Superconducting magnet device and bus bar assembly for superconducting magnet device

Abstract

A bus bar assembly (20) for a superconducting magnet device comprises an outer bus bar (40a) and an inner bus bar (40b). The outer bus bar (40a) connects a first superconducting-coil-side cable (34a) and a first power-supply-side cable (36a), and forms an outer deflection route (44a) together with the first superconducting-coil-side cable (34a) and the first power-supply-side cable (36a). The inner bus bar (40b) connects a second superconducting-coil-side cable (34b) and a second power-supply-side cable (36b), and forms an inner deflection route (44b) together with the second superconducting-coil-side cable (34b) and the second power-supply-side cable (36b). The outer deflection route (44a) and the inner deflection route (44b) are deflected in parallel, and the route length of the outer deflection route (44a) is greater than the route length of the inner deflection route (44b).

Description

Superconducting magnet device and bus bar assembly for superconducting magnet device

[0001] The present invention relates to a superconducting magnet device and a bus bar assembly for a superconducting magnet device.

[0002] Generally, a superconducting magnet device comprises a superconducting coil and a vacuum vessel that houses the coil in a cryogenically cooled state. The power supply for the superconducting coil is located outside the vacuum vessel. Coil electrodes connected to the superconducting coil are provided outside the vacuum vessel, and the power supply and coil electrodes are connected by power supply cables.

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

[0004] The present inventors have studied the above-mentioned superconducting magnet device and recognized the following problem. At least a portion of the power feed cable is routed along a predetermined route outside the vacuum vessel. The route of the power feed cable may include at least one cable deflection point. As superconducting magnet devices have become smaller through recent research and development, the area on the surface of the vacuum vessel in which the power feed cable can be arranged has become smaller, and therefore it is desirable to reduce the bending radius of the power feed cable at the cable deflection point. However, the power feed cable must be deflected at a bending radius larger than the allowable bending radius specified in its specifications. This constraint may hinder efforts to save space for cable arrangement.

[0005] An exemplary object of an embodiment of the present invention is to provide a technique that helps reduce the space required for cable placement in a superconducting magnet device.

[0006] According to one aspect of the present invention, a superconducting magnet apparatus includes a superconducting coil, a power supply, first and second superconducting coil side cables connected to the superconducting coil, first and second power supply side cables connected to the power supply, and a bus bar assembly including an outer bus bar and an inner bus bar. The outer bus bar connects the first superconducting coil side cable to the first power supply side cable and forms an outer deflection route together with the first superconducting coil side cable and the first power supply side cable. The inner bus bar connects the second superconducting coil side cable to the second power supply side cable and forms an inner deflection route together with the second superconducting coil side cable and the second power supply side cable. The outer deflection route and the inner deflection route are deflected in parallel, and the route length of the outer deflection route is longer than the route length of the inner deflection route.

[0007] According to one aspect of the present invention, a bus bar assembly for a superconducting magnet apparatus includes an outer bus bar that connects a first superconducting coil side cable to a first power supply side cable and forms an outer deflection route together with the first superconducting coil side cable and the first power supply side cable, and an inner bus bar that connects a second superconducting coil side cable to a second power supply side cable and forms an inner deflection route together with the second superconducting coil side cable and the second power supply side cable. The outer deflection route and the inner deflection route are deflected in parallel, and the route length of the outer deflection route is longer than the route length of the inner deflection route.

[0008] According to the present invention, it is possible to provide a technique that is useful for saving space for cable arrangement in a superconducting magnet device.

[0009] FIG. 1 is a schematic diagram showing a superconducting magnet device according to an embodiment. FIG. 2 is a cross-sectional view schematically showing a cross section of line AA of the superconducting magnet device shown in FIG. 1. FIG. 3 is a plan view schematically showing an example of a busbar assembly according to an embodiment that can be mounted in a superconducting magnet device. FIG. 4 is a schematic diagram illustrating forces acting on the busbar assembly shown in FIG. 3. FIG. 5 is a plan view schematically showing another example of a busbar assembly according to an embodiment. FIG. 6 is a plan view schematically showing another example of a busbar assembly according to an embodiment. FIG. 7 is a plan view schematically showing another example of a busbar assembly according to an embodiment.

[0010] 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.

[0011] Fig. 1 is a schematic diagram showing a superconducting magnet device 10 according to an embodiment. Fig. 2 is a cross-sectional view showing a schematic cross section of the superconducting magnet device 10 shown in Fig. 1 taken along line A-A. As an exemplary application, the superconducting magnet device 10 is mounted in high-magnetic-field equipment as a magnetic field source for accelerators such as cyclotrons and synchrocyclotrons, or other high-magnetic-field equipment, and can generate the high magnetic fields required for the equipment.

[0012] The superconducting magnet apparatus 10 includes a superconducting coil 12, a power supply 13 for the superconducting coil 12, a vacuum vessel 14 that houses the superconducting coil 12, a current lead 16 connected to the superconducting coil 12 and installed in the vacuum vessel 14, a power supply cable 18 that is arranged outside the vacuum vessel 14 and connects the power supply 13 to the current lead 16, and a bus bar assembly 20 that is installed in the vacuum vessel 14 for routing the power supply cable 18.

[0013] 2, the superconducting magnet device 10 may be provided with a pair of superconducting coils 12. These two superconducting coils 12 may have annular shapes of the same diameter centered on a central axis C, and may be spaced apart from each other in the axial direction (the direction of the central axis C). The superconducting coils 12 can generate an axial magnetic field radially inward.

[0014] The vacuum vessel 14 provides within its interior a cryogenic vacuum environment 22 suitable for bringing the superconducting coils 12 into a superconducting state. The vacuum vessel 14 is, for example, a cryostat. As an example, the vacuum vessel 14 may have a cylindrical shape surrounding the superconducting coils 12. The vacuum vessel 14 is formed of a metallic material such as stainless steel or other suitable high-strength material so as to withstand ambient pressure (e.g., atmospheric pressure). A heat shield 24 is also disposed in the cryogenic vacuum environment 22 within the vacuum vessel 14, surrounding the superconducting coils 12 to reduce heat penetration into the superconducting coils 12. In this example, two heat shields 24 are provided, one for each pair of superconducting coils 12.

[0015] The vacuum vessel 14 is also provided with a pair of poles 26 disposed in its hollow portion and a yoke 28 that, together with the poles 26, forms a magnetic circuit. These two poles 26 are disposed inside the corresponding superconducting coils 12, and form superconducting electromagnets with iron cores. The yoke 28 includes an upper yoke 28a and a lower yoke 28b, and surrounds the vacuum vessel 14. When the superconducting magnet device 10 is used as a cyclotron, an ion source and an acceleration electrode can be disposed in the gap 30 between the poles 26, although not shown in FIG. 2 .

[0016] The superconducting coil 12 is thermally coupled to, for example, a two-stage Gifford-McMahon (GM) refrigerator or other type of cryogenic refrigerator 32, and is used in a state cooled to a cryogenic temperature below the superconducting transition temperature. The heat shield 24 may be cooled to a first cooling temperature, for example, 30 K to 80 K, in a high-temperature cooling stage of the cryogenic refrigerator 32, and the superconducting coil 12 may be cooled to a second cooling temperature lower than the first cooling temperature, for example, 3 K to 20 K, in a low-temperature cooling stage. In this example, the superconducting magnet apparatus 10 is configured as a so-called conduction-cooled type in which the superconducting coil 12 is directly cooled by the cryogenic refrigerator 32, but may also be cooled by a so-called immersion-cooled type in which the superconducting coil 12 is cooled by a cryogenic liquid refrigerant such as liquid helium.

[0017] The power supply 13 is located outside the vacuum vessel 14 and is electrically connected to the superconducting coil 12 by a current lead 16 and a power supply cable 18. An excitation current is supplied from the power supply 13 to the superconducting coil 12 through the current lead 16 and the power supply cable 18. This enables the superconducting magnet apparatus 10 to generate a strong magnetic field. The power supply 13 may be located in a building or room separate from the vacuum vessel 14.

[0018] The current leads 16 are provided in pairs, at least on the positive and negative sides. As shown in Fig. 1, an airtight terminal 16a is provided at the end of the current lead 16 on the ambient environment side (room temperature side) for introducing current into the vacuum vessel 14 through the wall of the vacuum vessel 14. In the example shown, the airtight terminal 16a is installed on the top surface of the vacuum vessel 14, but this arrangement is not limited thereto. The opposite end (low temperature side) of the current lead 16 is connected to the superconducting coil 12 inside the vacuum vessel 14.

[0019] The power supply cable 18 includes a first superconducting coil side cable 34a and a second superconducting coil side cable 34b connected to the superconducting coil 12, and a first power supply side cable 36a and a second power supply side cable 36b connected to the power supply 13. The first superconducting coil side cable 34a and the second superconducting coil side cable 34b extend parallel to each other at least near the bus bar assembly 20 and are connected to the bus bar assembly 20. Furthermore, the first power supply side cable 36a and the second power supply side cable 36b extend parallel to each other at least near the bus bar assembly 20 and are connected to the bus bar assembly 20.

[0020] In this example, the first superconducting coil side cable 34a and the first power supply side cable 36a are used as positive electrode side power feeders, and the second superconducting coil side cable 34b and the second power supply side cable 36b are used as negative electrode side power feeders. Therefore, one end of the first superconducting coil side cable 34a is connected to the hermetic terminal 16a of the positive electrode side current lead 16, and the other end is connected to one end of the first power supply side cable 36a via the bus bar assembly 20. The other end of the first power supply side cable 36a is connected to the positive electrode of the power supply 13. Furthermore, one end of the second superconducting coil side cable 34b is connected to the hermetic terminal 16a of the negative electrode side current lead 16, and the other end is connected to one end of the second power supply side cable 36b via the bus bar assembly 20. The other end of the second power supply side cable 36b is connected to the negative electrode of the power supply 13. Conversely to this example, the first superconducting coil side cable 34a and the first power supply side cable 36a may be used as the negative electrode side power supply line, and the second superconducting coil side cable 34b and the second power supply side cable 36b may be used as the positive electrode side power supply line.

[0021] The first superconducting coil side cable 34a and the second superconducting coil side cable 34b may be supported by a flexible cable support 38. As described above, the yoke 28 may include an upper yoke 28a and a lower yoke 28b. In order to ensure a working space for accessing the vacuum vessel 14 from the outside during maintenance of the superconducting magnet device 10, the yoke 28 may be configured so that the upper yoke 28a can be moved upward and away from the lower yoke 28b. The cable support 38 has one end connected to the upper yoke 28a and the other end connected to the lower yoke 28b, and may support these power supply cables so as to allow the first superconducting coil side cable 34a and the second superconducting coil side cable 34b to move in accordance with the movement of the upper yoke 28a relative to the lower yoke 28b.

[0022] As will be described later, the bus bar assembly 20 provides a cable routing structure that allows the power supply cable 18 to be deflected at any angle (90 degrees in the illustrated example) along the surface of the vacuum vessel 14. In an exemplary arrangement, the bus bar assembly 20 may be mounted on the surface of the yoke 28. In the illustrated example, the bus bar assembly 20 is mounted on the side surface of the lower yoke 28b, for example.

[0023] FIG. 3 is a plan view schematically illustrating an example of a busbar assembly 20 that can be mounted on the superconducting magnet device 10 according to an embodiment. The busbar assembly 20 includes a plurality of busbars, for example, an outer busbar 40a and an inner busbar 40b. The outer busbar 40a and the inner busbar 40b are arranged in parallel. These busbars are formed of a good conductor, for example, copper or aluminum. The busbar assembly 20 also includes a support 42 having a support surface 42a. The support 42 may be formed of a metal material, for example, stainless steel, or other appropriate material. The outer busbar 40a and the inner busbar 40b are each supported on the support 42 via an insulating material on the support surface 42a.

[0024] The outer busbar 40a connects the first superconducting coil side cable 34a and the first power supply side cable 36a, and forms an outer deflection route 44a together with the first superconducting coil side cable 34a and the first power supply side cable 36a. The inner busbar 42b connects the second superconducting coil side cable 34b and the second power supply side cable 36b, and forms an inner deflection route 44b together with the second superconducting coil side cable 34b and the second power supply side cable 36b.

[0025] The outer deflection route 44a and the inner deflection route 44b are deflected in parallel. The outer deflection route 44a is deflected 90 degrees along the support surface 42a from a start point A1 to an end point B1 on the support surface 42a, and the inner deflection route 44b is deflected 90 degrees along the support surface 42a from a start point A2 to an end point B2 on the support surface 42a, inside the outer deflection route 44a.

[0026] Therefore, the route length of the outer deflection route 44a (i.e., the length along the outer deflection route 44a from the start point A1 to the end point B1 of the outer deflection route 44a) is longer than the route length of the inner deflection route 44b (i.e., the length along the inner deflection route 44b from the start point A2 to the end point B2 of the inner deflection route 44b). To achieve this, the length L1 of the outer bus bar 40a along the outer deflection route 44a is longer than the length L2 of the inner bus bar 40b along the inner deflection route 44b.

[0027] In this example, the direction of the power feed cable 18 is switched using the outer bus bar 40a and the inner bus bar 40b, so the power feed cable 18 itself is not bent due to cable deflection near the bus bar assembly 20. The first superconducting coil side cable 34a is attached to one end of the outer bus bar 40a so as to form a 90-degree angle with the outer bus bar 40a, and the second superconducting coil side cable 34b is attached to one end of the inner bus bar 40b so as to form a 90-degree angle with the inner bus bar 40b. The first superconducting coil side cable 34a and the second superconducting coil side cable 34b extend linearly from the outer bus bar 40a and the inner bus bar 40b, respectively. In addition, the first power supply side cable 36a extends linearly from the other end of the outer bus bar 40a in the length direction of the outer bus bar 40a, and the second power supply side cable 36b extends linearly from the other end of the inner bus bar 40b in the length direction of the inner bus bar 40b.

[0028] For ease of understanding, FIG. 1 shows the allowable bending radius R specified for the power feed cable 18. In other words, the power feed cable 18 is not allowed to bend at a radius smaller than the allowable bending radius R. While the allowable bending radius R of the power feed cable 18 can be somewhat large, as shown in FIG. 3, the bending radius r that can be achieved by the bus bar assembly 20 can be smaller than the allowable bending radius R. This is because, as described above, the cable direction is switched between the outer bus bar 40a and the inner bus bar 40b, and there is no need to bend the power feed cable 18 itself. However, the power feed cable 18 may be bent to some extent if required for routing.

[0029] In this way, the bus bar assembly 20 according to the embodiment can accommodate the deflection of the power supply cable 18 in a smaller space. Therefore, according to the embodiment, it is possible to adapt to the miniaturization of the superconducting magnet device 10 and achieve space-saving cable arrangement.

[0030] 4 is a schematic diagram illustrating forces acting on the bus bar assembly 20 shown in FIG. 3. In this example, as described above, the first superconducting coil side cable 34a, the outer bus bar 40a, and the first power supply side cable 36a are connected to the positive pole of the power supply 13, and the second superconducting coil side cable 34b, the inner bus bar 40b, and the second power supply side cable 36b are connected to the negative pole of the power supply 13. When the superconducting coil 12 is excited by the power supply 13, a current I1 flowing through the outer bus bar 40a and a current I2 flowing through the inner bus bar 40b have the same magnitude but are directed in opposite directions. A magnetic field B generated by the superconducting coil 12 can have a direction along the support surface 42a of the support body 42 around the bus bar assembly 20.

[0031] The force F1 acting on the outer bus bar 40a due to the current I1 and the magnetic field B and the force F2 acting on the inner bus bar 40b due to the current I2 and the magnetic field B are in opposite directions and can at least partially cancel each other out. Therefore, the resultant force acting on the support 42 is reduced. The force required to fasten the bus bar assembly 20 to the vacuum vessel 14 (e.g., the bolt fastening force in the case of bolt fastening) can be reduced, simplifying the fastening structure of the bus bar assembly 20. These advantages can be obtained by a configuration in which one of the first power supply side cable 36a and the second power supply side cable 36b is connected to the positive electrode of the power supply 13, and the other of the first power supply side cable 36a and the second power supply side cable 36b is connected to the negative electrode of the power supply 13.

[0032] 3, the outer busbar 40a and the inner busbar 40b may be supported at a predetermined inter-busbar distance D. The inter-busbar distance D may be determined so that the inter-busbar electric field generated between the outer busbar 40a and the inner busbar 40b when the superconducting magnet device 10 is operated at a rated current is below a predetermined upper limit. Here, the predetermined upper limit of the inter-busbar electric field may be determined from the perspective of preventing discharge between the outer busbar 40a and the inner busbar 40b. The predetermined upper limit of the inter-busbar electric field may be, for example, 0.1 kV / m or more, or 1 kV / m or more. The predetermined upper limit of the inter-busbar electric field may be, for example, 100 MV / m or less, or 100 kV / m or less, or 10 kV / m or less.

[0033] 5 is a plan view schematically illustrating another example of a busbar assembly 20 according to an embodiment. As shown in the figure, the busbar assembly 20 may include an insulating member 46 disposed between the outer busbar 40a and the inner busbar 40b. The insulating member 46 may be a wall provided on the support body 42 to separate the outer busbar 40a from the inner busbar 40b. The insulating member 46 may be formed of, for example, fiber-reinforced plastic (FRP) such as glass fiber-reinforced plastic (GFRP), or other suitable insulating material. This configuration also reduces the risk of discharge between the outer busbar 40a and the inner busbar 40b.

[0034] 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.

[0035] In the above embodiment, an example has been described in which the power feed cable 18 on the superconducting coil 12 side and the power feed cable 18 on the power source 13 side are connected one-to-one by the bus bar assembly 20, but the present invention is not limited to this. As will be described below with reference to Fig. 6, the bus bar assembly 20 may be configured to branch or merge the power feed cables 18.

[0036] 6 is a plan view schematically illustrating another example of the bus bar assembly 20 according to the embodiment. As shown in the figure, the first power supply side cable 36a may include multiple power supply side cables, and the outer bus bar 40a may branch the first superconducting coil side cable 34a into multiple power supply side cables. Similarly, the second power supply side cable 36b may include multiple power supply side cables. The inner bus bar 40b may branch the second superconducting coil side cable 34b into multiple power supply side cables.

[0037] Although not shown, the first superconducting coil side cable 34a may include a plurality of coil side cables, and the outer bus bar 40a may branch the first power supply side cable 36a into a plurality of coil side cables. The second superconducting coil side cable 34b may include a plurality of coil side cables, and the inner bus bar 40b may branch the second power supply side cable 36b into a plurality of coil side cables.

[0038] In the above embodiment, the bus bar assembly 20 has been described as having two bus bars (40a, 40b), but the present invention is not limited to this. As will be described below with reference to Fig. 7, the bus bar assembly 20 may include three or more bus bars, and these bus bars may deflect three or more power supply cables 18. The lengths of these bus bars may be determined such that the bus bars located on the outer periphery of the cable deflection are longer.

[0039] 7 is a plan view schematically illustrating another example of the bus bar assembly 20 according to the embodiment. The bus bar assembly 20 may include a third bus bar 40c in addition to the outer bus bar 40a and the inner bus bar 40b. The third bus bar 40c can connect the third superconducting coil side cable 34c and the third power supply side cable 36c so as to switch the direction of the third superconducting coil side cable 34c relative to the third power supply side cable 36c. The third bus bar 40c may be shorter than the inner bus bar 40b and may be positioned more inward than the inner bus bar 40b.

[0040] The third superconducting coil side cable 34c and the third power supply side cable 36c may be a third power supply cable connecting the superconducting coil 12 and the power supply 13. The superconducting magnet device 10 may be provided with an auxiliary superconducting coil different from the superconducting coil 12, or a normal conducting coil, or other electrical equipment such as a measuring instrument, and the third superconducting coil side cable 34c and the third power supply side cable 36c may be power supply cables connecting such equipment and the power supply 13.

[0041] Fig. 8 is a plan view schematically showing another example of a bus bar assembly 20 according to an embodiment. In the example shown in Fig. 8, the bus bar assembly 20 includes an outer bus bar 40a, an inner bus bar 40b, and a third bus bar 40c, as in the example shown in Fig. 7. As shown in the figure, the bus bar assembly 20 can achieve 180-degree cable deflection in a small space using these three bus bars.

[0042] If necessary, multiple bus bar assemblies 20 may be provided in the superconducting magnet apparatus 10. For example, if the route of the power supply cable 18 includes multiple deflection points, a bus bar assembly 20 may be provided for each deflection point.

[0043] 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.

[0044] The present invention can be used in the fields of superconducting magnet devices and bus bar assemblies for superconducting magnet devices.

[0045] 10 Superconducting magnet device, 12 Superconducting coil, 13 Power supply, 20 Bus bar assembly, 34a First superconducting coil side cable, 34b Second superconducting coil side cable, 36a First power supply side cable, 36b Second power supply side cable, 40a Outer bus bar, 40b Inner bus bar, 42 Support, 44a Outer deflection route, 44b Inner deflection route, 46 Insulating member.

Claims

1. A superconducting magnet device comprising: a superconducting coil; a power supply; a first superconducting coil side cable and a second superconducting coil side cable connected to the superconducting coil; a first power supply side cable and a second power supply side cable connected to the power supply; an outer busbar connecting the first superconducting coil side cable to the first power supply side cable and forming an outer deflection route together with the first superconducting coil side cable and the first power supply side cable; and an inner busbar connecting the second superconducting coil side cable to the second power supply side cable and forming an inner deflection route together with the second superconducting coil side cable and the second power supply side cable, wherein the outer deflection route and the inner deflection route are deflected in parallel, and the route length of the outer deflection route is longer than the route length of the inner deflection route.

2. A superconducting magnet apparatus according to claim 1, wherein the length of said outer bus bar along said outer deflection route is longer than the length of said inner bus bar along said inner deflection route.

3. A superconducting magnet device according to claim 1 or 2, characterized in that the busbar assembly comprises a support that supports the outer busbar and the inner busbar at a distance between the busbars that is determined so that the electric field between the outer busbar and the inner busbar when the superconducting magnet device is operated at a rated current is below a predetermined upper limit value.

4. A superconducting magnet apparatus according to claim 1 or 2, wherein said bus bar assembly comprises an insulating member disposed between said outer bus bar and said inner bus bar.

5. A superconducting magnet device according to claim 1 or 2, characterized in that the bus bar assembly is configured so that an electromagnetic force acting on the outer bus bar when the superconducting coil is excited by the power supply and an electromagnetic force acting on the inner bus bar when the superconducting coil is excited by the power supply are at least partially canceled out.

6. A superconducting magnet device as described in claim 1 or 2, characterized in that one of the first power supply side cable and the second power supply side cable is connected to the positive pole of the power supply, and the other of the first power supply side cable and the second power supply side cable is connected to the negative pole of the power supply.

7. A superconducting magnet device according to claim 1 or 2, characterized in that the first power supply side cable and the second power supply side cable each include a plurality of cables.

8. A superconducting magnet apparatus according to claim 1 or 2, wherein the bus bar assembly further comprises a third bus bar connecting a third superconducting coil side cable and a third power supply side cable.

9. A superconducting magnet device as described in claim 1 or 2, characterized in that the bus bar assembly deflects the first superconducting coil side cable by 90 degrees relative to the first power supply side cable, and deflects the second superconducting coil side cable by 90 degrees relative to the second power supply side cable.

10. A superconducting magnet device as described in claim 1 or 2, characterized in that the bus bar assembly deflects the first superconducting coil side cable by 180 degrees relative to the first power supply side cable, and deflects the second superconducting coil side cable by 180 degrees relative to the second power supply side cable.

11. A busbar assembly for a superconducting magnet device comprising: an outer busbar connecting a first superconducting coil side cable and a first power supply side cable and forming an outer deflection route together with said first superconducting coil side cable and said first power supply side cable; and an inner busbar connecting a second superconducting coil side cable and a second power supply side cable and forming an inner deflection route together with said second superconducting coil side cable and said second power supply side cable, wherein said outer deflection route and said inner deflection route are deflected in parallel, and the route length of said outer deflection route is longer than the route length of said inner deflection route.

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