A method and system for designing magnets using induced current

Abstract

The present invention relates to a method and system for designing a magnet using an induced current, which includes: determining the field type of an external magnetic field and the coil distribution profile according to physical requirements, and determining the conductor shell shape according to the coil distribution profile; calculating the eddy current distribution generated by the conductor shell under the external magnetic field, and obtaining a preliminary discrete coil distribution after discretizing the eddy current distribution; parameter modeling of the discretized coil position, adjusting the coil distribution, and optimizing the magnetic field at the coil end; converting the magnetic field and current distribution data on the optimized coil into a Lorentz force distribution and loading it into a finite element model for structural simulation, and mechanically designing the coil skeleton and the magnet structure according to the simulation results, and after the structural design of the cold body is completed, designing a cryostat from the inside out. The present invention has no special restrictions on the field shape and the coil cross-sectional distribution, has extremely high flexibility, can cope with the design requirements of various complex magnetic field systems, and can be applied in the field of magnet optimization design technology.

Description

Technical Field

[0001] The present invention relates to the technical field of magnet optimization design, and in particular to a method and system for designing a magnet using an induced current. Background Art

[0002] Coil-dominated superconducting magnets, which mainly rely on spatial current distribution to generate magnetic fields, are another type of magnet commonly used in accelerator applications. They have the advantages of light structure, variable field patterns, and linear magnetic fields. Superconducting dipole magnet coils are mainly of the following types according to the coil structure: Cos-Theta coils, Commom coils, Block type coils, and Canted-Cosine-Theta coils. The four types of superconducting coils have their own characteristics in terms of magnetic excitation effects, coil structures, and winding difficulty. Various types of coils have different applications in different devices. With the application of accelerators in medical and other fields, coil-dominated superconducting magnets have gradually become an important choice for superconducting accelerators.

[0003] The design of coil-type superconducting magnets mainly generates a specific magnetic field by analytically solving the spatial current distribution. When the required magnetic field is a standard two-pole, four-pole, or six-pole magnetic field, and the magnet cross section is circular, the coil distribution can be quickly given by analytical solution. Common CCT&DCT coils are designed and optimized using this analytical solution.

[0004] When the required magnetic field is relatively complex or the coil shape is not a circular cross-section, the analytical solution of its spatial current distribution becomes difficult to obtain. It is difficult to quickly give the coil distribution through analytical calculation. The design and optimization of magnets in these special scenarios become relatively difficult. For example, when the required magnetic field is not a standard magnetic field, the analytical difficulty increases, and the complex coil expression is not conducive to subsequent optimization and design. For example, when the actual space is limited, a circular magnet cross-section cannot be used or changing the cross-section can greatly reduce the cost of the magnet and improve space utilization. Faced with non-circular cross-sections, traditional design methods also find it difficult to give analytical current distribution, making it difficult to conduct further magnet design and optimization. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method and system for designing magnets using induced current, which has no special restrictions on field shape and coil cross-sectional distribution, has extremely high flexibility, and can meet the design requirements of various complex magnetic field systems.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a method for designing a magnet using an induced current, which comprises: determining the field type of an external magnetic field and a coil distribution profile according to physical requirements, and determining the shape of a conductor shell according to the coil distribution profile; calculating the eddy current distribution generated by the conductor shell under the external magnetic field, and discretizing the eddy current distribution to obtain a preliminary discrete coil distribution; performing parameterized modeling on the discretized coil position, adjusting the coil distribution, and optimizing the magnetic field generated by the coil according to design requirements; converting the magnetic field and current distribution data on the optimized coil into a Lorentz force distribution and loading it into a finite element model for structural simulation, performing mechanical design of a coil skeleton and a magnet structure according to the simulation results, and performing a low-temperature thermostat design after the structural design of the cold body is completed.

[0007] Furthermore, the calculation of the eddy current distribution generated by the conductor shell under the external magnetic field is performed using a finite element method.

[0008] Further, the calculation of the eddy current distribution generated by the conductor shell under the external magnetic field includes:

[0009] In AC operation, an induced current is generated on the surface of the conductor shell. When the magnetic field inside the conductor shell is 0, it is considered that the induced current in the conductor shell generates a magnetic field equal in magnitude and opposite in direction to the external magnetic field.

[0010] The desired induced current distribution is taken out along the conductor shell cross-sectional path, and the taken out induced current is integrated along the conductor shell cross-sectional path to form a current integral-path curve.

[0011] Furthermore, the skin depth of the induced current in the conductor shell is smaller than the thickness of the conductor shell.

[0012] Furthermore, the parameter modeling is performed on the discretized coil positions, the coil distribution is adjusted, and the magnetic field at the coil ends is optimized, including:

[0013] Determine the parametric equation form of the required optimized coil distribution according to the magnet function and actual magnetic field requirements;

[0014] A parameterized equation is established according to the coil distribution, and the distribution of the coil in space is constrained by various parameters in the parameterized equation;

[0015] According to the mapping relationship between the optimization parameters and the physical targets, the corresponding optimization algorithm is called to optimize and design the magnetic field and coil of the magnet.

[0016] Furthermore, multiple feedback iterations are performed between the mechanical design and the cryostat design and the magnetic field and coil design to form a magnet coil solution that meets actual processing conditions and physical requirements.

[0017] A system for designing magnets using induced currents comprises: a primary processing module, which determines the field type of an external magnetic field and a coil distribution profile according to physical requirements, and determines the conductor shell shape according to the coil distribution profile; an eddy current distribution calculation module, which calculates the eddy current distribution generated by the conductor shell under the external magnetic field, and obtains a preliminary discrete coil distribution after discretizing the eddy current distribution; a coil setting module, which performs parameter modeling on the discretized coil position, adjusts the coil distribution, and optimizes the magnetic field at the coil end; an engineering design module, which converts the magnetic field and current distribution data on the optimized coil into a Lorentz force distribution and loads it into a finite element model for structural simulation, performs mechanical design of the coil skeleton and the magnet structure according to the simulation results, and designs a cryostat from the inside out after the structural design of the cold body is completed.

[0018] Furthermore, in the eddy current distribution calculation module, a finite element method is used to calculate the eddy current distribution generated by the conductor shell under an external magnetic field.

[0019] Further, the eddy current distribution calculation module includes:

[0020] The magnetic field generating module generates an induced current on the surface of the conductor shell during AC operation. When the magnetic field inside the conductor shell is 0, it is considered that the induced current in the conductor shell generates a magnetic field equal in magnitude and opposite in direction to the external magnetic field.

[0021] The distribution acquisition module extracts the desired induced current distribution along the conductor shell cross-sectional path, and integrates the extracted induced current along the conductor shell cross-sectional path to form a current integral-path curve.

[0022] Furthermore, the skin depth of the induced current in the conductor shell is smaller than the thickness of the conductor shell.

[0023] The present invention adopts the above technical solution, which has the following advantages:

[0024] 1. After preliminary eddy current calculation, discretization, end processing optimization and other processes, the present invention can realize the electromagnetic design of the required magnetic field within a reasonable range, achieve physical goals through special cross-sections or special field distribution, save space and cost, or obtain better magnetic field quality.

[0025] 2. The present invention determines the coil distribution by adding a conductor shell of any shape and determines the field shape by adding an arbitrary magnetic field. There is no special restriction on the field shape and the coil cross-sectional distribution. It has extremely high flexibility and can meet the design requirements of various complex magnetic field systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a process of designing a magnet using an induced current in one embodiment of the present invention;

[0027] Figure 2is a schematic diagram of a magnetic field of a magnet optimized by using an induced current in one embodiment of the present invention;

[0028] Reference numerals:

[0029] 1. External magnetic field, 2. Conductor shell, 3. Induced current, 4. Discrete coil generates magnetic field, 5. Discrete coil. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] The method and system for optimizing magnetic field design using induced current provided by the present invention is to use induced current to design a magnetic coil of a specific field type, use the induced current generated by a conductor shell with a specified shape, and then discretize the induced current distribution to obtain a discrete coil distribution. When a specific field type is given by the outside world, due to the shielding effect of the conductor on the external field, the internal magnetic field is 0. At this time, the magnetic field generated by the induced current on the surface of the conductor must be equal to the external magnetic field in magnitude and opposite in direction. In this way, when the external field is an arbitrary field, corresponding eddy currents will be generated on the surface of the conductor, and the magnetic field formed by the eddy currents is the external magnetic field. The magnetic field distribution that needs to be designed is determined by the external magnetic field, and the coil shape is determined by the contour of the conductor shell. The special conductor shell shape represents a special eddy current distribution.

[0033] By discretizing the eddy current distribution and gradually optimizing the coil position, special coils that meet different physical requirements can be obtained. According to different physical requirements, the corresponding conductor shell and external magnetic field are set, and the required complex field pattern can be designed conveniently and quickly using the induced current.

[0034] In one embodiment of the present invention, a method for designing a magnet using an induced current is provided. In this embodiment, Figure 1 As shown, the method comprises the following steps:

[0035] 1) Determine the field type of the external magnetic field and the coil distribution profile according to physical requirements, and determine the conductor shell shape according to the coil distribution profile;

[0036] 2) Calculate the eddy current distribution generated by the conductor shell under the external magnetic field, and discretize the eddy current distribution to obtain a preliminary discrete coil distribution;

[0037] 3) Perform parameter modeling on the discretized coil positions, adjust the coil distribution, and optimize the magnetic field generated by the coil according to design requirements;

[0038] 4) The magnetic field and current distribution data on the optimized superconducting coil are converted into Lorentz force distribution and loaded into the finite element model for structural simulation. The mechanical design of the coil frame and magnet structure is carried out according to the simulation results. After the structural design of the cold body is completed, the low-temperature thermostat is designed.

[0039] In the above step 2), the finite element method (such as CST, opera, etc.) is used to calculate the eddy current distribution of the conductor shell of a specified shape under an external magnetic field, including the following steps:

[0040] 2.1) During AC operation, an induced current is generated on the surface of the conductor shell, thereby preventing the external magnetic field from entering the conductor shell. When the magnetic field inside the conductor shell is 0, it can be considered that the induced current in the conductor shell generates a magnetic field that is equal in magnitude and opposite in direction to the external magnetic field.

[0041] 2.2) Take out the desired induced current distribution along the conductor shell cross-sectional path. Integrate the taken out induced current along the conductor shell cross-sectional path to form a current integral-path curve.

[0042] In the above embodiment, since the induced current (i.e., eddy current) can only be generated in a changing field, the operating frequency of the background magnetic field needs to be preset. The operating frequency is arbitrary, and the conductor shell is set by changing the thickness and the conductivity of the material used to ensure that the skin depth of the induced current in the conductor shell is smaller than the thickness of the conductor shell.

[0043] In the above step 3), parameter modeling is performed for the discretized coil positions, the coil distribution is adjusted, and the magnetic field generated by the coil is optimized according to the design requirements. The use of multi-parameter modeling provides a high degree of freedom for the optimization of coil-dominated superconducting magnets with complex structures and shapes, and specifically includes the following steps:

[0044] 3.1) Determine the parametric equation form for optimizing coil distribution according to the magnet function and actual magnetic field requirements;

[0045] When the number of coil turns is small, the coil space coordinates can be directly used as optimization setting parameters;

[0046] When the number of coil turns is large, the spatial coordinate distribution of the coil can be fitted with a polynomial / Fourier series, and the fitting coefficients can be used as optimization setting parameters.

[0047] 3.2) Establish a parameterized equation based on the coil distribution, and constrain the spatial distribution of the coil through each parameter in the parameterized equation.

[0048] 3.3) According to the mapping relationship between the optimization parameters and physical objectives such as uniformity, the corresponding optimization algorithm (such as genetic algorithm, particle swarm algorithm, etc.) is called to optimize and design the magnetic field and coil of the magnet.

[0049] In the above step 4), since the complete superconducting magnet design also needs to comprehensively consider the mechanical and thermal related structural design requirements on the basis of electromagnetic optimization design, and finally form the cold body design and low temperature thermostat design of the superconducting magnet, after obtaining the complete magnetic field optimization design, the magnetic field and current distribution data on the superconducting coil are converted into Lorentz force distribution and loaded into the finite element model, and the structural simulation is carried out using the finite element calculation software ANSYS. The mechanical design of the coil skeleton and the magnet structure is carried out according to the simulation results, and after completing the structural design of the cold body, the low temperature thermostat is designed from the inside out.

[0050] In the above embodiment, the mechanical design and the design of the cryostat need multiple feedback iterations between the magnetic field and the coil design. For example, after analyzing the stress-strain calculation results, it may be found that the coil shape needs to be adjusted to avoid stress concentration areas. After completing the magnet skeleton design and performing structural analysis, some parts need to be strengthened to reduce deformation. After multiple iterations, a magnet coil solution that meets actual processing conditions and physical requirements is finally formed.

[0051] Example:

[0052] In this embodiment, a rectangular cross-section dipole magnetic field is used as an example. Figure 2 As shown in the figure, it is a schematic diagram for designing the magnetic field. According to physical requirements, the coil distribution profile is determined to be a rectangular distribution, and the external magnetic field is determined to be a uniform dipole magnetic field. Therefore, in the finite element software, a uniform dipole magnetic field is used as the background magnetic field 1, and a rectangular conductor shell 2 with a preset thickness is established as the conductor shell according to the coil distribution profile. Since the induced current can only be generated in a changing field, the background magnetic field selects a preset operating frequency. The operating frequency is arbitrary, but it is necessary to ensure that the skin depth of the induced current in the conductor shell is less than the thickness of the conductor shell.

[0053] The finite element method is used to solve the current distribution in the conductor shell under a specific external magnetic field. During AC operation, an induced current is generated on the surface of the conductor, thereby preventing the external magnetic field from entering the interior of the conductor shell. When the magnetic field inside the conductor shell is 0, it can be considered that the induced current in the conductor shell generates a magnetic field that is equal to the external magnetic field in magnitude and opposite in direction. At this time, the desired induced current distribution is taken out along the conductor cross-sectional path. After the taken induced current is integrated along the conductor cross-sectional path, a current integral-path curve is formed.

[0054] According to the required magnetic field, the ampere-turns NI required by the magnet itself is determined, and the total number of turns N is determined so that the single-coil current I is within a suitable range. Subsequently, discretization is performed in the current integral-path force curve, and a discrete coil 5 with a certain distribution can be obtained according to the discretization.

[0055] At this time, the magnetic field 4 generated by the offline coil is the dipole magnetic field to be designed, and the coil distribution 5 is the rectangular cross section required by the design. Thus, the dipole magnetic field coil with a rectangular cross section is designed by the induced current.

[0056] In one embodiment of the present invention, a system for designing a magnet using an induction current is provided, comprising:

[0057] The primary processing module determines the field type of the external magnetic field and the coil distribution profile according to physical requirements, and determines the conductor shell shape according to the coil distribution profile;

[0058] The eddy current distribution calculation module calculates the eddy current distribution generated by the conductor shell under the external magnetic field, and discretizes the eddy current distribution to obtain the preliminary discrete coil distribution;

[0059] The coil setting module performs parameter modeling for the discretized coil position, adjusts the coil distribution, and optimizes the magnetic field at the coil end;

[0060] The engineering design module converts the magnetic field and current distribution data on the optimized coil into Lorentz force distribution and loads it into the finite element model for structural simulation. The mechanical design of the coil skeleton and magnet structure is carried out according to the simulation results. After the structural design of the cold body is completed, the cryostat is designed from the inside out.

[0061] In the above embodiment, in the eddy current distribution calculation module, the finite element method is used to calculate the eddy current distribution generated by the conductor shell under the external magnetic field.

[0062] In the above embodiment, the eddy current distribution calculation module also includes:

[0063] The magnetic field generating module generates an induced current on the surface of the conductor shell during AC operation. When the magnetic field inside the conductor shell is 0, it is considered that the induced current in the conductor shell generates a magnetic field equal in magnitude and opposite in direction to the external magnetic field.

[0064] The distribution acquisition module extracts the desired induced current distribution along the conductor shell cross-sectional path, and integrates the extracted induced current along the conductor shell cross-sectional path to form a current integral-path curve.

[0065] In the above embodiments, the skin depth of the induced current in the conductor shell is smaller than the thickness of the conductor shell.

[0066] The system provided in this embodiment is used to execute the above-mentioned method embodiments. Please refer to the above-mentioned embodiments for specific processes and detailed contents, which will not be repeated here.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing a magnet using induced current, It is characterized in that include: Determine the field type of the external magnetic field and the coil distribution profile according to physical requirements, and determine the conductor shell shape according to the coil distribution profile; Calculate the eddy current distribution generated by the conductor shell under the external magnetic field, and discretize the eddy current distribution to obtain the preliminary discrete coil distribution; Perform parameter modeling on the discretized coil positions, adjust the coil distribution, and optimize the magnetic field generated by the coils according to design requirements; The magnetic field and current distribution data on the optimized coil are converted into Lorentz force distribution and loaded into the finite element model for structural simulation. The mechanical design of the coil skeleton and the magnet structure is carried out according to the simulation results. After the structural design of the cold body is completed, the design of the cryostat is carried out. The calculation of the eddy current distribution generated by the conductor shell under the external magnetic field is performed using a finite element method; The method for calculating the eddy current distribution generated by a conductor shell under an external magnetic field includes: In AC operation, an induced current is generated on the surface of the conductor shell. When the magnetic field inside the conductor shell is 0, it is considered that the induced current in the conductor shell generates a magnetic field equal in magnitude and opposite in direction to the external magnetic field. The desired induced current distribution is taken out along the conductor shell cross-sectional path, and the taken out induced current is integrated along the conductor shell cross-sectional path to form a current integral-path curve.

2. The method for designing a magnet using an induced current as claimed in claim 1, It is characterized in that The skin depth of the induced current in the conductor shell is less than the thickness of the conductor shell.

3. The method for designing a magnet using an induced current as claimed in claim 1, It is characterized in that The method of performing parameter modeling on the discretized coil positions, adjusting the coil distribution, and optimizing the magnetic field at the coil ends includes: Determine the parametric equation form of the required optimized coil distribution according to the magnet function and actual magnetic field requirements; A parameterized equation is established according to the coil distribution, and the distribution of the coil in space is constrained by various parameters in the parameterized equation; According to the mapping relationship between the optimization parameters and the physical targets, the corresponding optimization algorithm is called to optimize and design the magnetic field and coil of the magnet.

4. The method for designing a magnet using an induction current as claimed in claim 1, It is characterized in that The mechanical design and the cryostat design are iterated multiple times with the magnetic field and coil design to form a magnet coil solution that meets actual processing conditions and physical requirements.

5. A system for designing magnets using induced currents, It is characterized in that include: The primary processing module determines the field type of the external magnetic field and the coil distribution profile according to physical requirements, and determines the conductor shell shape according to the coil distribution profile; The eddy current distribution calculation module calculates the eddy current distribution generated by the conductor shell under the external magnetic field, and discretizes the eddy current distribution to obtain the preliminary discrete coil distribution; The coil setting module performs parameter modeling on the discretized coil position, adjusts the coil distribution, and optimizes the magnetic field at the coil end; The engineering design module converts the magnetic field and current distribution data on the optimized coil into Lorentz force distribution and loads it into the finite element model for structural simulation. The mechanical design of the coil skeleton and magnet structure is carried out according to the simulation results. After the structural design of the cold body is completed, the cryostat is designed from the inside out. In the eddy current distribution calculation module, a finite element method is used to calculate the eddy current distribution generated by the conductor shell under an external magnetic field; The eddy current distribution calculation module includes: The magnetic field generating module generates an induced current on the surface of the conductor shell during AC operation. When the magnetic field inside the conductor shell is 0, it is considered that the induced current in the conductor shell generates a magnetic field equal in magnitude and opposite in direction to the external magnetic field. The distribution acquisition module extracts the desired induced current distribution along the conductor shell cross-sectional path, and integrates the extracted induced current along the conductor shell cross-sectional path to form a current integral-path curve.

6. The system for designing a magnet using an induction current as claimed in claim 5, It is characterized in that The skin depth of the induced current in the conductor shell is smaller than the thickness of the conductor shell.

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