High-field-intensity and high-uniformity Halbach array magnet capable of self-shimming and design method of high-field-intensity and high-uniformity Halbach array magnet

Abstract

The invention provides a high-field-intensity and high-uniformity Halbach array magnet used in a magnetic resonance system and a design method, and relates to the technical field of magnetic resonance magnet devices, and the Halbach array magnet has the advantages of compact structure, low cost, miniaturization and the like. And meanwhile, the structure allows the magnetic block to move axially and radially and the ferromagnetic sheet to compensate the nonuniformity of the magnetic field caused by the processing error and the assembling error of the magnetic block, so that the signal quality of the magnetic resonance system is improved, and the magnetic resonance magnetic field sensor has great practical significance and social demands for the research and development of miniaturized and low-cost magnetic resonance instruments and the popularization of the magnetic resonance technology.

Description

Technical Field

[0001] This invention relates to the field of magnetic resonance magnet device technology, and particularly to a high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming and its design method. Background Technology

[0002] Compact, high-field-strength, and highly uniform Halbach magnets are primarily used in miniaturized magnetic resonance imaging (MRI) systems. The constraints of size and signal quality requirements in specific applications make the design of compact, high-field-strength, and highly uniform Halbach magnets a major technical challenge in the development of miniaturized MRI equipment.

[0003] Miniaturized magnetic resonance (MR) devices include small-aperture MR relaxors and MR spectrometers. MR relaxors often employ C- or H-type permanent magnet configurations. These configurations have low magnetic material utilization, are relatively heavy, and do not require high magnetic field uniformity, potentially limiting the application scenarios of miniaturized MR devices. MR spectrometers, compared to MR relaxors, offer higher field strength and magnetic field uniformity. They often employ Halbach magnet configurations. This structure eliminates the need for a yoke, offering advantages such as compact structure, high field strength, and low scattering field. Axial multi-layer Halbach magnet structures compensate for disturbances caused by truncation and segmentation, and shimming techniques compensate for errors introduced during magnet block manufacturing and assembly. Stacking shimming magnets is the most common shimming method. This is achieved by rotating, moving, attaching shimming ferromagnetic sheets, or placing shimming magnets around the magnet to generate a compensating magnetic field and correct magnetic field inhomogeneities in the target region. However, these strategies have the following problems: iterative replacement of ferromagnetic sheets reduces the repeatability of the shimming device installation, and the processing error of the replaced ferromagnetic sheets reduces the shimming accuracy and increases magnetic field disturbance; when using magnetic sheets for shimming, the shimming magnetic sheets have demagnetization problems; since the Halbach magnet is composed of magnetic blocks with different magnetization directions, the shimming ferromagnetic sheets at different positions are subjected to forces of different magnitudes and directions, which reduces the installation accuracy of the shimming ferromagnetic sheets and may even affect the magnetization of the iron sheets, thus reducing the shimming accuracy.

[0004] Currently, only Nanalysis and Magritek have published patents mentioning the Halbach structure used in their commercially available miniaturized magnetic resonance spectrometers. Nanalysis's NMReady series utilizes high-permeability poles to efficiently converge magnetic field lines, enhancing magnetic field strength and improving uniformity. Movable pole strips behind the poles further improve uniformity. However, this method places the poles within the magnet aperture, occupying valuable space and hindering the development of compact, high-field-strength, and highly uniform Halbach magnets. Magritek improves magnetic field uniformity through radial movement of the magnet, but this also results in internal space requirements, leading to larger Halbach magnets and a heavier overall product compared to Nanalysis.

[0005] In summary, the existing similar technologies / products and their shortcomings and deficiencies are as follows:

[0006] 1) Patent barriers: The patents of Magritek and Nanalysis do not provide detailed designs.

[0007] 2) Occupies the internal space of the magnet aperture: This problem exists in all current Halbach magnets.

[0008] 3) Demagnetization problem of high-field Halbach magnets: When the background magnetic field of the magnet is higher than the intrinsic coercive magnetic field of the magnet itself, the magnet and the passive shim will face the risk of demagnetization.

[0009] 4) Low shimming accuracy: When using an independent passive shimming structure, the processing error of the shimming magnetic sheet and the positional error caused by force during multiple iterations will reduce the shimming accuracy.

[0010] 5) The shimming process is cumbersome: When using an independent passive shimming structure, the fabrication and fixing of the shimming magnetic sheet and the insertion and removal of the shimming bracket increase the shimming complexity.

[0011] To address the shortcomings of existing products and technologies, this invention aims to provide a compact high-field-strength, high-uniformity Halbach array magnet design that integrates efficient passive shimming. This establishes a comprehensive design methodology for high-field-strength, high-uniformity Halbach magnets, from optimization to efficient shimming adjustment. Furthermore, this solution improves magnetic field uniformity by moving the magnetic blocks within each ring, providing an additional degree of freedom for block movement compared to Magritek products, thus increasing the flexibility of shimming. It features a compact structure, high shimming accuracy, simplicity, and economy. Summary of the Invention

[0012] To achieve the above-mentioned objectives and other advantages of the present invention, the first objective of the present invention is to provide a design method for a high-field-strength, highly uniform Halbach array magnet capable of self-uniforming. The Halbach array magnet has a multi-layered structure, including radial and axial multi-layered structures. Each layer of magnet consists of multiple magnetic blocks forming a roughly ring-shaped structure, with the axial central axes of each layer coinciding. The magnetization follows a dipole Halbach magnetization pattern. Radial or axial movement of the magnetic blocks is used to improve the uniformity of the magnetic field. The method includes the following steps:

[0013] Record the initial position and label of each magnetic block;

[0014] The magnetic field distribution of the magnet system in the target area under the initial state is measured. N measurement points are evenly distributed on the surface of the measurement area, and the spherical harmonic function of the initial magnetic field is expanded.

[0015] Establish a radial or axial moving magnetic block array that can generate corresponding harmonic terms, and establish its moving step size and the harmonic term amplitude matrix;

[0016] Set the radial or axial movement range of the magnetic block according to its movable range, and establish the objective equation and constraints;

[0017] The radial or axial movement step size of each magnetic block array is optimized using an optimization algorithm, and the moving magnetic blocks are iteratively moved to homogenize the field.

[0018] Furthermore, the calculation of each magnetic block is achieved by introducing a magnetic potential vector. By correcting the direction vector Calculation located at The magnetization vector at that point is The magnet is in position The magnetic field generated at the location; combined with the shape integral of the magnetic blocks, the spatial magnetic field of magnetic blocks with different shapes and magnetization directions is calculated, and the spatial magnetic field generated by the movement of each magnetic block array is obtained by superposition:

[0019]

[0020] Where μ0 is the free permeability. It is a magnetic field.

[0021] Furthermore, the step of expanding the initial magnetic field spherical harmonic function specifically involves decomposing the magnetic field on the surface of the target region into a spherical harmonic function to obtain the spherical harmonic function expansion in Cartesian coordinates:

[0022]

[0023] Where x, y, and z are coordinates in the Cartesian coordinate system, and r is the radius.

[0024] Furthermore, the objective equation and constraints are as follows:

[0025]

[0026] St C s =A*X

[0027] x k ≥PX≥0

[0028] Define matrix P to constrain the maximum displacement of the magnetic block at each position, and w(n,m) is a weight function used to adjust the influence of certain harmonic terms on the overall optimization. and Let A and X be the harmonic coefficients of the initial magnetic field and the compensating magnetic field generated by the moving magnetic block array, respectively; A is the source matrix of the passive shim, containing the harmonic components generated by the movement of each group of magnetic block arrays; X is the displacement of each group of magnetic block arrays; x... kThis represents the displacement that can still be moved at the corresponding magnetic block position after the k-th iteration.

[0029] Furthermore, it also includes the following steps:

[0030] After each movement of the magnetic blocks, the positions of each magnetic block are corrected in the model, and the relationship model between the magnetic block movement step size and the amount of harmonics generated is updated to improve the purity and efficiency of the generated harmonics.

[0031] Furthermore, it also includes the following steps:

[0032] Set a main magnetic field strength constraint, and use the main magnetic field strength after shimming to guide the next round of shimming, so as to reduce the loss of main magnetic field strength due to shimming.

[0033] Furthermore, it also includes the following steps:

[0034] When optimizing the uniformity of the Halbach array magnet structure, optimization is performed on either the locally combined Halbach rings or directly on the entire Halbach array magnet.

[0035] The second objective of this invention is to provide a high-field-strength, high-uniformity Halbach array magnet that can self-uniform the field. Using the method described above, the magnet has a multi-layer structure, including multi-layer structures in the radial and axial directions. Each layer of the magnet consists of multiple magnetic blocks forming a roughly ring-shaped structure, and the axial central axis of each layer of the magnet coincides. The magnetization law is dipole Halbach magnetization.

[0036] Furthermore, gaps or no gaps are left between the layers of Halbach rings in the radial direction. When gaps are left, the magnetic field uniformity is improved by radially moving the magnetic blocks and attaching ferromagnetic sheets.

[0037] Furthermore, gaps or no gaps are left between the Halbach rings in the axial direction. When gaps are left, the magnetic field uniformity is improved by axial movement of the magnetic blocks and by attaching ferromagnetic sheets.

[0038] Furthermore, the magnetic blocks that make up each layer of Halbach rings are cylindrical, rectangular, or other polygonal in shape.

[0039] Furthermore, the magnetic blocks that make up each layer of Halbach rings may be the same or different in size, and each layer of Halbach rings may have the same or different inner diameter, outer diameter, and height.

[0040] Furthermore, the magnetic blocks that make up each layer of Halbach rings use the same magnetic material or different magnetic materials; when different magnetic materials are used, the radial inner layer magnets use highly coercive magnetic materials to reduce or avoid demagnetization of the Halbach array magnets.

[0041] Furthermore, the strength of the central magnetic field can be enhanced by increasing the amount of soft magnetic material.

[0042] Furthermore, the movement of the magnetic blocks and the application of ferromagnetic sheets for shimming are carried out after the entire magnetic block assembly process or during the assembly process.

[0043] A third objective of the present invention is to provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method.

[0044] A fourth objective of the present invention is to provide a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described method.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] This invention provides a high-field-strength, high-uniformity Halbach array magnet for magnetic resonance systems and its design method, relating to the field of magnetic resonance magnet device technology. This Halbach array magnet has advantages such as compact structure, low cost, and miniaturization. Simultaneously, the structure allows for axial and radial movement of the magnet blocks and the attachment of ferromagnetic sheets to compensate for magnetic field inhomogeneities caused by magnet block processing and assembly errors, thereby improving the signal quality of the magnetic resonance system. This invention has significant practical implications and social demand for the development of miniaturized, low-cost magnetic resonance instruments and the popularization of magnetic resonance technology.

[0047] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0048] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0049] Figure 1 A schematic diagram of a high-field-strength, highly uniform Halbach array magnet that can self-uniform its field.

[0050] Figure 2 Flowchart of a design method for a self-uniform high-field-strength, highly uniform Halbach array magnet;

[0051] Figure 3 A schematic diagram of computer equipment;

[0052] Figure 4This is a schematic diagram of a computer-readable storage medium.

[0053] In the figure: 1. Halbach array magnet; 11. Radial multilayer structure; 110. Halbach ring in the radial direction; 111. Magnetic block of Halbach ring in the radial direction; 12. Axial multilayer structure; 120. Halbach ring in the axial direction; 121. Magnetic block of Halbach ring in the axial direction. Detailed Implementation

[0054] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0055] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0056] The drawing numbers in this application are only used to distinguish the steps in the scheme and are not used to limit the execution order of the steps. The specific execution order is as described in the specification.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0058] This invention provides a novel, self-uniform, high-field-strength, high-uniformity Halbach array magnet design suitable for magnetic resonance systems. The magnet consists of a multi-layered Halbach ring array, including multi-layered structures in both the axial and radial directions. Each Halbach ring layer comprises multiple magnetic blocks forming a roughly ring-shaped structure. The Halbach rings can be fabricated from different types of magnetic materials and are coaxially arranged, allowing the magnetic blocks constituting each Halbach ring to move axially and radially, generating a compensating magnetic field to improve magnetic field uniformity.

[0059] Specific implementation method: Based on vector potential theory, the spatial magnetic field of each layer of Halbach ring is calculated by superimposing the shape, size and spatial arrangement of the Halbach ring magnetic blocks, and a highly uniform Halbach magnet optimization model for the target area is established; for the optimized highly uniform Halbach magnet, based on the spherical harmonic function expansion method, a magnetic block radial or axial moving array that can respond to the harmonic magnetic field is constructed. For the magnetic field harmonic expansion of the target area, the magnetic field uniformity is improved by generating a compensation magnetic field by optimizing the step size of each group of magnetic block moving arrays.

[0060] Compared to conventional C-type, H-type, and single-sided magnet configurations, Halbach magnets do not require a yoke and offer advantages such as compact structure, high field strength, and low scattering field, making them widely used in magnetic resonance systems. High-field-strength, highly uniform Halbach magnets can significantly enhance the sensitivity and resolution of magnetic resonance signals, and the development of this type of magnet is of great significance for improving the quality of magnetic resonance signals. An ideal Halbach magnet is an infinitely long, continuously magnetized structure that generates a high-field-strength, highly uniform magnetic field at the magnet's center. However, due to the truncation and segmented magnetization in actual implementations, the magnetic field uniformity of Halbach magnets deteriorates. Furthermore, due to errors in magnet block processing and assembly, as well as the demagnetization of magnet blocks in high-field Halbach magnets, the magnetic field uniformity of assembled Halbach magnets is severely reduced, making them unsuitable for magnetic resonance systems.

[0061] Currently, common Halbach magnet designs include those for low-to-medium field (≤1T) high uniformity and those for high field. The low-to-medium field (≤1T) high uniformity Halbach magnet design typically employs an axially multi-layered Halbach magnet structure, combined with bonded ferromagnetic sheets to improve magnetic field uniformity. However, this shimming method suffers from issues such as reduced Halbach magnet aperture, low shimming accuracy, and a non-compact magnet structure. High-field Halbach magnet designs are primarily used in high-field applications such as particle accelerators and nuclear fusion devices, and these designs do not prioritize magnetic field uniformity.

[0062] Based on this, this invention proposes a design scheme for a self-uniform high-field-strength, high-uniformity Halbach magnet. An optimization model for the target region is established based on vector potential theory to design the high-field-strength, high-uniformity Halbach magnet. A magnetic block moving array capable of compensating for the magnetic field is constructed using the spherical harmonic function expansion method to uniformly uniform the actual Halbach magnet. Furthermore, appropriate magnetic materials are selected based on the background magnetic field of each layer of the Halbach magnet to reduce or prevent demagnetization. This design scheme features a compact structure, high uniformization accuracy, simplicity, and economy. This technology is applicable to the use of compact high-field-strength, high-uniformity...

[0063] Halbach array magnet magnetic resonance systems, especially miniaturized magnetic resonance devices, have significant application potential, bringing new innovations and progress to related fields. This invention relates to the field of magnetic resonance system technology, and particularly to a compact permanent magnet structure design capable of generating high-intensity, highly uniform magnetic fields. The specific solution is as follows:

[0064] Example 1

[0065] A self-uniform high-field-strength, highly uniform Halbach array magnet, such as Figure 1As shown, the Halbach array magnet 1 has a multi-layer structure, including a radial multi-layer structure 11 and an axial multi-layer structure 12. Each layer of magnet consists of multiple magnetic blocks forming a roughly ring-shaped structure, and the axial central axis of each layer of magnet coincides. The magnetization law is dipole Halbach magnetization.

[0066] like Figure 1 As shown, gaps or no gaps may be left between the layers of Halbach rings 110 in the radial direction. When gaps are left, the magnetic blocks 111 are allowed to move radially and the ferromagnetic sheets are pasted on to improve the uniformity of the magnetic field.

[0067] In the axial direction, there may be gaps or no gaps between the layers of Halbach rings 120. When gaps are left, the magnetic field uniformity can be improved by axial movement of the magnetic block 121 and by attaching ferromagnetic sheets.

[0068] Furthermore, the magnetic blocks that make up each layer of Halbach rings can be cylindrical, rectangular, or other polygonal in shape.

[0069] Furthermore, the size of the magnetic blocks that make up each layer of Halbach rings can be the same or different, and each layer of Halbach rings can have the same or different inner diameter, outer diameter, and height.

[0070] Furthermore, the magnetic blocks that make up each layer of Halbach rings can be made of the same magnetic material or different magnetic materials. When using different magnetic materials, the radial inner layer magnets can use highly coercive magnetic materials to reduce or avoid demagnetization of the Halbach magnets.

[0071] Furthermore, the strength of the central magnetic field can be enhanced by increasing the amount of soft magnetic material.

[0072] The multi-layer Halbach ring magnet structure is mainly used to increase the magnetic field strength and magnetic field uniformity in the target area of ​​the magnet center. Under the premise of ensuring the magnetic field uniformity in the target area of ​​the magnet center, the magnetic field uniformity is improved by radial or axial movement of the magnetic blocks and pasting ferromagnetic sheets. The magnetic block movement and pasting of ferromagnetic sheets for field uniformity can be carried out after the entire magnetic block assembly or during the assembly.

[0073] A detailed description of the uniform field method using radial or axial movement of the magnetic block can be found in the corresponding description in the following method embodiments, and will not be repeated here.

[0074] In one embodiment, Figure 1 A 1.5T- structure consisting of an inner and outer layer of five Halbach rings.

[0075] The Halbach array magnet consists of 16 trapezoidal magnetic blocks with dovetails in each Halbach ring. The inner diameter of the magnet is 30 mm, and the outer diameter is 182 mm. The inner layer magnet comprises three Halbach rings with identical inner diameters. After optimization for uniformity, the outer diameters of the upper and lower Halbach rings are the same and slightly larger than those of the middle Halbach ring. All three layers are compact, with no gaps between the magnetic blocks forming the rings and between the three layers of Halbach rings. The outer layer magnet consists of two identical Halbach rings with a gap between them. This gap allows the magnet to move and generate a compensating magnetic field to improve magnetic field uniformity. The gap between these rings was determined to be 8.6 mm after optimization for uniformity of the outer layer. The final Halbach magnet design has a capacity of 1.5 T, and the magnetic field non-uniformity in the DSV5mm region is 13 ppm. Example 2

[0076] A design method for a self-uniform high-field-strength, high-uniformity Halbach array magnet is provided, based on the self-uniform high-field-strength, high-uniformity Halbach array magnet provided in Example 1. For a detailed description of the self-uniform high-field-strength, high-uniformity Halbach array magnet, please refer to the corresponding description in the above-described examples of the self-uniform high-field-strength, high-uniformity Halbach array magnet; it will not be repeated here. Figure 1 As shown, the Halbach array magnet 1 has a multi-layer structure, including a radial multi-layer structure 11 and an axial multi-layer structure 12. Each layer of magnet consists of multiple magnetic blocks forming a roughly ring-shaped structure, and the axial central axis of each layer coincides. The magnetization law is dipole Halbach magnetization. The uniformity of the magnetic field is improved by using radial or axial movement of the magnetic blocks, such as... Figure 2 As shown, the method includes the following steps:

[0077] Record the initial position and label of each magnetic block;

[0078] The magnetic field distribution of the magnet system in the target area under the initial state is measured. N measurement points are evenly distributed on the surface of the measurement area, and the spherical harmonic function of the initial magnetic field is expanded.

[0079] Establish a radial or axial moving magnetic block array that can generate corresponding harmonic terms, and establish its moving step size and the harmonic term amplitude matrix;

[0080] Set the radial or axial movement range of the magnetic block according to its movable range, and establish the objective equation and constraints;

[0081] The radial or axial movement step size of each magnetic block array is optimized using an optimization algorithm, and the moving magnetic blocks are iteratively moved to homogenize the field.

[0082] Furthermore, the calculation of each magnetic block is achieved by introducing a magnetic potential vector. By correcting the direction vector Calculation located at The magnetization vector at that point is The magnet is in position The magnetic field generated at the location; combined with the shape integral of the magnetic blocks, the spatial magnetic field of magnetic blocks with different shapes and magnetization directions is calculated, and the spatial magnetic field generated by the movement of each magnetic block array is obtained by superposition:

[0083]

[0084] Where μ0 is the free permeability. It is a magnetic field.

[0085] Furthermore, the step of expanding the initial magnetic field spherical harmonic function specifically involves decomposing the magnetic field on the surface of the target region into a spherical harmonic function to obtain the spherical harmonic function expansion in Cartesian coordinates:

[0086]

[0087] Where x, y, and z are coordinates in the Cartesian coordinate system, and r is the radius.

[0088] Furthermore, the objective equation and constraints are as follows:

[0089]

[0090] St C s =A*X

[0091] x k ≥PX≥0

[0092] Define matrix P to constrain the maximum displacement of the magnetic block at each position, and w(n,m) is a weight function used to adjust the influence of certain harmonic terms on the overall optimization. and Let A and X be the harmonic coefficients of the initial magnetic field and the compensating magnetic field generated by the moving magnetic block array, respectively; A is the source matrix of the passive shim, containing the harmonic components generated by the movement of each group of magnetic block arrays; X is the displacement of each group of magnetic block arrays; x... k This represents the displacement that can still be moved at the corresponding magnetic block position after the k-th iteration.

[0093] In some embodiments, the steps further include:

[0094] After each movement of the magnetic blocks, the position of each magnetic block can be corrected in the model, and the relationship model between the magnetic block movement step size and the amount of harmonics generated can be updated to improve the purity and efficiency of the generated harmonics.

[0095] Furthermore, it also includes the following steps:

[0096] The main magnetic field strength constraint can be set, and the main magnetic field strength after shimming can guide the next round of shimming, thereby reducing the loss of the main magnetic field strength due to shimming.

[0097] Furthermore, it also includes the following steps:

[0098] When optimizing the uniformity of this multi-layer Halbach structure, optimization can be performed on the Halbach rings of local combinations separately, or directly on the entire Halbach magnet.

[0099] Example 3

[0100] A computer device 200, such as Figure 3 As shown, the system includes a memory 210, a processor 220, and a computer program 230 stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of a self-shielding, high-field-strength, high-uniformity Halbach array magnet design method. For a detailed description of the method, please refer to the corresponding description in the above method embodiments; it will not be repeated here.

[0101] Example 4

[0102] A computer-readable storage medium, such as Figure 4 As shown, a computer program is stored thereon. When executed by a processor, this computer program implements the steps of a self-shielding, high-field-strength, high-uniformity Halbach array magnet design method. For a detailed description of the method, please refer to the corresponding description in the above method embodiments; it will not be repeated here.

[0103] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0104] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

[0105] The apparatus, computer device, and non-volatile computer storage medium and method provided in the embodiments of this specification are corresponding. Therefore, the apparatus, computer device, and non-volatile computer storage medium also have similar beneficial technical effects as the corresponding method. Since the beneficial technical effects of the method have been described in detail above, the beneficial technical effects of the corresponding apparatus, computer device, and non-volatile computer storage medium will not be repeated here.

[0106] Those skilled in the art will also know that, besides implementing the controller in the form of purely computer-readable program code, the same functions can be achieved by logically programming the method steps, making the controller take the form of logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers (PLCs), and embedded microcontrollers. Therefore, such a controller can be considered a hardware component, and the devices included within it for implementing various functions can also be considered structures within that hardware component. Alternatively, the devices for implementing various functions can be considered as both software units implementing the method and structures within a hardware component.

[0107] The systems, apparatuses, or units described in the above embodiments can be implemented by computer chips or physical entities, or by products with certain functions. For ease of description, the above apparatuses are described separately as various units based on their functions. Of course, when implementing one or more embodiments of this specification, the functions of each unit can be implemented in one or more software and / or hardware.

[0108] Those skilled in the art will understand that the embodiments of this specification can be provided as methods, systems, or computer program products. Therefore, the embodiments of this specification can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the embodiments of this specification can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0109] This specification is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this specification. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0110] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0111] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0112] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0113] This specification may be described in the general context of computer-executable instructions, such as program units, that are executed by a computer. Generally, program units include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. This specification may also be practiced in distributed computing environments, where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program units may reside in local and remote computer storage media, including storage devices.

[0114] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0115] The above description is merely an embodiment of this specification and is not intended to limit the scope of one or more embodiments of this specification. Various modifications and variations can be made to one or more embodiments of this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of one or more embodiments of this specification should be included within the scope of the claims of one or more embodiments of this specification.

Claims

1. A design method for a self-uniforming, high-field-strength, high-uniformity Halbach array magnet, characterized in that, The Halbach array magnet configuration is a multi-layer structure, including radial and axial multi-layer structures. Each layer of magnets consists of multiple magnetic blocks forming a roughly ring-shaped structure, and the axial central axes of each layer of magnets coincide. The magnetization law is dipole Halbach magnetization. The magnetic field uniformity is improved by moving the magnetic blocks radially or axially. The method includes the following steps: Record the initial position and label of each magnetic block; The magnetic field distribution of the magnet system in the target area under the initial state is measured. N measurement points are evenly distributed on the surface of the measurement area, and the spherical harmonic function of the initial magnetic field is expanded. Establish a radial or axial moving magnetic block array that can generate corresponding harmonic terms, and establish its moving step size and the harmonic term amplitude matrix; Set the radial or axial movement range of the magnetic block according to its movable range, and establish the objective equation and constraints; The radial or axial movement step size of each magnetic block array is optimized using an optimization algorithm, and the moving magnetic blocks are iteratively moved to homogenize the field.

2. The design method for a self-uniform high-field-strength, high-uniformity Halbach array magnet as described in claim 1, characterized in that: The calculation of each magnetic block is achieved by introducing a magnetic potential vector. By correcting the direction vector Calculation located at The magnetization vector at that point is The magnet is in position The magnetic field generated at the location; combined with the shape integral of the magnetic blocks, the spatial magnetic field of magnetic blocks with different shapes and magnetization directions is calculated, and the spatial magnetic field generated by the movement of each magnetic block array is obtained by superposition: Where μ0 is the free permeability. It is a magnetic field.

3. The design method for a self-uniform high-field-strength, high-uniformity Halbach array magnet as described in claim 2, characterized in that: The step of expanding the initial magnetic field spherical harmonic function specifically involves decomposing the magnetic field on the surface of the target region into a spherical harmonic function to obtain the spherical harmonic function expansion in Cartesian coordinates: Where x, y, and z are coordinates in the Cartesian coordinate system, and r is the radius.

4. The design method for a self-uniform high-field-strength, high-uniformity Halbach array magnet as described in claim 3, characterized in that, The objective equation and constraints are as follows: Define matrix P to constrain the maximum displacement of the magnetic block at each position, and w(n,m) is a weight function used to adjust the influence of certain harmonic terms on the overall optimization. and Let A and X be the harmonic coefficients of the initial magnetic field and the compensating magnetic field generated by the moving magnetic block array, respectively; A is the source matrix of the passive shim, containing the harmonic components generated by the movement of each group of magnetic block arrays; X is the displacement of each group of magnetic block arrays; x... k This represents the displacement that can still be moved at the corresponding magnetic block position after the k-th iteration.

5. The design method for a self-uniforming, high-field-strength, high-uniformity Halbach array magnet as described in claim 1, characterized in that, It also includes the following steps: After each movement of the magnetic blocks, the positions of each magnetic block are corrected in the model, and the relationship model between the magnetic block movement step size and the amount of harmonics generated is updated to improve the purity and efficiency of the generated harmonics.

6. The design method for a self-uniform high-field-strength, high-uniformity Halbach array magnet as described in claim 1, characterized in that, It also includes the following steps: Set a main magnetic field strength constraint, and use the main magnetic field strength after shimming to guide the next round of shimming, so as to reduce the loss of main magnetic field strength due to shimming.

7. The design method for a self-uniforming, high-field-strength, high-uniformity Halbach array magnet as described in claim 1, characterized in that, It also includes the following steps: When optimizing the uniformity of the Halbach array magnet structure, optimization is performed on either the locally combined Halbach rings or directly on the entire Halbach array magnet.

8. A high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming, employing the method described in any one of claims 1 to 7, characterized in that, The magnet configuration is a multi-layer structure, including multi-layer structures in the radial and axial directions. Each layer of magnet consists of multiple magnetic blocks forming a roughly ring-shaped structure, and the axial central axis of each layer of magnet coincides. The magnetization law is dipole Halbach magnetization.

9. A high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming as described in claim 8, characterized in that: In the radial direction, there may be gaps or no gaps between the layers of Halbach rings. When there are gaps, the magnetic field uniformity is improved by radially moving the magnetic blocks and attaching ferromagnetic sheets.

10. A high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming as described in claim 9, characterized in that: In the axial direction, there may be gaps or no gaps between the layers of Halbach rings. When there are gaps, the magnetic field uniformity is improved by moving the magnetic blocks axially and attaching ferromagnetic sheets.

11. A high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming as described in claim 10, characterized in that: The magnetic blocks that make up each layer of Halbach rings are cylindrical, rectangular, or other polygonal in shape.

12. A high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming as described in claim 10, characterized in that: The magnetic blocks that make up each layer of Halbach rings may be the same or different in size, and each layer of Halbach rings may have the same or different inner diameter, outer diameter and height.

13. A high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming as described in claim 10, characterized in that: The magnetic blocks that make up each layer of Halbach rings use the same magnetic material or different magnetic materials; when different magnetic materials are used, the radial inner layer magnets use highly coercive magnetic materials to reduce or avoid demagnetization of the Halbach array magnets.

14. A high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming as described in claim 10, characterized in that: It can increase the strength of the central magnetic field by adding soft magnetic materials.

15. A high-field-strength, high-uniformity Halbach array magnet capable of self-uniforming as described in claim 10, characterized in that: The movement of the magnetic blocks and the application of ferromagnetic sheets for shimming are performed after the entire magnetic block assembly process or during the assembly process.

16. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 7.

17. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 7.

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