Ion sources, circular accelerators, and particle therapy systems

Abstract

To provide an ion source which enables cooling and gas supply to a discharge chamber to be made compatible with each other by compact configuration, and to provide a circular accelerator and a particle-beam radiation therapy system.SOLUTION: An ion source comprises: a cathode 33; cathode support equipment 35 which supports the cathode 33 and supplies voltage to the cathode; cooling pipes 24, 25 which cool the cathode support equipment 35; and gas supply flow channels 22, 22A, 22B, 22C, 22D which supply gas to a discharge chamber 36. The cooling pipes 24, 25 are arranged on the inner side of the gas supply flow channels 22, 22A, 22B, 22C, 22D.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an ion source suitable for use in a circular accelerator, and further to a circular accelerator and a particle beam therapy system. [Background technology]

[0002] Patent Document 1 describes an internal negative ion source for a cyclotron having a cylindrical anode, a discharge chamber formed by the space inside the anode, two cathodes arranged on both ends of the discharge chamber, and an ion outlet formed in the anode for extracting ions from the discharge chamber to the outside, in which a recess for a low electron temperature region is formed in a wall portion of the anode between the discharge chamber and the ion outlet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3464406 Summary of the Invention [Problem to be solved by the invention]

[0004] An ion source is a device that generates plasma internally and extracts a portion of the plasma as a charged beam from an extraction port. It is used, for example, in accelerators used in proton beam cancer treatment and particle physics research.

[0005] The ion source is connected to a water-cooled pipe for cooling the discharge chamber and a pipe for supplying a sample gas, which is a raw material for the extracted ions, from an external supply source. Patent Document 1 describes an example of such an ion source for a cyclotron.

[0006] When connecting water-cooled pipes and gas pipes to the ion source of an accelerator, holes must be drilled in the magnetic poles when inserting them perpendicular to the plane of the RF accelerating electrode, but it is desirable to make such holes as small as possible. Also, insulation is required to prevent discharge between the charging part and the surrounding magnetic poles.

[0007] However, in Patent Document 1, the water cooling pipe and the gas supply pipe are arranged independently, which means that the diameter of the ion source becomes large when the pipes are bundled together, and the holes in the magnetic poles become large because an insulation distance is required for each pipe, which makes the accelerator easier to manufacture and makes it difficult to miniaturize.

[0008] An object of the present invention is to provide an ion source, a circular accelerator, and a particle beam therapy system that can achieve both cooling and gas supply to a discharge chamber with a compact configuration. [Means for solving the problem]

[0009] The present invention includes a number of means for solving the above problems, and one example thereof is a discharge chamber comprising a cathode, a cathode support that supports the cathode and applies and supplies a voltage to the cathode, a cooling flow path that cools the cathode support, and a gas supply flow path that supplies a gas to a discharge chamber, and the cooling flow path is disposed on the inner circumferential side of the gas supply flow path. [Effects of the Invention]

[0010] According to the present invention, it is possible to achieve both cooling and gas supply to the discharge chamber with a compact configuration. Objects, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing the overall configuration of a particle beam therapy system using a circular accelerator according to the present invention. [Figure 2] FIG. 2 is a diagram showing a side cross section of the circular accelerator shown in FIG. [Figure 3] FIG. 2 is a diagram showing a cross section of the circular accelerator shown in FIG. [Figure 4] FIG. 2 is a diagram showing an outline of a side view of the ion source and its surroundings in the embodiment. [Figure 5] FIG. 10 is a schematic diagram showing a side view of the ion source and its surroundings according to the first modification. [Figure 6]FIG. 10 is a schematic diagram showing a side view of the ion source and its surroundings according to Modification 2. [Figure 7] FIG. 11 is a schematic diagram showing a side view of the ion source and its surroundings according to Modification 3. [Figure 8] FIG. 10 is a schematic diagram showing a side view of the ion source and its surroundings according to a fourth modification. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of the ion source, circular accelerator, and particle beam therapy system of the present invention will be described with reference to Figures 1 to 8. The following embodiments are merely examples, and the present invention is not limited to the specific embodiments described below. The present invention itself can be modified into various forms other than the following embodiments.

[0013] In the drawings used in this specification, identical or corresponding components are denoted by the same or similar reference numerals, and repeated description of these components may be omitted.

[0014] First, the overall configuration of a particle therapy system and the configuration of related devices will be described with reference to Fig. 1. Fig. 1 is a diagram showing the overall configuration of a particle therapy system according to this embodiment.

[0015] The particle beam therapy system 100 shown in FIG. 1 includes a cyclotron-type circular accelerator 50, a beam transport system 52, an irradiation device 54, a treatment table 40, a control device 56, and the like.

[0016] In the particle beam therapy system 100, ions generated by the ion source 3 are accelerated by the circular accelerator 50 to form an ion beam. The ion beam accelerated to a desired energy by the circular accelerator 50 is extracted from the circular accelerator 50 and transported to the irradiation device 54 by the beam transport system 52. The transported ion beam is shaped by the irradiation device 54 to match the shape of the affected area, and a predetermined amount of ion is irradiated onto the target of the patient 45 lying on the treatment couch 40.

[0017] The operation of each device and equipment in the particle beam therapy system 100, including the circular accelerator 50, is controlled by a control device 56.

[0018] Next, the structure of the circular accelerator 50 will be described with reference to Figures 2 and 3. Figure 2 is a cross-sectional side view of the accelerator of this embodiment, and Figure 3 is a cross-sectional view.

[0019] 2 and 3, a cyclotron-type circular accelerator 50 is composed of a main magnetic pole 1, an annular coil 2, a vacuum vessel 6, a radio-frequency acceleration electrode 8, and an ion source 3. The ion source is not limited to the form shown in Fig. 4, which will be described later, and any one of ion sources 3A, 3B, 3C, and 3D shown in any one of Figs. 5 to 8 can be used.

[0020] The main magnetic pole 1 is a pair of magnetic bodies arranged to face each other, and is made of, for example, iron. The main magnetic pole 1 is provided with a pair of upper and lower magnetic poles 10 facing each other so as to generate an orbit 12 of the beam, and a magnetic field is generated between the magnetic poles 10.

[0021] For example, a magnetic field B0 as shown in Fig. 2 is generated by the magnetic pole 10, and a gradient magnetic field is formed from the center of rotation of the magnetic pole 10 outward, thereby generating a focusing force on the circulating ion beam and realizing stable rotation. The surface shapes of the opposing faces in the pole gap of the pair of upper and lower magnetic poles 10 that generate the magnetic field B0 are symmetrical. Alternatively, the magnetic poles can be shaped to have an uneven surface in the direction of beam propagation, thereby adding a focusing effect.

[0022] The vacuum vessel 6 is sandwiched between the main magnetic poles 1, and forms a single vacuum vessel with the magnetic poles 10 as its inner surface, and also constitutes a magnetic circuit. The vacuum vessel 6 is made of a non-magnetic material. Note that a separate vacuum vessel may be provided within the gap between the magnetic poles 10, without the magnetic poles 10 as its inner surface.

[0023] The toroidal coil 2 is installed on the atmospheric side of the vacuum vessel 6, and generates a magnetic field of B0 between the pair of upper and lower main poles 1. The toroidal coil 2 can generate a magnetic field whether it is a coil made of normal conducting material or a coil made of superconducting material. The toroidal coil 2 may be installed inside the vacuum vessel 6, and is not particularly limited.

[0024] The ion source 3 is disposed inside the magnetic pole 10. Plasma is formed in the discharge chamber 36 by electrons extracted from the cathode 33 in the discharge chamber 36. A high frequency electric field is generated between the high frequency acceleration electrode 8 and the ion source 3, and between the high frequency power supply 20 and the ground electrode 9, which has the same potential as the ion source 3. The high frequency electric field causes ions to be extracted from the plasma generated in the discharge chamber 36 through the extraction hole 37, and an extraction beam 15 is formed.

[0025] The extracted beam 15 thus formed moves in a spiral orbit 12 due to the magnetic field B0 generated by the magnetic pole 10 and the electric field generated in the acceleration gap 7 between the RF acceleration electrode 8 and the ground electrode 9, and is accelerated each time it passes through the acceleration gap 7, increasing its energy until it reaches a predetermined energy level, after which it is extracted outside the main magnetic pole 1. The beam quantity at this time is measured by a current monitor 17.

[0026] Next, the details of the ion source 3 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the details of the ion source 3 of Fig. 2, in which the ion source 3 is arranged in a direction parallel to the magnetic field generated by the magnetic pole 10.

[0027] The ion source 3 shown in FIG. 4 is installed between opposing magnetic poles 10, and includes a discharge chamber 36 for generating ions parallel to the central axis of the circulating ion beam.

[0028] More specifically, the ion source 3 is a PIG (Penning Ionization Gauge) type ion source 3 that includes a cathode 33 that generates electrons, a cathode support 35 that supports the cathode 33 and applies and supplies a voltage to the cathode 33, a discharge power supply 21 that applies a discharge voltage between the cathode 33 and a discharge vessel 39 that serves as an anode, a discharge chamber 36 that generates ions by the applied voltage, an extraction hole 37 that extracts ions from the discharge chamber 36, the discharge vessel 39, etc.

[0029] The ion source 3 is further provided with a gas supply passage 22 for supplying the sample gas supplied from a gas supply source 28 to the discharge chamber 36, and cooling pipes 24 and 25 for cooling the cathode support 35 and the cathode 33.

[0030] In the ion source 3 of this embodiment, the cooling pipes 24, 25 and the gas supply flow path 22 have a triple structure in which the three pipes share a common central axis, and also have a coaxial structure, with the cooling pipe 24 on the supply side of the cooling water being at the very center, the cooling pipe 25 on the discharge side of the cooling water being at the second axis from the center, and the gas supply flow path 22 being at the outermost axis.

[0031] A refrigerant, for example, cooling water, is supplied from a coolant supply source 23 to the cooling pipe 24 to cool the cathode support 35 and the cathode 33 via this cathode support 35, and the refrigerant used for cooling is sent to the coolant return section 26 via the cooling pipe 25.

[0032] The cooling pipes 24, 25 are not limited to the case where the cooling pipe 24 on the refrigerant supply side is on the inner periphery side and the cooling pipe 25 on the return side is on the outer periphery side, but the cooling pipe on the return side may be on the inner periphery side and the cooling pipe on the supply side on the outer periphery side. In either case, the gas supply passage 22 is located on the outer periphery of the cooling pipe on the outer periphery side.

[0033] As shown in FIG. 4, the cross-sectional area of ​​gas supply hole 29, which is the outlet of gas supply channel 22, is smaller than the cross-sectional area of ​​gas supply channel 22 itself.

[0034] Furthermore, gas supply hole 29 is arranged vertically above extraction hole 37 that extracts generated ions from ion source 3. Note that, since the ion source 3 is inserted from above in the vertical direction into magnetic pole 10, the gas supply hole 29 is arranged vertically above extraction hole 37 that extracts generated ions from ion source 3 in the above embodiment. However, if the ion source 3 is inserted from below in the vertical direction into magnetic pole 10, gas supply hole 29 may be arranged vertically below extraction hole 37.

[0035] In the ion source 3, a voltage is applied by the discharge power supply 21 through the cooling tubes 24, 25 and the cathode support 35 between the cathode 33 and a discharge vessel 39 electrically connected to the ground electrode 9. By making the cathode 33 have a negative potential with respect to the discharge vessel 39, electrons are drawn from the cathode 33 toward the discharge chamber 36.

[0036] Since the cooling pipes 24, 25 are at high voltage and the gas supply flow path 22 is grounded, an insulating spacer 27 is provided between the cooling pipes 24, 25 and the gas supply flow path 22 to create a gap between the cooling pipes 24, 25 and the gas supply flow path 22, thereby preventing discharge from occurring in the gas supply flow path 22.

[0037] In the coaxial structure of this embodiment, the electric field between the cooling pipes 24, 25 on the high-voltage side and the gas supply flow path 22 on the ground side becomes uniform, so that the insulation distance can be shortened and the piping system of the ion source 3 can be made smaller.

[0038] The ion source 3 is inserted from above the main pole 1 through a hole that penetrates the main pole 1 and the magnetic pole 10. Here, the hole provided in the main pole 1 or the magnetic pole 10 affects and changes the distribution of the magnetic field B0 generated between the magnetic poles 10. The smaller the diameter of the hole, the less the effect on the magnetic field B0, which can be easily corrected by changing the shape of the magnetic pole 10 or by installing a separate piece of iron, etc.

[0039] Therefore, by using a coaxial structure, the holes to be drilled in the main pole 1 and the magnetic pole 10 can be made smaller, which makes it easier to design the accelerator.

[0040] The cooling pipes 24, 25 and the gas supply passage 22 are made of a conductive material, preferably stainless steel, but not limited to this material. The insulating spacer 27 may be made of alumina, FRP, or other electrically insulating material, but is not limited to this material.

[0041] In this embodiment, water is flowing as a coolant through the cooling pipes 24 and 25, but air cooling or oil cooling may also be used and there is no particular limitation.

[0042] Modified examples of the ion source will be described below with reference to FIGS.

[0043] Fig. 5 shows an ion source 3A according to Modification 1. The ion source 3A shown in Fig. 5 is different from the ion source 3 shown in Fig. 4 above in that the central axes of the cooling pipes 24 and 25 are not coaxial with the central axis of the gas supply flow path 22A but are shifted from the central axis of the gas supply flow path 22A.

[0044] Fig. 6 shows an ion source 3B according to Modification 2. The ion source 3B shown in Fig. 6 is different from the ion source 3 shown in Fig. 4 in that gas supply holes 29B, which supply gas from gas supply passage 22B to discharge chamber 36, are arranged only on the extraction hole 37 side. In this ion source 3B, the amount of gas supplied to discharge chamber 36 can be reduced, and therefore gas can be appropriately supplied to discharge chamber 36 where plasma is generated.

[0045] Fig. 7 shows an ion source 3C according to Modification 3. The ion source 3C shown in Fig. 7 is different from the ion source 3 shown in Fig. 4 above in that a small-diameter insulating gas pipe 30C is arranged inside a gas supply flow path 22C, and gas is supplied to a discharge chamber 36 from the extraction hole 37 side.

[0046] Fig. 8 shows an ion source 3D according to Modification 4. The ion source 3D shown in Fig. 8 is different from the ion source 3 shown in Fig. 4 in that the central axes of the cooling pipes 24 and 25 are not coaxial with but eccentric to the gas supply flow path 22D, as in the ion source 3A shown in Fig. 5, and that a small-diameter insulating gas pipe 30D is arranged inside the gas supply flow path 22D, as in the ion source 3C shown in Fig. 7, and gas is supplied to the discharge chamber 36 from the extraction hole 37 side.

[0047] Next, the effects of this embodiment will be described.

[0048] The ion sources 3, 3A, 3B, 3C, and 3D of the present embodiment described above include a cathode 33, a cathode support 35 that supports the cathode 33 and applies and supplies a voltage, cooling pipes 24 and 25 that cool the cathode support 35, and gas supply passages 22, 22A, 22B, 22C, and 22D that supply gas to the discharge chamber 36. The cooling pipes 24 and 25 are arranged on the inner periphery of the gas supply passages 22, 22A, 22B, 22C, and 22D, and this configuration makes it easier to reduce the size of the cooling system and the raw material supply system than if independent pipes were combined together, thereby enabling the ion source to be made smaller.

[0049] Furthermore, since the gas supply flow paths 22, 22A, 22B, 22C, and 22D and the cooling pipes 24 and 25 are integrated into a triple-structure pipe, the structure is essentially the same as when a single pipe is arranged, making it easier to achieve miniaturization.

[0050] Furthermore, since the cooling pipes 24 and 25 and the gas supply passages 22 and 22B share a common axis, a structure that is simpler than combining independent pipes can be achieved, and therefore miniaturization can be more easily achieved.

[0051] Furthermore, by displacing the central axes of the cooling pipes 24 and 25 from the central axes of the gas supply passages 22A and 22D, it is possible to prevent the gas from diffusing in the gas supply passage 22A and not reaching the discharge chamber 36 when the gas supply amount is small, thereby enabling the gas to be supplied appropriately. Also, by reducing the cross-sectional area of ​​the gas passage, it is possible to reduce the size of the holes penetrating the main pole 1 and the magnetic pole 10, thereby enabling further miniaturization of the ion sources 3A and 3D.

[0052] Furthermore, since the cross-sectional area of ​​the gas supply holes 29, 29A, 29B, which are the outlets of the gas supply flow paths 22, 22A, 22B, is smaller than the cross-sectional area of ​​the gas supply flow paths 22, 22A, 22B, the sample gas can be prevented from diffusing and being supplied to the discharge chamber 36, and excessive gas supply can be avoided.

[0053] Furthermore, since the gas supply holes 29, 29A, 29B, and 29D are arranged vertically above or below the extraction hole 37 that extracts the generated ions from the ion sources 3, 3A, 3B, 3C, and 3D, the sample gas can be supplied in an area close to the discharge chamber 36, and the sample gas can be ionized more efficiently.

[0054] Furthermore, gas supply flow paths 22C and 22D further include gas pipes 30C and 30D provided in the outermost pipes, so that even a small amount of gas can be easily supplied to discharge chamber .

[0055] Furthermore, the cooling pipes 24 and 25 have the refrigerant supply side on the inner periphery and the return side on the outer periphery, so that piping of a general configuration can be used, and manufacturability can also be improved.

[0056] Furthermore, the circular accelerator 50 equipped with the ion sources 3, 3A, 3B, 3C, and 3D as described above, and the particle beam therapy system 100 equipped with such a circular accelerator 50 can be made smaller by miniaturizing the ion sources 3, 3A, 3B, 3C, and 3D.

[0057] <Other> The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. The above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to having all of the described configurations.

[0058] For example, the type of circular accelerator 50 is not limited to a cyclotron type accelerator having magnetic poles with unevenness on the magnetic poles 10, but can also be used for a synchrocyclotron type accelerator having magnetic poles tilted from the center of the magnetic poles 10 and modulating the frequency of high-frequency acceleration.

[0059] A synchrocyclotron accelerator is a type of accelerator that is an improved version of a cyclotron. It repeatedly accelerates charged particles moving circularly between large magnetic poles by applying a frequency-modulated high-frequency electric field. At the speed of light, the mass of the accelerated particles increases due to relativistic effects, and the period of the circular motion of the charged particles in the magnetic field increases in proportion to the mass. This resulting discrepancy in period with the high-frequency voltage is eliminated by modulating the frequency.

[0060] Since the synchrocyclotron accelerator has the same configuration as the cyclotron accelerator, the ion sources 3, 3A, 3B, 3C, and 3D can be disposed within the main magnetic pole 1, and the same effect can be obtained.

[0061] The ion source of the present invention may be in the following form.

[0062] (1) A discharge chamber is provided with a cathode, a cathode support that supports the cathode and applies and supplies voltage, a cooling flow path that cools the cathode support, and a gas supply flow path that supplies gas to a discharge chamber, and the cooling flow path is disposed on the inner circumferential side of the gas supply flow path.

[0063] (2) In the ion source described in (1), the cooling channel and the gas supply channel are integrated into a triple-structured tube.

[0064] (3) In the ion source according to (1) or (2), the cooling channel and the gas supply channel have a common axis.

[0065] (4) In the ion source according to (1) or (2), the central axis of the cooling passage is arranged to be shifted from the central axis of the gas supply passage.

[0066] (5) In the ion source according to any one of (1) to (4), the cross-sectional area of ​​the gas supply hole, which is the outlet of the gas supply passage, is smaller than the cross-sectional area of ​​the gas supply passage.

[0067] (6) In the ion source described in any one of (1) to (5), a gas supply hole, which is an outlet of the gas supply flow path, is arranged vertically above or below an extraction hole that extracts the generated ions from the ion source.

[0068] (7) In the ion source according to any one of (2) to (6), the gas supply passage is formed by a pipe further provided inside the outermost pipe.

[0069] (8) In the ion source according to any one of (1) to (7), the cooling flow passage has a coolant supply side on the inner circumferential side and a coolant return side on the outer circumferential side. [Explanation of symbols]

[0070] 1...Main magnetic pole 2...Toric coil 3,3A,3B,3C,3D…Ion source 6...Vacuum container 7…Acceleration gap 8...High frequency acceleration electrode 9...Ground electrode 10...Magnetic pole 12...Orbit 15...Extraction beam 17...Current monitor 20…High frequency power supply 21…Discharge power supply 22, 22A, 22B, 22C, 22D...Gas supply passages 23…Coolant supply source 24, 25...Cooling pipes (cooling channels) 26... Coolant return section 27...Insulating spacer 28...Gas supply source 29, 29A, 29B, 29D...Gas supply holes 30C, 30D...Gas piping 33...Cathode 35...Cathode support 36...discharge chamber 37...Drawer hole 39...Discharge vessel 40...Treatment table 45...patient 50...Circular accelerator 52...Beam transport system 54…Irradiation device 56...Control device 100...Particle beam therapy system

Claims

1. A cathode; a cathode support that supports the cathode and applies and supplies a voltage; a cooling channel for cooling the cathode support; a gas supply passage for supplying gas to the discharge chamber; The cooling flow path is disposed on the inner circumferential side of the gas supply flow path. Ion source.

2. 10. The ion source of claim 1, The cooling flow path and the gas supply flow path are integrated into a triple-structured pipe. Ion source.

3. 3. The ion source of claim 2, The cooling channel and the gas supply channel have a common axis. Ion source.

4. 3. The ion source of claim 2, The central axis of the cooling channel is shifted from the central axis of the gas supply channel. Ion source.

5. 10. The ion source of claim 1, The cross-sectional area of ​​the gas supply hole, which is the outlet of the gas supply flow path, is smaller than the cross-sectional area of ​​the gas supply flow path. Ion source.

6. 10. The ion source of claim 1, A gas supply hole, which is an outlet of the gas supply flow path, is arranged vertically above or below an extraction hole that extracts the generated ions from the ion source. Ion source.

7. 3. The ion source of claim 2, The gas supply flow path further includes a pipe provided in the outermost pipe. Ion source.

8. 10. The ion source of claim 1, The cooling flow path has a coolant supply side on the inner periphery side and a coolant return side on the outer periphery side. Ion source.

9. Opposing magnetic poles, an accelerating electrode; the ion source according to any one of claims 1 to 8, which is installed between the opposing magnetic poles and arranged parallel to the central axis of the circulating ion beam; Circular accelerator.

10. The circular accelerator according to claim 9; Beam transport system and an irradiation device; Equipped with a treatment table and Particle therapy system.

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