Superconducting magnet device

Abstract

A superconducting magnet device (10) comprises: a vacuum container (12); a superconducting coil which is disposed in the vacuum container (12); a plurality of cold heads (32) which are provided to the vacuum container (12) and which cool the superconducting coil; a plurality of compressors (34) which are disposed outside the vacuum container (12); a plurality of working gas pipes (36) which connect the plurality of cold heads (32) to the plurality of compressors (34); and a pipe support (40) which is disposed outside the vacuum container (12) and closer to the vacuum container (12) than the plurality of compressors (34) and which supports the plurality of working gas pipes (36). The plurality of working gas pipes (36) are routed along individual routes from the plurality of cold heads (32) to the pipe support (40) and are routed along a common route from the pipe support (40) toward the plurality of compressors (34).

Description

Superconducting magnet device

[0001] The present invention relates to a superconducting magnet device.

[0002] Generally, a superconducting magnet device includes a superconducting coil and a vacuum vessel that houses the superconducting coil. The superconducting magnet device also includes a cryogenic refrigerator for cooling the superconducting coil to cryogenic temperatures.

[0003] Japanese Patent Application Laid-Open No. 2013-258116

[0004] A cryogenic refrigerator typically includes a cold head and a compressor for supplying and discharging a working gas, such as helium gas, to the cold head. The cold head is installed in the vacuum vessel of a superconducting magnet device, and the compressor is located outside the vacuum vessel. The cold head and the compressor are connected by a working gas pipe to circulate the working gas between them. The working gas pipe may be fixed to the outer surface of the vacuum vessel. To provide the desired cooling performance, multiple cryogenic refrigerators can be installed in one superconducting magnet device. In this case, the number of working gas pipes increases according to the number of installed cryogenic refrigerators. However, as superconducting magnet devices become smaller through recent research and development, the surface area of ​​the vacuum vessel that can be used to fix the working gas pipes tends to become smaller.

[0005] An exemplary object of an embodiment of the present invention is to provide a superconducting magnet apparatus that allows for organized routing of working gas piping for a cryogenic refrigerator.

[0006] According to one aspect of the present invention, a superconducting magnet apparatus includes a vacuum vessel, a superconducting coil disposed within the vacuum vessel, a plurality of cold heads installed in the vacuum vessel for cooling the superconducting coil, a plurality of compressors disposed outside the vacuum vessel, a plurality of working gas pipes connecting the plurality of cold heads to the plurality of compressors, and a piping support disposed outside the vacuum vessel and closer to the vacuum vessel than the plurality of compressors and supporting the plurality of working gas pipes. The plurality of working gas pipes are routed along individual routes from the plurality of cold heads to the piping support, and further routed along a common route from the piping support to the plurality of compressors.

[0007] According to the present invention, it is possible to provide a superconducting magnet device that enables the routing of the working gas piping of the cryogenic refrigerator in an organized manner.

[0008] Fig. 1 is a schematic diagram showing a superconducting magnet device according to an embodiment. Fig. 2 is a cross-sectional view showing the internal structure of the superconducting magnet device shown in Fig. 1. Fig. 3 is a view taken along the line AA of the superconducting magnet device shown in Fig. 1. Fig. 4 is a schematic diagram showing exemplary piping arrangement according to an embodiment.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description and drawings, identical or equivalent components, parts, and processes are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience to facilitate explanation, and should not be interpreted as 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.

[0010] Fig. 1 is a schematic perspective view showing a superconducting magnet device 10 according to an embodiment. Fig. 2 is a cross-sectional view showing the internal structure of the superconducting magnet device 10 shown in Fig. 1. Fig. 2 shows a cross section including the central axis C of the superconducting magnet device 10. Fig. 3 is a view taken along the arrows A-A of the superconducting magnet device 10 shown in Fig. 1. Fig. 3 shows the bottom surface of the superconducting magnet device 10 when viewed from below in the direction of the central axis C.

[0011] As an exemplary application, the superconducting magnet device 10 may be mounted on a superconducting accelerator such as a superconducting cyclotron or a superconducting synchrocyclotron, and used as a magnetic field source for such a superconducting accelerator.

[0012] The superconducting magnet device 10 includes a vacuum vessel 12 , a superconducting coil 14 disposed within the vacuum vessel 12 , and a plurality of cryogenic refrigerators 30 for cooling the superconducting coil 14 .

[0013] The vacuum vessel 12 provides an internal space with a cryogenic vacuum environment suitable for bringing the superconducting coil 14 into a superconducting state. The vacuum vessel 12 is, for example, a cryostat. The vacuum vessel 12 is formed of a metal material such as stainless steel or other suitable high-strength material so as to withstand ambient pressure (e.g., atmospheric pressure). A heat shield 16 may be disposed in the cryogenic vacuum environment within the vacuum vessel 12, surrounding the superconducting coil 14 to reduce heat penetration into the superconducting coil 14. A heat insulating material may be provided between the vacuum vessel 12 and the heat shield 16 to improve thermal insulation performance.

[0014] The vacuum vessel 12 also includes a yoke 18 that surrounds the vacuum vessel 12. The yoke 18 functions as a return yoke for the superconducting magnet device 10. The yoke 18 is attached to the outside of the vacuum vessel 12. To enable access to the vacuum vessel 12 from the outside, the yoke 18 may be formed from a plurality of separable yoke portions. For example, the yoke 18 may be formed from an upper yoke portion 18a corresponding to the upper half of the yoke 18 and a lower yoke portion 18b corresponding to the lower half of the yoke 18.

[0015] As an example, the vacuum vessel 12 may have a cylindrical shape surrounding the superconducting coil 14. The vacuum vessel 12 is placed on the floor 20 so that its central axis C is perpendicular to the floor 20. Like the vacuum vessel 12, the yoke 18 may also have a cylindrical shape coaxially surrounding the vacuum vessel 12. However, the vacuum vessel 12 and the yoke 18 are not limited to such a specific shape and may have other shapes, such as a square box shape.

[0016] The vacuum vessel 12 may include a support structure 22 that supports the vacuum vessel 12 on a floor surface 20. As an example, the support structure 22 may include a plurality of support legs, each extending parallel to the central axis C and connecting the yoke 18 (e.g., the lower yoke portion 18b) to the floor surface 20. These support legs may be attached to the outer periphery of the lower surface of the yoke 18. The support legs may be arranged at equal angular intervals around the central axis C, for example, four support legs may be arranged at 90-degree intervals.

[0017] An equipment arrangement space 24 for arranging the components of the superconducting magnet device 10 is formed below the vacuum vessel 12, more specifically, between the yoke 18 and the floor surface 20. The components of the superconducting magnet device 10 to be installed in the vacuum vessel 12 may be arranged in the equipment arrangement space 24. For example, a cryogenic refrigerator 30 may be arranged in the equipment arrangement space 24. Other components may also be arranged in the equipment arrangement space 24, such as a vacuum pump such as a cryopump that evacuates the vacuum vessel 12, and equipment for supplying power to the superconducting coil 14.

[0018] The superconducting coil 14 is electrically connected to a power supply (not shown) located outside the vacuum vessel 12. An excitation current is supplied to the superconducting coil 14 from the power supply, thereby enabling the superconducting magnet device 10 to generate a strong magnetic field. The power supply may be located in a building or room separate from the vacuum vessel 12.

[0019] When the superconducting magnet device 10 is used as a cyclotron, a pair of superconducting coils 14 may be provided in the vacuum vessel 12, spaced apart in the direction of the central axis C. These two superconducting coils 14 have annular shapes of the same diameter centered on the central axis C, and can generate an axial magnetic field radially inward. A pole 19 may be disposed inside each superconducting coil 14, forming a magnetic circuit together with the superconducting coil 14 and the yoke 18. An ion source and an acceleration electrode may be disposed in the gap 26 between these poles 19.

[0020] Each of the multiple cryogenic refrigerators 30 includes a cold head 32 installed in the vacuum vessel 12 to cool the superconducting coil 14, a compressor 34 that supplies and exhausts a working gas (e.g., helium gas) to and from the cold head 32, and a working gas pipe 36 that connects the cold head 32 and the compressor 34. The cold head 32 is also called an expander. The cold head 32 and the compressor 34 form a refrigeration cycle for the working gas, thereby allowing the cryogenic refrigerators 30 to provide cryogenic cooling. In this example, four cryogenic refrigerators 30 are provided. As an example, the cryogenic refrigerators 30 may be two-stage Gifford-McMahon (GM) refrigerators.

[0021] In this example, the cold heads 32 are installed below the vacuum vessel 12. The cold heads 32 may be arranged at equal angular intervals around the central axis C (for example, four cold heads 32 may be arranged at 90-degree intervals).

[0022] The cold head 32 includes a drive unit 32a attached to the outside of the vacuum vessel 12 and a low-temperature unit extending from the drive unit 32a into the vacuum vessel 12. The drive unit 32a is attached to the vacuum vessel 12 below the yoke 18 (e.g., the lower yoke portion 18b) and is disposed in the equipment arrangement space 24. The drive unit 32a is provided with a drive mechanism such as a motor that drives the cold head 32. The drive unit 32a may also be provided with a pressure switching valve that cyclically switches the working gas pressure in the cold head 32 between high and low pressures.

[0023] The low-temperature section of the cold head 32 may include a first cooling stage cooled to a first cooling temperature (e.g., 30 K to 80 K) and a second cooling stage cooled to a second cooling temperature (e.g., 3 K to 20 K) lower than the first cooling temperature. The first cooling stage may cool the thermal shield 16, and the second cooling stage may cool the superconducting coil 14. The superconducting coil 14 is used in a state cooled to an extremely low temperature below the superconducting transition temperature.

[0024] The compressor 34 is configured to recover the working gas of the cryogenic refrigerator 30 from the cold head 32, pressurize the recovered working gas, and supply the working gas to the cold head 32 again. The compressor 34 is disposed outside the vacuum vessel 12. For protection from leakage magnetic fields and / or radiation, the compressor 34 may be disposed away from the vacuum vessel 12. For example, the compressor 34 may be disposed in a building or room (e.g., an underground pit) separate from the vacuum vessel 12.

[0025] The working gas piping 36 connects the cold head 32 and the compressor 34 so as to circulate working gas between the cold head 32 and the compressor 34. The working gas piping 36 may include a set of piping, i.e., a high-pressure pipe for flowing high-pressure working gas supplied from the compressor 34 to the cold head 32, and a low-pressure pipe for flowing low-pressure working gas returned from the cold head 32 to the compressor 34.

[0026] The working gas piping 36 may be a flexible pipe and may be routed to have at least one bend between the cold head 32 and the compressor 34. Alternatively, the working gas piping 36 may be a rigid pipe or a combination of straight and bent pipes.

[0027] In this embodiment, the superconducting magnet device 10 has a plurality of cryogenic refrigerators 30, and therefore a plurality of cold heads 32 and a plurality of compressors 34 are connected by a plurality of working gas pipes 36. Each of the plurality of working gas pipes 36 connects a corresponding one of the plurality of cold heads 32 to a corresponding one of the plurality of compressors 34.

[0028] In this example, the superconducting magnet device 10 is configured as a so-called conduction-cooled type in which the superconducting coils 14 are directly cooled by the cryogenic refrigerator 30, but it may also be cooled by a so-called immersion-cooled type in which the superconducting coils 14 are cooled by a cryogenic liquid refrigerant such as liquid helium. In the immersion-cooled type, the cryogenic refrigerator 30 re-condenses the vaporized cryogenic liquid refrigerant, thereby cooling the superconducting coils 14.

[0029] As long as the cryocooler 30 can provide the desired cryogenic temperature, it may be a single-stage GM refrigerator, or it may be a pulse tube refrigerator, a Stirling refrigerator, or any other type of single-stage or multi-stage cryocooler.

[0030] The superconducting magnet apparatus 10 further includes a piping support 40 that supports the multiple working gas piping 36. The piping support 40 is disposed outside the vacuum vessel 12 and closer to the vacuum vessel 12 than the multiple compressors 34. The piping support 40 is disposed adjacent to the vacuum vessel 12 in the height direction of the vacuum vessel 12 (i.e., in the direction of the central axis C).

[0031] In this embodiment, the piping support 40 is disposed adjacent to and below the vacuum vessel 12. The piping support 40 is disposed between the yoke 18 and the floor 20 and extends in the height direction of the vacuum vessel 12. The piping support 40 is attached to the underside of the yoke 18 (e.g., the lower yoke portion 18b). Additionally or alternatively, the piping support 40 may be attached to the floor 20. In this example, the piping support 40 is disposed radially inward of the support structure 22. Alternatively, the piping support 40 may be disposed radially outward of the support structure 22.

[0032] The piping support 40 extends around at least a portion of the circumference of the vacuum vessel 12. For example, the piping support 40 may extend over an angle of at least 90 degrees around the central axis C. In this example, the piping support 40 extends around the entire circumference of the vacuum vessel 12. The piping support 40 at least partially surrounds the equipment arrangement space 24.

[0033] Like the vacuum vessel 12 and the yoke 18, the piping support 40 may have a cylindrical shape centered on the central axis C. If the piping support 40 extends around a portion of the circumference of the vacuum vessel 12, the piping support 40 may have the shape of a portion of a cylinder. Alternatively, the piping support 40 may have another shape, such as a box shape.

[0034] In this way, the piping support 40 is arranged to at least partially surround at least one cold head 32 out of the multiple cold heads 32 or at least one other component installed in the vacuum vessel 12. Specifically, the piping support 40 is arranged to at least partially surround the drive unit 32a of the cold head 32 and the working gas piping 36. Note that in FIG. 1 , a portion of the piping support 40 is cut away to show the working gas piping 36 that is arranged inside the piping support 40 and supported by the piping support 40.

[0035] The piping support 40 has at least one opening 42 that allows access to at least one cold head 32 or at least one other component. As shown in Fig. 3, the piping support 40 may have a mesh member (e.g., a wire mesh) having mesh holes as the at least one opening 42. This allows workers to easily access the equipment arranged in the equipment arrangement space 24.

[0036] In this embodiment, the multiple working gas pipes 36 are routed along individual routes from the multiple cold heads 32 to the pipe support 40, and then routed along a common route from the pipe support 40 to the multiple compressors 34. In other words, the multiple working gas pipes 36 extend individually from the multiple cold heads 32 that are distributed on the vacuum vessel 12 to the pipe support 40, are gathered on the pipe support 40, and further extend to the multiple compressors 34 in close proximity to each other.

[0037] Each working gas pipe 36 may include a cold head side portion 36a connected to the cold head 32, an intermediate portion 36b supported by the pipe support 40, and a compressor side portion 36c connected to the compressor 34. The cold head side portion 36a may be connected to the compressor side portion 36c by the intermediate portion 36b. The cold head side portion 36a and at least a portion of the intermediate portion 36b may be routed along separate routes. The remainder of the intermediate portion 36b and the compressor side portion 36c may be routed along a common route.

[0038] The working gas pipe 36 may have multiple curved portions. If the working gas pipe 36 is a flexible pipe, the curved portions may be formed by bending the flexible pipe. If the working gas pipe 36 is a rigid pipe, the curved portions may be formed by bending pipe, such as an elbow.

[0039] 2, the working gas pipe 36 may have a first curved portion 38a formed between the cold head portion 36a and the intermediate portion 36b. The cold head portion 36a may extend radially outward from the cold head 32 and bend downward toward the central axis C at the first curved portion 38a.

[0040] The intermediate portion 36b may have a first portion 36b1 and a second portion 36b2. The first portion 36b1 may extend downward from the first curved portion 38a in the direction of the central axis C. The first portion 36b1 may be adjacent to the inside of the piping support 40 and fixed to the piping support 40. A second curved portion 38b may be formed between the first portion 36b1 and the second portion 36b2. The intermediate portion 36b may be curved at the second curved portion 38b toward the circumferential direction of the vacuum vessel 12. The second portion 36b2 may extend in the circumferential direction of the vacuum vessel 12. Similar to the first portion 36b1, the second portion 36b2 may be adjacent to the inside of the piping support 40 and fixed to the piping support 40.

[0041] A third curved portion 38c may be formed between the intermediate portion 36b and the compressor-side portion 36c. The second portion 36b2 of the intermediate portion 36b may be curved downward toward the central axis C at the third curved portion 38c. The intermediate portions 36b of each working gas pipe 36 may be gathered at the same angular position about the central axis C. The compressor-side portion 36c may detach from the pipe support 40 at this common angular position and extend from the third curved portion 38c toward the compressor 34. The compressor-side portion 36c may have at least one curved portion along the way.

[0042] In this embodiment, the intervals between the portions of the working gas pipes 36 routed along a common route are narrower than the intervals between the portions of the working gas pipes 36 routed along individual routes. In other words, the intervals between the compressor side portions 36c of the working gas pipes 36 are narrower than the intervals between the cold head side portions 36a of the working gas pipes 36. This allows the portions of the working gas pipes 36 routed along the common route to be bundled together. The working gas pipes 36 bundled in this manner may be fixed together to the pipe support 40.

[0043] The dimension of the pipe support 40 in the height direction of the vacuum vessel 12 may be at least twice the allowable bending radius R of at least one of the multiple working gas pipes 36. The allowable bending radius R represents the minimum bending radius specified as a specification for the working gas pipe 36. In other words, the working gas pipe 36 is not allowed to bend at a bending radius smaller than the allowable bending radius R. The allowable bending radius is not limited to the bending radius of a flexible pipe, but may also be the radius of an elbow pipe. As described above, the working gas pipe 36 may be curved at least in two places. As shown in FIG. 4 , the height of the curved working gas pipe 36 may be twice the allowable bending radius R (2R). Therefore, by setting the height of the pipe support 40 to be at least twice the allowable bending radius R, the curved working gas pipe 36 can be accommodated within the pipe support 40.

[0044] According to the embodiment, the piping support 40 can be used to route the working gas piping 36 of the cryogenic refrigerator 30 in an organized manner. The restriction on the space available for arranging the working gas piping 36, which is caused by the reduction in the surface area of ​​the vacuum vessel 12 due to the miniaturization of the superconducting magnet device 10, is alleviated by the use of the piping support 40. In addition, an equipment arrangement space 24 can be provided adjacent to the piping support 40. By using the equipment arrangement space 24 as a work area for maintenance of the superconducting magnet device 10, the workability of maintenance can be improved.

[0045] 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, and that various design changes and 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 created by combining embodiments will have the combined effects of the respective combined embodiments.

[0046] In the above embodiment, the case where the piping support 40 is disposed below the vacuum vessel 12 has been described as an example, but other arrangements of the piping support 40 are also possible. For example, the piping support 40 may be disposed adjacent to the vacuum vessel 12 on the upper side of the vacuum vessel 12. In this case, the piping support 40 may be attached to the upper yoke portion 18a.

[0047] The piping support 40 does not necessarily have to be disposed at a position offset from the vacuum vessel 12 in the height direction of the vacuum vessel 12. The piping support 40 may be disposed so as to at least partially overlap the vacuum vessel 12 in the height direction of the vacuum vessel 12. For example, the piping support 40 may be disposed radially outside the vacuum vessel 12 so as to surround the vacuum vessel 12.

[0048] The superconducting magnet device 10 may include multiple piping supports 40. For example, the superconducting magnet device 10 may include a piping support 40 disposed below the vacuum vessel 12 and an additional piping support 40 disposed above the vacuum vessel 12.

[0049] In the above-described embodiment, the cold head 32 of the cryogenic refrigerator 30 is installed below the vacuum vessel 12 as an example. However, the cold head 32 may be installed in other positions. For example, the cold head 32 may be installed above the vacuum vessel 12. In this case, the piping support 40 may be arranged above the vacuum vessel 12 to support the working gas piping 36 extending from the cold head 32 installed above the vacuum vessel 12 to the compressor 34. Alternatively, the cold head 32 may be installed on a side wall (e.g., a cylindrical side wall) of the vacuum vessel 12. In this case, the piping support 40 may be arranged around the periphery of the vacuum vessel 12.

[0050] In addition to the working gas piping 36, the piping support 40 may support electrical wiring of the cryogenic refrigerator 30, such as electrical wiring connecting the cold head 32 and the compressor 34. If a cryopump for evacuating the vacuum vessel 12 is installed in the vacuum vessel 12, the piping support 40 may support working gas piping and / or electrical wiring of the cryogenic refrigerator that is part of the cryopump. The piping support 40 may also support piping and / or wiring of at least one other component installed in the vacuum vessel 12.

[0051] In the above embodiment, the superconducting magnet device 10 is described as a part of a superconducting accelerator, but the superconducting magnet device 10 may be used for other purposes. For example, the superconducting magnet device 10 may be installed in high-magnetic field equipment as a magnetic field source for high-magnetic field equipment, such as a single crystal pulling device, an NMR system, an MRI system, or a high-energy physics system such as a nuclear fusion system, to generate the high magnetic field required for the equipment.

[0052] The present invention has been described using specific terms based on the embodiments, but the embodiments merely illustrate one aspect of the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments as long as they do not deviate from the concept of the present invention as defined in the claims.

[0053] The present invention can be used in the field of superconducting magnet devices.

[0054] 10 Superconducting magnet device, 12 Vacuum vessel, 14 Superconducting coil, 18 Yoke, 32 Cold head, 34 Compressor, 36 Working gas piping, 40 Piping support.

Claims

1. A superconducting magnet apparatus comprising: a vacuum vessel; a superconducting coil disposed within the vacuum vessel; a plurality of cold heads installed in the vacuum vessel for cooling the superconducting coil; a plurality of compressors disposed outside the vacuum vessel; a plurality of working gas pipes connecting the plurality of cold heads to the plurality of compressors; and a piping support disposed outside the vacuum vessel and closer to the vacuum vessel than the plurality of compressors, for supporting the plurality of working gas pipes, wherein the plurality of working gas pipes are routed along individual routes from the plurality of cold heads to the piping support, and further routed along a common route from the piping support to the plurality of compressors.

2. A superconducting magnet device as described in claim 1, characterized in that the spacing between the portions of the plurality of working gas pipes routed along the common route is narrower than the spacing between the portions of the plurality of working gas pipes routed along the individual routes.

3. A superconducting magnet apparatus according to claim 1, wherein said piping support is disposed adjacent to said vacuum vessel in the height direction of said vacuum vessel.

4. A superconducting magnet apparatus according to claim 1, characterized in that the vacuum vessel is provided with a yoke surrounding the vacuum vessel, and the piping support is attached to the yoke.

5. A superconducting magnet apparatus as defined in claim 1, wherein said piping support extends around at least a portion of the circumference of said vacuum vessel.

6. A superconducting magnet device as described in claim 1, characterized in that the dimension of the piping support in the height direction of the vacuum vessel is at least twice the allowable bending radius of at least one of the plurality of working gas piping.

7. A superconducting magnet apparatus as described in any one of claims 1 to 6, characterized in that the piping support is arranged to at least partially surround at least one cold head among the plurality of cold heads or at least one other component installed in the vacuum vessel, and the piping support is provided with at least one opening that allows access to the at least one cold head or the at least one other component.

8. A superconducting magnet apparatus according to claim 7, wherein said piping support comprises a mesh member having a mesh as said at least one opening.

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