthermore, this embodiment also investigated the effect of the number of high specific heat core wires on the suppression effect. For example... Figure 3 As shown, arrangements of 2, 4, 6, 8, and 10 high-specific-heat core wires were respectively provided. Figure 4 The corresponding simulation results show that the more high-specific-heat core wires there are, the fewer magnetic flux jumps occur, meaning that the number of high-specific-heat core wires is directly proportional to the suppression effect of magnetic flux jumps. Considering both the manufacturing difficulty and the suppression effect, this embodiment preferably uses a scheme with seven high-specific-heat core wires evenly arranged.

[0045] Example 2: Optimal mass ratio of high specific heat material to copper Based on the central layout structure provided in Example 1, this example further defines the mass ratio of high specific heat material to Cu inside the core wire. The influence of different ratios on magnetic flux jumps was investigated through simulation calculations at three linear ramp magnetic field scanning rates of 10 mT / s, 20 mT / s, and 100 mT / s. Figure 7The optimal high specific heat core wire arrangement scheme is shown, with the central blue core wire being the high specific heat core wire. Under this configuration, the effect of the mass fraction of high specific heat material (0~100wt.%, with a step size of 5wt.%) on suppressing magnetic flux jump was systematically studied. Figure 8 The corresponding simulation results show that when the mass fraction of the high specific heat material is in the range of 50%-75% (i.e., the mass ratio is between 1:1 and 3:1), the wire exhibits the best suppression effect and the fewest magnetic flux jumps under different external magnetic field scanning rates. When the mass fraction is too low (≤25%), the thermal buffering capacity is insufficient. When the mass fraction of the high specific heat material reaches 75%, its suppression effect on magnetic flux jumps tends to saturate. If its mass ratio is further increased, it will not only increase the manufacturing cost but also lead to a significant reduction in the proportion of the copper matrix (120), thereby worsening the overall thermal conductivity of the high specific heat core wire and ultimately weakening the suppression ability on magnetic flux jumps. The calculation results show that when the volume ratio of the high specific heat material to Cu is in the range of 2:1 to 4:1, the wire exhibits the best suppression effect under different external magnetic field scanning rates. Therefore, the preferred volume ratio range of the high specific heat material to Cu in this invention is 2:1 to 4:1, and the most preferred is 3:1.

[0046] Example 3: Synergistic Suppression of Composite Magnetic Buffer Components To further improve the stability of the wire under low field conditions, this embodiment, based on embodiments 1 and 2, adds a layer of ferromagnetic material around the strand as a magnetic buffer component 300. Figure 9 The wire configurations with magnetic buffer components are shown. The buffer layer thickness δ selected in this study includes a series of evolution schemes with no buffer layer (0 mm) and 0.1~1 mm (in increments of 0.1 mm). Figure 10 The corresponding simulation results show that in the low-field region (-0.4T to 0.4T), the ferromagnetic material exhibits strong cohesive magnetism, which can effectively reduce the local actual magnetic field of the superconducting core wire 110, thereby delaying the magnetic flux jump triggering. As the thickness of the magnetic buffer component 300 increases, the suppression effect first strengthens and then tends to saturate. Simulation results are as follows: Figure 10 As shown, the suppression effect is optimal when the thickness of the magnetic buffer component 300 is 0.3 mm, reducing the number of magnetic flux jumps by approximately 33% compared to the wire without the magnetic buffer component 300. When the thickness exceeds 0.3 mm, the improvement in suppression effect becomes less pronounced, and an excessively thick magnetic buffer layer increases the wire diameter and reduces the engineering current density. Therefore, the preferred thickness range for the magnetic buffer component 300 in this embodiment is [0.0 mm, 1.0 mm], with 0.3 mm being the most preferred. This ferromagnetic buffer layer, in synergy with the internal high-specific-heat core wire, further enhances the thermomagnetic stability of the wire under low-field and high-sweep-speed conditions.

[0047] This invention introduces high specific heat material into the existing internal tin method of fabrication in the form of a core wire. It is highly compatible with existing assembly and drawing processes, requiring no fundamental adjustment to the original fabrication process and is easy to implement on existing production lines. The high specific heat core wire unit and magnetic buffer assembly (300) are introduced in a modular manner, and their parameters such as quantity, position, and thickness are easier to adjust according to requirements, thereby achieving a flexible trade-off between stability improvement and engineering critical current density. This technical solution can suppress magnetic flux jumps in a wider range of magnetic field amplitude and frequency, effectively solving the magnetocaloric instability problem of Nb3Sn superconducting strands under low field.

[0048] This invention achieves full-condition flux jump suppression from low to high field and from low to high speed scanning through the coordinated design of an internal high-specific-heat core wire and an external ferromagnetic buffer assembly. The high-specific-heat core wire is positioned in the central non-reactive region of the copper substrate 120, without occupying the design space of the superconducting core wire 110, thus significantly improving thermomagnetic stability without reducing the engineering critical current density. Simultaneously, this invention establishes an electromagnetic-thermal coupling numerical model, using the radial position of the high-specific-heat core wire, the volume ratio of the high-specific-heat material to copper, and the thickness of the magnetic buffer assembly as design variables for parametric simulation. This allows for precise selection of optimal structural parameters, making the suppression effect predictable and the structural parameters quantifiable, avoiding the uncertainties of traditional trial-and-error methods.

[0049] The high-specific-heat core wire of this invention adopts the same hexagonal structure and drawing and tube-packing process as the superconducting core wire 110. The magnetic buffer assembly is integrated by covering or jacketing. The modular design eliminates the need for fundamental changes to the core process flow, making it easy to implement on existing production lines. Calculation results show that at different magnetic field scanning rates from 10mT / s to 100mT / s, the number of magnetic flux jumps is significantly reduced, and the strand stability is significantly improved. In engineering applications, this will effectively reduce the number of magnet training cycles, reduce the risk of quench detection misjudgment caused by voltage spikes, and significantly improve the operational stability and reliability of high-field magnets (such as 12-16T and above hybrid magnets).

[0050] Existing technologies have not systematically optimized the spatial distribution of high specific heat materials or their volume ratio with the copper substrate, nor have they considered the synergistic suppression mechanism of high specific heat absorption and ferromagnetic shielding. Therefore, compared with existing technologies, the superconducting wire provided by this invention has the following advantages:

[0051] 1. This invention integrates a high-specific-heat-temperature material core wire inside a superconducting wire, while simultaneously forming a composite ferromagnetic layer on the outside, creating a dual-mechanism synergistic suppression system of internal heat absorption and external magnetic shielding. The high-specific-heat-temperature material absorbs a large amount of heat when magnetic flux jumps, delaying local temperature rise; the strong magnetic focusing properties of the ferromagnetic layer under low field conditions can densely gather and bind externally intruding magnetic flux lines within the ferromagnetic layer, thereby significantly reducing the amount of magnetic flux entering the wire. The two mechanisms complement each other, and are particularly effective in suppressing the frequency and amplitude of magnetic flux jumps, especially under low field (less than 1T) and high magnetic field sweep speed (greater than or equal to 20mT / s) conditions. In contrast, existing ferromagnetic shielding solutions (such as CN202310518348) can only passively shield the magnetic field and cannot solve the problem of internal heat accumulation; active heating solutions (such as CN202410619833) have limited response speed and are unable to cope with millisecond-level transient magnetic flux jump events.

[0052] 2. This invention employs a purely passive suppression mechanism, eliminating the need for heating components, temperature sensors, and real-time control systems. This avoids reliability issues arising from system complexity, control delays, and heating component failures inherent in active heating solutions. Furthermore, it does not introduce additional heat load, thus avoiding burden on the cryogenic refrigeration system and making it suitable for long-term, high-stability superconducting magnet operation scenarios.

[0053] 3. This invention places the high specific heat core wire in the central region of the copper substrate, utilizing the non-reactive region space at the center of the inner tin-type wire, without occupying the design position of the superconducting core wire or reducing the number of Nb3Sn superconducting core wires. Simultaneously, the ferromagnetic layer is placed on the outside of the wire and does not participate in the superconducting phase formation process. Therefore, this invention achieves the spatial synergy advantage of internal enthalpy stabilization and external dynamic magnetic shielding. This design scheme achieves a thin-walled external ferromagnetic layer without replacing the superconducting core wire, balancing high engineering current carrying capacity and excellent dynamic thermomagnetic stability.

[0054] 4. The high specific heat core wire preparation process (powder mixing, sleeve encapsulation, rotary forging, and drawing) used in this invention is highly compatible with the existing assembly and drawing processes of Nb3Sn superconducting wires using the internal tin method, requiring no fundamental modification to the original production line. The ferromagnetic layer can be achieved through electroplating or winding, a simple process with controllable costs. Compared to active heating solutions that require additional heating components and insulation layers, the process complexity of this invention is significantly reduced, making it suitable for mass production.

[0055] 5. The number, position, and volume ratio of the high-specific-heat core wire to the copper substrate (preferably 2:1 to 4:1, most preferably 3:1), as well as the thickness of the ferromagnetic layer, can all be modularly adjusted according to specific operating conditions, thereby achieving a flexible trade-off between magnetothermal stability and current-carrying capacity in different application scenarios. In existing technologies, ferromagnetic shielding schemes (such as CN202310518348) can only adjust the thickness of the ferromagnetic layer and cannot adjust the internal heat capacity; active heating schemes (such as CN202410619833) have more complex parameter adjustments and are limited by the thermal response characteristics of the heating component.

[0056] 6. The technical solution of this invention is not only applicable to Nb3Sn superconducting wires, but can also be extended to other superconducting material systems prone to flux jumps. It maintains a stable suppression effect over a wide magnetic field range (especially in the low field region) and a wide sweep rate range, effectively solving the problem of poor suppression effect in existing technologies under high excitation rates and low magnetic field conditions.

[0057] Specific limitations regarding the superconducting wire computational system can be found in the limitations of the superconducting wire described above, and will not be repeated here. The various modules in the aforementioned superconducting wire and the system for suppressing flux jumps in the superconducting wire can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independent of the processor in a computer device, or stored in software in the memory of a computer device, so that the processor can call and execute the corresponding operations of each module.

[0058] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. Furthermore, the above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A superconducting wire, characterized in that, It includes a reference superconducting strand (100), a thermal buffer assembly (200), and a magnetic buffer assembly (300). The thermal buffer assembly (200) is axially positioned at the center of the reference superconducting strand (100); the thermal buffer assembly (200) is composed of multiple high specific heat core wires, each of which is a hexagonal core wire structure; the magnetic buffer assembly (300) is circumferentially positioned outside the reference superconducting strand (100), and the magnetic buffer assembly (300) is made of ferromagnetic material.

2. The superconducting wire according to claim 1, characterized in that, The high specific heat core wire is made by mixing rare earth compounds and copper powder in a preset ratio.

3. The superconducting wire according to claim 1, characterized in that, The high specific heat core wire is obtained by uniformly mixing high specific heat powder with copper powder and pressing it into a precursor rod. The precursor rod is then filled into a copper billet, and the wire is obtained by first drawing, cutting, second tube loading, and then drawing again.

4. A superconducting wire according to claim 1, characterized in that, The thickness of the ferromagnetic material in the magnetic buffer assembly (300) ranges from [0.0 mm to 1.0 mm].

5. A superconducting wire according to claim 1, characterized in that, The magnetic buffer assembly (300) is made by electroplating or winding process and is placed outside the reference superconducting strand (100).

6. A superconducting wire according to claim 1, characterized in that, The reference superconducting strand (100) includes a superconducting core wire (110) and a copper substrate (120), wherein the superconducting core wire (110) is embedded in the copper substrate (120).

7. A superconducting wire according to claim 1, characterized in that, The heat buffer assembly (200) consists of seven high specific heat core wires.

8. A superconducting wire according to claim 2, characterized in that, The rare earth compounds are Gd₂O₃, GdAlO₃, Gd₂O₂S, PrCu₂, PrB₆, NdSn₃, and Nd. 0.9 Pr 0.1 Any one of Sn3, HoCu2, HoCu5, CeCu6, and CeAl2.

9. A superconducting wire according to claim 1, characterized in that, The internal thermal buffer assembly (200) is used to absorb the Joule heat generated by the magnetic flux movement and delay the temperature rise of the superconducting core wire (110); the external magnetic buffer assembly (300) is used to reduce the actual magnetic field borne by the superconducting core wire (110); the internal high specific heat core wire and the external magnetic buffer assembly (300) work together to achieve full-condition magnetic flux jump suppression.

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