Technical Field
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The present invention relates to an iron core-equipped superconducting magnet, an accelerator including the iron core-equipped superconducting magnet, and a particle beam therapy apparatus including the accelerator.
Background Art
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A high-energy ion beam used in particle beam therapy, physical experiments, or the like is generated using an accelerator. For example, a cyclotron, a synchrotron, a synchrocyclotron, and the like are known as accelerators that obtain a beam having kinetic energy per nucleus of about 200 MeV (PTL 1). Components such as a dee electrode and a dummy dee electrode are attached to a magnetic pole.
Citation List
Patent Literature
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Summary of Invention
Technical Problem
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In an iron core-equipped superconducting accelerator such as a superconducting cyclotron or a superconducting synchrocyclotron, various types of components are disposed between magnetic poles. Therefore, it is necessary to mount a support member for supporting the components between the magnetic poles. However, in a case where strong support is required, for example, precise positioning is required, a hole is formed in a magnetic pole portion, and a rod-shaped support member is inserted into the hole. When the support member is made of a magnetic material, a portion protruding upward from the hole causes an error magnetic field. On the other hand, when the support member is made of a non-magnetic material, the portion inserted into the hole portion may cause an error magnetic field.
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Therefore, the present disclosure provides an iron core-equipped superconducting magnet, an accelerator including the iron core-equipped superconducting magnet, and a particle beam therapy apparatus including the accelerator capable of supporting a component in a predetermined space between magnetic poles while restricting an influence on a magnetic field distribution.
Solution to Problem
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In order to solve the above problem, an iron core-equipped superconducting magnet according to the invention is configured including: a plurality of iron core portions provided to face each other in an axial direction and dividable in the axial direction; a superconducting coil provided around each of magnetic poles formed at the plurality of iron core portions; and at least one support member configured to support a component provided in a predetermined space between the magnetic poles from at least one of the magnetic poles. A portion of the support member protruding from the magnetic pole to the predetermined space is formed of a non-magnetic material.
Advantageous Effects of Invention
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According to the invention, since the portion of the support member protruding to the predetermined space between the magnetic poles is formed of a non-magnetic material, it is possible to support the component in the predetermined space while restricting an influence on a magnetic field distribution.
Brief Description of Drawings
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- [FIG. 1] FIG. 1 is a side view of an accelerator including an iron core-equipped superconducting magnet.
- [FIG. 2] FIG. 2 is a plan view of the accelerator.
- [FIG. 3] FIG. 3 is an axial cross-sectional view of the accelerator.
- [FIG. 4] FIG. 4 is an enlarged view of the accelerator in a different cross section.
- [FIG. 5] FIG. 5 is an enlarged cross-sectional view of a support member.
- [FIG. 6] FIG. 6 is a diagram illustrating a state in which an upper iron core portion is displaced upward.
- [FIG. 7] FIG. 7 is an overall configuration diagram of a particle beam therapy apparatus using an accelerator.
- [FIG. 8] FIG. 8 is an enlarged cross-sectional view of a support member according to Embodiment 2.
- [FIG. 9] FIG. 9 is an enlarged sectional view of a support member according to Embodiment 3.
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An illustrative diagram schematically illustrates a state.
Description of Embodiments
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Hereinafter, an iron core-equipped superconducting magnet and an accelerator including the iron core-equipped superconducting magnet will be described with reference to the drawings. Further, a particle beam therapy apparatus including the accelerator will also be described.
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The present disclosure provides an iron core-equipped superconducting magnet capable of restricting generation of an error magnetic field with respect to a predetermined magnetic field distribution even when a support member is disposed on a magnetic pole. In the present disclosure, the support member disposed on the magnetic pole is formed as a composite component in which a magnetic material and a non-magnetic material are bonded. A portion of the support member formed of the magnetic material is inserted into a hole formed in the magnetic pole. A portion protruding from the hole is formed of the non-magnetic material. Accordingly, according to the present disclosure, it is possible to restrict generation of an error magnetic field with respect to a predetermined magnetic field distribution.
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In the present disclosure, the support member includes a base end support portion provided in the magnetic pole and formed of a magnetic material, and a tip end support portion provided in a manner of protruding from the magnetic pole to a predetermined space and formed of a non-magnetic material, and the base end support portion and the tip end support portion are integrated.
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In the present disclosure, the base end support portion is embedded in a hole portion formed in the magnetic pole.
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In the present disclosure, a correction magnetic body having a volume corresponding to a space on a bottom side of the hole portion into which the base end support portion is not inserted is attached to the tip end support portion.
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In the present disclosure, the base end support portion is protruded to the predetermined space by the volume corresponding to the space on the bottom side of the hole portion into which the base end support portion is not inserted.
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In the present disclosure, each magnetic pole is formed to have a predetermined three-dimensional shape.
[Embodiment 1]
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Embodiment 1 will be described with reference to FIGS. 1 to 6. FIG. 1 is a side view of an accelerator 10. FIG. 2 is a plan view of the accelerator 10. FIG. 3 is an axial cross-sectional view of the accelerator 10.
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A total of four elevating members 40 may be provided on an outer peripheral side of a main electromagnet 11 at intervals of 90 degrees, or a total of three elevating members 40 may be provided on the outer peripheral side of the main electromagnet 11 at intervals of 120 degrees. Alternatively, five or more elevating members 40 may be provided on the outer peripheral side of the main electromagnet 11.
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The accelerator 10 is, for example, a variable energy accelerator of a frequency modulation type. The accelerator 10 is a circular accelerator that has a temporally constant magnetic field as a main magnetic field and accelerates ions (protons, carbon, or the like), which circulate in the main magnetic field, by a radio-frequency electric field.
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The accelerator 10 includes a radio-frequency acceleration cavity 101 (see FIG. 7) that forms an acceleration electric field for accelerating ions, a rotary variable capacitor (not shown) for modulating the frequency of the acceleration electric field, an additional magnetic field generating shim (not shown) that applies a kick action from a stable region to ions circulating by a 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, from the accelerator 1, ions to which the kick action is applied by the additional magnetic field generating shim, a low-level radio frequency generator (not shown) that controls the acceleration electric field, and a disturbance radio frequency control device (not shown) that controls the disturbance electric field. The accelerator 10 has a region in which a plurality of annular circulating trajectories of respective ions having different energy are aggregated and a region in which annular circulating trajectories are dispersed, and ions making an entry in different cycles circulate simultaneously with substantially the same energy.
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The main electromagnet 11 of the accelerator 10 is provided with a plurality of refrigerator ports 30 and a plurality of elevating members 40. A plurality of (for example, two) refrigerator ports 30 are provided on each of an upper surface side and a lower surface side of the main electromagnet 11. As described above, the plurality of elevating members 40 are provided apart from each other on the outer peripheral side of the main electromagnet 11. A plurality of support legs 50 are provided on the lower surface side of the main electromagnet 11. The main electromagnet 11 is supported on a floor (not shown) by the support legs 50.
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The main electromagnet 11 of the accelerator 10 includes, for example, an upper iron core portion 12 positioned on an axially upper side and a lower iron portion 13 positioned on an axially lower side. The upper iron core portion 12 and the lower iron core portion 13 are provided to face each other in an axial direction (up-down direction) and can be divided in the axial direction. A dividing line 14 is formed between the upper iron core portion 12 and the lower iron core portion 13. As will be described later with reference to FIG. 6, when the upper iron core portion 12 is separated from the lower iron core portion 13 and displaced upward, an opening appears in the main electromagnet 11 along the dividing line 14. An operator can perform maintenance work on components inside the main electromagnet 1 through the opening.
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Examples of the maintenance work include measurement of a magnetic field in the main electromagnet 11, adjustment of a magnetic field correction component (not shown) based on a measurement result of the magnetic field, and inspection or replacement of a component (not shown) such as a radio-frequency kicker.
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As illustrated in FIG. 3, the magnetic poles 121 and 131 facing each other in the up-down direction are provided at a central portion of the main electromagnet 11. The magnetic pole 121 is provided at a central portion of a lower surface of the upper iron core portion 12, and the magnetic pole 131 is provided at a central portion of an upper surface of the lower iron core portion 13. A predetermined main magnetic field is generated by the magnetic poles 121 and 131. The magnetic poles 121 and 131 are formed in a predetermined three-dimensional shape. The term "three-dimensional shape" as used herein means a shape that is more complicated than a flat surface and has a curved portion or the like, rather than being formed entirely flat. The three-dimensional shape may include a partially flat surface.
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A space facing the magnetic poles 121 and 131 is a beam passage region 16 in which an ion beam circulates. The beam passage region 16 corresponds to a "predetermined space". A superconducting coil (main coil) 23 is provided along inner walls of the upper iron core portion 12 and the lower iron core portion 13 so as to surround the main magnetic poles 121 and 131.
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Specifically, the upper superconducting coil 23 is provided on an inner peripheral surface of the upper iron core portion 12 so as to surround an outside of the magnetic pole 121. The lower superconducting coil 23 is provided on an inner peripheral surface of the lower iron core portion 13 so as to surround an outside of the magnetic pole 131. Each superconducting coil 23 is attached to and supported by a coil frame 22.
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An outside of the coil frame 22 is surrounded by a coil portion shield plate 21. A shield plate surrounding the refrigerator port 30 provided on an upper side of the main electromagnet 11 is connected to an upper side of the coil portion shield plate 21. A shield plate surrounding the refrigerator port 30 provided on a lower side of the main electromagnet 11 is connected to a lower side of the coil portion shield plate 21. The shield plate 21 restricts heat outside the shield plate 21 from being transferred to the superconducting coil 23 on an inner side of the shield plate 21.
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The superconducting coil 23, the coil frame 22, and the coil portion shield plate 21 are provided inside a coil portion vacuum chamber 20. The coil portion vacuum chamber 20 is also called a cryostat. The coil portion vacuum chamber 20 maintains the vacuum and temperature therein. The temperature in the coil portion vacuum chamber 20 is maintained by the cooling capacity of each refrigerator port 30.
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An 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 ports for connecting the outside and the beam passage region 16. For example, a beam emission through port (not shown) for extracting an accelerated beam and a beam monitor mounting hole (not shown) for mounting a beam monitor are provided in an intermediate portion 14 of the main electromagnet 11. In addition, a through port for leading a coil conductor of the superconducting coil 23 out to the outside and a through port for inputting radio-frequency power to an acceleration electrode (both ports not shown) are provided in the intermediate portion of the main electromagnet 11.
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The elevating member 40 will be described. A plurality of elevating members 40 are provided around the main electromagnet 11, and a lower side of body portions thereof is attached to an outer peripheral surface of the lower iron core portion 13. The elevating member 40 may be an electric type, a hydraulic type, or a pneumatic type. A tip end of a rod 41 of the elevating member 40 is attached to an outer peripheral surface of the upper iron core portion 12. The elevating member 40 can displace only the upper iron core portion 12 upward in the axial direction of the main electromagnet 11 by extending the rod 41. The elevating member 40 places the upper iron core portion 12 on the lower iron core portion 13 by contracting the rod 41. The elevating member 40 operates according to a control signal from a control device (not shown). The above-described cryogenic refrigerator (refrigerator port 30) also operates according to a control signal from a control device (not shown).
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FIG. 4 is a view of the accelerator 10 in a different cross section. In the beam passage region 16 formed between the magnetic poles 121 and 131, for example, components 200 such as a dee electrode, an iron piece for magnetic field adjustment, and an ion source are disposed. Although FIG. 4 shows that only one component 200 is disposed, a plurality of components 200 are actually disposed. The component 200 may also be referred to as a supported member.
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The component 200 is supported from one or both of the magnetic poles 121 and 131 by at least one support member 100. Although FIG. 4 illustrates a case where the component 200 is supported by a plurality of support members 100 from both of the magnetic poles 121 and 131, the present disclosure is not limited thereto, and the component 200 may be supported by the support member 100 provided at the lower magnetic pole 131 or may be supported by the support member 100 provided at the upper magnetic pole 121. A plurality of components 200 supported in different directions are disposed in the beam passage region 16 (not shown).
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A position where the component 200 is disposed is not limited to a central portion in the axial direction of the beam passage region 16, and may be biased upward or downward. The support member 100 is provided at any position necessary for supporting the component 200 on surfaces of the magnetic poles 121 and 131 having a three-dimensional shape. The support member 100 may be provided on a curved surface or a flat surface.
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In the support member 100, a portion (120) protruding from the magnetic pole to the beam passage region 16 as a "predetermined space" is formed of a non-magnetic material. Specifically, the support member 100 includes a base end support portion 110 provided in the magnetic pole and formed of a magnetic material, and a tip end support portion 120 provided in a manner of protruding from the magnetic pole to the beam passage region 16 and formed of a non-magnetic material. Examples of the non-magnetic material include SUS316 and SUS304.
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As illustrated in an enlarged view of FIG. 5, the base end support portion 110 and the tip end support portion 120 are integrated. For example, a tip end side 113 of a head portion 111 of the base end support portion 110 and a base end side 123 of a first portion 121 of the tip end support portion 120 are firmly connected to each other using a fixing technique such as friction bonding, explosive cladding, or hot isostatic pressing (HIP).
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The base end support portion 110 is formed of a magnetic material such as pure iron. The base end support portion 110 may be formed of the same magnetic material as the magnetic pole, or may be formed of a different magnetic material. The base end support portion 110 is formed in a bolt shape from a magnetic material. The base end support portion 110 has the head portion 111 and a screw portion 112.
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A hole portion 115 through which the base end support portion 110 is inserted is formed in the magnetic pole in the axial direction. The hole portion 115 is a bolt insertion hole, and a substantially conical space 116 is formed in a bottom portion thereof. The space 116 corresponds to a "bottom-side space" into which the screw portion 112 is not inserted. The side of the hole portion 115 facing the bottom space 116 is an opening 117 that opens at a surface of the magnetic pole. The support member 100 is firmly and detachably fixed to the magnetic pole by inserting and screwing the base end support portion 110 into the hole portion 115. The support member 100 can also be removed from the magnetic pole for maintenance and replacement. A screw plug made of a magnetic material corresponding to the base end support portion 110 may be inserted into the hole portion 115, from which the support member 100 is removed, to close the hole.
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In other words, the base end support portion 110 is detachably fitted or screwed into the hole portion 115. When it is not necessary to remove the support member 100 from the magnetic pole, the base end support portion 110 can be undetachably attached to the hole portion 115.
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The tip end support portion 120 is integrated with the base end support portion 110, and protrudes to the beam passage region 16 to support the component 200. The tip end support portion 120 includes, for example, the large-diameter first portion 121 connected to the base end support portion 110 and a small-diameter second portion 122 protruding from the first portion 121, and a tip end side 124 of the second portion 122 is in contact with the component 200. The magnitude relationship between the diameter dimension of the first portion 121 and the diameter dimension of the second portion 122 may be reversed. A cross-sectional shape of the first portion 121 and the second portion 122 is not limited to a circular shape, and may be a rectangular shape, a polygonal shape, an elliptical shape, or the like. The cross-sectional shape of the first portion 121 and the cross-sectional shape of the second portion 122 may be similar or different.
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FIG. 6 schematically illustrates a state in which the upper iron core portion 12 is displaced upward. When the coupling between the upper iron core portion 12 and the lower iron core portion 13 is released and the rod 41 of each elevating member 40 is extended, the upper iron core portion 12 moves upward. When the upper iron core portion 12 is displaced upward, the upper side of the coil portion vacuum chamber 20 is exposed. Accordingly, the operator can perform maintenance of the component 200, magnetic force measurement, setting of a magnetic force adjustment device, and the like.
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FIG. 7 is an overall configuration diagram of a particle beam therapy apparatus 1 using the accelerator 10. The particle beam therapy apparatus 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 therapy plan database 7, and a therapy planning device 8.
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The radio-frequency acceleration cavity 101 forms, through a radio frequency power input through port (not shown), an acceleration electric field for accelerating ions to form an ion beam. The radio-frequency acceleration cavity 101 is provided with, for example, a dee electrode for acceleration and a rotary variable capacitor for modulating the frequency of an acceleration electric field (both not shown).
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An ion source 103 for supplying hydrogen ions is disposed at a position shifted from a center of an upper portion of the main electromagnet 11. The ion source 103 supplies ions to the beam passage region 16 inside the accelerator 10 through a beam entrance through port (not shown).
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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 a target in a patient PT fixed to the treatment table 4 with the beam transported by the beam transport system 2. The overall control device 5 controls the accelerator 10, the beam transport system 2, and the irradiation device 3. The irradiation control device 6 controls beam irradiation on a target. The therapy plan database 7 stores a therapy plan created by the therapy planning device 8. The therapy planning device 8 creates a beam irradiation plan for the target.
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In the particle beam therapy apparatus 1, energy and dose of a particle beam for irradiation are determined by therapy planning. The energy and dose of the particle beam determined by the therapy planning are sequentially input from the overall control device 5 to the irradiation control device 6. When the target is irradiated with an appropriate dose, the particle beam therapy apparatus 1 shifts to the next energy and irradiates the target with the beam again.
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According to the particle beam therapy apparatus 1 configured as described above, since the accelerator 10 described above is provided, it is possible to restrict the generation of the error magnetic field and to further improve the reliability.
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According to the present disclosure, since the base end side of the support member 100 can be attached to the magnetic pole, the component 200 can be supported. The support member 100 can firmly support the component 200 since the base end support portion 110 is inserted into and fixed to the hole portion 115 formed in the magnetic pole.
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Since the base end support portion 110 of the support member 100 is formed of the same magnetic material as the material of the magnetic pole, the loss of the iron core by the volume of the hole portion 115 can be restricted and the generation of the error magnetic field can be reduced.
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Since the tip end support portion 120 of the support member 100 is formed of a non-magnetic material, it is possible to prevent the tip end support portion 120 from causing an error magnetic field even when the tip end support portion 120 protrudes into the beam passage region 16.
[Embodiment 2]
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Embodiment 2 will be described with reference to FIG. 8. In the following embodiments including the present embodiment, differences from Embodiment 1 will be mainly described. In a support member 100A of Embodiment 2, a correction magnetic body 130 having a volume corresponding to the space 116 on the bottom side of the hole portion 115 into which the base end support portion 110 is not inserted is attached to the tip end support portion 120.
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The correction magnetic body 130 is formed as, for example, an annular member such as a washer, and is attached to an outer periphery, a stepped portion, or the like on the lower side of the first portion 121 of the tip end support portion 120. Generation of an error magnetic field can be further restricted by bringing the surface of the magnetic pole and the correction magnetic body 130 as close as possible.
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The present embodiment configured as described above also exhibits the same effects as those in Embodiment 1. Further, in the present embodiment, since the correction magnetic body 130 having a volume corresponding to the volume of the space 116 on the bottom side of the hole portion 115 that is not filled with the base end support portion 110 made of a magnetic material is provided at the tip end support portion 120, the generation of an error magnetic field can be suppressed. The volume of the correction magnetic body 130 and the volume of the space 116 on the bottom side do not need to be exactly the same.
[Embodiment 3]
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Embodiment 3 will be described with reference to FIG. 9. In a support member 100B of the present embodiment, a head portion 111B of a base end support portion 110B is caused to protrude into a predetermined space 16 by a predetermined amount H1, that is, by a volume corresponding to the space 116 on the bottom side of the hole portion 115 into which the base end support portion 110B is not inserted.
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The present embodiment configured as described above also exhibits the same effects as those in Embodiments 1 and 2. Further, in the present embodiment, since the head portion 111B of the base end support portion 110B is protruded to the beam passage region 16 by the predetermined amount H1 without using the correction magnetic body 130, the number of components can be reduced as compared with that in Embodiment 2.
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The invention is not limited to the above-described embodiments. Those skilled in the art can perform various additions, modifications, or the like within the scope of the invention. The above-described embodiments are not limited to the configuration examples illustrated in the accompanying drawings. The configurations and the processing methods of the embodiments can be appropriately changed within a range of achieving the object of the invention. For example, the shape of the refrigerator port installation region is not limited to the illustrated shape.
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In addition, components of the invention can be freely selected, and an invention including the selected components is also included in the invention. Further, the configurations described in the claims can also be combined in addition to the combinations described in the claims.
Reference Signs List
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- 1:
- particle beam therapy apparatus
- 2:
- beam transport system
- 3:
- irradiation device
- 4:
- treatment table
- 5:
- overall control device
- 6:
- irradiation control device
- 7:
- therapy plan database
- 8:
- therapy planning device
- 10:
- accelerator
- 11:
- main electromagnet
- 12:
- upper iron core portion
- 13:
- lower iron core portion
- 14:
- dividing line
- 16:
- beam passage region
- 20:
- coil portion vacuum chamber
- 23:
- superconducting coil
- 30:
- refrigerator port
- 40:
- elevating member
- 100, 100A, 100B:
- support member
- 110, 110B:
- base end support portion 110
- 115:
- hole portion
- 116:
- space on bottom side
- 120:
- tip end support portion
- 130:
- correction magnetic body
- 200:
- component