Superconducting magnet with iron core, accelerator provided with superconducting magnet with iron core, and particle beam therapy device provided with accelerator

Abstract

The present invention makes it possible to support an apparatus in a predetermined space between magnetic poles while also curbing any impact on the magnetic field distribution. A superconducting magnet 11 with iron core is provided with: a plurality of iron core sections 12, 13 that are provided facing opposite one another in the axial direction and can be split in the axial direction; superconducting coils 23 provided in the periphery of magnetic poles 121, 131 respectively formed at middle sections of the plurality of iron core sections; and at least one support member 100 supporting, from at least one of the magnetic poles, an apparatus 200 provided in a predetermined space 16 between the magnetic poles. A section 120, of the support member, protruding out from the magnetic pole into the predetermined space is formed of a non-magnetic material.

Description

Superconducting magnet with iron core, accelerator equipped with superconducting magnet with iron core, and particle beam therapy device equipped with accelerator

[0001] The present invention relates to a superconducting magnet with an iron core, an accelerator equipped with a superconducting magnet with an iron core, and a particle beam therapy system equipped with an accelerator.

[0002] High-energy ion beams used in particle beam therapy, physics experiments, and the like are generated using accelerators. Known accelerators that produce beams with a kinetic energy per nucleon of around 200 MeV include, for example, cyclotrons, synchrotrons, and synchrocyclotrons (see Patent Document 1). Devices such as dee electrodes and dummy dee electrodes are attached to the magnetic poles.

[0003] Special table 2020-511170 publication

[0004] In superconducting accelerators with iron cores, such as superconducting cyclotrons or superconducting synchrocyclotrons, various devices are installed between the magnetic poles. Therefore, support members must be installed between the magnetic poles to support the devices. However, when precise positioning or other strong support is required, holes are formed in the magnetic poles and rod-shaped support members are inserted into the holes. If the support members are made of a magnetic material, the parts that protrude upward from the holes can cause an error magnetic field. In contrast, if the support members are made of a non-magnetic material, the parts inserted into the holes can cause an error magnetic field.

[0005] Therefore, the present disclosure provides a superconducting magnet with an iron core that can support equipment in a specified space between each magnetic pole while suppressing the effect on the magnetic field distribution, an accelerator equipped with a superconducting magnet with an iron core, and a particle beam therapy device equipped with an accelerator.

[0006] In order to solve the above problems, the superconducting magnet with an iron core according to the present invention comprises a plurality of iron core sections arranged axially opposite each other and divisible in the axial direction, a superconducting coil arranged around each magnetic pole formed in the plurality of iron core sections, and at least one support member that supports equipment arranged in a specified space between the magnetic poles from at least one of the magnetic poles, and the portion of the support member that protrudes from the magnetic pole into the specified space is made of a non-magnetic material.

[0007] According to the present invention, the portion of the support member that protrudes into the specified space between the magnetic poles is made of a non-magnetic material, so that the equipment can be supported in the specified space while suppressing the effect on the magnetic field distribution.

[0008] 1 is a side view of an accelerator having a superconducting magnet with an iron core; a plan view of the accelerator; an axial cross-sectional view of the accelerator; a view showing the accelerator in different enlarged cross sections; a cross-sectional view showing an enlarged support member; an explanatory view showing a state in which the upper iron core portion has been displaced upward; an overall configuration diagram of a particle beam therapy device using an accelerator; a cross-sectional view showing an enlarged support member according to a second embodiment; a cross-sectional view showing an enlarged support member according to a third embodiment; an explanatory view schematically showing a state;

[0009] Hereinafter, a superconducting magnet with an iron core and an accelerator equipped with the superconducting magnet with an iron core will be described with reference to the drawings, and a particle beam therapy system equipped with the accelerator will also be described.

[0010] The present disclosure provides a superconducting magnet with an iron core that can suppress the generation of error magnetic fields relative to a predetermined magnetic field distribution even when support members are installed on the magnetic poles. In the present disclosure, the support members placed on the magnetic poles are formed as composite parts made by joining magnetic and non-magnetic materials. The portions of the support members made of magnetic material are inserted into holes formed in the magnetic poles. The portions protruding from the holes are made of non-magnetic material. As a result, the present disclosure makes it possible to suppress the generation of error magnetic fields relative to a predetermined magnetic field distribution.

[0011] In the present disclosure, the support member comprises a base-end support portion that is provided within the magnetic pole and is made of a magnetic material, and a tip-end support portion that protrudes from the magnetic pole into a predetermined space and is made of a non-magnetic material, and the base-end support portion and the tip-end support portion are integrated.

[0012] In the present disclosure, the base support portion is embedded in a hole formed in the magnetic pole.

[0013] In the present disclosure, a corrective magnetic body having a volume equivalent to the space on the bottom side of the hole into which the base end support part is not inserted is attached to the tip end support part.

[0014] In the present disclosure, the base-end support portion protrudes into a predetermined space by an amount corresponding to the volume of the space on the bottom side of the hole that the base-end support portion is not inserted into.

[0015] In this disclosure, each magnetic pole is formed to have a predetermined three-dimensional shape.

[0016] Example 1 will be described with reference to Figures 1 to 6. Figure 1 is a side view of an accelerator 10. Figure 2 is a plan view of the accelerator 10. Figure 3 is an axial cross-sectional view of the accelerator 10.

[0017] A total of four lifting members 40 may be provided on the outer periphery of the main electromagnet 11, spaced apart by 90 degrees, or a total of three lifting members 40 may be provided on the outer periphery of the main electromagnet 11, spaced apart by 120 degrees. Alternatively, five or more lifting members 40 may be provided on the outer periphery of the main electromagnet 11.

[0018] The accelerator 10 is, for example, a frequency-modulated variable energy accelerator. This accelerator 10 is a circular accelerator that has a time-constant magnetic field as a main magnetic field and accelerates ions (protons, carbon, etc.) circulating in the main magnetic field by a high-frequency electric field.

[0019] The accelerator 10 includes a radio frequency acceleration cavity 101 (see FIG. 7) that forms an accelerating electric field for accelerating ions, a rotary variable capacitor (not shown) for modulating the frequency of the accelerating electric field, an additional magnetic field generating shim (not shown) that gives a kicking action from a stable region to circulating ions by the magnetic field formed by magnetic poles 121 and 131 (see FIG. 3), a disturbance electrode (not shown) that generates a disturbance electric field for extracting ions that have been kicked by the additional magnetic field generating shim from the accelerator 1, a low-level radio frequency generator (not shown) that controls the accelerating electric field, and a disturbance radio frequency controller (not shown) that controls the disturbance electric field. The accelerator 10 has a region where the circular orbits of multiple ions, each orbiting with different energies, converge and a region where they separate, and ions injected in different cycles orbit simultaneously with approximately the same energy.

[0020] The main electromagnet 11 of the accelerator 10 is provided with a plurality of refrigerator ports 30 and a plurality of lifting members 40. A plurality of (for example, two) refrigerator ports 30 are provided on each of the upper and lower surfaces of the main electromagnet 11. As described above, a plurality of lifting members 40 are provided spaced apart on the outer periphery of the main electromagnet 11. A plurality of support legs 50 are provided on the lower surface of the main electromagnet 11. The main electromagnet 11 is supported by the support legs 50 on a floor (not shown).

[0021] The main electromagnet 11 of the accelerator 10 includes, for example, an upper core portion 12 located axially above and a lower core portion 13 located axially below. The upper core portion 12 and the lower core portion 13 are arranged opposite each other in the axial direction (vertical direction) and can be separated in the axial direction. A parting line 14 is formed between the upper core portion 12 and the lower core portion 13. As will be described later with reference to FIG. 6 , by separating the upper core portion 12 from the lower core portion 13 and displacing it upward, an opening appears in the main electromagnet 11 along the parting line 14. Workers can perform maintenance work on the equipment inside the main electromagnet 11 through this opening.

[0022] Maintenance work may include, for example, measuring the magnetic field within the main electromagnet 11, adjusting magnetic field correction equipment (not shown) based on the results of the magnetic field measurement, and inspecting or replacing equipment such as a high-frequency kicker (not shown).

[0023] As shown in FIG. 3 , magnetic poles 121 and 131 facing each other are provided in the center of the main electromagnet 11. A magnetic pole 121 is provided in the center of the lower surface of the upper core portion 12, and another magnetic pole 131 is provided in the center of the upper surface of the lower core portion 13. These magnetic poles 121 and 131 generate a predetermined main magnetic field. The magnetic poles 121 and 131 are formed in a predetermined three-dimensional shape. Here, the three-dimensional shape does not mean that the entire surface is formed flat, but rather that the shape has curved portions or the like, and is more complex than a flat surface. The three-dimensional shape may also include partially flat surfaces.

[0024] The space between the magnetic poles 121 and 131 is a beam passage region 16 through which the ion beam circulates. The beam passage region 16 corresponds to the "predetermined space." The superconducting coil (main coil) 23 is provided along the inner walls of the upper core portion 12 and the lower core portion 13, surrounding the magnetic poles 121 and 131.

[0025] More specifically, an upper superconducting coil 23 is provided on the inner peripheral surface of the upper core portion 12 so as to surround the outside of the magnetic pole 121. A lower superconducting coil 23 is provided on the inner peripheral surface of the lower core portion 13 so as to surround the outside of the magnetic pole 131. Each superconducting coil 23 is attached to and supported by the coil frame 22.

[0026] The outside of the coil frame 22 is surrounded by a coil section shield plate 21. A shield plate surrounding a refrigerator port 30 provided above the main electromagnet 11 is connected to the upper side of the coil section shield plate 21. A shield plate surrounding a refrigerator port 30 provided below the main electromagnet 11 is connected to the lower side of the coil section shield plate 21. The shield plate 21 prevents heat from the outside from being transferred to the superconducting coil 23 inside the shield plate 21.

[0027] The superconducting coil 23, the coil frame 22, and the coil shield plate 21 are provided inside a coil vacuum vessel 20. The coil vacuum vessel 20 is also called a cryostat. The coil vacuum vessel 20 maintains the vacuum and temperature inside. The temperature inside the coil vacuum vessel 20 is maintained by the cooling capacity of each refrigerator port 30.

[0028] The inside of the main electromagnet 11 is evacuated by a vacuum pump (not shown). The main electromagnet 11 is provided with a plurality of through-holes for connecting the outside with the beam passing region 16. For example, a beam extraction through-hole (not shown) for extracting the accelerated beam and a beam monitor mounting hole (not shown) for mounting a beam monitor are provided in the middle portion 14 of the main electromagnet 11. In addition, a through-hole for extracting the coil conductor of the superconducting coil 23 to the outside and a through-hole for inputting high-frequency power to the acceleration electrode (neither of which are shown) are provided in the middle portion of the main electromagnet 11.

[0029] The lifting members 40 will now be described. A plurality of lifting members 40 are provided around the main electromagnet 11, and the lower sides of their main bodies are attached to the outer peripheral surface of the lower core portion 13. The lifting members 40 may be electrically operated, hydraulically operated, or pneumatically operated. The tips of the rods 41 of the lifting members 40 are attached to the outer peripheral surface of the upper core portion 12. The lifting members 40 can displace only the upper core portion 12 axially upward of the main electromagnet 11 by extending the rods 41. The lifting members 40 can place the upper core portion 12 on the lower core portion 13 by retracting the rods 41. The lifting members 40 operate in accordance with control signals from a control device (not shown). The above-mentioned cryogenic refrigerator (refrigerator port 30) also operates in accordance with control signals from a control device (not shown).

[0030] 4 is a diagram showing the accelerator 10 in a different cross section. In the beam passage region 16 formed between the magnetic poles 121 and 131, devices 200 such as dee electrodes, iron pieces for adjusting the magnetic field, and an ion source are installed. Although FIG. 4 shows only one device 200 installed, in reality, multiple devices 200 are installed. The device 200 can also be called a supported member.

[0031] The device 200 is supported from one or both of the magnetic poles 121 and 131 by at least one support member 100. While Fig. 4 shows a case where the device 200 is supported by a plurality of support members 100 from both of the magnetic poles 121 and 131, the device 200 is not limited to this, and may be supported by a support member 100 provided on the lower magnetic pole 131, or may be supported by a support member 100 provided on the upper magnetic pole 121. A plurality of devices 200 (not shown) supported in different directions are arranged in the beam passing region 16.

[0032] The installation position of the device 200 is not limited to the axial center of the beam passing region 16, but may be offset to either the top or bottom. The support member 100 is provided at any location on the surfaces of the magnetic poles 121 and 131, which have three-dimensional shapes, that is necessary to support the device 200. The location where the support member 100 is provided may be a curved surface or a flat surface.

[0033] The support member 100 has a portion (120) that protrudes from the magnetic pole into the beam passage area 16, which is the "predetermined space," and is made of a non-magnetic material. More specifically, the support member 100 includes a base end support portion 110 that is provided within the magnetic pole and is made of a magnetic material, and a tip end support portion 120 that protrudes from the magnetic pole into the beam passage area 16 and is made of a non-magnetic material. Examples of non-magnetic materials include SUS316 and SUS304.

[0034] 5, the base-end support portion 110 and the tip-end support portion 120 are integrated. For example, a fixing technique such as friction welding, explosive bonding, or HIP (hot isostatic pressing) is used to firmly connect the tip side 113 of the head portion 111 of the base-end support portion 110 and the base side 123 of the first portion 121 of the tip-end support portion 120.

[0035] The base-end support part 110 is made of a magnetic material such as pure iron. The base-end support part 110 may be made of the same magnetic material as the magnetic poles, or may be made of a different magnetic material. The base-end support part 110 is made of a magnetic material and has a bolt shape. The base-end support part 110 has a head part 111 and a threaded part 112.

[0036] The magnetic pole has an axially formed hole 115 through which the base support portion 110 is inserted. The hole 115 is a bolt insertion hole, and a substantially conical space 116 is formed at its bottom. The space 116 corresponds to a "bottom space" into which the threaded portion 112 is not inserted. The side of the hole 115 opposite the bottom space 116 is an opening 117 that opens to the surface of the magnetic pole. The support member 100 is firmly and detachably fixed to the magnetic pole by inserting and threading the base support portion 110 into the hole 115. The support member 100 can also be removed from the magnetic pole for maintenance and replacement. The hole 115 from which the support member 100 has been removed can be blocked by inserting a screw plug or similar object made of a magnetic material that corresponds to the base support portion 110.

[0037] In other words, the base-end support part 110 is detachably fitted or screwed into the hole part 115. If there is no need to remove the support member 100 from the magnetic pole, the base-end support part 110 can be attached to the hole part 115 in an undetachable manner.

[0038] The distal support section 120 is integrated with the proximal support section 110 and protrudes into the beam passing region 16 to support the device 200. The distal support section 120 includes, for example, a large-diameter first section 121 connected to the proximal support section 110 and a small-diameter second section 122 protruding from the first section 121, with the distal end 124 of the second section 122 contacting the device 200. The relationship between the diameter of the first section 121 and the diameter of the second section 122 may be reversed. The cross-sectional shapes of the first section 121 and the second section 122 are not limited to being circular, and may be rectangular, polygonal, elliptical, or the like. The cross-sectional shapes of the first section 121 and the second section 122 may be similar or different.

[0039] 6 schematically shows the state in which the upper core section 12 has been displaced upward. When the connection between the upper core section 12 and the lower core section 13 is released and the rods 41 of each lifting member 40 are extended, the upper core section 12 moves upward. When the upper core section 12 is displaced upward, the top side of the coil section vacuum vessel 20 is exposed. This allows workers to perform maintenance on the equipment 200, measure magnetic force, set the magnetic force adjustment device, etc.

[0040] 7 is a diagram showing the overall configuration of a particle beam therapy system 1 that uses an accelerator 10. The particle beam therapy system 1 includes the accelerator 10, a beam transport system 2, an irradiation device 3, a treatment table 4, an overall control device 5, an irradiation control device 6, a treatment plan database 7, and a treatment planning device 8.

[0041] The RF acceleration cavity 101 forms an accelerating electric field for accelerating ions into an ion beam through a RF power input through-hole (not shown). The RF acceleration cavity 101 is equipped with, for example, an acceleration dee electrode and a rotary variable capacitor (neither of which is shown) for modulating the frequency of the accelerating electric field.

[0042] An ion source 103 for supplying hydrogen ions is installed at a position offset from the center above the main electromagnet 11. The ion source 103 supplies ions to a beam passage region 16 inside the accelerator 10 through a beam injection through-hole (not shown).

[0043] The beam transport system 2 is a mechanism that transports the ion beam accelerated by the accelerator 10 to the irradiation device 3. The irradiation device 3 is a device that irradiates the beam transported by the beam transport system 2 onto a target within a patient PT fixed to a treatment table 4. An overall control device 5 controls the accelerator 10, the beam transport system 2, and the irradiation device 3. An irradiation control device 6 controls the beam irradiation onto the target. A treatment plan database 7 stores treatment plans created by a treatment planning device 8. The treatment planning device 8 creates a beam irradiation plan for the target.

[0044] In the particle beam therapy system 1, the energy and dose of the particle beam to be irradiated are determined by a treatment plan. The energy and dose of the particle beam determined by the treatment plan are sequentially input from the overall control device 5 to the irradiation control device 6. After irradiating the target with an appropriate dose, the particle beam therapy system 1 shifts to the next energy and irradiates the target with the beam again.

[0045] According to the particle beam therapy system 1 configured as above, since it includes the accelerator 10 described above, it is possible to suppress the generation of error magnetic fields, and it is possible to further improve reliability.

[0046] According to the present disclosure, the base end side of the support member 100 can be attached to the magnetic pole, thereby supporting the device 200. The base end support part 110 of the support member 100 is inserted into and fixed to the hole 115 formed in the magnetic pole, thereby enabling the support member 100 to firmly support the device 200.

[0047] Since the base end support portion 110 of the support member 100 is formed from a magnetic material similar to the material of the magnetic poles, it is possible to prevent the iron core from being damaged by the volume of the hole portion 115, thereby reducing the generation of an error magnetic field.

[0048] The tip support part 120 of the support member 100 is made of a non-magnetic material, so even if the tip support part 120 protrudes into the beam passing region 16, it can be prevented from causing an error magnetic field.

[0049] Example 2 will be described using Figure 8. In the following examples, including this example, differences from Example 1 will be mainly described. In the support member 100A of Example 2, a corrective magnetic body 130 having a volume equivalent to the bottom-side space 116 of the hole 115 into which the base-end support part 110 is not inserted is attached to the tip-end support part 120.

[0050] The corrective magnetic body 130 is formed as, for example, an annular member such as a washer, and is attached to the outer periphery or a stepped portion of the lower side of the first portion 121 of the tip-side support part 120. By bringing the surface of the magnetic pole and the corrective magnetic body 130 as close as possible to each other, the generation of an error magnetic field can be further suppressed.

[0051] This embodiment configured in this manner also achieves the same effects as embodiment 1. Furthermore, in this embodiment, the corrective magnetic body 130 having a volume corresponding to the volume of the bottom space 116 of the hole 115 that is not filled by the base-end support portion 110 made of a magnetic material is provided in the tip-end support portion 120, so that the generation of an error magnetic field can be suppressed. Note that the volume of the corrective magnetic body 130 and the volume of the bottom space 116 do not need to strictly match.

[0052] Example 3 will be described with reference to Figure 9. In the support member 100B of this example, the head 111B of the base-end support part 110B protrudes into the predetermined space 16 by a predetermined amount H1, which is the volume of the bottom-side space 116 of the hole 115 that the base-end support part 110B is not inserted into.

[0053] This embodiment configured in this manner also achieves the same effects as those of Embodiments 1 and 2. Furthermore, in this embodiment, the head 111B of the base-end support portion 110B is protruded into the beam passing area 16 by a predetermined amount H1 without using the corrective magnetic body 130, so that the number of parts can be reduced compared to Embodiment 2.

[0054] The present invention is not limited to the above-described embodiments. Those skilled in the art can make various additions and modifications within the scope of the present invention. The above-described embodiments are not limited to the configuration examples shown in the accompanying drawings. The configurations and processing methods of the embodiments can be modified as appropriate within the scope of achieving the object of the present invention. For example, the shape of the refrigerator port installation area is not limited to that shown in the drawings.

[0055] Furthermore, the components of the present invention can be selected arbitrarily, and the invention including the selected components is also included in the present invention. Furthermore, the components described in the claims can be combined in combinations other than those explicitly stated in the claims.

[0056] 1: particle beam therapy device, 2: beam transport system, 3: irradiation device, 4: treatment table, 5: overall control device, 6: irradiation control device, 7: treatment plan database, 8: treatment planning device, 10: accelerator, 11: main electromagnet, 12: upper iron core section, 13: lower iron core section, 14: dividing line, 16: beam passing area, 20: coil section vacuum vessel, 23: superconducting coil, 30: refrigerator port, 40: lifting member, 100, 100A, 100B: support member, 110, 110B: base end side support section 110, 115: hole section, 116: bottom side space, 120: tip end side support section, 130: corrective magnetic material, 200: equipment

Claims

1. A superconducting magnet with an iron core, comprising: a plurality of iron core sections arranged opposite each other in the axial direction and separable in the axial direction; a superconducting coil arranged around each of the magnetic poles formed in the plurality of iron core sections; and at least one support member that supports, from at least one of the magnetic poles, a device arranged in a specified space between the magnetic poles, wherein the portion of the support member that protrudes from the magnetic poles into the specified space is made of a non-magnetic material.

2. A superconducting magnet with an iron core as described in claim 1, wherein the support member comprises a base end support part formed of a magnetic material and disposed within the magnetic pole, and a tip end support part formed of a non-magnetic material and disposed so as to protrude from the magnetic pole into the specified space, and the base end support part and the tip end support part are integrated.

3. The superconducting magnet with an iron core according to claim 2, wherein the base end support portion is embedded in a hole formed in the magnetic pole.

4. A superconducting magnet as set forth in claim 3, wherein a corrective magnetic body having a volume equivalent to the space on the bottom side of said hole into which said base end support part is not inserted is attached to said tip end support part.

5. A superconducting magnet as set forth in claim 3, wherein the base end support part protrudes into the specified space by an amount equivalent to a volume of the space on the bottom side of the hole into which the base end support part is not inserted.

6. The superconducting magnet according to claim 1, wherein each of the magnetic poles is formed to have a predetermined three-dimensional shape.

7. An accelerator comprising a superconducting magnet with an iron core according to any one of claims 1 to 6.

8. A particle beam therapy system comprising: an irradiation device for irradiating a target with a beam accelerated by the accelerator according to claim 7; and a control device for controlling the accelerator and the irradiation device.

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