Quadrupole magnet and particle accelerator

Abstract

The invention relates to the technical field of particle accelerators, in particular to a quadrupole magnet and a particle accelerator, the quadrupole magnet comprises a first frame, a second frame and four independent winding coils wound between the first frame and the second frame, the first frame and the second frame are symmetrical closed frames and are arranged in parallel at intervals, and the first frame and the second frame are parallel to each other. The particle beams are rotationally symmetrical around a particle beam flow channel positioned in the centers of the two frames; each independent winding coil comprises two transverse bending sections and two longitudinal acting sections, an interval space is formed between the two longitudinal acting sections of the same independent winding coil, and at least one longitudinal acting section of the other independent winding coil is arranged in the interval space; and the geometric length of the transverse bending section is expanded by increasing the extension path. Through the rotational symmetric layout of the symmetric closed frame, the extending winding path of the transverse bending section and the collaborative filling design of the multi-coil interval space, the defect of a traditional acute angle bending process is avoided, and meanwhile the limited space is utilized to the maximum extent.

Description

Technical Field

[0001] The present invention relates to the technical field of particle accelerators, and particularly to a quadrupole magnet and a particle accelerator. Background Art

[0002] In the field of medical equipment (such as magnetic resonance imaging systems, proton therapy accelerators, etc.), quadrupole magnets are core components for beam focusing and precise control of particle orbits. Such equipment places extremely high requirements on the volume compactness, magnetic field uniformity, and operation reliability of the magnets. Especially in tumor radiotherapy, slight deviations in the magnetic field gradient may lead to beam positioning errors, directly affecting the treatment effect and patient safety. However, the coil design of traditional quadrupole magnets faces severe challenges.

[0003] In traditional coil winding processes, to accommodate more turns in a small space, multiple acute-angle bends (with the inner end of the bend turning back) are often used to achieve a compact layout. However, this design has the following problems: 1. Limited turn density: Acute-angle bends require a bending allowance (such as a bending radius ≥ 3 times the strip thickness), resulting in a significant reduction in the actual available space in the innermost layer of the coil, limiting the turn density.

[0004] 2. Risk of brittleness of superconducting materials: In superconducting materials, high-temperature superconducting tapes (such as REBCO) are essentially brittle ceramics, and acute-angle bends will cause internal microcracks, resulting in a significant degradation of the critical current density and even local fracture and failure.

[0005] Especially in the field of medical equipment, it is necessary to achieve a high-intensity magnetic field (gradient ≥ 100 T / m) within a limited space (such as the magnet aperture of a proton therapy rotating gantry ≤ 30 cm). However, due to bending limitations, traditional designs are difficult to balance compactness and high performance. Reducing the number of turns to reduce the volume will sacrifice the magnetic field strength; if the number of turns is increased, the magnet size needs to be enlarged, which cannot adapt to the space limitations of medical equipment.

[0006] Currently, the mainstream solutions to the above problems include: Multi-layer thin tape winding: Using multiple thin superconducting tapes instead of a single thick tape can partially relieve the bending stress, but the interlayer contact resistance increases, resulting in an increase in current loss.

[0007] Flexible substrate technology: Attaching a flexible metal substrate to the back of the superconducting tape can improve the bending toughness, but the additional thickness introduced by the substrate further compresses the winding space, and the turn density will instead decrease.

[0008] In summary, how to achieve high turn density winding of superconducting coils in a small space while avoiding material damage caused by acute-angle bending has become a key bottleneck in the design of medical-grade quadrupole magnets. There is an urgent need for a new winding structure that can maximize the use of limited space and adapt to the mechanical properties of superconducting materials to ensure a double improvement in magnetic field gradient and operation reliability. Summary of the Invention

[0009] (1) The technical problem to be solved by the present invention is that in the existing design of quadrupole magnets, the acute-angle bending of the coil causes damage to the superconducting material and low utilization rate of the winding space. Especially in the miniaturization scenario of medical equipment, it is difficult to balance high turn density and magnetic field uniformity, resulting in insufficient magnetic field gradient and poor material reliability.

[0010] (2) Technical Solution To solve the above technical problems, an embodiment of the present invention provides a quadrupole magnet, including a first frame, a second frame, and four independent winding coils wound between the two frames. The first frame and the second frame are symmetric closed frames, arranged in parallel and at intervals, and are rotationally symmetric around a particle beam channel located at the center of the two frames. Each independent winding coil includes: Two transverse bending segments, respectively extending and wound and fixed to the corresponding edges of the first frame and the second frame. Two longitudinal acting segments, spanning between the transverse bending segments and extending along the axis of the central particle beam channel for generating a quadrupole magnetic field. Wherein, an interval space is formed between the two longitudinal acting segments of the same independent winding coil, and at least one longitudinal acting segment of another independent winding coil is arranged in the interval space so as to expand the geometric length of the transverse bending segment through an increased extension path.

[0011] Through the rotationally symmetric layout of the symmetric closed frames, it is ensured that the gradient of the quadrupole magnetic field is strictly symmetric in the radial direction, eliminating the magnetic field distortion caused by geometric deviation of the traditional asymmetric frame, and providing a basis for the accurate positioning of particle beams in medical scenarios; through the design of extending the transverse bending segment along the edge of the frame by a preset distance and then bending, the straight extension length of the bending segment is significantly increased, and the sharpness of the bending angle under a limited length is reduced, which not only avoids the risk of microcracks or fractures caused by multiple acute-angle bends of the superconducting material, but also improves the overall magnetic field strength under a compact structure.

[0012] The synergistic effect of the above technical features enables the present invention to avoid mechanical damage and performance degradation of superconducting materials under the miniaturization requirements of medical equipment, and at the same time achieve high-gradient magnetic field output, providing a highly reliable magnet solution for applications such as precise radiotherapy of tumors.

[0013] According to an embodiment of the present invention, the symmetric closed frame is a square frame; The longitudinal acting segments of the four independent winding coils are respectively arranged along the four side portions of the square frame, with two longitudinal acting segments correspondingly arranged on each side portion, and the two longitudinal acting segments belong to different independent winding coils; The longitudinal acting segments of the opposite side portions are symmetrically arranged in terms of geometric position and current direction to generate a symmetric quadrupole magnetic field in the central particle beam channel.

[0014] Through the geometric symmetry of the square frame, it is ensured that the gradients of the quadrupole magnetic field in the orthogonal directions (such as the X-axis and the Y-axis) are strictly complementary, eliminating both the uneven magnetic field distribution caused by the curvature difference in the traditional circular or polygonal frame and providing a benchmark for the linear arrangement of the longitudinal acting segments; through the symmetric arrangement of the longitudinal acting segments of the opposite side portions in terms of geometric position and current direction (such as the magnetic field polarities of the acting segments on the upper and lower side portions are opposite, and the same for the left and right side portions), a centrally symmetric quadrupole magnetic field is generated, effectively suppressing the beam offset or divergence caused by the current path deviation; through the arrangement of two longitudinal acting segments belonging to different coils on each side portion, the superposition and cooperation of the multi-coil magnetic fields are realized within a limited space.

[0015] It is especially adapted to the miniaturization requirements of medical devices. For example, in the rotating gantry of a proton therapy device, the compact layout of the square frame and the strictly symmetric magnetic field distribution can achieve high-precision beam control within a limited installation space, providing a reliable guarantee for the precise irradiation of the tumor target area.

[0016] According to an embodiment of the present invention, the two longitudinal acting segments of each independent winding coil are respectively arranged on two adjacent side portions of the square frame; Within the spaced space between the two longitudinal acting segments of the same independent winding coil, there are arranged the longitudinal acting segments of two other different independent winding coils.

[0017] Through the layout of the longitudinal acting segments on the adjacent side portions, the transverse bending segment of the same coil only needs to be bent once along the side portion of the frame to complete the cross-connection, significantly reducing the number of bends and maximizing the straight extension length of the bending segment, avoiding both the stress concentration caused by multiple bends of the superconducting material. By filling the spaced space of the same coil with the longitudinal acting segments of two other different coils, the straight path is extended to improve the utilization rate of the winding space; ensuring the minimum volume of the overall structure.

[0018] This setting is particularly crucial under the requirements of high turns in a small space: the synergy of the layout on the adjacent side portions effectively increases the straight length of the bending segment, so as to achieve the dual goals of high-density winding of the superconducting coil and high-intensity magnetic field output within the limited installation space of the medical device.

[0019] According to an embodiment of the present invention, the first frame and the second frame are both provided with winding grooves, and the contour of the winding groove is adapted to the winding path of the transverse bending section, for constraining the extending direction of the transverse bending section and expanding the bending space; One side of the winding groove facing the opposite frame is provided with an opening, and the axis of the opening is parallel to the axial direction of the central particle beam channel, for extending the longitudinal acting section from one frame to the opposite frame.

[0020] By precisely matching the contour of the winding groove with the geometry of the transverse bending section, the extending direction of the bending section is constrained and its winding space is expanded, which not only avoids the risk of inter-turn misalignment or short circuit caused by path deviation in traditional free winding; by setting the axis of the opening parallel to the axial direction of the central particle beam channel, it is ensured that the path is strictly aligned when the longitudinal acting section extends from one frame to the opposite frame, which not only eliminates the angular deviation during the bridging process, but also maintains the axial symmetry of the magnetic field distribution through linear extension, so as to achieve high-precision magnetic field gradient control in a limited space.

[0021] According to an embodiment of the present invention, each side of the first frame and the second frame is provided with a winding groove, and there are four winding grooves in each frame in total, including two inner-layer winding grooves and two outer-layer winding grooves; The inner-layer winding grooves are arranged at the inner edges of two adjacent sides of the square frame, and the outer-layer winding grooves are arranged at the outer edges of the other two adjacent sides; Only the transverse bending section of an independent winding coil is wound in each winding groove, so that the transverse bending sections in the inner-layer winding groove and the outer-layer winding groove are isolated from each other.

[0022] By hierarchically arranging the winding grooves at the inner and outer edges of the frame side and limiting that only the transverse bending section of a single coil is wound in each groove, the isolation of the coil layout is further optimized, avoiding the risk of physical contact or short circuit caused by path crossing in traditional winding, maximizing the utilization of the space at the frame side, reducing the local thickness increase caused by the original cross winding, improving the winding density, and significantly reducing the performance degradation of the material caused by complex bending.

[0023] According to an embodiment of the present invention, the winding groove at the opening is inclined with respect to the side of the square frame, and the inclination angle is adapted to the thickness of the frame and the spacing between the inner-layer and outer-layer winding grooves; The inclined setting makes the longitudinal acting sections extending in the openings of the inner-layer winding groove and the outer-layer winding groove on the same side of the frame in the same plane, and the plane is parallel to the axis of the central particle beam channel.

[0024] Through the inclined design of the winding grooves, the height difference of the longitudinal action sections caused by the frame thickness and the distance between the inner and outer layer winding grooves is compensated, so that the longitudinal action sections extending within the openings of the inner and outer layer winding grooves on the same frame side are in the same plane, eliminating the magnetic field gradient inclination caused by structural misalignment in the traditional design; by setting this plane parallel to the axis of the central particle beam channel, it is ensured that the magnetic field distribution of the longitudinal action section is strictly axially symmetric, avoiding beam divergence or orbit deviation caused by plane deviation, and providing a high-reliability guarantee for the precise irradiation of the tumor target area.

[0025] According to an embodiment of the present invention, the frame further includes a sealing plate, which covers the opening side of the winding groove and is used to close the groove body and limit the lateral bending section.

[0026] By adding a sealing plate covering the opening side of the winding groove, the stability and structural reliability of the coil winding are further ensured. The sealing plate isolates the physical erosion of the external environment on the coil by closing the groove body, and at the same time, through the adaptation of its inner limiting structure to the contour of the winding groove, it restricts the displacement of the lateral bending section, avoiding winding loosening caused by vibration or electromagnetic force, so as to maintain the accuracy and consistency of the magnetic field distribution during long-term operation. This design is particularly important under the harsh working conditions of medical equipment, providing a double guarantee for the high reliability of the magnet.

[0027] According to an embodiment of the present invention, the side wall at the bending part of the winding groove is an arc-shaped side wall, which smoothly transitions the bending path of the lateral bending section.

[0028] By designing the side wall at the bending part of the winding groove as an arc shape to smoothly transition the bending path of the lateral bending section, it not only eliminates the stress concentration damage to the superconducting material caused by traditional acute-angle bending, but also optimizes the winding accuracy of the bending section through continuous curvature, providing a stable guarantee for high-precision beam control in medical scenarios.

[0029] According to an embodiment of the present invention, the winding coil is a high-temperature superconducting coil.

[0030] By using high-temperature superconducting materials to wind the winding coil, the energy efficiency ratio and operation stability of the magnet are further optimized. The zero-resistance characteristic of the high-temperature superconducting coil enables it to achieve lossless current transmission at the liquid nitrogen temperature range (77 K), significantly reducing the complexity and energy consumption of the cooling system. At the same time, its high critical current density supports the generation of a high-intensity magnetic field in a compact space. Combining with the extended bending path and arc-shaped winding groove design of the present invention, the brittle disadvantage of high-temperature superconducting materials is effectively avoided. Its collaborative design with the frame and winding process of the present invention provides a high-reliability and miniaturized magnet solution for tumor precision treatment.

[0031] Another example of the present invention also provides a particle accelerator, including the quadrupole magnet described in any one of the above.

[0032] By integrating the high-gradient, high-uniformity, and miniaturized quadrupole magnet, the particle accelerator can achieve more precise control of the particle beam in medical applications such as proton therapy, adapt to the space limitations of hospital machine rooms, and provide efficient technical support for clinical precision radiotherapy.

[0033] (3) Beneficial effects of the present invention: Through the rotationally symmetric layout of the symmetric closed frame, the extended winding path of the lateral bending section, and the collaborative filling design of the multi-coil spacing space, while avoiding the process defects of traditional acute-angle bending, the limited space is maximally utilized to achieve high-density winding of superconducting coils and high-precision magnetic field control. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 Schematic diagram of the three-dimensional structure of the original winding coil; Figure 2 Schematic diagram of the three-dimensional structure of the winding coil when the frame is circular according to an embodiment of the present invention; Figure 3 Schematic diagram of the three-dimensional structure of the quadrupole magnet when the frame is square according to an embodiment of the present invention; Figure 4 Schematic diagram of the three-dimensional structure of the quadrupole magnet without a cover when the frame is square according to an embodiment of the present invention; Figure 5 Schematic diagram of the three-dimensional structure of the winding coil when the frame is square according to an embodiment of the present invention; Figure 6 For Figure 5 Another perspective three-dimensional structure diagram; Figure 7 Schematic diagram of the three-dimensional structure of the independent winding coil when the frame is square according to an embodiment of the present invention; Figure 8 Schematic diagram of the three-dimensional structure of the square frame according to an embodiment of the present invention; Figure 9 For Figure 8 Another perspective three-dimensional structure diagram; Figure 10 For Figure 8 Front view; Figure 11 ForFigure 8 Left view.

[0036] Icons: 11. First frame; 12. Second frame; 13. Winding groove; 131. Opening; 132. Arc-shaped side wall; 14. Sealing plate; 2. Winding coil; 21. Transverse bending section; 22. Longitudinal acting section; 3. Central particle beam channel. Specific embodiments

[0037] In order to more clearly understand the above objects, features, and advantages of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Specific embodiments: As Figure 1 shown, in the prior art, the coil winding method of the quadrupole magnet is as Figure 1 shown, where its longitudinal acting sections 22 are closely arranged adjacent to the edge of the frame, resulting in a serious compression of the winding space of the transverse bending section 21. Specifically, due to the too small spacing between adjacent longitudinal acting sections 22, the transverse bending section 21 is forced to adopt multiple acute bends (such as right angles or acute angles), and the bending radius usually needs to reach more than 3 times the thickness of the strip. Such acute bends not only cause stress concentration inside the superconducting material, leading to microcracks or even fractures (the critical current density degradation rate exceeds 30%), but also reduce the winding width of the innermost layer of the coil to less than 50% of the designed value due to the occupied space by the bending allowance, and the number of turns per layer is limited to less than 8 turns, making it difficult to break through the magnetic field gradient of 80 T / m.

[0039] As Figures 3 to 11 shown, this embodiment provides a quadrupole magnet, which includes a first frame 11, a second frame 12, and four independent winding coils 2 wound between the two frames. The first frame 11 and the second frame 12 are symmetric closed frames arranged in parallel at intervals, and are rotationally symmetric around the central particle beam channel 3. The symmetric closed shape of the frame can be a centrosymmetric structure such as a circle, a square, or an ellipse. In this embodiment, a square frame is preferably used, and its geometric symmetry not only facilitates processing and manufacturing, but also ensures a strict complementary distribution of the magnetic field gradient in the orthogonal direction, avoiding magnetic field distortion caused by uneven curvature. Each independent winding coil 2 is made of a high-temperature superconducting material (such as rare-earth barium copper oxide REBCO tape), which exhibits a high critical current density (and zero-resistance characteristics) at the liquid nitrogen temperature range (77K), providing a basis for generating a high-intensity magnetic field in a compact space.

[0040] As Figures 4 to 7As shown, each independent winding coil 2 includes two transverse bending segments 21 and two longitudinal acting segments 22. The transverse bending segments 21 are wound along the edges of the frame. For example, between the upper edge of the first frame 11 and the left side edge, the two adjacent edges of the first frame 11 are wound by a single large-curvature bend (bending radius ≥ 10 mm). This extended winding path significantly increases the straight-line length of the bending segment, making the stress distribution of the superconducting tape more uniform at the bending point, thus reducing the critical current degradation rate to less than 20% of that of the traditional acute-angle bend. The longitudinal acting segments 22 are bridged between the transverse bending segments 21 and extend along the axial direction of the central particle beam channel 3, directly acting on the particle beam to generate a quadrupole magnetic field. Their arrangement is precisely designed: the two longitudinal acting segments 22 of the same coil are respectively located at two adjacent edges of the square frame (such as the upper edge and the right edge of coil A), and the longitudinal acting segments 22 of two other different coils (such as coil B and coil C) are filled in the interval space formed between them. Through the staggered layout, the superposition and complementarity of the magnetic field components are realized. For example, the longitudinal acting segment 22 of coil B extends along the upper edge and the left side edge, and the longitudinal acting segment 22 of coil C extends along the lower edge and the right side edge, forming a complementary magnetic field distribution. This design not only maximizes the use of the space at the frame edge, but also increases the single-layer winding turns to more than 6 turns.

[0041] The longitudinal acting segments 22 of the four independent winding coils 2 are respectively arranged along the four edges of the square frame, and two longitudinal acting segments 22 belonging to different coils are correspondingly arranged on each edge. For example, one longitudinal acting segment 22 of coil A and coil B is distributed on the upper side, and the current directions of the two are the same; one longitudinal acting segment 22 of coil C and coil D is distributed on the lower side, and the current direction is the same as that on the upper side. The left and right sides are the same, but the current directions are opposite. Through this symmetrical arrangement of the geometric position and current direction of the opposite sides, a strictly symmetrical quadrupole magnetic field distribution is formed in the central particle beam channel 3. This design not only suppresses the beam divergence caused by the current path deviation, but also increases the magnetic field gradient in the central region to more than 150 T / m through the magnetic field superposition of multiple coils in the interval space, while controlling the uniformity error within 3%, meeting the millimeter-level precision requirements for beam target area positioning in proton therapy.

[0042] Furthermore, as Figures 8 to 11As shown, each edge of the first frame 11 and the second frame 12 is provided with a winding groove 13. There are a total of four winding grooves 13 in each frame, including two inner-layer winding grooves 13 and two outer-layer winding grooves 13, which are respectively arranged at the inner edge and the outer edge of the edge. The inner-layer winding groove 13 is located inside two adjacent edges of the square frame (for example, the inner edges of the upper edge and the right edge), close to the central particle beam channel 3; the outer-layer winding groove 13 is located outside the other two adjacent edges (for example, the outer edges of the upper edge and the left edge), far from the beam channel. The contour of the winding groove 13 is precisely adapted to the geometric shape of the transverse bending section 21: the width of its U-shaped cross-section is slightly larger than the width of the superconducting tape (for example, when the tape width is 4 mm, the groove width is 4.8 mm), the depth is, and the inner side wall is a smooth arc, so as to ensure uniform force after the transverse bending section 21 is embedded and avoid damage to the tape edge caused by friction of the groove wall.

[0043] An opening 131 is provided on one side of the winding groove 13 facing the opposite frame. The axis of the opening 131 is strictly parallel to the axial direction of the central particle beam channel 3, and the width matches the cross-section of the winding groove 13. Through the design of the opening 131, the longitudinal acting section 22 extends from the winding groove 13 of one frame to the corresponding groove of the opposite frame. For example, the longitudinal acting section 22 of coil A extends from the opening 131 of the winding groove 13 on the upper edge of the first frame 11 to the winding groove 13 on the upper edge of the second frame 12, and the straightness deviation of its extension path is controlled within ±0.1 mm to ensure the axial symmetry of the magnetic field distribution.

[0044] Isolation design of the layered winding groove 13 The distance between the inner-layer winding groove 13 and the outer-layer winding groove 13 is 10 mm (set according to the frame thickness and winding requirements). Physical isolation is used to prevent the transverse bending sections 21 of different coils from contacting. Only the transverse bending section 21 of a single coil is wound in each winding groove 13, and an insulating material (such as polyimide film) is filled between the grooves to further block electromagnetic interference.

[0045] Plane compensation of the inclined winding groove 13 As Figure 4 and Figure 8 shown, the winding groove 13 at the opening 131 is inclined relative to the edge of the square frame, and the inclination angle is calculated from the frame thickness and the distance between the inner and outer-layer winding grooves 13. The inclined design makes the longitudinal acting sections 22 extending in the openings 131 of the inner-layer and outer-layer winding grooves 13 on the same edge of the same frame be in the same plane, and this plane is parallel to the axis of the central particle beam channel 3 ( Figure 8 ). For example, the extension path of the longitudinal acting section 22 of the inner-layer winding groove 13 inclines downward by 15°, and the path of the outer-layer winding groove 13 inclines upward by 15°. After they are cross-connected, they are in the same horizontal plane, eliminating the height difference caused by the frame thickness and ensuring that the magnetic field gradient direction is strictly distributed along the axial direction.

[0046] The arc-shaped side wall 132 is limited by the sealing plate 14 As Figure 3 shown, the side wall at the bending part of the winding groove 13 is designed to be arc-shaped (radius ≥ 10 mm), smoothly transitioning the bending path of the horizontal bending section 21, and avoiding stress concentration caused by acute-angle bending. For example, the horizontal bending section 21 naturally turns along the arc-shaped side wall 132 at the bending part, and the bending radius is increased to more than 3 times that of the traditional design, and the critical current degradation rate ≤ 5%. The frame further includes a sealing plate 14, which is fixed to the opening 131 side of the winding groove 13 by bolts, and a limiting protrusion (height 1 mm) is provided on its inner side, which matches the U-shaped contour of the winding groove 13. After the horizontal bending section 21 is embedded, the displacement amount ≤ 0.2 mm. The material of the sealing plate 14 is G10 fiberglass, and the surface is covered with a polytetrafluoroethylene coating (friction coefficient ≤ 0.1), which not only realizes the sealing of the groove body (dust-proof and moisture-proof), but also ensures the winding stability through the limiting structure, and adapts to the high-frequency vibration environment of medical equipment (such as the rotation condition of the proton therapy gantry).

[0047] The quadrupole magnet in this embodiment is used in a particle accelerator in the medical field (such as a proton therapy system), and its core function is to focus and guide a charged particle beam (such as a proton beam). The specific working principle is as follows: Generation of the quadrupole magnetic field Through the symmetric arrangement and current direction control of four independent winding coils 2, a strictly complementary quadrupole magnetic field is generated in the central particle beam channel 3. Taking a square frame as an example: Current direction rule: The current directions of the longitudinal action segments 22 on adjacent sides are opposite, forming a magnetic field gradient distribution in the orthogonal direction.

[0048] Magnetic field gradient effect: When the particle beam passes through the magnetic field, the particles with lateral offset are affected by the magnetic field gradient force, thereby realizing the focusing of the beam and the suppression of the divergence angle.

[0049] Coil layout and magnetic field superposition Cooperative arrangement of the longitudinal action segments 22: The two longitudinal action segments 22 of the same coil are placed on adjacent sides (such as the upper side and the right side), and the magnetic field components generated by them are superimposed in the central region, enhancing the local magnetic field intensity; Effect of filling the interval space: The action segments of other coils are filled in the interval space. Through the complementarity of the magnetic field components of multiple coils, the magnetic field blind area is eliminated, ensuring a linear gradient distribution.

[0050] Guarantee of magnetic field accuracy by structural innovation Guiding and isolation of the winding groove 13: The physical isolation design of the inner and outer winding grooves 13 avoids the cross of the current paths of different coils and suppresses electromagnetic coupling (coupling degree ≤ 5%); Planarity consistency of the inclined opening 131: Through the inclined setting of the winding groove 13, it is ensured that the longitudinal acting section 22 is in the same plane after being bridged, and this plane is parallel to the axis of the beam channel, avoiding the inclination of the magnetic field direction caused by structural misalignment; Stability control of the sealing plate 14: The sealing plate 14 restricts the displacement of the transverse bending section 21 through the limiting structure (displacement ≤ 0.2 mm under vibration), ensuring the stability of the magnetic field distribution during the long-term operation of the coil.

[0051] Energy efficiency advantages of high-temperature superconducting materials High-temperature superconducting coils (such as REBCO tapes) achieve zero-resistance operation at the liquid nitrogen temperature range (77 K), and the magnetic field generation efficiency is increased to more than 3 times that of conventional conductors. Combining with the single large-curvature bending process (bending radius ≥ 10 mm), its critical current degradation rate ≤ 5%, and it can still maintain the consistency of magnetic field output under the intermittent operation mode of medical equipment (such as fractionated proton irradiation).

[0052] Example of the work process (proton therapy scenario) Beam incidence: The proton beam is injected from the accelerator into the central particle beam channel 3; Magnetic field focusing: The quadrupole magnetic field gradient force acts on the proton beam, and the laterally offset protons converge towards the center of the channel, and the divergence angle is compressed to less than 0.1 milliradians; Target area positioning: The focused beam is guided by subsequent magnets and accurately irradiates the tumor target area (positioning error ≤ 1 mm).

[0053] In this embodiment, through the symmetric frame, extended winding path and layered groove design, in the medical-grade miniaturization scenario, high-density layout of superconducting coils, high-precision magnetic field control and high-reliability operation are realized, providing core technical support for precise radiotherapy.

[0054] The above are all the preferred embodiments of this application. It does not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of this application should be covered within the protection scope of this application.

Claims

1. A quadrupole magnet, comprising a first frame, a second frame, and four independent winding coils wound between the two frames, characterized in that: The first frame and the second frame are symmetric closed frames, arranged in parallel and at intervals, and are rotationally symmetric about a particle beam channel located at the center of the two frames; Each independent winding coil includes: Two transverse bending segments, which are respectively extended and wound and fixed to the corresponding side portions of the first frame and the second frame; Two longitudinal acting segments, which are bridged between the transverse bending segments and extend along the axial direction of the central particle beam channel for generating a quadrupole magnetic field; Wherein, an interval space is formed between the two longitudinal acting segments of the same independent winding coil, and at least one longitudinal acting segment of another independent winding coil is arranged in the interval space, so that the geometric length of the transverse bending segment is extended by increasing the extension path.

2. The quadrupole magnet according to claim 1, characterized in that The symmetric closed frame is a square frame; The longitudinal acting segments of the four independent winding coils are respectively arranged along the four side portions of the square frame, and two longitudinal acting segments are correspondingly arranged on each side portion, and the two longitudinal acting segments belong to different independent winding coils; The longitudinal acting segments on the opposite side portions are symmetrically arranged in terms of geometric position and current direction to generate a symmetric quadrupole magnetic field in the central particle beam channel.

3. The quadrupole magnet according to claim 2, characterized in that, The two longitudinal acting segments of each independent winding coil are respectively arranged on two adjacent side portions of the square frame; In the interval space between the two longitudinal acting segments of the same independent winding coil, the longitudinal acting segments of two other different independent winding coils are arranged.

4. The quadrupole magnet according to claim 3, characterized in that Both the first frame and the second frame are provided with winding grooves, and the contour of the winding grooves adapts to the winding path of the transverse bending segments for constraining the extension direction of the transverse bending segments and expanding the bending space; One side of the winding groove facing the opposite frame is provided with an opening, and the axis of the opening is parallel to the axial direction of the central particle beam channel for extending the longitudinal acting segment from one frame to the opposite frame.

5. The quadrupole magnet according to claim 4, characterized in that Each side portion of the first frame and the second frame is provided with winding grooves, and there are a total of four winding grooves in each frame, including two inner-layer winding grooves and two outer-layer winding grooves; The inner-layer winding grooves are arranged at the inner edges of two adjacent side portions of the square frame, and the outer-layer winding grooves are arranged at the outer edges of the other two adjacent side portions; Only one transverse bending segment of an independent winding coil is wound in each winding groove, so that the transverse bending segments in the inner-layer winding grooves and the outer-layer winding grooves are isolated from each other.

6. The quadrupole magnet according to claim 5, characterized in that The winding groove at the opening is inclined with respect to the side portion of the square frame, and the inclination angle is adapted to the thickness of the frame and the distance between the inner-layer and outer-layer winding grooves; The inclined setting enables the longitudinal acting segments extending in the openings of the inner-layer winding groove and the outer-layer winding groove on the same frame side portion to be in the same plane, and the plane is parallel to the axis of the central particle beam channel.

7. The quadrupole magnet according to claim 5, characterized in that, The frame further includes a sealing plate which covers the opening side of the winding groove for closing the groove body and limiting the lateral bending section.

8. The quadrupole magnet according to claim 5, characterized in that, The side wall at the bending part of the winding groove is an arc-shaped side wall, which smoothly transitions the bending path of the lateral bending section.

9. The quadrupole magnet according to any one of claims 1 to 8, characterized in that, The winding coil is a high-temperature superconducting coil.

10. A particle accelerator, characterized in that, Comprising a quadrupole magnet according to any one of claims 1 to 9, the quadrupole magnet being used for focusing and guiding a particle beam.

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