Superconducting magnet device and cyclotron accelerator

Abstract

The present invention relates to a superconducting magnet device and a cyclotron accelerator, which can improve access to internal equipment. The superconducting magnet device (10) includes: a superconducting coil; and a hollow cylindrical cryostat (20) having an outer peripheral wall (22) and an inner peripheral wall (23) connected to each other to define an annular vacuum region in which the superconducting coil is arranged. The cryostat (20) has a tubular partition wall (40) connecting the outer peripheral wall (22) and the inner peripheral wall (23), and the tubular partition wall (40) forms a cavity (42) on its inner side that is separated from the vacuum region by the tubular partition wall (40). The outer peripheral wall (22) has an opening (44) that is wide in the circumferential direction of the cryostat (20), and the opening (44) is connected to the hollow portion (24) of the cryostat that is radially inward of the inner peripheral wall (23) through the cavity (42).

Description

Technical Field

[0001] This application claims the benefit of priority based on Japanese Patent Application No. 2021-065751, filed on April 8, 2021. The entire contents of this Japanese patent application are incorporated herein by reference.

[0002] The present invention relates to a superconducting magnet device and a cyclotron accelerator. Background Art

[0003] Conventionally, there is known a superconducting magnet device including a toroidal superconducting coil and a hollow cylindrical vacuum container accommodating the superconducting coil. The device is used in various high magnetic field utilizing devices such as a cyclotron.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-43117

[0005] In such superconducting magnet devices, a hollow portion radially inwardly of the vacuum vessel often forms an enclosed space surrounded by the vacuum vessel and other components, with associated equipment located within this enclosed space. During the use of superconducting magnet devices, these internal devices may require maintenance such as inspection and replacement by personnel. However, adequate consideration has not always been given to ensuring access to the enclosed space from outside the vacuum vessel, leaving room for improvement. Summary of the Invention

[0006] One of the exemplary objects of one embodiment of the present invention is to provide a superconducting magnet apparatus capable of improving access to internal equipment.

[0007] According to one embodiment of the present invention, a superconducting magnet device includes: a superconducting coil; and a hollow cylindrical cryostat having an outer peripheral wall and an inner peripheral wall connected to each other to define a vacuum region in which the superconducting coil is disposed. The cryostat includes a tubular partition connecting the outer peripheral wall and the inner peripheral wall, the tubular partition forming a cavity within the cavity that is separated from the vacuum region by the tubular partition. The outer peripheral wall includes an opening extending wide in the circumferential direction of the cryostat, and the opening communicates with a hollow portion of the cryostat located radially inward of the inner peripheral wall through the cavity.

[0008] According to one embodiment of the present invention, a cyclotron includes: the above-mentioned superconducting magnet device; an acceleration section arranged in the hollow portion of the cryostat, which accelerates charged particles while causing them to spiral around; and an extraction section extending through the cavity toward the opening portion and extracting the charged particles accelerated by the acceleration section.

[0009] Effects of the Invention

[0010] According to the present invention, it is possible to provide a superconducting magnet device capable of improving access to internal equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a diagram schematically showing an example of a cyclotron according to the embodiment.

[0012] Figure 2 It indicates schematically Figure 1 A cross-sectional view of the cyclotron taken along line XX is shown.

[0013] Figure 3 It indicates schematically Figure 1 A cross-sectional view of the cyclotron taken along line YY is shown.

[0014] Figure 4 It is a perspective view schematically showing the appearance of a superconducting magnet device according to the embodiment.

[0015] Figure 5 It is a front view schematically showing an opening portion according to the embodiment.

[0016] Explanation of symbols

[0017] 10-superconducting magnet device, 12-superconducting coil, 20-cryostat, 21-vacuum region, 22-outer peripheral wall, 23-inner peripheral wall, 24-cryostat hollow portion, 40-tubular partition wall, 40a-inner surface, 42-cavity, 44-opening, 46-opening flange, 46a-flange surface, 48-vacuum sealing component, 100-cyclotron, 110-acceleration portion, 120-extraction portion. DETAILED DESCRIPTION

[0018] Hereinafter, the method for implementing the present invention will be described in detail with reference to the accompanying drawings. In the description and the drawings, the same or equivalent components, parts, and processes are marked with the same symbols, and repeated descriptions are appropriately omitted. The proportions and shapes of the various parts shown in the drawings are appropriately set for the convenience of explanation and are not to be interpreted as limiting unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention in any way. All the features or their combinations described in the embodiments are not necessarily the essence of the invention.

[0019] Figure 1 It is a diagram schematically showing an example of a cyclotron according to the embodiment. Figure 2 It indicates schematically Figure 1 A cross-sectional view of the cyclotron along line XX is shown. Figure 3 It indicates schematically Figure 1 The cross-sectional view of the cyclotron shown is taken along the YY line.

[0020] like Figure 1As shown, the cyclotron 100 is a circular accelerator that accelerates charged particles and outputs a charged particle beam 102. Charged particles include, for example, protons, heavy particles (heavy ions), and electrons. The cyclotron 100 is used, for example, as an accelerator for charged particle beam therapy. Furthermore, the cyclotron 100 can be used in other devices utilizing charged particles.

[0021] The cyclotron 100 includes a superconducting magnet device 10, an acceleration unit 110, and an extraction unit 120. Figure 1 In FIG. 1 , for ease of understanding, the iron core provided in the cyclotron 100 is omitted from illustration, and several internal components arranged in a closed space surrounded by the iron core are schematically shown.

[0022] If reference Figures 1 to 3 The superconducting magnet device 10 includes a pair of superconducting coils 12 and a cryostat 20 that houses these two superconducting coils 12. The two superconducting coils 12 have annular shapes of equal diameter centered on a central axis C and are spaced apart from each other in the axial direction (direction of the central axis C). The cryostat 20 is an airtight container that provides the superconducting coils 12 with an ultra-low temperature vacuum environment that allows them to enter a superconducting state.

[0023] The cryostat 20 has a hollow cylindrical shape arranged coaxially with the central axis C, and has an outer peripheral wall 22 and an inner peripheral wall 23 connected to each other so as to define a vacuum region 21 in which the superconducting coil 12 is arranged. A magnetic field is generated in the axial direction by the superconducting coil 12 in a cryostat hollow portion 24 located radially inward of the inner peripheral wall 23 of the cryostat 20.

[0024] like Figure 3 As shown, in cryostat 20, two heat shields 14 are provided corresponding to each pair of superconducting coils 12. In order to reduce heat intrusion into each superconducting coil 12, heat shields 14 are arranged in vacuum region 21 so as to surround each superconducting coil 12.

[0025] And, as Figure 2 As shown, the cyclotron 100 includes a pair of magnetic poles 26 disposed in the cryostat hollow portion 24 and a yoke 28 that forms a magnetic circuit together with the magnetic poles 26. The two magnetic poles 26 are respectively disposed inside the corresponding superconducting coils 12, forming a superconducting electromagnet with an iron core. The yoke 28 surrounds the cryostat 20 and the cryostat hollow portion 24, and forms a closed space that isolates the cryostat hollow portion 24 from the outside. The accelerator 110 is disposed in the gap 30 between the magnetic poles 26, which is part of the closed space. Figure 2 Illustration omitted.

[0026] The cryostat 20 is provided with a cryogenic refrigerator 32 for cooling the superconducting coil 12. The cryogenic refrigerator 32 includes a compressor (not shown) for a refrigerant gas (e.g., helium) and an expander, also known as a cold head. The compressor and expander constitute a refrigeration cycle of the cryogenic refrigerator 32, thereby providing ultra-low temperature cooling. The cold head of the cryogenic refrigerator 32 is connected to (or directly mounted on) the superconducting coil 12 via an appropriate heat transfer component and is thermally coupled to the superconducting coil 12. In other words, in this embodiment, the superconducting coil 12 is not cooled by immersing it in a cryogenic refrigerant such as liquid helium. Instead, the cryogenic refrigerator 32 cools the superconducting coil 12 through conductive cooling.

[0027] If the cryogenic refrigerator 32 is a two-stage type, the heat shield 14 can be cooled to a first cooling temperature, e.g., 30K to 80K, during the high-stage cooling phase of the cold head. The superconducting coil 12 can be cooled to a second cooling temperature, e.g., 3K to 20K, lower than the first cooling temperature, during the low-stage cooling phase of the cold head. As an example, the cryogenic refrigerator 32 is a Gifford-McMahon (GM) refrigerator, but may also be a pulse tube refrigerator, a Stirling refrigerator, or another type of cryogenic refrigerator. While multiple cryogenic refrigerators 32 are typically provided in the cryostat 20, only one is shown in the figure for simplicity.

[0028] In this embodiment, the cryostat 20 has a tubular partition wall 40 connecting the outer peripheral wall 22 and the inner peripheral wall 23. The tubular partition wall 40 defines a cavity 42 on its inner side, which is separated from the vacuum region 21 by the tubular partition wall 40. The cavity 42 extends from the outer peripheral wall 22 to the inner peripheral wall 23. The outer peripheral wall 22 has an opening 44 extending in the circumferential direction of the cryostat 20. The opening 44 communicates with the cryostat hollow portion 24 located radially inward of the inner peripheral wall 23 through the cavity 42.

[0029] In addition, the cryostat 20 may be provided with related components such as a current terminal portion for supplying power from an external power source to the superconducting coil 12, a load support body for supporting the superconducting coil 12 on the cryostat 20, and a measurement device for a charged particle beam. However, for the sake of simplicity, further description and illustration are omitted in this specification.

[0030] like Figure 1 As shown, the accelerator 110 is disposed within the cryostat hollow portion 24 and is configured to accelerate charged particles while causing them to spiral around. The accelerator 110 includes an accelerating electrode 112, also known as a D-shaped electrode. Charged particles are supplied to the center of the accelerator 110 from a charged particle source (not shown). The charged particles are accelerated along a spiral acceleration track 114 by the electric field generated by the accelerating electrode 112 and the axial magnetic field generated by the superconducting coil 12.

[0031] The extraction unit 120 is configured to extract the charged particles accelerated by the accelerator 110 from the accelerator 110 to the outside of the cyclotron 100. The charged particles extracted from the accelerator 110 by the extraction unit 120 are extracted from the cryostat hollow portion 24 through the cavity 42 and the opening 44.

[0032] As an exemplary structure, the extraction unit 120 includes a deflection plate 122, a magnetic channel 124 disposed downstream of the deflection plate 122, and a beam extraction duct 126 disposed downstream of the magnetic channel 124. Charged particles traveling on the outermost periphery of the acceleration track 114 are deflected toward an extraction track 128 by the deflection plate 122 and the magnetic channel 124. Charged particles traveling on the extraction track 128 are extracted to the outside of the cyclotron 100 through the beam extraction duct 126. The charged particle beam 102 thus extracted travels to the beam irradiation unit via a beam transport system (not shown).

[0033] At least a portion of the extraction portion 120, such as a beam extraction pipe 126, is housed in the cavity 42. The beam extraction pipe 126 extends from the cryostat hollow portion 24 through the cavity 42 and the opening 44 to the outside of the cryostat 20. Figure 1 As shown, the beam extraction pipe 126 extends in a plane perpendicular to the axial direction in a direction inclined relative to the radial direction of the cryostat 20. Therefore, the tubular partition wall 40 extends in the inclined direction in which the extraction portion 120 extends and connects the outer peripheral wall 22 to the inner peripheral wall 23.

[0034] like Figure 3 As shown, the opening portion 44 having a wide width in the circumferential direction is axially ( Figure 3 The tubular partition wall 40 is disposed between the pair of superconducting coils 12 in the vertical direction (in the middle and upper directions). The tubular partition wall 40 passes between the pair of superconducting coils 12 to connect the outer peripheral wall 22 and the inner peripheral wall 23. As described above, since each superconducting coil 12 is surrounded by the heat shield 14, the tubular partition wall 40 is located between the two heat shields 14 surrounding the two superconducting coils 12. In this way, the tubular partition wall 40 can avoid interference with the superconducting coils 12 and the heat shield 14.

[0035] One end of the tubular bulkhead 40 is joined to the outer peripheral wall 22, and the other end of the tubular bulkhead 40 is joined to the inner peripheral wall 23. The tubular bulkhead 40 is joined to the outer peripheral wall 22 and the inner peripheral wall 23 by a suitable joining method such as welding. In this way, the airtightness of the joints between the tubular bulkhead 40, the outer peripheral wall 22, and the inner peripheral wall 23 is ensured.

[0036] The tubular partition wall 40 has at least one flat inner surface 40a facing the cavity 42. In this embodiment, the inner surface 40a corresponds to the lower surface of the tubular partition wall 40. When setting equipment (for example, the deflection plate 122, the magnetic channel 124, the beam extraction pipe 126, etc. as components of the extraction portion 120) in the cavity 42 within the tubular partition wall 40, the flat inner surface 40a can be used as the surface on which the equipment is set. In this way, the equipment can be set more easily than a surface curved like a cylinder. Similarly, the upper surface and side surfaces of the tubular partition wall 40 can also be flat, and these surfaces can also be used as surfaces on which the equipment is set.

[0037] Figure 4 It is a perspective view schematically showing the appearance of a superconducting magnet device according to the embodiment. Figure 5 It is a front view schematically showing the opening 44 according to the embodiment.

[0038] like Figures 3 to 5 As shown, an opening flange 46 is provided on the outer peripheral wall 22. The opening flange 46 has a flange surface 46a that faces radially outward and is flat, and an opening portion 44 that is wide in the circumferential direction is provided on the flange surface 46a. The circumferential width W of the opening portion 44 is greater than the axial height H of the opening portion 44. For example, the width W can be 2 to 10 times the height H. The opening flange 46 is a circumferentially elongated square flange, prepared as a component separate from the outer peripheral wall 22, and fixed to the outer peripheral wall 22 at the junction between the outer peripheral wall 22 and the tubular partition wall 40. In this way, the opening portion 44 becomes the entrance from the outside to the cavity 42 in the tubular partition wall 40.

[0039] Furthermore, a vacuum seal 48 is attached to the flange surface 46a so as to surround the circumferentially wide opening 44. A receiving groove for receiving the vacuum seal 48 is formed in the flange surface 46a so as to surround the opening 44, and the vacuum seal 48 can also be accommodated in this receiving groove. In this manner, when a mating flange 50 (e.g., a flange of another vacuum piping) is connected to the opening flange 46, the vacuum seal 48 is sandwiched between the two flanges, maintaining internal airtightness.

[0040] The vacuum seal 48 can be, for example, a metal seal (a metal O-ring). In the case of a seal made of synthetic resin, since the vacuum seal 48 is positioned near the extraction portion 120, there is concern that the vacuum seal 48 may be affected by radiation from the charged particle beam extracted through the extraction portion 120 (e.g., degradation due to radiation). By using a metal seal as the vacuum seal 48, these adverse effects can be mitigated, and the long-term reliability of the vacuum seal can be improved.

[0041] However, in existing cyclotrons, when a component needs to be installed through the cryostat, the typical design is to install a cylindrical through-wall on the cryostat with a minimum internal volume for the component to pass through. Because the through-wall and the component are extremely close or in contact, there is little or no gap between them.

[0042] As mentioned at the beginning of this specification, various related equipment is located in the enclosed space further inside the cryostat, and these equipment may require periodic maintenance. In the superconducting magnet device 10 according to the embodiment, the cavity 42 within the tubular partition wall 40 and the cryostat hollow portion 24 further inside the cryostat 20 are accessible through the circumferentially wide opening 44. Therefore, the superconducting magnet device 10 according to the embodiment improves accessibility from outside the cryostat 20 to the equipment located in the cavity 42 and the cryostat hollow portion 24.

[0043] The present invention has been described above based on embodiments. Those skilled in the art will appreciate that the present invention is not limited to the aforementioned embodiments and that various design changes and modifications are possible, and that such modifications fall within the scope of the present invention. Features described in connection with one embodiment may also be applied to other embodiments. New embodiments created through combination may have the effects of each of the combined embodiments.

[0044] In the above embodiment, only one opening 44 and cavity 42 are provided in the cryostat 20. However, multiple openings 44 and cavities 42 may be provided. These openings 44 and cavities 42 may be provided at different positions around the circumference of the cryostat 20 (e.g., at equal intervals in the circumferential direction). The cyclotron 100 includes at least one lead-out portion 120, and each lead-out portion 120 may extend through a corresponding opening 44 and cavity 42. Furthermore, there may be openings 44 and cavities 42 without a lead-out portion 120.

[0045] The superconducting magnet device 10 can be mounted on a device other than the cyclotron 100. For example, the superconducting magnet device 10 can be mounted on a high-magnetic field utilizing device as a magnetic field source for a high-energy physics system such as a single crystal pulling device, an NMR system, an MRI system, an accelerator, a nuclear fusion system, or other high-magnetic field utilizing device, thereby generating the high magnetic field required by the device.

[0046] The superconducting coils 12 do not necessarily need to be arranged in a pair of upper and lower arrangements within the cryostat 20. Depending on the application and design of the superconducting magnet apparatus 10, the superconducting coils 12 may be arranged in other arrangements. For example, a plurality of superconducting coils 12 may be arranged along the circumference of the cryostat 20 between the outer circumferential wall 22 and the inner circumferential wall 23 of the cryostat 20, and the arrangement may be such that the central axis of each superconducting coil 12 is aligned with the radial direction of the cryostat 20.

[0047] The present invention is described using specific words according to the embodiment, but the embodiment merely represents one aspect of the principle and application of the present invention. In the embodiment, many variations or configuration changes are allowed without departing from the scope of the idea of ​​the present invention specified in the scope of the patent claims.

Claims

1. A superconducting magnet device, characterized in that: have: superconducting coils; and A hollow cylindrical cryostat having an outer peripheral wall and an inner peripheral wall connected to each other to define a vacuum region in which the superconducting coil is arranged. The cryostat has a tubular partition wall connecting the outer peripheral wall and the inner peripheral wall, the tubular partition wall forming a cavity inside thereof that is separated from the vacuum region by the tubular partition wall. The outer peripheral wall has an opening portion that is wide in the circumferential direction of the cryostat. The opening portion communicates with a hollow portion of the cryostat located radially inward of the inner peripheral wall through the cavity.

2. The superconducting magnet device according to claim 1, characterized in that The tubular partition wall has at least one flat inner surface facing the cavity.

3. The superconducting magnet device according to claim 1 or 2, characterized in that: The superconducting magnet device includes a pair of superconducting coils, each of the pair of superconducting coils being composed of the superconducting coil and another superconducting coil disposed in the cryostat at an axial distance from the superconducting coil, and each of the pair of superconducting coils generating a magnetic field in the axial direction of the hollow portion of the cryostat. The opening portion having a wide width in the circumferential direction is arranged between the pair of superconducting coils in the axial direction, and the tubular partition wall connects the outer peripheral wall and the inner peripheral wall through the space between the pair of superconducting coils.

4. The superconducting magnet device according to claim 1 or 2, characterized in that: The circumferential width of the opening is greater than the axial height of the opening.

5. The superconducting magnet device according to claim 1 or 2, characterized in that: The outer peripheral wall is provided with an opening flange having a flange surface having an opening that is wide in the circumferential direction, and the vacuum sealing member is attached to the flange surface so as to surround the opening that is wide in the circumferential direction.

6. A cyclotron, characterized in that: have: The superconducting magnet device according to any one of claims 1 to 5; an accelerating portion, disposed in the hollow portion of the cryostat, for accelerating the charged particles while causing them to spiral around; and The extraction unit extracts the charged particles accelerated by the acceleration unit from the hollow portion of the cryostat through the cavity and the opening.

Images