Superconducting magnet devices and cyclotrons

Abstract

To provide a superconducting magnet device enabling improved access to internal equipment.SOLUTION: A superconducting magnet device 10 includes: a superconducting coil; and a hollow tubular cryostat 20 having an outer peripheral wall 22 and an inner peripheral wall 23 connected to each other so as to define an annular vacuum region where the superconducting coil is disposed. The cryostat 20 has a tubular partition wall 40 connecting the outer peripheral wall 22 and the inner peripheral wall 23, and a cavity 42 partitioned from the vacuum region by the tubular partition wall 40 is formed inside the tubular partition wall 40. The outer peripheral wall 22 has an opening portion 44 wide in the circumferential direction of the cryostat 20, and the opening portion 44 communicates with a cryostat hollow portion 24 radially inside the inner peripheral wall 23 through the cavity 42.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a superconducting magnet device and a cyclotron. [Background technology]

[0002] 2. Description of the Related Art Conventionally, superconducting magnet devices having a circular superconducting coil and a hollow cylindrical vacuum vessel for accommodating the coil have been known and are used in various devices utilizing high magnetic fields, such as cyclotrons. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-43117 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned superconducting magnet device, a closed space surrounded by the vacuum vessel and other members is formed in the hollow part on the radial inner side of the vacuum vessel, and related equipment is often installed in this closed space. During the operation of the superconducting magnet device, the internal equipment may require maintenance work by workers, such as inspection and replacement, but accessibility to the closed space from outside the vacuum vessel is not always fully considered, and there is room for improvement.

[0005] One exemplary object of certain aspects of the present invention is to provide a superconducting magnet device that allows improved access to the internal machinery. [Means for solving the problem]

[0006] According to one aspect 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 has a tubular partition connecting the outer peripheral wall and the inner peripheral wall, and the tubular partition forms a cavity inside the tubular partition that is separated from the vacuum region by the tubular partition. The outer peripheral wall has a wide opening in the circumferential direction of the cryostat, and the opening communicates through the cavity with a hollow portion of the cryostat that is radially inward from the inner peripheral wall.

[0007] According to one aspect of the present invention, a cyclotron includes the above-described superconducting magnet device, an acceleration section disposed in a hollow portion of the cryostat and accelerating charged particles while causing them to orbit in a spiral shape, and an extraction section extending through the cavity to an opening and extracting the charged particles accelerated by the acceleration section. Effect of the Invention

[0008] According to the present invention, it is possible to provide a superconducting magnet apparatus that allows improved access to the internal machinery. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a cyclotron according to an embodiment. [Diagram 2] 2 is a cross-sectional view showing a schematic cross section of the cyclotron shown in FIG. 1 taken along line XX. [Diagram 3] 2 is a cross-sectional view showing a schematic cross section of the cyclotron shown in FIG. 1 taken along line YY. [Figure 4] 1 is a perspective view showing a schematic external view of a superconducting magnet device according to an embodiment; [Diagram 5] FIG. 4 is a front view showing a schematic view of an opening according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processes are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience in order to facilitate the description, and are not to be interpreted as being limiting unless otherwise specified. The embodiments are merely examples, and do not limit the scope of the present invention in any way. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0011] Fig. 1 is a diagram showing an example of a cyclotron according to an embodiment. Fig. 2 is a cross-sectional view showing a cross section of the cyclotron shown in Fig. 1 taken along line XX. Fig. 3 is a cross-sectional view showing a cross section of the cyclotron shown in Fig. 1 taken along line YY.

[0012] As shown in Fig. 1, the cyclotron 100 is a circular accelerator that accelerates charged particles to output a charged particle beam 102. Examples of the charged particles include protons, heavy particles (heavy ions), and electrons. The cyclotron 100 is used, for example, as an accelerator for charged particle beam therapy. The cyclotron 100 may also be used in other charged particle devices.

[0013] Cyclotron 100 includes a superconducting magnet device 10, an acceleration section 110, and an extraction section 120. In order to facilitate understanding, an iron core provided in cyclotron 100 is not shown in Fig. 1, and several internal components arranged in a closed space surrounded by the iron core are shown diagrammatically.

[0014] 1 to 3, a superconducting magnet device 10 includes a pair of superconducting coils 12 and a cryostat 20 that houses the two superconducting coils 12. The two superconducting coils 12 have annular shapes of the same diameter centered on a central axis C, and are spaced apart from each other in the axial direction (the direction of the central axis C). The cryostat 20 is an airtight container that provides the superconducting coils 12 with an extremely low temperature vacuum environment for bringing the superconducting coils 12 into a superconducting state.

[0015] 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. In a cryostat hollow portion 24 radially inward from the inner peripheral wall 23 of the cryostat 20, a magnetic field is generated in the axial direction by the superconducting coil 12.

[0016] 3, the cryostat 20 is provided with two heat shields 14 corresponding to each of the pair of superconducting coils 12. The heat shields 14 are disposed in the vacuum region 21 so as to surround each superconducting coil 12 in order to reduce heat penetration into each superconducting coil 12.

[0017] As shown in Fig. 2, the cyclotron 100 also includes a pair of poles 26 arranged in the cryostat hollow portion 24, and a yoke 28 that constitutes a magnetic circuit together with the poles 26. These two poles 26 are arranged inside the corresponding superconducting coils 12, and constitute superconducting electromagnets with iron cores. The yoke 28 surrounds the cryostat 20 and the cryostat hollow portion 24, making the cryostat hollow portion 24 a closed space isolated from the outside. An acceleration section 110 is arranged in the gap 30 between the poles 26, which is part of this closed space, although not shown in Fig. 2.

[0018] 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 gas) and an expander also called a cold head. The compressor and the expander form a refrigeration cycle of the cryogenic refrigerator 32, thereby providing cryogenic cooling. The cold head of the cryogenic refrigerator 32 is connected (or directly attached) to the superconducting coil 12 via an appropriate heat transfer member, and is thermally coupled to the superconducting coil 12. That is, in this embodiment, the superconducting coil 12 is not cooled by immersing it in a cryogenic refrigerant such as liquid helium, but the cryogenic refrigerator 32 cools the superconducting coil 12 by conduction cooling.

[0019] When the cryocooler 32 is of a two-stage type, the heat shield 14 may be cooled to a first cooling temperature, for example, 30K to 80K, in the cooling stage of the high temperature stage of the cold head, and the superconducting coil 12 may be cooled to a second cooling temperature, for example, 3K to 20K, lower than the first cooling temperature, in the cooling stage of the low temperature stage of the cold head. The cryocooler 32 is, for example, a Gifford-McMahon (GM) cryocooler, but may also be a pulse tube cryocooler, a Stirling cryocooler, or any other type of cryocooler. Typically, multiple cryocoolers 32 are installed in the cryostat 20, but only one is shown in the figure for simplicity.

[0020] In this embodiment, the cryostat 20 has a tubular partition 40 connecting the outer peripheral wall 22 and the inner peripheral wall 23, and the tubular partition 40 forms a cavity 42 inside the tubular partition 40, which is separated from the vacuum region 21 by the tubular partition 40. The cavity 42 penetrates from the outer peripheral wall 22 to the inner peripheral wall 23. The outer peripheral wall 22 has a wide opening 44 in the circumferential direction of the cryostat 20, and the opening 44 communicates with the cryostat hollow portion 24 located radially inward from the inner peripheral wall 23 through the cavity 42.

[0021] The cryostat 20 may be provided with related components such as a current terminal for supplying power from an external power source to the superconducting coil 12, a load support for supporting the superconducting coil 12 on the cryostat 20, and measuring equipment for the charged particle beam, but for the sake of simplicity, further explanation and illustration will be omitted in this document.

[0022] As shown in Fig. 1, the acceleration section 110 is disposed in the cryostat hollow section 24 and is configured to accelerate charged particles while causing them to circulate in a spiral shape. The acceleration section 110 has an acceleration electrode 112 also called a Dee electrode. Charged particles are supplied to the center of the acceleration section 110 from a charged particle source (not shown). The charged particles are accelerated along a spiral acceleration trajectory 114 by an electric field generated by the acceleration electrode 112 and an axial magnetic field generated by the superconducting coil 12.

[0023] The extraction unit 120 is configured to extract the charged particles accelerated in the acceleration unit 110 from the acceleration unit 110 to the outside of the cyclotron 100. The charged particles extracted from the acceleration unit 110 by the extraction unit 120 are extracted from the cryostat hollow portion 24 through the cavity 42 and the opening 44.

[0024] As an exemplary configuration, the extraction unit 120 includes a deflector 122, a magnetic channel 124 disposed downstream of the deflector 122, and a beam extraction duct 126 disposed downstream of the magnetic channel 124. The deflector 122 and the magnetic channel 124 deflect the charged particles moving along the outermost periphery of the acceleration orbit 116 to an extraction orbit 128. The charged particles moving along the extraction orbit 128 are extracted to the outside of the cyclotron 100 through the beam extraction duct 126. The charged particle beam 102 extracted in this manner travels to the beam irradiation unit via a beam transport system (not shown).

[0025] At least a part of the extraction section 120, for example, a beam extraction duct 126, is housed in the cavity 42. The beam extraction duct 126 extends from the cryostat hollow section 24 to the outside of the cryostat 20 through the cavity 42 and the opening 44. As shown in Fig. 1, the beam extraction duct 126 extends in a direction oblique to the radial direction of the cryostat 20 in a plane perpendicular to the axial direction. Thus, the tubular partition 40 extends in a direction oblique to the extension of the extraction section 120, and connects the outer peripheral wall 22 to the inner peripheral wall 23.

[0026] 3, the circumferentially wide opening 44 is disposed between the pair of superconducting coils 12 in the axial direction (the vertical direction in FIG. 3), and the tubular partition 40 passes between the pair of superconducting coils 12 to connect the outer peripheral wall 22 and the inner peripheral wall 23. Since each superconducting coil 12 is surrounded by a thermal shield 14 as described above, the tubular partition 40 is positioned between the two thermal shields 14 surrounding the two superconducting coils 12. In this way, the tubular partition 40 can avoid interference with the superconducting coils 12 and the thermal shield 14.

[0027] One end of the tubular partition wall 40 is joined to the outer peripheral wall 22, and the other end of the tubular partition wall 40 is joined to the inner peripheral wall 23. An appropriate joining method such as welding is used to join the tubular partition wall 40 to the outer peripheral wall 22 and the inner peripheral wall 23, respectively. In this way, airtightness is ensured at the joints between the tubular partition wall 40 and the outer peripheral wall 22 and the inner peripheral wall 23, respectively.

[0028] The tubular partition 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 40. When installing equipment (e.g., equipment that is a component of the extraction section 120, such as the deflector 122, the magnetic channel 124, the beam extraction duct 126, etc.) in the cavity 42 inside the tubular partition 40, the flat inner surface 40a can be used as an installation surface for the equipment. In this way, the equipment can be installed more easily than on a curved surface such as a cylinder. Similarly, the upper surface or side surface of the tubular partition 40 may be flat, and these surfaces may be used as installation surfaces for the equipment.

[0029] Fig. 4 is a perspective view showing a typical appearance of a superconducting magnet device according to the embodiment, and Fig. 5 is a schematic front view showing an opening 44 according to the embodiment.

[0030] As shown in Figs. 3 to 5, the outer peripheral wall 22 is provided with an opening flange 46. The opening flange 46 has a flat flange surface 46a facing radially outward, and a circumferentially wide opening 44 is provided on this flange surface 46a. The circumferential width W of the opening 44 is greater than the axial height H of the opening 44. For example, the width W may be 2 to 10 times the height H. The opening flange 46 is a rectangular flange elongated in the circumferential direction, and is prepared as a separate member from the outer peripheral wall 22 and fixed to the outer peripheral wall 22 at the joint between the outer peripheral wall 22 and the tubular partition wall 40. Thus, the opening 44 becomes an entrance from the outside to the cavity 42 in the tubular partition wall 40.

[0031] Furthermore, the vacuum sealing member 48 is attached to the flange surface 46a so as to surround the circumferentially wide opening 44. A receiving groove for receiving the vacuum sealing member 48 may be formed in the flange surface 46a so as to surround the opening 44, and the vacuum sealing member 48 may be housed in this receiving groove. In this way, when the mating flange 50 (e.g., a flange portion of another vacuum pipe) is connected to the opening flange 46, the vacuum sealing member 48 is sandwiched between the two flanges, thereby maintaining internal airtightness.

[0032] The vacuum sealing member 48 may be, for example, a metal seal (a metal O-ring). In the case of a sealing member made of synthetic resin, the vacuum sealing member 48 is disposed near the draw-out portion 120, and so there is concern about the influence of radiation (e.g., deterioration due to radiation) on the vacuum sealing member 48 caused by the charged particle beam drawn out through the draw-out portion 120. In contrast, by employing a metal seal as the vacuum sealing member 48, such adverse effects can be reduced and the long-term reliability of the vacuum seal can be improved.

[0033] In existing cyclotrons, when a component needs to be installed through the cryostat, the cryostat is typically designed with a cylindrical through-wall with a minimal internal volume to allow the component to pass through, and the through-wall and the component are in close proximity or in contact with each other, with little or no clearance between them.

[0034] As mentioned at the beginning of this document, various related devices may be arranged in the closed space inside the cryostat, and maintenance work on these devices may be required from time to time. In the superconducting magnet device 10 according to the embodiment, the cavity 42 in the tubular partition 40 and the cryostat hollow portion 24 inside the cryostat 20 can be accessed 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 devices arranged in the cavity 42 and the cryostat hollow portion 24.

[0035] The present invention has been described above based on examples. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, that various design changes are possible, that various modifications are possible, and that such modifications are also within the scope of the present invention. Various features described in relation to one embodiment can also be applied to other embodiments. A new embodiment resulting from a combination has the combined effects of each of the combined embodiments.

[0036] In the embodiment described above, the cryostat 20 is provided with only one opening 44 and cavity 42, but a plurality of openings 44 and cavities 42 may be provided. These openings 44 and cavities 42 may be provided at different positions in the circumferential direction of the cryostat 20 (e.g., at equal intervals in the circumferential direction). The cyclotron 100 may include at least one extraction section 120, and each extraction section 120 may extend through a corresponding opening 44 and cavity 42. Also, there may be an opening 44 and a cavity 42 without an extraction section 120.

[0037] The superconducting magnet device 10 may be mounted on devices other than the cyclotron 100. For example, the superconducting magnet device 10 may be mounted on high magnetic field devices as a magnetic field source for high energy physics systems such as single crystal pulling devices, NMR systems, MRI systems, accelerators, and nuclear fusion systems, or other high magnetic field devices, and may generate a high magnetic field required by the devices.

[0038] It is not essential that the superconducting coils 12 are arranged in pairs, one above the other, in the cryostat 20, and the superconducting coils 12 may be arranged in other ways depending on the application and design of the superconducting magnet device 10. For example, a plurality of superconducting coils 12 may be arranged in the circumferential direction of the cryostat 20 between the outer peripheral wall 22 and the inner peripheral wall 23 of the cryostat 20, with the central axis of each superconducting coil 12 coinciding with the radial direction of the cryostat 20.

[0039] The present invention has been described using specific terms based on the embodiments, but the embodiments merely show one aspect of the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments without departing from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0040] 10 superconducting magnet device, 12 superconducting coil, 20 cryostat, 21 vacuum region, 22 outer peripheral wall, 23 inner peripheral wall, 24 cryostat hollow section, 40 tubular partition, 40a inner surface, 42 cavity, 44 opening, 46 opening flange, 46a flange surface, 48 vacuum sealing member, 100 cyclotron, 110 acceleration section, 120 extraction section.

Claims

1. A superconducting coil; 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 has a tubular partition wall connecting the outer peripheral wall and the inner peripheral wall, the tubular partition wall forming a cavity therein that is separated from the vacuum region by the tubular partition wall, a hollow portion of the cryostat radially inward from the inner wall, the hollow portion being connected through the cavity to the hollow portion of the cryostat radially inward from the inner wall, the hollow portion being connected through the cavity to the outer wall, the hollow portion being connected through the cavity to the inner wall, the hollow portion being connected through the cavity to the cryostat radially inward from the inner wall, the hollow portion being connected through the cavity to the inner wall, the hollow portion being connected through the cavity to the hollow portion of the cryostat ...

2. 2. The superconducting magnet apparatus of claim 1, wherein said tubular septum has at least one flat inner surface facing said cavity.

3. a pair of superconducting coils, each of which generates an axial magnetic field in a hollow portion of the cryostat, the pair of superconducting coils including the superconducting coil and another superconducting coil disposed in the cryostat and spaced apart from the superconducting coil in the axial direction; 3. The superconducting magnet device according to claim 1, wherein the circumferentially wide opening is disposed between the pair of superconducting coils in the axial direction, and the tubular partition passes between the pair of superconducting coils to connect the outer peripheral wall and the inner peripheral wall.

4. 4. The superconducting magnet apparatus according to claim 1, wherein the circumferential width of the opening is greater than the axial height of the opening.

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

6. A superconducting magnet device according to any one of claims 1 to 5, an acceleration unit disposed in a hollow portion of the cryostat and accelerating the charged particles while causing them to circulate in a spiral shape; an extraction section that extracts the charged particles accelerated by the acceleration section from the hollow section of the cryostat through the cavity and the opening.

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