A DCT superconducting magnet structure

Abstract

The present invention relates to a DCT superconducting magnet structure, characterized by comprising a cylindrical electromagnetic wire formed by a plurality of monopole coils, the cylindrical electromagnetic wire being solidified on a skeleton to form a magnet structure, and the monopole coils being connected in series. Each monopole coil includes N turns of electromagnetic wire arranged in a spaced-apart arrangement, where N is an integer representing the total number of turns of electromagnetic wire in the monopole coil. The proposed DCT superconducting magnet structure can generate a high-quality multipolar magnetic field without requiring an iron core. The cylindrical structure enables a multi-layer nested structure, making it suitable for applications with varying apertures and magnetic field requirements, thus possessing a wide range of applications.

Description

Technical Field

[0001] The present invention relates to a magnet structure, in particular to a DCT (Discrete Cosine Theta) superconducting magnet structure capable of generating high-quality magnetic fields. Background Art

[0002] Electromagnetic coils are widely used in various fields of society, from induction cookers, a vital part of daily life, to medical MRI equipment, from elementary school science toys to scientists' large-scale accelerators. With the advancement of science and technology, electromagnetic coils have evolved from inefficient and low-energy conventional coils to highly efficient and high-energy superconducting magnets. Simultaneously, driven by the demands of industrial society and scientific and technological development, especially the demands of modern particle accelerator magnets, higher requirements have been placed on the structural design of electromagnetic coils, such as the ability to excite high-quality multipole fields or combined magnetic fields with unique field shapes.

[0003] Currently, common coil structures include solenoids, racetrack coils, saddle-shaped coils, and canted coil (CCT) coils. Theoretically, all required magnetic fields can be approximated by optimized combinations of these coil structures. For example, two parallel solenoids produce an approximately ideal dipole field in the gap; four rotationally symmetrically arranged racetrack coils can produce a quadrupole lens field, and so on. Except for the CCT coil, the magnetic fields approximated by the remaining magnet structure combinations contain many background multipoles and have very poor magnetic field quality. Usually, complex shimming coils are required to achieve high-quality magnetic field requirements. Although the CCT coil can generate a high-quality multipole field in the warm hole area, it needs to offset the simultaneously excited solenoid field, resulting in low excitation efficiency of the structure. Summary of the Invention

[0004] In view of the above problems, the object of the present invention is to provide a DCT superconducting magnet structure based on superconducting multi-strand cables that can generate high field, high uniformity and compact structure.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is as follows: a DCT superconducting magnet structure, comprising a cylindrical electromagnetic wire surrounded by a plurality of monopole coils, wherein the cylindrical electromagnetic wire is solidified on a frame to form a cylindrical magnet structure, and the monopole coils are connected in series;

[0006] Each of the monopolar coils includes N turns of electromagnetic coils arranged in a spaced-apart manner, wherein N is an integer, which is the total number of turns of electromagnetic wire of the monopolar coil.

[0007] The above-mentioned DCT superconducting magnet structure, further, the current density J of the cylindrical electromagnetic wire is approximately distributed in the circumferential direction in the shape of cos(mθ), that is, j z=j0cos(mθ), where j0 is the current density through the cross section of the electromagnetic wire, j z is the Z component of the circumferentially distributed equivalent current density, m is the 2m-pole magnetic field required by the magnetic field design, and θ is the angle rotating counterclockwise around the Z axis with the x-axis as the starting point. Taking a two-pole DCT coil as an example, the cylinder axis is the Z axis, the coil pole head direction is the Y axis, and the direction perpendicular to the Z axis on the inter-pole symmetry plane of the coil is the X axis. The XYZ coordinate system forms a Cartesian coordinate system.

[0008] The above-mentioned DCT superconducting magnet structure further has the cylindrical electromagnetic wires having a circumferential position distribution that satisfies the stream function sin(mθ)=(i-1 / 2) / N, wherein i is the electromagnetic wire number, which is any integer between {1, N}.

[0009] The above-mentioned DCT superconducting magnet structure further has a current line angle distribution θ i =Arcsin((i-1 / 2) / N) / m.

[0010] The above-mentioned DCT superconducting magnet structure, further, the straight edge segment coordinates of each turn of the cylindrical electromagnetic wire are (Rcos(mθ i ), Rsin(mθ i ), z), where R is the radius of the electromagnetic wire in the polar coordinate system. The coordinate z of the arc segment of each continuous turn of the cylindrical electromagnetic wire satisfies the stream function: cos(π·(z-hl) / (2·he))·sin(mθ)=(i-1 / 2) / N, where hl refers to half the length of the straight edge segment and he refers to the maximum length of the coil arc segment in the z direction.

[0011] The above-mentioned DCT superconducting magnet structure can further be nested in multiple layers, and multiple coaxial DCT superconducting magnet structures with different R are combined to form a magnet with a set magnetic field requirement. The multi-layer combined DCT superconducting magnet structure can be powered by connecting in series or in parallel, or can be powered independently, where R is the radius of the electromagnetic wire distribution in the polar coordinate system.

[0012] In the above-mentioned DCT superconducting magnet structure, further, each coil turn is made of a superconducting multi-strand cable.

[0013] In the above-mentioned DCT superconducting magnet structure, further, the superconducting multi-strand cable is formed by twisting or braiding a plurality of uninsulated superconducting wires.

[0014] In the above-mentioned DCT superconducting magnet structure, further, the superconducting multi-strand cable is formed by twisting or braiding multiple insulated superconducting wires.

[0015] In the above-mentioned DCT superconducting magnet structure, further, the monopole coil is wound by a continuous electromagnetic wire, and the turn transition mode of the N-turn electromagnetic coil adopts arc segment cross transition, straight edge segment extended transition or straight edge segment cross transition.

[0016] The present invention has the following advantages due to the adoption of the above technical solution:

[0017] 1. The present invention proposes a DCT superconducting magnet structure, whose equivalent current density Jz is distributed approximately in the circumferential direction according to the law of cos(mθ). Theoretically, the magnetic field excited by this current density distribution has a natural pure 2m pole. Compared with the multipole field generation mechanism of the CCT coil by canceling the axial component of the field, the excitation efficiency of the DCT coil is much higher.

[0018] 2. The DCT superconducting coil of the present invention can obtain a high-quality multi-pole magnetic field without an iron core;

[0019] 3. The DCT superconducting coil of the present invention is a cylindrical electromagnetic wire formed by a plurality of monopole coils. The cylindrical electromagnetic wire can realize a multi-layer nested structure, which is suitable for fields with different apertures and different magnetic field requirements. It can realize the compact design of a multifunctional combined magnet and has a very wide application space.

[0020] 4. Each turn of the coil of the present invention can be made of a superconducting multi-strand cable. In the field of superconducting magnets, the cylindrical nested structure makes it easier to achieve layered optimization design of current density, thereby maximizing the excitation efficiency of the superconducting wire.

[0021] 5. The present invention utilizes a multi-strand superconducting cable to effectively increase the engineering current density required for excitation, while also facilitating the precise routing of slotted and inlaid wires for magnet manufacturing. The end-to-end connection of individual wires in a superconducting cable, which is twisted or braided from multiple insulated superconducting wires, significantly reduces the power supply requirements of the magnet, thereby significantly reducing the development or purchase costs of related equipment.

[0022] In summary, in the current era of rapid scientific development, the DCT superconducting magnet structure provided by the present invention makes it possible to meet the requirements of high-field, high-uniformity and compact magnet structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. Throughout the drawings, the same reference numerals are used to denote the same components. In the drawings:

[0024] Figure 1Schematic diagram of the distribution of current lines corresponding to a dipole magnet, a quadrupole magnet, a sextupole magnet, and an octupole magnet in the first quadrant of the XY plane of the DCT superconducting magnet structure according to an embodiment of the present invention;

[0025] Figure 2 Schematic diagram of the structure of a DCT type dipole field magnet according to an embodiment of the present invention;

[0026] Figure 3 Schematic diagram of the structure of a DCT type quadrupole field magnet according to an embodiment of the present invention;

[0027] Figure 4 Schematic diagram of the structure of a DCT type sextupole magnet according to an embodiment of the present invention;

[0028] Figure 5 Schematic diagram of the DCT octupole field magnet structure according to an embodiment of the present invention.

[0029] Figure 6 Schematic diagram of the current line inter-turn transition scheme of the monopolar coil according to an embodiment of the present invention;

[0030] Figure 7 Schematic diagrams of two typical "7-strand" superconducting cables with different single-strand insulation methods used in embodiments of the present invention. DETAILED DESCRIPTION

[0031] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0032] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an", and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0033] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates otherwise, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0034] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside," "outside," "below," "above," etc. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0035] like Figure 1 、 Figure 2 As shown, the DCT superconducting magnet structure provided in this embodiment includes several monopole coils 1 arranged in a cylindrical electromagnetic wire. The cylindrical electromagnetic wire is solidified on a cylindrical frame to form the cylindrical magnet structure. The monopole coils 1 are connected in series, and each monopole coil 1 includes N turns of electromagnetic wire arranged in a spaced-apart arrangement, where N is a positive integer representing the total number of turns of electromagnetic wire per layer of monopole coils 1. The cylindrical electromagnetic wire arrangement facilitates the nesting of DCT magnet structures with different R values, facilitating magnet performance enhancement or functional combination designs.

[0036] Furthermore, this embodiment adopts the principle that the current density is cos(mθ) distributed to generate a pure 2m-pole magnetic field, and adopts a DCT coil structure to approximate the cos(mθ) distribution requirement of the current density by discrete current line positions, wherein the equivalent current density j of the cylindrical electromagnetic wire is z The annular distribution is approximately cos(mθ) distribution, that is, j z =j0cos(mθ), where j0 is the current density through the cross section of the electromagnetic wire, j zis the Z component of the circumferentially distributed equivalent current density, representing the actual current required for a pure 2m-pole magnetic field. m refers to the coil being composed of 2m monopoles, and θ refers to the angle rotated counterclockwise around the Z axis, starting from the X axis. Taking a two-pole DCT coil as an example, the coordinate system XYZ represents directions, with the cylinder axis as the Z axis, the direction of the two-pole coil pole tip as the Y axis, and the direction perpendicular to the Z axis on the inter-pole symmetry plane of the two-pole DCT coil as the X axis. Together, XYZ form a Cartesian coordinate system. For ease of description, the X, Y, and Z axes in this embodiment are merely used to distinguish the three coordinate axes. In actual use, these names should not be limiting, and the names of the coordinate axes can be defined as needed.

[0037] Furthermore, the position distribution of the cylindrical electromagnetic wire in the circumferential direction (the direction of growth along θ) satisfies the stream function sin(mθ) = (i-1 / 2) / N distribution, where i is the electromagnetic wire number, which is any integer between {1, N}; θ is the position angle corresponding to the i-th turn of the electromagnetic wire. The current line angle distribution required for a 2m-pole magnetic field can be obtained through the stream function as θ i =Arcsin((i-1 / 2) / N) / m. Therefore, the coordinates of the straight edge of each turn of the cylindrical electromagnetic wire are (Rcos(mθ i ), Rsin(mθ i ), z), R is the radius of the electromagnetic wire distribution in polar coordinates; the arc segment of each continuous turn of the cylindrical electromagnetic wire is required to have a coordinate z that satisfies the stream function: cos(π·(z-hl) / (2·he))·sin(mθ)=(i-1 / 2) / N. This corrects the tail field effect of the non-infinite length coil and optimizes the overall integrated field quality of the magnet, where hl is half the length of the straight-side segment; he is the maximum length of the coil arc segment in the z direction. Different stream functions can be set for the arc segment electromagnetic wire position as required, such as uniform spacing distribution between adjacent turns (the spacing between adjacent turns always remains the same) or uniform spacing distribution at the farthest end of the arc segment (only the spacing between turns at the farthest end of the arc segment is controlled to ensure optimal turn density without spatial interference between turns).

[0038] Furthermore, as shown in 2 to 5, when m takes different positive integers, the DCT coil can obtain a pure 2m-pole magnetic field, specifically:

[0039] like Figure 1 As shown, when m=1, a dipole magnetic field with a high uniformity in the space surrounded by the electromagnetic wire (gap) can be designed;

[0040] like Figure 2 As shown, when m=2, a quadrupole magnetic field with a high gradient field quality in the space surrounded by the electromagnetic wires (gap) can be designed;

[0041] like Figure 3As shown, when m=3, a sextupole magnetic field with a high second-order gradient field quality in the space surrounded by the electromagnetic wires (gap) can be designed;

[0042] like Figure 4 As shown, when m=4, an octupole magnetic field with a high second-order gradient field quality in the space surrounded by the electromagnetic wire (gap) can be designed;

[0043] …

[0044] By analogy, any 2m-pole magnet can be obtained by using the value of m, and compared with 2m-pole magnets of other coil types, it has a naturally higher field quality.

[0045] Furthermore, the DCT coils of this embodiment can be nested in multiple layers, i.e., a series of DCT coils with increasing R can be provided to achieve magnetic field enhancement in the gap region or a multifunctional combination. Magnetic field enhancement refers to the joint excitation of multiple coaxial 2m-pole DCT coils with different Rs to achieve a magnetic field enhancement effect. Multifunctional combination refers to the combination of multiple coaxial DCT coils with different Rs and different ms to form a magnet with special field shape requirements, such as a two-pole DCT and a four-pole DCT combination. The multi-layered combined DCT coils can be connected in series or in parallel for power supply, or can be powered independently.

[0046] Further, such as Figure 6 As shown in FIG, in the specific implementation process of the monopole coil of the DCT superconducting magnet structure, it is necessary to design the necessary turn-to-turn transition so that the required coil structure can be completed by winding a continuous electromagnetic wire. This turn-to-turn transition method can be selected in any way, such as Figure 6 (a) shows the arc segment cross transition, Figure 6 (b) The straight edge segment is extended or Figure 6 (c) The straight edge segment cross transition method shown.

[0047] Furthermore, each turn of the coil electromagnetic wire is made of a multi-strand superconducting cable, such as a 7-strand superconducting twisted cable, etc. The superconducting material is such as NbTi, Nb3Sn, etc., which is not limited to this example. Figure 7 As shown in (a), the superconducting multi-strand cable can be made by twisting or braiding multiple uninsulated superconducting wires; or Figure 7 As shown in (b), the superconducting multi-strand cable can also be made by twisting or braiding multiple insulated superconducting wires.

[0048] The above embodiments are only used to illustrate the present invention, wherein the structure, connection mode and manufacturing process of each component can be changed. Any equivalent transformations and improvements based on the technical solution of the present invention should not be excluded from the scope of protection of the present invention.

Claims

1. A DCT superconducting magnet structure, characterized in that: It includes a cylindrical electromagnetic wire surrounded by a plurality of monopole coils, wherein the cylindrical electromagnetic wire is solidified on a frame to form a cylindrical magnet structure, and the monopole coils are connected in series; Each of the monopolar coils comprises N turns of electromagnetic coils arranged in a spaced-apart manner, wherein N is an integer and is the total number of turns of electromagnetic wire of the monopolar coil; The current density J of the cylindrical electromagnetic wire is distributed in the annular direction. The regular distribution of ,in, is the current density through the cross section of the electromagnetic wire, is the equivalent current density Z component of the annular distribution, m is the 2m pole magnetic field required by the magnetic field design, The angle is the counterclockwise rotation around the Z axis with the x-axis as the starting point. Taking the two-pole DCT coil as an example, the cylinder axis is the Z axis, the coil pole head direction is the Y axis, and the direction perpendicular to the Z axis on the coil inter-pole symmetry plane is the X axis. XYZ forms a Cartesian coordinate system. The position distribution of the cylindrical electromagnetic wire in the annular direction satisfies the stream function ,in, i is the electromagnetic wire serial number, which is any integer between {1, N}; Current line angle distribution ; The straight edge coordinates of each turn of the cylindrical electromagnetic wire are ( , , ), where R is the radius of the electromagnetic wire in the polar coordinate system. The arc segment of each turn of the cylindrical electromagnetic wire must have a coordinate z that satisfies the stream function: , where hl refers to half the length of the straight side segment, and he refers to the maximum length of the coil arc segment in the z direction; Each turn of the coil is made of a superconducting multi-strand cable; the superconducting multi-strand cable is formed by twisting or braiding a plurality of uninsulated superconducting wires; or the superconducting multi-strand cable is formed by twisting or braiding a plurality of insulated superconducting wires; The DCT superconducting magnet structure is a multi-layer nested combination, using multiple coaxial DCT superconducting magnet structures with different R to form a magnet with a set magnetic field requirement. The multi-layer combined DCT superconducting magnet structure is powered by series or parallel connection, and can also be powered independently, where R is the radius of the electromagnetic wire distribution in the polar coordinate system.

2. The DCT superconducting magnet structure according to claim 1, characterized in that: The monopole coil is wound by a continuous electromagnetic wire, and the turn transition mode of the N-turn electromagnetic coil adopts arc segment cross transition, straight edge segment extension transition or straight edge segment cross transition.

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