Superconducting magnet coil strip combination method based on different formulas

Abstract

The invention relates to the field of superconducting tape manufacturing, and provides a superconducting magnet coil tape combination method based on different formulas, which comprises the following steps: S1, acquiring magnetic field characteristics of coils at different positions of a superconducting magnet, the magnetic field characteristics comprising a ratio of a vertical magnetic field component to a parallel magnetic field component in a magnetic field, and a ratio of the vertical magnetic field component to the parallel magnetic field component in the magnetic field; different positions of the superconducting magnet are divided into a vertical magnetic field component leading position, a parallel magnetic field component leading position and a vertical parallel magnetic field component balancing position; s2, for coils at different positions of the superconducting magnet in the S1, preparing strips by adopting three different pinning formulas, and respectively adapting to magnetic field characteristics at different positions of the superconducting magnet; s3, coils are wound at the corresponding positions of the superconducting magnet through the strip in the S2, and the coils are connected in series to form the superconducting magnet. Precise matching of the strip performance and magnet space magnetic field distribution is achieved, the material utilization efficiency is improved while the magnet performance is guaranteed, the manufacturing cost is reduced, and the reliability of magnet operation is enhanced.

Description

[0001] This application is a divisional application of the following original application: Original application filing date: November 28, 2025; Original application... Application No.: 202511768364.9; Original Invention Title: Strip Combination Method for Coils at Different Positions in a Superconducting Magnet Law. Technical Field

[0002] This invention relates to the field of superconducting tape manufacturing technology, specifically, to a method for assembling superconducting magnet coil tapes based on different formulations. More particularly, it relates to a method for assembling superconducting tapes for different coils of a magnet. Background Technology

[0003] Second-generation high-temperature superconducting tapes, especially REBCOs represented by rare-earth barium copper oxide (such as EuBa2Cu3O3), are used in high-temperature superconducting tapes. 7-δ High-temperature superconducting (HTSU) tapes have been considered a revolutionary technology in the energy, medical, scientific research, and transportation fields since their invention. Their key advantage lies in their ability to exhibit zero resistance, perfect diamagnetism, and extremely high current-carrying capacity even under strong magnetic fields, all at relatively easily achievable and low-cost conditions in the liquid nitrogen temperature range (77K). It is estimated that the global high-temperature superconducting market will grow from $1.5 billion in 2023 to $4.8 billion in 2030, driven primarily by applications such as superconducting cables, magnetic resonance imaging (MRI) equipment, tokamak fusion devices, and maglev trains—areas with urgent needs for strong magnetic fields and high-efficiency energy transmission.

[0004] For practical superconducting materials (generally type II superconductors), an external current drives magnetic flux vortex motion, generating resistance. Fortunately, it has been discovered that defects in superconductors can impede magnetic flux motion, a phenomenon known as flux pinning. Figure 1 This is a schematic diagram illustrating the principle of magnetic flux vortex motion.

[0005] REBCO tape, with its superior current-carrying capacity under high fields and its ability to suppress Lorentz forces in magnetic fields through flux pinning, has become one of the preferred materials for constructing high-field magnets. However, the layered crystal structure of REBCO tape causes its flux pinning ability to exhibit high sensitivity to the direction of the magnetic field, i.e., anisotropy. Figure 2 The test results shown, which examine the critical current of REBCO tapes with different pinning properties under a temperature of 77K and a magnetic field of 1T, as a function of angle, directly demonstrate this anisotropy.

[0006] Figure 3 The diagram illustrates the states of the strip under perpendicular and parallel fields. Specifically, when the strip, which is dominated by parallel field properties, is in a perpendicular field, the critical current density can drop sharply to 15%-50% of that in a parallel field. This intrinsic characteristic of the material poses a challenge to the design of superconducting magnets. In actual operating magnets, the direction of the magnetic field varies complexly with spatial position.

[0007] Figure 4The diagram illustrates the distribution of magnetic field angles for the coils and strips within a magnet. It shows that different turns of the coil, and even different parts of the same turn, experience different magnetic field angles. Since superconducting coils in a magnet are typically connected in series, the current flowing through all coils must be identical. Therefore, the safe operating current for the entire coil and even the entire magnet often needs to be estimated using the lowest value of the strip under the full magnetic field angle.

[0008] This scenario, where the weakest link determines the magnet's performance, traps superconducting magnets in a performance-cost dilemma. Considering the performance differences caused by fluctuations in equipment parameters during mass production, as well as the complexity and high cost of adjusting production processes, current engineering practices typically procure strips based on only a single performance standard. While this avoids excessively high process costs, it results in significant performance redundancy in the strips. More critically, because the quench propagation speed of high-temperature superconducting materials is relatively slow, ideally, the magnet needs to achieve uniform quench as it approaches its limit. However, the use of strips with only a single performance characteristic inevitably creates a weak point region within the magnet. When quench occurs in this region, other regions remain in a subcritical state. This asynchronous quench characteristic severely threatens the operational stability of the magnet.

[0009] To address this challenge, the industry has primarily sought solutions on two levels. At the materials level, patent document CN118197706A attempts to enhance the pinning ability of the tape under specific magnetic field angles by using ion irradiation to ensure uniform epitaxial penetration of the superconducting layer through the pinning center, thereby improving the magnetic field performance of the superconducting tape. However, this method presents an irreconcilable contradiction: while it can improve the performance of the tape at specific magnetic field angles, the columnar structure that strengthens the perpendicular field performance significantly disrupts the crystal integrity of the superconducting layer, leading to a decrease in the material's intrinsic critical current performance.

[0010] At the magnet design level, some studies have attempted to combine superconducting tapes with different properties. For example, patent document CN103035353A proposed a scheme using Bi-based and Y-based tapes in parallel. However, such methods have obvious limitations: Bi-based tapes themselves are severely limited in strong parallel fields, and the parallel connection of heterogeneous material systems will introduce complex issues such as uneven current distribution, joint resistance, and thermal stability, and significantly increase the complexity of the supply chain and process control.

[0011] In summary, existing technologies have failed to systematically solve the problem of balancing the performance of superconducting coils in complex, multi-angle magnetic field environments. Therefore, there is an urgent need in this field for an innovative design concept that can overcome the limitations of single-material performance and enable superconducting magnets to operate stably and efficiently under all magnetic field angles in space without significantly increasing cost and complexity.

[0012] Patent document CN114360846B discloses a high-field superconducting magnet with a multi-coil combination and its fabrication method. By setting up nested superconducting coils, the space utilization of the superconducting coils is improved, and the total current density of the high-field superconducting magnet is increased through structural improvements. Its drawback is that, because it does not consider the compatibility of the superconducting tape material with the magnetic field direction at the magnet's location, there is still a significant loss in critical current density, and it does not solve the problem of material cost waste in existing superconducting tape technologies. Summary of the Invention

[0013] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for combining superconducting tapes for different coils in a magnet.

[0014] A method for combining strips of coils at different positions in a superconducting magnet according to the present invention includes: S1: Obtain the magnetic field characteristics at different positions of the coil in the superconducting magnet. The magnetic field characteristics include the ratio of the vertical magnetic field component to the parallel magnetic field component in the magnetic field. The vertical magnetic field component is parallel to the radial direction of the superconducting magnet, and the parallel magnetic field component is parallel to the axial direction of the superconducting magnet. The different positions of the superconducting magnet are divided into positions dominated by the vertical magnetic field component, positions dominated by the parallel magnetic field component, and positions where the vertical and parallel magnetic field components are balanced. S2: For coils at different positions of the superconducting magnet in S1, select strips that are suitable for the magnetic field characteristics of the corresponding positions. S3: Using the strip material adapted to different magnetic field characteristics in S2, coils are wound at corresponding positions of the superconducting magnet, and the coils are connected in series to form a superconducting magnet.

[0015] Preferably, θ represents the angle between the surface normal of the strip and the direction of the magnetic field in which the strip is located; The magnetic field at the dominant position of the vertical magnetic field component conforms to -30°<θ≤30°; The magnetic field at the dominant position of the parallel magnetic field component conforms to 60°<θ≤120°; The magnetic field at the equilibrium position of the vertical-parallel magnetic field components conforms to 30°<θ≤60° or 120°<θ≤150°.

[0016] Preferably, in a vertical magnetic field, θ = 0°, and in a parallel magnetic field, θ = 90°.

[0017] Preferably, PLD equipment is selected to produce the strip used in S2. The ratio of the critical current of the strip under a vertical magnetic field to that under a parallel magnetic field is called the critical current ratio. The critical current ratio is related to the PLD equipment used. Strips produced by the same PLD equipment under the same process parameters have a critical current ratio fluctuation of less than 10%, and exhibit consistent performance. The critical current ratio of strips produced by different PLD equipment under the same process parameters varies by 10% to 30%, which has performance differentiation. Different PLD equipment can stably produce strips with critical current ratios that are compatible with the dominant positions of the vertical magnetic field component, the dominant positions of the parallel magnetic field component, or the balanced positions of the vertical and parallel magnetic field components on the superconducting magnet.

[0018] Preferably, the strip used in S2 is produced using PLD equipment, including the following steps: Establish an equipment performance database and statistically analyze the types of strips produced by different PLD equipment under the same process parameters, including: strips suitable for positions dominated by vertical magnetic field components, positions dominated by parallel magnetic field components, and positions where vertical and parallel magnetic field components are balanced. Quickly select PLD equipment capable of producing strips in the above three positions; The selected PLD equipment is used to produce strips, which are then used to wind coils at the locations where the vertical magnetic field component dominates, the parallel magnetic field component dominates, or the vertical and parallel magnetic field components are balanced, corresponding to the superconducting magnet.

[0019] Preferably, in S2, three different stapled formulations are used to prepare the strip: Formula A enables the tape to form nanoparticle pinning centers and is suitable for the dominant position of parallel magnetic field components on superconducting magnets; Formula B enables the strip to form a columnar pinning center and is suitable for the dominant position of the vertical magnetic field component on a superconducting magnet; Formula C employs a hybrid pinning system, making the strip suitable for the balanced position of vertical-parallel magnetic field components on superconducting magnets.

[0020] Preferably, in S2, the method for selecting the suitable tape is as follows: a tape comprising two layers of different pinning characteristics in the superconducting layer is selected, wherein the bottom layer of the superconducting layer is located on the side closer to the tape substrate, and the top layer of the superconducting layer is located on the side farther from the tape substrate, and: The bottom layer includes columnar pinning, and the top layer includes in-plane nanoparticle pinning; or The bottom layer consists of in-plane nanoparticle pinning, and the top layer consists of columnar pinning.

[0021] Preferably, in S2, the method of selecting the appropriate strip is as follows: select a strip with the same pinning formula, cut it into different widths, and the strips of different widths are respectively suitable for coils at different positions of the superconducting magnet; Among them, the coil suitable for the position where the vertical magnetic field component is dominant uses a strip of the first width; A coil suitable for positions where vertical and parallel magnetic field components are balanced, using strip of the second width; Suitable for coils where the parallel magnetic field component dominates, using strip of the third width; First width > Second width > Third width.

[0022] Preferably, S2 includes detecting the strip performance using a rapid testing method, comprising the following steps: S2.1: The critical current curve of the strip at all angles was tested under the conditions of 77K temperature and 1T magnetic field. S2.2: Use a vibrating sample magnetometer to test the lifting coefficient of the sample under different temperatures and magnetic fields; S2.3: Combining the measured improvement coefficient, the test data are extrapolated to the actual working conditions based on the following fitting formula: Curved Lorentz Peak:

[0023] Curve Gaussian peak:

[0024] In the formula, I0 represents the overall intensity of the curve; Γ represents the peak shape parameter; θ is the angle between the normal to the strip surface and the direction of the background magnetic field; I c (θ) represents the critical current density of the strip at angle θ; θ0 is the angle corresponding to the peak value of the anisotropic curve.

[0025] When θ0=90°, Lorentz peak 1 and Gauss peak are obtained. Lorentz peak 1 represents the pinning ability of the ab plane of the tape, and Gauss peak represents the pinning ability of the doped phase of the tape. When θ0=0°, Lorentz peak 2 is obtained, which represents the overall pinning level of the strip.

[0026] Preferably, in S1, the different positions of the coil are as follows: positions 1 to 6 are arranged sequentially along the axis of the superconducting magnet. Positions 1 and 6 are located at both ends of the superconducting magnet and are the dominant positions of the vertical magnetic field component. Positions 3 and 4 are located in the middle of the superconducting magnet and are the dominant positions of the parallel magnetic field component. Positions 2 and 5 are located between positions 1 and 6 and positions 3 and 4, respectively, and are all positions where the vertical and parallel magnetic field components are balanced.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention significantly reduces the total amount of strip material required for the magnet by matching high-performance strips to different magnetic field angle regions of the magnet, thereby reducing material costs without compromising the overall performance of the magnet.

[0028] 2. This invention utilizes the performance differences caused by inherent production process fluctuations in different pulsed laser deposition (PLD) equipment to transform the "process fluctuation difficulties" that originally required painstaking control into a resource that can be actively utilized, thereby achieving directional and precise production of strip pinning characteristics.

[0029] 3. This invention optimizes the design of the magnet by dividing it into zones, so that the limiting current of the strip material in each part of the magnet tends to be consistent, effectively avoiding the risk of local overheating and greatly reducing the probability of the magnet burning out due to quench propagation failure. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 The background technology of this invention mainly embodies the principle of magnetic flux vortex motion; Figure 2 The background technology of this invention mainly reflects the anisotropy test results of strips with different pinning properties at 77K / 1T; Figure 3 The background technology of this invention mainly illustrates the state of the strip in a vertical field and a parallel field; Figure 4 The background of this invention is mainly illustrated by the schematic diagram showing the distribution of the magnetic field angles of the coil and the strip in the magnet; Figure 5 This is a diagram illustrating the anisotropic extrapolation model of the strip material, which is dominated by parallel field pinning performance, as shown in the embodiments of the present invention. Figure 6 This is a schematic diagram illustrating the vertical and parallel field performance components of strips produced by different PLD devices, as shown in the embodiments of the present invention. Figure 7 This is a display of the normalized results of anisotropy testing of strip produced by three PLD devices at 77K / 1T in an embodiment of the present invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0032] This embodiment can be specifically applied to the optimization of the main magnet in a 1.5T cranial magnetic resonance imaging (MRI) system. The superconducting magnet consists of multiple coils arranged along the axial direction and stacked in series. The magnetic field lines of the magnetic field formed by the superconducting magnet are distributed as follows: Figure 4As shown in the figure, θ represents the angle between the surface normal of the strip and the direction of the background magnetic field. Specifically, the perpendicular magnetic field component is parallel to the radial direction of the superconducting magnet, θ = 0°, and the parallel magnetic field component is parallel to the axial direction of the superconducting magnet, θ = 90°.

[0033] S1: Obtain the magnetic field characteristics at different positions of the coil in the superconducting magnet. The magnetic field characteristics include the ratio of the vertical magnetic field component to the parallel magnetic field component in the magnetic field. The vertical magnetic field component is parallel to the radial direction of the superconducting magnet, and the parallel magnetic field component is parallel to the axial direction of the superconducting magnet. The different positions of the superconducting magnet are divided into positions dominated by the vertical magnetic field component, positions dominated by the parallel magnetic field component, and positions where the vertical and parallel magnetic field components are balanced.

[0034] by Figure 4 Taking the coils in the example, we can see that the superconducting magnet can include coils 1 to 6 arranged along the axial direction, which are divided into three categories: coils 1 and 6 are located at the two ends of the magnet, where the magnetic field θ is relatively small, usually -30° < θ ≤ 30°, and the strip material bears a higher vertical magnetic field component, belonging to the position where the vertical magnetic field component dominates; while coils 3 and 4 are close to the central plane of the superconducting magnet, where θ is relatively large, usually 60° < θ ≤ 120°, and the strip material mainly bears the effect of the parallel magnetic field component, belonging to the position where the parallel magnetic field component dominates; coils 2 and 5 are located between coils 1 and 3 and coils 4 and 6, respectively, and bear a relatively balanced vertical and parallel magnetic field components, usually 30° < θ ≤ 60° or 120° < θ ≤ 150°, belonging to the position where the vertical and parallel magnetic field components are balanced.

[0035] The remaining steps of the present invention include: S2: For coils at different positions of the superconducting magnet in S1, select strips that are suitable for the magnetic field characteristics of the corresponding positions. S3: Using the strip material adapted to different magnetic field characteristics in S2, coils are wound at corresponding positions of the superconducting magnet, and the coils are connected in series to form a superconducting magnet.

[0036] For the same type of strip material, the critical current can vary by approximately 2 to 8 times depending on the angle of the magnetic field. The critical current can be estimated based on a material model, which is as follows:

[0037] in, θ is the angle between the normal to the strip surface and the direction of the background magnetic field; T represents temperature; B is the magnetic field strength; I c (θ,T,B) represents the critical current value of the superconducting tape under specified temperature, magnetic field and angle. I c(77K, 0T) is the critical current value of the superconducting tape at a temperature of 77K and a magnetic field strength of 0T; LF(θ,T,B) is the critical current enhancement factor of the superconducting tape under specified temperature, magnetic field and angle. * indicates multiplication.

[0038] In traditional design frameworks, the overall performance of a magnet is limited by the coils positioned at the most unfavorable magnetic field angle (such as a perpendicular field). To compensate for these local performance limitations and ensure safe magnet operation, designers must uniformly select higher-performance superconducting tapes for the entire magnet. For example, the critical current density of the tape at a self-field of 77K must satisfy J... c >2200A / mm 2 Considering the magnet volume and ampere-turns, the total strip material usage is approximately 4.8 km², resulting in a strip material cost of up to 792,000 yuan based on current market prices. Further analysis of the matching degree between the magnetic field angles of each coil and the actual performance of the strip reveals that the average current utilization rate of the strip at 1.5T is only 40%, indicating significant material waste. This invention provides different schemes in the following embodiment group to optimize the strip material combination, improve current utilization, and reduce strip material costs.

[0039] Example 1 To achieve efficient utilization of superconducting tape performance and reduce magnet manufacturing costs, this embodiment provides a superconducting tape combination method based on directional screening using PLD equipment. The core of this method is to produce tapes that are compatible with the magnetic field characteristics of different positions of the coil by screening specific PLD equipment and then applying them precisely.

[0040] In the early stages, based on extensive testing data from previous engineering practices, a correlation was established between the pinning performance of PLD equipment and the pinning performance of REBCO tape with the same pinning formulation. Figure 6 As shown, a database of equipment performance is established to statistically analyze the types of strips produced by different PLD equipment under the same process parameters, including strips suitable for positions dominated by the vertical magnetic field component, positions dominated by the parallel magnetic field component, and positions where the vertical and parallel magnetic field components are balanced. Subsequently, PLD equipment capable of producing strips in these three positions is quickly selected. Finally, the selected PLD equipment is used to produce strips, and coils are wound using these strips at the positions corresponding to the vertical magnetic field component dominance, parallel magnetic field component dominance, or vertical and parallel magnetic field component balance of the superconducting magnet.

[0041] The ratio of the critical current of a strip under a vertical magnetic field to the critical current under a parallel magnetic field is called the critical current ratio. This critical current ratio is significantly correlated with the PLD equipment used: test results show that strips produced by Pe equipment have strong vertical field performance and weak parallel field performance, and their critical current ratio is relatively high; strips produced by Pm equipment have strong parallel field performance and weak vertical field performance, and their critical current ratio is relatively low; strips produced by Pa equipment have balanced vertical and parallel field performance, and their critical current ratio is between the former two.

[0042] Vertical field performance refers to the critical current density of the strip when it is placed in a vertical magnetic field, where the vertical magnetic field is defined as the angle θ = 0° between the strip surface normal and the background magnetic field direction. Parallel field performance refers to the critical current density of the strip when it is placed in a parallel magnetic field, where the parallel magnetic field is defined as the angle θ = 90° between the strip surface normal and the background magnetic field direction. The critical current density of the strip in a vertical or parallel field directly reflects its pinning ability in the corresponding magnetic field direction; the stronger the pinning ability, the higher the corresponding critical current density. Further testing and verification show that multiple batches of strip produced continuously by the same PLD equipment under the same process parameters exhibit a critical current ratio fluctuation of less than 10%, demonstrating good performance consistency. However, strips produced by different PLD equipment under the same process parameters show a critical current ratio difference of 10% to 30%, indicating significant performance differentiation. This characteristic enables different PLD equipment to stably produce strips with critical current ratios adapted to specific magnetic field environments. For example, the Pe equipment can stably produce strips with critical current ratios adapted to positions dominated by the vertical magnetic field component, the Pm equipment can stably produce strips with critical current ratios adapted to positions dominated by the parallel magnetic field component, and the Pa equipment can stably produce strips with critical current ratios adapted to positions where the vertical and parallel magnetic field components are balanced.

[0043] against Figure 4 The superconducting magnet shown has coils 1 to 6 arranged sequentially along its axis. Based on the magnetic field characteristics of each coil position, three PLD (Pa to Pm) machines (Pe, Pm, and Pa) were selected from 13 PLD machines for strip production and matching applications. Specifically, coil positions 1 and 6 are located at the magnet's end and bear a higher vertical magnetic field component, so strips produced by the Pe machine were selected. Coil positions 3 and 4 are close to the magnet's central plane and mainly bear a parallel magnetic field component, so strips produced by the Pm machine were selected. Coil positions 2 and 5 are located between positions 1 and 3, and between positions 4 and 6, respectively, and bear a more balanced vertical and parallel magnetic field component, so strips produced by the Pa machine were selected.

[0044] After implementing the above scheme, the critical current decay rate of the superconducting tapes in all coils under a 1.5T background magnetic field was controlled at approximately 70%, which is 15% lower than the critical current decay rate of the superconducting magnet assembled by randomly configuring tapes before implementing the directional screening scheme, effectively ensuring the overall performance balance of the magnet. Regarding material usage and cost, in this embodiment, the critical current density of the tapes required for the magnet only needs to meet J... c >1467A / mm 2 Given that J can be prepared using conventional processes c With a tape thickness >1900A / mm², this solution utilizes this tape. Due to the increased overall critical current of the magnet coil, the superconducting magnet performance is improved. Reducing the total tape usage allows the superconducting magnet to achieve the same performance as with randomly configured tape. Calculations show that the total tape length can be reduced to 3.2km. This embodiment uses tape produced using conventional processes, incurring no additional material costs. Due to the reduced total length, the total tape cost is lowered to 422,000 yuan, a reduction of over 53%.

[0045] Another comparative approach is to apply the tape produced by a single device of Pe, Pa, or Pm to coils at all locations within the superconducting magnet. Assuming this approach is used to produce a tape of the same length as in this embodiment (3.2 km), due to the different magnetic field conditions of different coils on the magnet, unsuitable magnetic field conditions will inevitably exist, leading to a significant reduction in the critical current value. To meet the magnet performance requirements, the required J of the tape... c The threshold and corresponding costs will increase significantly: when producing using only PE equipment, J c The requirement is >2600A / mm², with a total cost of 704,000 yuan, an increase of 67% compared to the solution in this embodiment; when using only Pa equipment for production, J c The requirement is >2200A / mm², with a total cost of 528,000 yuan, an increase of 25% compared to the solution in this embodiment; when using only Pm equipment for production, J c The required strength is >2300A / mm², with a total cost of 640,000 yuan, which is 52% higher than the solution in this embodiment. The above comparison further verifies the significant advantage of this directional screening strip solution in cost control.

[0046] To ensure that the produced strip meets the design requirements, five samples were randomly selected from the strip produced by the three machines (Pe, Pm, and Pa) and their compatibility was verified using a rapid testing method: S2.1 Test the critical current curve of the strip at all angles under the conditions of 77K temperature and 1T magnetic field; S2.2, Use a vibrating sample magnetometer to test the lifting coefficient of the sample under different temperatures and magnetic fields; S2.3, combining the measured improvement coefficient, extrapolates the test data to the actual working conditions based on the Lorentz peak formula and the Gauss peak formula.

[0047] Curved Lorentz Peak:

[0048] Curve Gaussian peak:

[0049] In the formula, I0 represents the overall intensity of the curve; Γ represents the peak shape parameter; θ: the angle between the surface normal of the strip and the direction of the background magnetic field; I c (θ): the critical current density of the strip at angle θ; θ0 is the angle corresponding to the peak value of the anisotropic curve.

[0050] When θ0 = 90°, Lorentz peak 1 and Gauss peak are obtained. Lorentz peak 1 represents the pinning capability of the strip's ab plane, and the orientation of the ab plane is... Figure 3 The diagram shows that the Gaussian peak represents the pinning ability of the doped phase in the ribbon; at θ0=0°, the Lorentz peak 2 is obtained, representing the overall pinning level of the ribbon. The Lorentz peak can only form a single peak shape at θ=θ0 under the condition 0<Γ<1. When Γ=1, a flat straight line is produced, indicating that I... c It is isotropic. The Gaussian peak is centered at θ=θ0, and Γ is any positive value: when Γ≤1 / √2, a single peak is formed; while when Γ>1 / √2, the function will bifurcate, producing a bimodal structure with a local minimum at θ=θ0.

[0051] Test results are as follows Figure 7 As shown, the performance of each sample is consistent with expectations. In summary, this embodiment systematically solves the bottleneck problem of high-field magnet performance caused by the anisotropy of REBCO tape by combining magnetic field angle analysis, PLD equipment directional screening with targeted production, and a zoned winding strategy. This significantly improves the utilization efficiency of superconducting tapes and reduces the manufacturing cost of equipment such as MRI magnets. This rapid detection method can also be used to detect superconducting tapes produced using methods from other embodiments.

[0052] Example 2 This embodiment provides a method for combining superconducting tapes with different pinning formulations. The core scheme involves using three REBCO tapes with different pinning properties. These tapes can be prepared using three different pinning formulations and are used to adapt to the magnetic field characteristics at different positions of the superconducting magnet coil, thereby optimizing the magnet performance. The magnetic field characteristics include: vertical magnetic field component dominance, parallel magnetic field component dominance, and vertical-parallel magnetic field component balance.

[0053] Different pinning components have a significant impact on the anisotropy of REBCO tapes. The specific characteristics of the three typical pinning formulations selected in this embodiment are as follows: Formulation A is mainly composed of low-concentration pinning elements, and the prepared tape forms a moderate pinning density (which can be 3.5% molar ratio). The tape forms nanoparticle pinning centers, giving the tape parallel field pinning capability and strong parallel field performance, suitable for the dominant position of the parallel magnetic field component on superconducting magnets; Formulation B forms pinning centers mainly composed of columnar pinning through formulation design, giving the tape strong perpendicular field performance, suitable for the dominant position of the perpendicular magnetic field component on superconducting magnets; Formulation C adopts a hybrid pinning system, and through the synergistic effect of two different pinning mechanisms, achieves a balance of magnetic field angle adaptation performance, giving the tape balanced perpendicular and parallel field performance, suitable for the balanced position of perpendicular and parallel magnetic field components on superconducting magnets.

[0054] An alternative implementation includes forming a tape with a hybrid pinning system using formulation C. The superconducting layer of the tape may have a multi-layer structure, comprising at least two layers. Specifically, the tape may have the double-layer heterogeneous pinning structure of Example 3, i.e., the bottom layer of the superconducting layer is located near the tape substrate, and the upper layer of the superconducting layer is located away from the tape substrate, and: the bottom layer includes columnar pinning, and the upper layer includes in-plane nanoparticle pinning; or the bottom layer includes in-plane nanoparticle pinning, and the upper layer includes columnar pinning. In this implementation, coils are wound using the tape with a double-layer superconducting layer in formulation C only at the vertical-parallel magnetic field component equilibrium position (i.e., the transition position between the vertical magnetic field component dominance position and the parallel magnetic field component dominance position); at other positions, such as the parallel magnetic field component dominance position on the superconducting magnet (i.e., the middle of the magnet), coils are wound using the tape of formulation A; and at the vertical magnetic field component dominance position (i.e., the end of the magnet), coils are wound using the tape of formulation B. This implementation can improve the utilization of the tape's current carrying capacity, thereby further saving costs and reducing performance idleness and waste.

[0055] When applying this scheme to the magnet of a 1.5T magnetic resonance imaging (MRI) system, precise matching is performed based on the magnetic field angle characteristics of different coil positions: For coils 1 and 6, which bear a high vertical magnetic field component, formulation B tape is selected to fully utilize its strong c-axis pinning capability and vertical field performance (c-axis orientation is in...). Figure 3 (As shown in the diagram). For coils 3 and 4, which mainly bear the parallel magnetic field component, formulation A tape is selected to leverage its excellent pinning performance and parallel field performance in the ab plane. For coils 2 and 5, which bear a mixed vertical and parallel magnetic field component, formulation C tape is selected to utilize its balanced all-angle magnetic field adaptation characteristics. After the above optimization configuration, the overall performance of the magnet is significantly improved, and the total tape length is reduced to 4.2 km compared with the traditional single-pinning formulation tape design.

[0056] Example 3 This embodiment provides a combination method based on a double-layer heterostructured superconducting tape. The core scheme is: to select a REBCO superconducting tape (preferably double-layered) with multiple layers of films with different pinning characteristics on the superconducting layer. By precisely controlling the spatial distribution of each film layer, the tape can be adapted to magnetic field environments dominated by vertical magnetic field components, dominated by parallel magnetic field components, and balanced by vertical and parallel magnetic field components, thereby achieving performance optimization and design simplification of superconducting magnets.

[0057] This embodiment focuses on developing a REBCO superconducting tape with a bilayer heterogeneous pinning structure. The superconducting layer employs a unique bilayer architecture: the bottom layer is located on the superconducting layer closer to the baseband, and the top layer is located on the superconducting layer farther from the baseband. Different types of pinning elements are used in the two layers. The bottom layer includes columnar pinning, and the top layer includes in-plane nanoparticle pinning, resulting in strong perpendicular field performance of the bottom layer and strong parallel field performance of the top layer. Alternatively, the bottom layer includes in-plane nanoparticle pinning, and the top layer includes columnar pinning, resulting in strong parallel field performance of the bottom layer and strong perpendicular field performance of the top layer.

[0058] To achieve a spatial gradient distribution of pinning morphology, precise control of PLD process parameters is employed during fabrication. Specific control methods include, but are not limited to: Option 1, keeping the total thickness of the superconducting layer constant, and adjusting the thickness ratio of the bottom layer to the top layer to change the spatial proportion of the two pinning properties; Option 2, keeping the thickness of one layer constant, and adjusting the thickness of the other layer to achieve gradient optimization of pinning performance; Simultaneously, parameters such as target composition, deposition temperature, laser energy density, and deposition rate in the PLD process can be adjusted to ensure that the pinning properties of the two layers meet the design requirements.

[0059] The prepared bilayer heterostructure tape was systematically characterized. The results showed that the critical current value of the tape under a vertical magnetic field (the angle between the tape surface normal and the magnetic field direction θ=0°) reached 75-80% of the critical current value under a parallel magnetic field (θ=90°), which is significantly better than the performance of tapes with a traditional single pinning mechanism, and the anisotropy is reduced. More importantly, the minimum critical current value of the tape across the entire magnetic field angle range is about 40% higher than that of tapes with a single pinning mechanism, demonstrating a balanced and comprehensive improvement in pinning performance.

[0060] When this type of double-layer heterogeneous pinning tape is applied to the magnet of a 1.5T magnetic resonance imaging (MRI) system, its more balanced all-angle magnetic field adaptation performance eliminates the need for selecting multiple tape models for different coil positions, as required in Examples 1 and 2, significantly simplifying the magnet design complexity. Test results show that using only this single type of double-layer heterogeneous pinning tape enables the overall magnet performance to reach 80% of the performance of the three different tape combination schemes in Example 1, while completely avoiding the procurement management and inventory allocation problems caused by multiple tapes, and significantly reducing the complexity of model identification and switching operations during coil winding. Calculations show that the total amount of magnet tape used in this scheme is 3.6 km, which also achieves a significant reduction in tape usage compared to the traditional single-pinning tape scheme.

[0061] Example 4 This embodiment provides a combination method based on the same pinning formula and superconducting tapes of different widths. The core solution is to select REBCO superconducting tapes with the same pinning formula, obtain tapes of different widths through a slitting process, and utilize the difference in current carrying capacity caused by the width difference to apply them to different positions in the superconducting magnet coil where the vertical magnetic field component is dominant, the parallel magnetic field component is dominant, and the vertical-parallel magnetic field components are balanced, so as to achieve optimal material configuration and cost optimization.

[0062] This embodiment proposes a gradient-width superconducting tape configuration scheme for a 1.5T magnetic resonance imaging (MRI) system magnet. The tape width is first for coils in positions dominated by the vertical magnetic field component, second for coils in positions with a balance between vertical and parallel magnetic field components, and third for coils in positions dominated by the parallel magnetic field component, with the first width > second width > third width. Specifically, precise matching and optimization are performed based on the magnetic field strength and angular characteristics of each coil region: For end coils 1 and 6, which bear high vertical magnetic field components and have the highest current density requirements, a 10mm wide tape (first width) is used; for transition region coils 2 and 5, which bear mixed vertical and parallel magnetic field components, a 6mm wide tape (second width) is used; and for central region coils 3 and 4, which mainly bear parallel magnetic field components and have relatively low current requirements, a 4mm wide tape (third width) is used.

[0063] In practical implementation, this solution optimizes configuration solely by grading and slicing REBCO tapes with the same pinning formula across different widths, without requiring adjustments to the tape formula or production equipment parameters. From a cost perspective, the market price of 10mm wide tape is approximately 2.2 times that of 4mm narrow tape, rather than the 2.5 times calculated based on the width ratio (10 / 4=2.5). This pricing mechanism provides the foundation for the high cost-effectiveness of this embodiment. Actual calculations show that after adopting the graded width configuration scheme of this embodiment, the total cost of the magnet tape is reduced to 687,000 yuan, a 13.3% reduction compared to the traditional single-width tape scheme.

[0064] Performance verification results show that this graded width scheme achieves optimal configuration of superconducting materials while ensuring the overall performance of the magnet meets design requirements: in the high-field region at the magnet's end, the 10mm wide strip provides greater total current carrying capacity, meeting the high current density requirements; while in the low-field region at the center, the 4mm narrow strip precisely matches the actual current demand, effectively avoiding waste caused by strip performance redundancy. Compared with traditional schemes, this scheme achieves a better balance between magnet manufacturing cost control and operational reliability.

[0065] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0066] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for assembling superconducting magnet coil strips based on different formulations, characterized in that, include: S1: Obtain the magnetic field characteristics at different locations of the coil in the superconducting magnet. These magnetic field characteristics include the ratio of the perpendicular magnetic field component to the parallel magnetic field component. The perpendicular magnetic field component is parallel to the radial direction of the superconducting magnet, and the parallel magnetic field component is parallel to the axial direction of the superconducting magnet. Different locations of the superconducting magnet are categorized as positions dominated by the perpendicular magnetic field component, positions dominated by the parallel magnetic field component, and positions dominated by the perpendicular magnetic field component. The position where the parallel magnetic field components are balanced; S2: For coils at different positions of the superconducting magnet in S1, three different pinning formulas are used to prepare tapes, and the three tapes are adapted to the magnetic field characteristics at different positions of the superconducting magnet. S3: Using the strip material adapted to different magnetic field characteristics in S2, coils are wound at corresponding positions of the superconducting magnet, and the coils are connected in series to form a superconducting magnet.

2. The method for assembling superconducting magnet coil strips based on different formulations as described in claim 1, characterized in that, θ represents the angle between the surface normal of the strip and the direction of the magnetic field in which the strip is located; the magnetic field at the dominant position of the vertical magnetic field component conforms to... 30°<θ≤30°, the magnetic field at the dominant position of the parallel magnetic field component conforms to 60°<θ≤120°, the vertical The magnetic field at the position where the parallel magnetic field components are balanced conforms to 30°<θ≤60° or 120°<θ≤150°.

3. The method for assembling superconducting magnet coil strips based on different formulations as described in claim 1, characterized in that, The three different anchoring formulations of the tape are as follows: Formula A gives the tape a specific pinning density, forming nanoparticle pinning centers; Formula B gives the tape columnar pinning centers; Formula C gives the tape a hybrid pinning system. The selection of suitable tapes is as follows: Formula A tape is suitable for positions where the parallel magnetic field component dominates on superconducting magnets, Formula B tape is suitable for positions where the vertical magnetic field component dominates, and Formula C tape is suitable for positions where the vertical and parallel magnetic field components are balanced.

4. The method for assembling superconducting magnet coil strips based on different formulations as described in claim 3, characterized in that, The tape of formulation C has a multi-layer superconducting layer, including at least two layers; The bottom layer of the superconducting layer is close to the tape substrate, and the top layer is far away from the tape substrate; the bottom layer includes columnar pinning, and the top layer includes in-plane nanoparticle pinning; or the bottom layer includes in-plane nanoparticle pinning, and the top layer includes columnar pinning.

5. The method for assembling superconducting magnet coil strips based on different formulations as described in claim 2, characterized in that, The coils of the superconducting magnet are arranged sequentially along the axial direction; the two ends of the superconducting magnet are the positions where the vertical magnetic field component dominates, and the coils are wound using strip material of formula A; the middle part of the superconducting magnet is the position where the parallel magnetic field component dominates, and the coils are wound using strip material of formula B; the area between the first two positions is perpendicular. The coil is wound with C-formula tape at the position where the parallel magnetic field components are balanced.

6. The method for assembling superconducting magnet coil strips based on different formulations as described in claim 1, characterized in that, The strips of the three different pinning formulations are cut into different widths, with the strip width suitable for the position where the vertical magnetic field component dominates being greater than the strip width suitable for the position where the vertical and parallel magnetic field components are balanced being greater than the strip width suitable for the position where the parallel magnetic field component dominates, in order to further adapt to the magnetic field characteristics of different positions of the superconducting magnet.

7. The method for assembling superconducting magnet coil strips based on different formulations as described in claim 1, characterized in that, S2 also includes testing the strip performance using a rapid testing method, with the following specific steps: S2.1: Critical current curves of the strip at all angles were tested under the conditions of 77K temperature and 1T magnetic field. S2.2: Use a vibrating sample magnetometer to test the lifting coefficient of the sample under different temperatures and magnetic fields; S2.3: Combining the measured improvement coefficient, the test data are extrapolated to the actual working conditions based on the following fitting formula: Curved Lorentz Peak: Curve Gaussian peak: In the formula, I0 represents the overall intensity of the curve; Γ represents the peak shape parameter; θ is the angle between the normal to the strip surface and the direction of the background magnetic field; I c (θ) represents the critical current density of the strip at angle θ; θ0 is the angle corresponding to the peak value of the anisotropy curve; When θ0=90°, Lorentz peak 1 and Gauss peak are obtained. Lorentz peak 1 represents the pinning ability of the ab plane of the tape, and Gauss peak represents the pinning ability of the doped phase of the tape. When θ0=0°, Lorentz peak 2 is obtained, which represents the overall pinning level of the strip.

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