Superconducting electromagnet device and charged particle beam therapy device

Abstract

To reduce the distance between a pair of coils while suppressing the effects of radiant heat. [Solution] The superconducting electromagnet device comprises a vacuum vessel that forms a vacuum space inside, a pair of superconducting coil units provided in the vacuum space, each superconducting coil unit containing at least one coil, at least one yoke to which the coils included in the pair of superconducting coil units are fixed, a shield disposed outside the yoke to maintain the internal space at a lower temperature than inside the vacuum vessel, and a heat transfer suppression unit that suppresses the transfer of radiant heat from the beam path side of the charged particle beam formed between the pair of superconducting coil units to the pair of superconducting coil units.

Description

Technical Field

[0001] The present invention relates to a superconducting magnet device and a charged particle beam therapy device.

Background Art

[0002] In a superconducting magnet device, a strong magnetic field is generated by passing a large current through a coil cooled to an extremely low temperature and having zero electrical resistance. Therefore, in order to generate a strong magnetic field, it is required to maintain the coil in an extremely low temperature state. Patent Document 1 proposes a cryogenic container in which a metal foil having a radiation rate equivalent to that of a buff-polished surface is attached to the surfaces of a refrigerant storage container, a shield tank, and a vacuum heat insulation tank that constitute the container. In this cryogenic container, by providing a metal foil having a radiation rate equivalent to that of a buff-polished surface, the processing cost is lower than that of buff polishing, and moreover, heat intrusion similar to that of buff polishing is reduced.

[0003] Further, Patent Document 2 discloses a particle beam irradiation device in which a superconducting magnet group composed of a plurality of superconducting magnets is arranged in a cryostat that maintains an extremely low temperature inside.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] [[ID=4२]] In order to generate a stronger magnetic field in a superconducting electromagnet device, it is conceivable to shorten the distance between a pair of coils. However, in the technology described in Patent Document 1, the walls of the cryogenic material storage container, shielding tank, and vacuum insulation tank are located between the pair of coils, making it difficult to shorten the distance between the pair of coils. On the other hand, in the technology described in Patent Document 2, the pair of coils are arranged within a single cryostat so as to straddle the path of the charged particle beam, which allows for a closer distance between the pair of coils compared to the case where the pair of coils are each located in separate cryostats. On the other hand, in order to maintain the pair of coils at extremely low temperatures, it is desirable to suppress the influence of radiant heat between the pair of coils, i.e., from the charged particle beam side.

[0006] This invention provides a technique for reducing the distance between a pair of coils while suppressing the effects of radiant heat. [Means for solving the problem]

[0007] The present invention may include the following embodiments. [Aspect 1] A superconducting electromagnet device, A vacuum vessel that forms a vacuum space inside, A pair of superconducting coil units provided in the vacuum space, each of which includes at least one coil, The pair of superconducting coil units includes at least one yoke to which the coils are fixed, A shield positioned outside the yoke in the vacuum space, the shield maintaining the internal space of the shield at a lower temperature than the external space of the shield, A superconducting electromagnet device comprising a radiant heat suppression section that reflects radiant heat transmitted from the outside of the yoke into the yoke. [Aspect 2] A superconducting electromagnet device according to Embodiment 1, The superconducting electromagnet device includes a heat transfer suppression unit that suppresses the transfer of radiant heat from the beam path side of a charged particle beam formed between the pair of superconducting coil units to the pair of superconducting coil units. [Aspect 3] A superconducting electromagnet device according to embodiment 2, The coils included in the pair of superconducting coil units include a structure in which a superconducting conductor is wound around a winding frame provided on the at least one yoke, The winding frame includes a first surface facing the beam path, The heat transfer suppression unit is arranged on the first surface. Superconducting electromagnet device. [Aspect 4] A superconducting electromagnet device according to embodiment 3, The heat transfer suppression unit is A layered first part that reflects radiant heat, A layered second portion that provides thermal insulation and insulation between the first portion and the winding frame, Equipped with, The first portion is provided closer to the beam path than the second portion, and reflects radiant heat from the beam path side. Superconducting electromagnet device. [Aspect 5] A superconducting electromagnet device according to embodiment 4, The aforementioned first part is composed of a deposited metal, a sputtered metal, or a polished metal. Superconducting electromagnet device. [Aspect 6] A superconducting electromagnet device according to embodiment 4, A plurality of the first parts, which are insulated from each other, are arranged on one reel. Superconducting electromagnet device. [Aspect 7] A superconducting electromagnet device according to embodiment 3, The heat transfer suppression portion is formed by polishing the first surface of the winding frame. Superconducting electromagnet device. [Aspect 8] The superconducting magnet device according to any one of Aspects 1 to 7, wherein the radiative heat suppression unit includes a suppression plate that suppresses the transmission of radiative heat from the outside of the shield to the pair of superconducting coil units and the at least one yoke inside the shield. Superconducting electromagnetic device. [Aspect 9] A charged particle beam irradiation device including the superconducting electromagnetic device according to any one of Aspects 1 to 7.

Brief Description of Drawings

[0008] [Figure 1] Side cross-section for explaining the outline of the superconducting electromagnetic device according to one embodiment [Figure 2] FIG. 2 schematically shows a cross-section taken along line A-A of the superconducting electromagnetic device in FIG. 1 (YZ cross-sectional view) [Figure 3] FIG. 3 schematically shows a cross-section taken along line B-B of the superconducting electromagnetic device in FIG. 1 (ZX cross-sectional view) [Figure 4] Explanatory drawing of the cooling structure of the superconducting electromagnetic device [Figure 5] Drawing for explaining the configuration of the heat transfer suppression unit [Figure 6] Drawing showing an example of the arrangement of the heat transfer suppression unit [Figure 7] Schematic configuration drawing of a charged particle beam irradiation device including a superconducting electromagnetic device [Figure 8] Explanatory drawing of the configuration of the superconducting electromagnetic device according to a modification [[ID=4O]]

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification, when simply described as "direction", it includes "positive direction" and "negative direction", and has a different meaning from "orientation". Therefore, when simply described as "predetermined direction", the orientation is not limited. On the other hand, if described as "+X direction", its direction is positively limited, and if described as "-X direction", its direction is negatively limited.

[0010] [Superconducting electromagnet device 1] <Overview> Figure 1 is a side cross-sectional view (XY cross-section) illustrating the outline of a superconducting electromagnet device 1 according to one embodiment. Figure 2 is a schematic diagram (YZ cross-section) showing the AA line cross-section of the superconducting electromagnet device 1 of Figure 1, and Figure 3 is a schematic diagram (ZX cross-section) showing the BB line cross-section of the superconducting electromagnet device 1 of Figure 1.

[0011] In this implementation, the superconducting electromagnet device 1 plays the role of a deflection electromagnet device that deflects the direction of propagation of the charged particle beam. As will be described in detail in [Charged Particle Beam Therapy Device], the superconducting electromagnet device 1 is used, for example, in the charged particle beam irradiation device 100 to irradiate the patient's isocenter with a charged particle beam from a predetermined direction. The superconducting electromagnet device 1 generally includes a vacuum vessel 10, a pair of superconducting coil units 20, a yoke 30, a shield 40, a suppression plate 50, a cooling unit 60, and a heat transfer suppression unit 80.

[0012] <Explanation of each element> (vacuum container 10) The vacuum vessel 10 (cryostat) forms a vacuum space 11 inside it. The inside of the vacuum vessel 10 is kept at an extremely low temperature. The effective magnetic field region may be kept as much of a vacuum as possible while maintaining the superconducting state of the superconducting electromagnet device 1 through which the charged particle beam passes. Examples of refrigerants used in the vacuum vessel 10 include helium gas, liquid helium, or liquid nitrogen. In this embodiment, a connection portion 12 that connects to a fan-shaped vacuum duct 124 (described later) is formed on the incident side of the charged particle beam in the vacuum vessel 10, and a window portion 13 made of Kapton® (polyimide film) is formed on the exit side of the charged particle beam.

[0013] (Pair of superconducting coil units 20) A pair of superconducting coil units 20 are provided in a vacuum space 11. The pair of superconducting coil units 20 includes a superconducting coil unit 20A and a superconducting coil unit 20B, and each superconducting coil unit includes at least one coil. In this embodiment, superconducting coil unit 20A includes coils 20A1 to 20A6, and superconducting coil unit 20B includes coils 20B1 to 20B6. However, the number of coils included in superconducting coil units 20A and 20B can be set as appropriate. For example, superconducting coil units 20A and 20B may each consist of a single coil, or they may each consist of 2 to 5 or 7 or more coils. The shapes of superconducting coil units 20A and 20B can also be set as appropriate.

[0014] A pair of superconducting coil units 20 can generate a magnetic field (effective magnetic field region) oriented perpendicular to the direction of propagation of the charged particle beam and the direction of the beam's deflection angle φ (Z direction in the figure). The shape of the effective magnetic field region and the magnetic flux density can be adjusted by adjusting the shape of the superconducting coils and magnetic poles, and by adjusting the flowing current.

[0015] Each coil in the pair of superconducting coil units 20 generates multiple uniform magnetic fields (effective magnetic field regions) oriented perpendicular to the direction of propagation of the charged particle beam before deflection and the direction of the beam's deflection angle φ (Z-axis direction in the figure). The shape of the effective magnetic field region and the magnetic flux density can be adjusted by adjusting the shape of the coils and magnetic poles and adjusting the flowing current.

[0016] (York 30) The yoke 30 secures the coils included in the pair of superconducting coil units 20. The yoke 30 includes a fixing section 31A to which coils 20A1 to 20A6 included in superconducting coil unit 20A are secured, and a fixing section 31B to which coils 20B1 to 20B6 included in superconducting coil unit 20B are secured. The fixing section 31A includes reel frames 31A1 to 31A6 around which coils 20A1 to 20A6 are wound and secured, respectively. The fixing section 31B also includes reel frames 31B1 to 31B6 around which coils 20B1 to 20B6 are wound and secured, respectively. In the following description, reel frames 31A1 to 31A6 and reel frames 31B1 to 31B6 may be collectively referred to as reel frames 31A1 to 31B6.

[0017] In this embodiment, all coils included in a pair of superconducting coil units 20 are fixed to a single yoke 30. However, multiple yokes may be provided, and at least two coils included in a pair of superconducting coil units 20 may be fixed to one or more of these yokes. Furthermore, by fixing at least two coils to a single yoke, the relative positions of the coils can be fixed. Therefore, the coils can be more easily arranged in an appropriate relative position.

[0018] Furthermore, the yoke 30 is fixed to the vacuum container 10 by horizontal protrusions. The number of horizontal protrusions is not limited, but two may be provided at each location facing the inner surface of the vacuum container 10.

[0019] Furthermore, in this embodiment, the beam path BP through which the charged particle beam passes is formed between the superconducting coil unit 20A and the superconducting coil unit 20B of the pair of superconducting coil units 20. The beam path BP may be formed with an extent on the YZ plane depending on the angle of incidence of the charged particle beam to the superconducting electromagnet device 1, the incident position, and the magnetic field generated by the pair of superconducting coil units 20.

[0020] In this embodiment, the beam path BP and the pair of superconducting coil units 20 are spatially connected. That is, the beam path BP and the pair of superconducting coil units 20 are provided in the vacuum space 11 and are not spatially isolated. This allows the distance between superconducting coil unit 20A and superconducting coil unit 20B to be brought closer compared to the case where the beam path BP and the pair of superconducting coil units 20 are spatially isolated, thereby enabling miniaturization of the superconducting electromagnet device 1. Furthermore, by bringing the distance between the coil units closer, the generated magnetic field can be made stronger when the same current is passed through it.

[0021] In cases where the beam path BP and the pair of superconducting coil units 20 are not spatially connected, for example, the superconducting coil unit 20A and the superconducting coil unit 20B are housed in separate vacuum vessels (cryostats), and the beam path BP is formed between these vacuum vessels. Alternatively, for example, the superconducting coil unit 20A and the superconducting coil unit 20B are housed in the same vacuum vessel, but a vacuum duct is provided between them, and this vacuum duct defines the beam path BP. In this embodiment, the distance between the superconducting coil unit 20A and the superconducting coil unit 20B can be brought closer compared to these cases.

[0022] (Shield 40) The shield 40 is provided in the vacuum space 11 and prevents radiant heat from flowing into the pair of superconducting coil units 20 and the yoke 30. The shield 40 keeps its internal space at a lower temperature than its external space. The shield 40 is made of, for example, an aluminum plate and is provided so as to surround the yoke 30. This can contribute to keeping the pair of superconducting coil units 20 at a very low temperature (for example, about 4K) by minimizing the inflow of radiant heat into the pair of superconducting coil units 20. In this embodiment, the shield 40 is cooled to about 50K by a cooling unit 60 described later, so that the vacuum space 11 of the vacuum vessel 10 is cooled in stages towards the center (multilayer cooling structure). The shield 40 includes an opening 41 and a permeable portion 42.

[0023] The aperture 41 is formed in the shield 40 to allow the charged particle beam to pass through. The aperture 41 is formed on the upstream side of the shield 40 in the direction of travel of the charged particle beam. The charged particle beam, having traveled towards the shield 40, passes through the aperture 41 and enters the inside of the shield 40 without penetrating the shield 40. By passing the charged particle beam through the aperture 41, beam scattering can be suppressed when the beam enters the shield 40.

[0024] The permeable section 42 is formed to allow the charged particle beam to pass through. The permeable section 42 is formed on the downstream side of the shield 40 in the direction of travel of the charged particle beam. The charged particle beam that has passed through the shield 40 passes through the permeable section 42 and exits to the outside of the shield 40. By covering the exit side of the beam path BP with the permeable section 42, the inflow of radiant heat into the shield 40 can be suppressed.

[0025] In this embodiment, the boundary between the vacuum space 11 of the vacuum vessel 10 and the atmospheric environment is a window portion 13 formed of Kapton® (polyimide film). Therefore, radiant heat is more likely to flow into the exit side of the shield 40 compared to the inlet side. Thus, by making the inlet side of the shield 40 an opening 41 and the exit side from the shield 40 a transparent portion 42, it becomes easier to achieve both suppression of beam scattering and prevention of radiant heat inflow.

[0026] (Heat transfer suppression section) The superconducting electromagnet device 1 includes a radiant heat suppression unit that suppresses the transfer of radiant heat from the outside of the yoke 30 into the yoke 30. In this embodiment, the radiant heat suppression unit includes a suppression plate 50 and a heat transfer suppression unit 80, which will be described later. The radiant heat suppression unit may include at least one of the suppression plate 50 and the heat transfer suppression unit 80, or it may include at least one other element that suppresses the transfer of radiant heat from the outside of the yoke 30 into the yoke 30.

[0027] (Suppression plate 50) The suppression plate 50 is a plate that prevents radiant heat from flowing into the pair of superconducting coil units 20 and the yoke 30 inside the shield 40 through the opening 41 of the shield 40. The material of the suppression plate 50 is, for example, aluminum. In this embodiment, the vacuum vessel 10 and the fan-shaped vacuum duct 124 connected to the vacuum vessel 10 are installed in contact with the ambient temperature (approximately 300K) atmosphere. The shield 40 prevents radiant heat from flowing from these ambient temperature (approximately 300K) regions into the yoke 30, etc., which has been cooled to approximately 4K, but the suppression plate 50 suppresses the inflow of radiant heat in areas that cannot be covered by the shield 40. The suppression plate 50 is installed so as to be in contact with the shield 40 and is therefore cooled to the same temperature (approximately 50K) as the shield 40 by the cooling unit 60.

[0028] Furthermore, the suppression plate 50 can be positioned such that radiant heat from the vacuum vessel 10, which is in contact with room temperature, does not reach the pair of superconducting coil units 20. As an example, in this embodiment, the suppression plate 50 is positioned so that it penetrates into the interior of the yoke 30 in the X direction when viewed from the Y direction. In other words, the suppression plate 50 and the yoke 30 are positioned so that they overlap in the X direction. This makes it possible to suppress the effects of radiant heat more effectively. For example, the radiant heat RH shown in Figure 3 could reach the yoke 30 if the suppression plate 50 were not provided, but this is suppressed by the presence of the suppression plate 50.

[0029] (Cooling section 60) Figure 4 shows the cooling structure of the superconducting electromagnet device 1. The cooling unit 60 cools the components inside the vacuum space 11. In this embodiment, the cooling unit 60 is a so-called multilayer cooling structure, cooling the shield 40 and the suppression plate 50 to approximately 50K, and the pair of superconducting coil units 20 and the yoke 30 to approximately 4K. By gradually lowering the temperature toward the interior of the vacuum space 11, the ultra-low temperature environment inside can be maintained more efficiently and stably. The number of cooling stages and the temperature in K at each stage can be set as appropriate.

[0030] The specific configuration of the cooling unit 60 can be designed as appropriate. In this embodiment, a multi-stage refrigerator capable of cooling to approximately 4K and approximately 50K is used as the cooling unit 60. The cooling unit 60 includes a refrigerator 61 and cold heads 62 and 63. The refrigerator 61 cools the cooling medium. The cold head 62 receives cooling from the cooling medium cooled by the refrigerator 61 and cools the object to be cooled in the vacuum container 10. In this embodiment, the cold head 62 cools the shield 40 to approximately 50K, and the cold head 63 cools the yoke 30 to approximately 4K.

[0031] In this embodiment, since a single yoke 30 secures all the coils included in a pair of superconducting coil units 20, there is no need to provide a cooling unit 60 for each yoke, and the coils can be cooled with a relatively small number of cooling units 60, thus enabling efficient cooling.

[0032] (Heat transfer suppression section 80) Figure 5 is an explanatory diagram of the configuration of the heat transfer suppression section 80. The heat transfer suppression section 80 suppresses the transfer of radiant heat from the beam path BP side of the charged particle beam to the pair of superconducting coil units 20. In this embodiment, as described above, the beam path BP and the pair of superconducting coil units 20 are provided in a vacuum space 11 and are not spatially isolated. This allows the distance between the superconducting coil unit 20A and the superconducting coil unit 20B to be brought closer. Furthermore, since the heat transfer suppression section 80 suppresses the transfer of radiant heat from the beam path BP side to the pair of superconducting coil units 20, the influence of radiant heat can be suppressed while bringing the distance between the pair of coils closer. In this embodiment, the heat transfer suppression section 80 is arranged on the surface of the winding frames 31A1 to 31B6 facing the beam path BP. The heat transfer suppression section 80 includes a reflective layer 81 and a heat insulating layer 82.

[0033] In this embodiment, one heat transfer suppression section 80 is provided across the faces of winding frames 31A1 to 31A facing the beam path BP, and another heat transfer suppression section 80 is provided across the faces of winding frames 31B1 to 31B facing the beam path BP. However, other configurations of the arrangement of the heat transfer suppression sections 80 are also possible. For example, one heat transfer suppression section 80 may be provided for each of the winding frames 31A1 to 31B6. Alternatively, for example, a plurality of reflective layers 81, insulated from each other, may be arranged on a single winding frame (e.g., 31A1).

[0034] The reflective layer 81 is a layered portion that reflects radiant heat from the beam path BP. For example, the reflective layer 81 is composed of deposited metal, sputtered metal, or polished metal. As will be described in more detail later, for example, the reflective layer 81 is composed of metallic materials such as gold, silver, copper, or alloys thereof.

[0035] The heat insulating layer 82 is a layered portion that provides heat insulation and insulation between the reflective layer 81 and the winding frames 31A1 to 31B6. As will be described in detail later, for example, the heat insulating layer 82 is made of reinforced plastic (FRP), particularly glass fiber reinforced plastic (GFRP), aramid fiber reinforced plastic (AFRP), etc. In this embodiment, the heat insulating layer 82 provides heat insulation and insulation between the reflective layer 81 and the winding frames 31A1 to 31B6. However, the heat transfer suppression section 80 may include a layer that provides heat insulation between the reflective layer 81 and the winding frames 31A1 to 31B6, and a layer that provides insulation between the reflective layer 81 and the winding frames 31A1 to 31B6. In other words, heat insulation and insulation between the reflective layer 81 and the winding frames 31A1 to 31B6 may be achieved by two or more layers.

[0036] In this embodiment, the reflective layer 81 is provided on the beam path BP side of the heat-insulating layer 82. This suppresses the transfer of radiant heat from the reflective layer 81 to the winding frames 31A1 to 31B6. That is, the reflective layer 81 reflects radiant heat from the beam path BP, but some of the radiant heat is transferred to the reflective layer 81 (hereinafter referred to as "radiant heat from the outside"). At this time, because the heat-insulating layer 82 insulates the reflective layer 81 from the winding frames 31A1 to 31B6, it is possible to suppress the transfer of radiant heat absorbed by the reflective layer 81 to the pair of superconducting coil units 20 via the winding frames 31A1 to 31B6. Furthermore, if the reflective layer 81 is made of a metallic material, when the magnetic field generated by the pair of superconducting coil units 20 changes, a current flows through the reflective layer 81 in a direction that cancels out the change, and radiant heat (Joule heat) is generated (hereinafter referred to as "radiant heat (Joule heat) caused by current"). In this case, the insulating layer 82 insulates and heats the reflective layer 81 from the winding frame 31A1 to 31B6, thereby suppressing the transfer of radiant heat emitted by the reflective layer 81 to the pair of superconducting coil units 20 via the winding frame 31A1 to 31B6. As a result, the pair of superconducting coil units 20 can be maintained at extremely low temperatures.

[0037] Furthermore, as described above, the heat transfer suppression section 80 suppresses the transfer of radiant heat to the pair of superconducting coil units 20, but the radiant heat generated within the shield 40 must be removed by the cooling section 60. To this end, the heat transfer suppression section 80 must be configured such that the sum of (1) radiant heat from the outside and (2) radiant heat (Joule heat) caused by the current does not exceed the cooling capacity of the cooling section 60. For example, the cooling capacity of the cooling section 60 may be 0.1 to 2.0 [W] at approximately 4K, and if a cooling section 60 with a cooling capacity of 2.0 [W] is used, the heat transfer suppression section 80 must be configured such that the sum of (1) and (2) above is 2.0 [W].

[0038] (1) The amount of radiant heat from the outside depends on the reflectance μ of the reflective layer 81. The greater the reflectance μ of the reflective layer 81, the less radiant heat is transmitted to the reflective layer 81. For example, by making the reflective layer 81 out of deposited metal, sputtered metal, or polished metal, the reflectance μ of the reflective layer 81 can be improved and the inflow of radiant heat from the outside can be suppressed.

[0039] (2) Radiant heat (Joule heat) caused by electric current can be reduced by lowering the resistance R of the reflective layer 81. The resistance R of the reflective layer 81 is expressed as ρ·L / S (ρ: resistivity [Ω / m], S: cross-sectional area [m²], L: length of the conductor (layer) [m]). Since resistivity ρ is a value inherent to the metal material, the resistance R can be lowered by using a metal material with low resistivity. For example, the material for the reflective layer 81 can be gold (2.35 × 10⁻⁸ Ω / m), silver (1.59 × 10⁻⁸ Ω / m), copper (1.6~2.3 × 10⁻⁸ Ω / m), or alloys thereof.

[0040] Furthermore, (2) in order to reduce radiant heat (Joule heat) caused by electric current, multiple reflective layers 81 insulated from each other may be arranged on a single winding frame. Figure 6 shows an example of the arrangement of the heat transfer suppression section 80. By dividing the reflective layers 81 in this way, the path of the current flowing through each reflective layer 81 when the magnetic field changes can be shortened, and the total amount of Joule heat generated can be reduced. For example, a heat insulating layer 82 may be provided for each of the multiple reflective layers 81. Alternatively, for example, multiple reflective layers 81 may be arranged spaced apart from each other on a single heat insulating layer 82. In other words, multiple sets of reflective layers 81 and heat insulating layers 82 constituting the heat transfer suppression section 80 may be provided, or the heat transfer suppression section 80 may be composed of a single heat insulating layer 82 and multiple reflective layers 81 arranged on it.

[0041] Furthermore, the heat-insulating insulating layer 82 suppresses the transmission of (1) radiant heat from the outside and (2) radiant heat (Joule heat) caused by the electric current to the pair of superconducting coil units 20. Examples of materials for the heat-insulating insulating layer 82 from the viewpoint of processability and thermal conductivity include reinforced plastics (FRP), especially glass fiber reinforced plastics (GFRP) and aramid fiber reinforced plastics (AFRP).

[0042] Furthermore, the radiant heat E generated in the reflective layer 81 is expressed as E = σεT₁₀A(W), where ε is the emissivity of the reflective layer 81, T is the surface temperature of the reflective layer 81 [K], σ is the Stefan-Boltzmann constant = 5.67 × 10⁻⁸ [W / (m²·K₄)], and A is the cross-sectional area of ​​the reflective layer 81 (m²).

[0043] The emissivity ε[W / (m²·K⁴)] does not depend on the material temperature, but it varies between 0 and 1 depending on the material and its atomic-level surface state. Therefore, a material is selected that does not exceed the cooling capacity of the refrigerator, depending on the temperature of the heat transfer suppression section 80 during cooling. Examples of such metals include gold, silver, and copper.

[0044] By adopting the configuration of the heat transfer suppression unit 80 described above, (1) radiant heat from the outside and (2) radiant heat (Joule heat) caused by electric current can be suppressed. Furthermore, (1) radiant heat from the outside can be suppressed more effectively by using the suppression plate 50 and the heat transfer suppression unit 80 described above in combination.

[0045] [Charged particle beam therapy device] Figure 7 is a schematic diagram of a charged particle beam irradiation device 100 equipped with a superconducting electromagnet device 1. The charged particle beam irradiation device 100 includes the superconducting electromagnet device 1. The charged particle beam irradiation device 100 may further include an accelerator 110 and a beam transport system 120.

[0046] The accelerator 110 is a device that generates a charged particle beam, and is, for example, a synchrotron, a cyclotron, or a linear accelerator. The charged particle beam generated in the accelerator 110 is guided to the superconducting electromagnet device 1 through the beam transport system 120.

[0047] The beam transport system 120 includes one or more charged particle beam adjusting means 121, a vacuum duct 122, a distribution electromagnet 123, and a fan-shaped vacuum duct 124. The accelerator 110, the charged particle beam adjusting means 121, and the distribution electromagnet 123 are connected by the vacuum duct 122, and the distribution electromagnet 123 and the superconducting electromagnet device 1 are connected by the fan-shaped vacuum duct 124. By making the shape of the fan-shaped vacuum duct 124 in the XY plane (see Figure 1) fan-shaped, even a charged particle beam deflected with a deflection angle φ of 10 degrees or more can pass through the vacuum duct, and it can be made smaller compared to a rectangular vacuum duct, reducing the installation space.

[0048] The charged particle beam is generated in the upstream accelerator 110, travels through the vacuum duct 122 and the fan-shaped vacuum duct 124 to avoid or reduce attenuation, and is guided to the downstream superconducting electromagnet device 1 while being adjusted by the charged particle beam adjustment means 121.

[0049] The charged particle beam adjustment means 121 may include, as appropriate according to the specifications, a beam slit for adjusting the beam shape and / or dose of the charged particle beam, an electromagnet for adjusting the direction of travel of the charged particle beam, a quadrupole electromagnet for adjusting the beam shape of the charged particle beam, and a steering electromagnet for fine-tuning the beam position of the charged particle beam.

[0050] The path of the charged particle beam from the distribution electromagnet 123 to the isocenter O (the affected area of ​​the patient) differs depending on the irradiation angle θ, which will be described later. As a result, the optical elements that the charged particle beam encounters also change depending on the irradiation angle θ, and the beam shape of the charged particle beam at the isocenter O may change depending on the irradiation angle θ. To address this, for example, a charged particle beam adjustment means 121 provided upstream of the superconducting electromagnet device 1 may be controlled for each irradiation angle θ to adjust the beam shape of the charged particle beam at the isocenter O to be appropriate.

[0051] The distribution electromagnet 123 is configured to continuously deflect the charged particle beam at a deflection angle φ and emit the charged particle beam to the superconducting electromagnet device 1. The superconducting electromagnet device 1 is configured to continuously change the irradiation angle θ of the incident charged particle beam directed toward the isocenter O according to the deflection angle φ.

[0052] [Differentiation] <Example 1> In the above embodiment, the reflective layer 81 and the heat insulating layer 82 of the heat transfer suppression section 80 are arranged on the surfaces of the winding frames 31A1 to 31B6 facing the beam path BP. However, the heat transfer suppression section 80 may also be formed by polishing the surfaces of the winding frames 31A1 to 31B6 facing the beam path BP. With this configuration as well, the reflectivity of the surfaces of the winding frames 31A1 to 31B6 facing the beam path BP can be increased to suppress the transfer of radiant heat to the pair of superconducting coil units 20 via the winding frames 31A1 to 31B6.

[0053] <Modification 2> Figure 8 is an explanatory diagram of the configuration of a modified superconducting electromagnet device. Hereafter, components similar to those in the above embodiment will be denoted by the same reference numerals and their descriptions will be omitted. In this modified example, some of the coils (coils 920A2, 920A5, 920B2, 920B5) of a pair of superconducting coil units 920 are offset in the Z direction relative to the other coils. Such an arrangement eliminates or reduces the problem of low magnetic field strength between adjacent effective magnetic field regions.

[0054] In this modified example, the heat transfer suppression section 980 is positioned along the surface facing the beam path BP of the coil that is located further inward when viewed from the X direction among the multiple coils, i.e., closer to the beam path BP. This makes it easier to install the heat transfer suppression section 80 while suppressing the inflow of radiant heat.

[0055] <Variation 3> The heat transfer suppression section 80 may be configured by placing a material with high thermal shielding properties between the beam path BP and the superconducting coil unit 20. For example, one configuration is to place a single copper foil between the beam path BP and the superconducting coil unit 20 as the heat transfer suppression section 80. In this case, it is preferable that the copper foil is mirror-finished to enhance its thermal shielding properties.

[0056] The present invention has been described above based on each embodiment. However, the present invention is not limited to the above embodiments, and modifications may be made without departing from the spirit of the invention. Furthermore, the technologies described in each embodiment may be combined as appropriate, or known technologies may be combined with the technologies of the above embodiments as appropriate. [Explanation of Symbols]

[0057] 1 Superconducting electromagnet device, 10 Vacuum vessel, 20 Pair of superconducting coil units, 30 Yoke, 80 Heat transfer suppression section

Claims

1. A superconducting electromagnet device, A vacuum vessel that forms a vacuum space inside, A pair of superconducting coil units provided in the vacuum space, each of which includes at least one coil, The pair of superconducting coil units includes at least one yoke to which the coils are fixed, A shield positioned outside the yoke in the vacuum space, the shield maintaining the internal space of the shield at a lower temperature than the external space of the shield, A superconducting electromagnet device comprising a radiant heat suppression section that reflects radiant heat transmitted from the outside of the yoke into the yoke.

2. A superconducting electromagnet device according to claim 1, The superconducting electromagnet device includes a heat transfer suppression unit that suppresses the transfer of radiant heat from the beam path side of a charged particle beam formed between the pair of superconducting coil units to the pair of superconducting coil units.

3. A superconducting electromagnet device according to claim 2, The coils included in the pair of superconducting coil units include a structure in which a superconducting conductor is wound around a winding frame provided on at least one yoke, The winding frame includes a first surface facing the beam path, The heat transfer suppression part is arranged on the first surface. Superconducting electromagnet device.

4. A superconducting electromagnet device according to claim 3, The heat transfer suppression unit is A layered first portion that reflects radiant heat, A layered second portion that provides thermal insulation and insulation between the first portion and the winding frame, Equipped with, The first portion is provided on the beam path side of the second portion and reflects radiant heat from the beam path side. Superconducting electromagnet device.

5. A superconducting electromagnet device according to claim 4, The first part is made of a deposited metal, a sputtered metal, or a polished metal. Superconducting electromagnet device.

6. A superconducting electromagnet device according to claim 4, A plurality of the first parts, which are insulated from each other, are arranged on one reel. Superconducting electromagnet device.

7. A superconducting electromagnet device according to claim 3, The heat transfer suppression portion is formed by polishing the first surface of the winding frame. Superconducting electromagnet device.

8. A superconducting magnet device according to claim 1, The radiant heat suppression section includes a suppression plate that suppresses the transfer of radiant heat from the outside of the shield to the pair of superconducting coil units and the at least one yoke inside the shield. Superconducting electromagnet device.

9. A charged particle beam irradiation device comprising the superconducting electromagnet device described in claim 1.

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