High-voltage, high-density PIG ion source and ion extraction method

Abstract

The cylindrical portion 12 is positioned so that its longitudinal direction is aligned with the vertical direction of the vacuum chamber. The multi-hole 13 is composed of multiple holes arranged along the longitudinal direction of the cylindrical portion on one side of the cylindrical portion. A pair of electrode portions 14a and 14b are provided at both ends of the cylindrical portion in the longitudinal direction. A pair of gas supply pipes 15a and 15b are provided at both ends of the cylindrical portion in the longitudinal direction. The extraction electrode 16 has an extraction hole facing the multi-hole. The vacuum control unit 501 creates a vacuum in the vacuum chamber. The magnetic field control unit 502 applies a magnetic field using the upper and lower electromagnets 11a and 11b. The supply control unit 503 supplies gas containing ionizable molecules to the gas supply pipe. The high-pressure control unit 504 applies high pressure between the electrode portions to generate positive ions inside the cylindrical portion. The extraction control unit 505 extracts the generated positive ions by applying a negative charge to the extraction electrode.

Description

Technical Field

[0001] The present invention relates to a high-voltage and high-density PIG ion source and an ion extraction method.

Background Art

[0002] An ion source means a device that ionizes atoms and molecules to generate charged ions (particles), and is adopted in particle accelerators used for radiation therapy such as BNCT (Boron Neutron Capture Therapy), ion implantation devices used for surface modification to control the electrical properties of semiconductors and substrates, and mass spectrometers used for structural analysis of compounds and proteins.

[0003] Conventionally, there are various technologies related to this ion source. For example, Japanese Patent Application Laid-Open No. 2000-243309 (Patent Document 1) discloses an internal negative ion source for a cyclotron having a cylindrical anode, a discharge chamber, two cathodes, and an ion extraction port. The discharge chamber is constituted by the inner space of the anode. The two cathodes are arranged on both ends of the discharge chamber, and the ion extraction port is formed in the anode to extract ions from the discharge chamber to the outside. Further, in the internal negative ion source for a cyclotron, a recess for a low electron temperature region is formed in the anode wall portion between the discharge chamber and the ion extraction port. Thereby, the probability that the plasma disappears at the anode wall is reduced, the discharge is stabilized, and it is said that stable ions can be generated in a sufficient amount.

[0004] Furthermore, Japanese Patent Publication No. 2006-173105 (Patent Document 2) discloses an ion source tube (300) that sustains plasma discharge. Here, the ion source tube (300) includes a slit opening (310), an end opening (314), and a housing cavity (312). The slit opening (310) is provided along the side surface of the ion source tube (300) and has a width less than 0.29 mm. The end opening (314) is provided within the end of the ion source tube (300), is smaller than the inner diameter of the ion source tube, and is offset by about 0 to 1.5 mm from the central axis (316) of the ion source tube (300) toward the slit opening (310). The cavity (312) houses the plasma discharge. This overcomes these and other drawbacks of known systems and methods and improves the lifespan and performance of the ion source.

[0005] Furthermore, Japanese Patent Publication No. 2021-530839 (Patent Document 3) discloses a low-erosion internal ion source for a cyclotron. The low-erosion internal ion source comprises a hollow body (11), a coaxial conductor (15), an expansion chamber (16), and an ion extraction opening (18). The hollow body (11) has inner walls (11a, 11b, 11c) that define a cylindrical cavity (13), and the coaxial conductor (15) is arranged inside the cavity (13) of the hollow body (11) and is arranged parallel to the longitudinal axis of the cavity (13). The expansion chamber (16) is connected to the cavity (13) via a plasma outlet hole (17) provided in the hollow body (11), and the ion extraction opening (18) is connected to the expansion chamber (16). The low-erosion internal ion source has the following features. The hollow body (11) has a power input (21) for injecting radio frequency energy into the cavity (13), and the inner wall of the hollow body (11) is conductive. At least one end (15a, 15b) of the coaxial conductor (15) is connected to at least one circular inner wall (11a, 11b) of the hollow body (11), forming a coaxial resonant cavity. The coaxial conductor (15) has a conductive projection (22) that extends radially into the cavity (13), and the conductive projection (22) is on the opposite side of the plasma exit hole (17). This makes it useful for low-erosion radio frequency ion sources, particularly when used as an internal ion source for cyclotrons.

[0006] Furthermore, Japanese Patent Publication No. 2023-137423 (Patent Document 4) discloses an ion source comprising a first electrode and a second electrode. The first electrode is cylindrical and has a first polarity, and the second electrode is provided at both ends of the first electrode. In the ion source, the wiring from the power supply is connected to the second electrode at one end of the first electrode, but the wiring from the power supply is not connected to the second electrode at the other end of the first electrode. This allows for miniaturization.

[0007] Furthermore, Non-Patent Document 1 (Pedro Calvo, “Experimental characterization of the internal ion source for the AMIT compactcyclotron”, NuclearInst. and MethodsinPhysicsResearch, A 1025 (2022), 166028) describes a study of the discharge characteristics of the AMIT cyclotron and discloses a new ion source test bench facility (IST) at CIEMAT. It states that this can improve ion source efficiency.

[0008] Furthermore, Non-Patent Document 2 (Shi-Wen Xu1, "Design and testing of an internal hot-cathode-type PIG ion source for superconducting cyclotron", NUCL SCI TECH (2019) 30:88) discloses the design of the ion source and test bench used in SC200. This suggests that the superconducting cyclotron SC200 can generate a 200 MeV, 400 nA proton beam for future particle beam therapy.

[0009] Furthermore, Non-Patent Document 3 (M. Cavenago, "HIGHCURRENTION SOURCES, BEAMDIAGNOSTICS ANDEMITTANCE MEASUREMENT", Proceedings of HIAT09, Venice, Italy E-06, pp. 341-345) discloses the design of a compact Allison scanner head. This document describes the optimization of the Allison scanner head parameters and the segmented structure of the electrodes. It states that this allows monovalent ion sources to easily exceed 1 kW of beam power, as in TRIPS (H+, 60 mA, 80 kV, currently installed in LNL) and NIO1 (H-, 130 mA distributed to nine beamlets, 60 kV, RFX and INFN-LNL projects). [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2000-243309 [Patent Document 2] Japanese Patent Publication No. 2006-173105 [Patent Document 3] Special Publication No. 2021-530839 [Patent Document 4] Japanese Patent Publication No. 2023-137423 [Non-patent literature]

[0011] [Non-Patent Document 1] Pedro Calvo, “Experimental characterization of the internal ion source for the AMIT compact cyclotron”, NuclearInst. andMethodsinPhysicsResearch,A 1025 (2022),166028 [Non-Patent Document 2] Shi-Wen Xu1 ,”Design and testing of an internal hot-cathode-type PIG ion source for superconducting cyclotron”, NUCL SCI TECH (2019) 30:88, [Non-Patent Document 3] M. Cavenago, “HIGHCURRENTIONSOURCES, BEAMDIAGNOSTICS ANDEMITTANCEMEASUREMENT”, Proceedings of HIAT09, Venice, Italy E-06, p341-p345 [Overview of the project] [Problems that the invention aims to solve]

[0012] If an ion source can draw out a large amount of positive ions (in other words, a large current) when a predetermined high voltage is applied, it will have a wide range of applications in fields where ion sources are used. However, there is still the challenge of not being able to obtain a large current.

[0013] For example, in particle accelerators used in radiation therapy such as BNCT, protons (also called positive hydrogen ions) are used as an ion beam to irradiate metals such as lithium, generating therapeutic neutrons. However, if the current of the ion beam output from the particle accelerator is weak, for example, 2 mA, the intensity of the subsequent therapeutic neutron beam will be weak, making it unsuitable for radiation therapy. Therefore, a higher current for the ion beam from the particle accelerator is preferable.

[0014] On the other hand, increasing the current of an ion beam requires a large amount of energy from the particle accelerator, which poses a challenge in terms of the size of the particle accelerator itself, making it difficult to put into practical use. Therefore, there has been a need for a particle accelerator that can output a high-current ion beam even at low energy levels.

[0015] Herein, the technology described in Patent Document 1 above targets negative hydrogen ions, and the technologies described in Patent Documents 2-4 and Non-Patent Documents 1-3 above use ion beams with currents similar to conventional ones and cannot be used for the aforementioned radiation therapy.

[0016] Therefore, the present invention has been made to solve the aforementioned problems, and aims to provide a high-voltage, high-density PIG ion source and ion extraction method that can extract a large current with low energy by optimizing the positive ion extraction method. [Means for solving the problem]

[0017] The high-voltage, high-density PIG ion source according to the present invention comprises a vacuum chamber, upper and lower electromagnets, a cylindrical section, a multi-hole, a pair of electrode sections, a pair of gas supply pipes, an extraction electrode, a vacuum control unit, a supply control unit, a magnetic field control unit, a high-voltage control unit, and an extraction control unit. The upper and lower electromagnets are provided in the vertical direction outside the vacuum chamber and generate a magnetic field in the vertical direction of the vacuum chamber. The cylindrical section is arranged longitudinally along the vertical direction of the vacuum chamber. The multi-hole is composed of a plurality of holes arranged along the longitudinal direction of the cylindrical section on one side surface in the longitudinal direction of the cylindrical section. The pair of electrode sections are provided at both ends in the longitudinal direction of the cylindrical section. The pair of gas supply pipes are provided at both ends in the longitudinal direction of the cylindrical section. The extraction electrode is arranged inside the vacuum chamber at a predetermined distance from the multi-hole and has an extraction hole facing the multi-hole. The vacuum control unit creates a vacuum in the vacuum chamber. The magnetic field control unit applies a magnetic field using the upper and lower electromagnets. The supply control unit supplies gas containing ionizable molecules to the gas supply pipe. The high-pressure control unit applies high pressure between the electrodes to generate positive ions inside the cylindrical section. The extraction control unit extracts the generated positive ions by applying a negative charge to the extraction electrode.

[0018] The ion extraction method according to the present invention is an ion extraction method for a high-voltage and high-density PIG ion source, and includes a vacuum control step, a magnetic field control step, a supply control step, a high-voltage control step, and an extraction control step. Here, each control step of the ion extraction method corresponds to each control unit of the high-voltage and high-density PIG ion source according to the present invention.

Effect of the Invention

[0019] According to the present invention, by optimizing the extraction form of positive ions, it becomes possible to extract a large current at low energy.

Brief Description of the Drawings

[0020] [Figure 1] It is a perspective view and a front view showing a particle accelerator using the high-voltage and high-density PIG ion source according to the first embodiment of the present invention. [Figure 2] It is a sectional view taken along line A-A and an enlarged sectional view taken along line A-A of the high-voltage and high-density PIG ion source according to the first embodiment of the present invention. [Figure 3] It is a perspective view, a plan view, a front view, a bottom view, a sectional view taken along line B-B, a sectional view taken along line C-C, a sectional view taken along line D-D, and a schematic sectional view of the high-voltage and high-density PIG ion source according to the first embodiment of the present invention. [Figure 4] It is a front view showing an application example of the multi-hole of the high-voltage and high-density PIG ion source according to the first embodiment of the present invention and a front view of a conventional ion source. [Figure 5] It is a functional block diagram of a particle accelerator using the high-voltage and high-density PIG ion source according to the first embodiment of the present invention. [Figure 6] It is a flowchart showing the execution procedure of the high-voltage and high-density PIG ion extraction method according to the first embodiment of the present invention. [Figure 7] It is a schematic sectional view showing the case where hydrogen gas is supplied and a high voltage is applied between the electrode portions, and a schematic sectional view showing the case where a negative charge is applied to the extraction electrode. [Figure 8] It is an enlarged sectional view taken along line A-A showing the case where a proton beam is extracted. [Figure 9] This shows a perspective view, a plan view, and a plan view with the protective part removed, illustrating an example of a high-voltage, high-density PIG ion source according to Embodiment 1 of the present invention. [Figure 10] Figure 10A shows an example of plasma generation in a high-voltage, high-density PIG ion source according to Embodiment 1 of the present invention, and Figure 10B shows an example of measuring the extraction current relative to the extraction voltage. [Figure 11] This graph shows an example of the relationship between extraction voltage and extraction current in a high-voltage, high-density PIG ion source according to Example 1 of the present invention. [Figure 12] This is a plan view showing a case where a proton beam is extracted in a particle accelerator using a high-voltage, high-density PIG ion source according to the second embodiment of the present invention. [Figure 13] This is a perspective view showing an example of a particle accelerator using a high-voltage, high-density PIG ion source according to a second embodiment of the present invention. [Figure 14] This is a perspective view and an exploded view showing an example of an ion source tube in a particle accelerator using a high-voltage, high-density PIG ion source according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0021] The following descriptions of embodiments of the present invention will be made with reference to the attached drawings to facilitate understanding of the invention. Note that the following embodiments are merely examples of the present invention and are not intended to limit the technical scope of the invention.

[0022] Now, as shown in Figures 1-3, the high-voltage, high-density PIG ion source 1 according to an embodiment of the present invention comprises a vacuum chamber 10, upper and lower electromagnets 11a and 11b, a cylindrical section 12, a multi-hole 13, a pair of electrode sections 14a and 14b, a pair of gas supply pipes 15a and 15b, an extraction electrode 16, and a control device 17.

[0023] Here, the vacuum chamber 10 is a container for extracting and using positive ions. For example, when the high-voltage, high-density PIG ion source 1 is used in a particle accelerator, the vacuum chamber 10 becomes an acceleration chamber. The vacuum chamber 10 can be, for example, a container for directly releasing positive ions (e.g., protons), or, in the case of an acceleration chamber 10, a container for accelerating positive ions while they are in rotational motion. While the high-voltage, high-density PIG ion source 1 is operating, the vacuum chamber 10 is maintained in a vacuum state. Specifically, the vacuum chamber 10 is configured in a cylindrical shape, as shown in Figures 1 and 2, and a predetermined vacuum exhaust pipe 101 is connected to it. The vacuum exhaust pipe 101 is connected to a vacuum generating device such as a vacuum pump (not shown). In addition, an inspection window 102 is installed on the side of the vacuum chamber 10 as appropriate, allowing the user to check the proton acceleration state inside the vacuum chamber 10 through the inspection window 102.

[0024] Furthermore, the upper and lower electromagnets 11a and 11b are installed in the vertical direction outside the vacuum chamber 10 and can generate a magnetic field in the vertical direction of the vacuum chamber 10. In addition, the upper and lower electromagnets 11a and 11b are configured in a disc shape, for example as shown in Figure 1, and the distribution of the vertical magnetic field relative to the vacuum chamber 10 can be dynamically controlled by the control device 17, which will be described later.

[0025] Furthermore, the cylindrical portion 12, which forms the main body of the ion source tube, is configured in a cylindrical shape, and its longitudinal direction is aligned with the vertical direction of the vacuum chamber 10. Here, for example, when hydrogen gas is supplied to the inside of the cylindrical portion 12 as an ionizable molecular gas, the supply of thermionic electrons and hydrogen gas, along with the application of high pressure to the inside of the cylindrical portion 12, generates plasma inside the cylindrical portion 12, and subsequently generates protons (positive hydrogen ions). There are no particular limitations on the type of ionizable molecular gas, but for example, in addition to hydrogen gas, helium gas can be used. Also, as shown in Figures 1-3, the cylindrical portion 12 has tapered surface shapes 12a and 12b at both ends in the longitudinal direction, and a planar shape 12c that extends from the tapered surface shapes 12a and 12b along the longitudinal direction. This makes it easy to arrange the multi-holes 13. Furthermore, as will be described later, the cylindrical portion 12 and the extraction electrode 16 can be easily positioned so that the multi-hole 13 faces the extraction hole 16a of the extraction electrode 16.

[0026] Furthermore, the multi-hole 13 is configured such that a plurality of holes 13a are arranged on one longitudinal side of the cylindrical portion 12, along the longitudinal direction of the cylindrical portion 12. Here, the multi-hole 13 is configured such that a plurality of holes 13a are arranged on the planar shape 12c of the cylindrical portion 12 with a predetermined hole spacing t between them. In the present invention, by using a plurality of holes 13a instead of one large hole, the aperture ratio for protons emitted from the cylindrical portion 12 is increased, and a large number of protons can be drawn into the vacuum chamber 10. For example, with the presence of the multi-hole 13, the aperture ratio is preferably in the range of 50% to 99%, and more preferably in the range of 60% to 99%.

[0027] Here, there are no particular limitations on the shape of the holes 13a of the multi-hole 13. For example, in Figure 3, the shape of the holes 13a is circular, but it may also be elliptical. In addition, as shown in Figure 4, for example, the shape of the holes 13a may be hexagonal, triangular, rectangular, or square. Furthermore, there are no particular limitations on the arrangement of the holes 13a. For example, they may be arranged in a staggered pattern, a square pattern, in a series, or in two rows, depending on the shape of the holes 13a, with a predetermined hole spacing t. For example, if the holes 13a are circular, have a diameter of 2.6 mm, and have a hole spacing t of 0.4 mm, arranging the holes 13a in a square pattern (arranged in a grid pattern vertically and horizontally) results in an opening ratio of approximately 59%, while arranging the holes 13a in a staggered pattern, as shown in Figure 3, results in an opening ratio of approximately 68%. Furthermore, as shown in Figure 4, if the holes 13a are hexagonal, the diagonal distance between them is 2.6 mm, and the spacing between them is t is 0.4 mm, arranging the holes 13a in a staggered pattern results in an opening ratio of approximately 75%. Also, if the holes 13a are equilateral triangles, one side of each hole is 2.6 mm, and the spacing between them is t is 0.4 mm, arranging the holes 13a in a staggered pattern (arranging equilateral triangles with their orientations reversed left and right in a staggered pattern) results in an opening ratio of approximately 75%. Furthermore, if the holes 13a are rectangular, the longer side is 2.6 mm, the shorter side is 2.0 mm, and the spacing between them is t is 0.4 mm, arranging the holes 13a in a square pattern results in an opening ratio of approximately 72%. Furthermore, if the holes 13a are square in shape, with a side length of 2.6 mm and a hole spacing t of 0.4 mm, then arranging the holes 13a in a square pattern results in an aperture ratio of approximately 75%. Here, the smaller the hole spacing t, the closer the aperture ratio approaches 99%. There are no particular limitations on the size (diameter, diagonal distance) of the holes 13a, but for example, it is preferable to be in the range of 1.0 mm to 20.0 mm, and even more preferable to be in the range of 1.0 mm to 10.0 mm. Similarly, there are no particular limitations on the hole spacing t, but for example, it is preferable to be in the range of 0.1 mm to 2.0 mm, and even more preferable to be in the range of 0.1 mm to 1.0 mm. In addition, in the conventional ion source tube 22, it is composed of an elongated slit shape 23, and it is understood that in this shape 23, the aperture ratio for protons in a predetermined target area including the slit shape 23 is extremely low.

[0028] Furthermore, the pair of electrode portions 14a and 14b are provided at both ends 12d and 12e in the longitudinal direction of the cylindrical portion 12. Here, the ends 12d and 12e in the longitudinal direction of the cylindrical portion 12 refer to, for example, the spaces on both sides of the cylindrical portion 12 in the longitudinal direction, as shown in Figure 3, and the pair of electrode portions 14a and 14b are installed in a floating manner in the spaces on both sides of the cylindrical portion 12 in the longitudinal direction. Note that the spaces on both sides of the cylindrical portion 12 in the longitudinal direction are usually protected by protective parts such as an exterior. The pair of electrode portions 14a and 14b are electrically connected to a high-voltage power supply (not shown), making it possible to apply high voltage between the cylindrical portions 12.

[0029] Furthermore, a pair of gas supply pipes 15a and 15b are provided at both ends 12d and 12e in the longitudinal direction of the cylindrical portion 12. Here, as shown in Figure 3, the tips 15a1 and 15b1 of the pair of gas supply pipes 15a and 15b are positioned toward a pair of electrode portions 14a and 14b. The pair of gas supply pipes 15a and 15b also extend outside the vacuum chamber 10 and are connected to a hydrogen gas cylinder (gas supply device) not shown.

[0030] Furthermore, the extraction electrode 16 is positioned inside the vacuum chamber 10 with a predetermined extraction interval d relative to the multi-hole 13 of the cylindrical portion 12, and has an extraction hole 16a facing the multi-hole 13. Here, the extraction electrode 16 is charged with a charge opposite to that of the proton in order to extract the proton generated in the cylindrical portion 12, and the extracted proton is passed through the extraction hole 16a and emitted to the outside. There are no particular limitations on the shape of the extraction hole 16a, but for example, as shown in Figure 2, it is configured as a rectangle with a size corresponding to the overall size of the multi-hole 13 of the cylindrical portion 12.

[0031] Furthermore, the control device 17 is a general-purpose computer and incorporates a CPU, ROM, RAM, HDD, SSD, etc. (not shown). The CPU, for example, uses RAM as a workspace and executes programs stored in the ROM, HDD, SSD, etc. Similarly, each control unit, which will be described later, is realized by the CPU executing programs.

[0032] Now, if the high-voltage, high-density PIG ion source 1 is simply configured to extract positive ions, the above configuration is sufficient. However, if the high-voltage, high-density PIG ion source 1 is used in a particle accelerator, it may be equipped with, for example, a holding section 18.

[0033] Here, as shown in Figure 2, the holding part 18 holds the cylindrical part 12 with the multi-holes 13 of the cylindrical part 12 tilted at a predetermined angle α with respect to the center line C of the vacuum chamber 10. For example, if the multi-holes 13 of the cylindrical part 12 of the holding part 18 are located near the center of the vacuum chamber 10, the angle α is in the range of 10 to 30 degrees. By providing the holding part 18 with an angle α, the beam of protons drawn out from the multi-holes 13 is appropriately rotated by the magnetic field of the upper and lower electromagnets 11a and 11b and can be drawn out to the outside.

[0034] Here, the holding part 18 holds the cylindrical part 12 in a predetermined position inside the vacuum chamber 10. The holding part 18 also includes an adjustment part that allows the position of the cylindrical part 12 to be adjusted at predetermined adjustment intervals along the left-right direction or the front-back direction of the vacuum chamber 10. This adjustment part allows for fine adjustment of the extraction interval d between the multi-hole 13 of the cylindrical part 12 and the extraction electrode 16, enabling proton extraction without generating a discharge between the cylindrical part 12 and the extraction electrode 16. For example, the adjustment part can be adjusted along the left-right direction or the front-back direction of the vacuum chamber 10 at predetermined adjustment intervals by providing an adjustment tool such as a screw on the cylindrical connecting part that constitutes the holding part 18 and fine-tuning the screw on the adjustment tool.

[0035] Next, the configuration and execution procedure of an embodiment of the present invention will be described with reference to Figures 5-7. Here, the first embodiment of the present invention will be described. First, the user turns on the power to each part of the high-voltage, high-density PIG ion source 1 to start the control device 17.

[0036] Once the operation of each part stabilizes, the user inputs a start key to the control device 17, and each control unit of the control device 17 starts operating. First, the vacuum control unit 501 of the control device 17 creates a vacuum in the vacuum chamber 10 (Figure 6: S101).

[0037] Here, there are no particular limitations on how the vacuum control unit 501 creates a vacuum. For example, the vacuum control unit 501 drives a vacuum generator (not shown) at the tip of a vacuum exhaust pipe 101 that communicates with the vacuum chamber 10 to draw air from inside the vacuum chamber 10 through the vacuum exhaust pipe 101, thereby creating a vacuum inside the vacuum chamber 10.

[0038] Furthermore, if a predetermined pressure sensor is installed inside the vacuum chamber 10, the vacuum control unit 501 obtains the vacuum level inside the vacuum chamber 10 from the pressure sensor and determines whether the vacuum level falls below a predetermined threshold. If the vacuum level exceeds the threshold, the vacuum control unit 501 continues to drive the vacuum generator. If the vacuum level falls below the threshold, the vacuum control unit 501 reduces the operation of the vacuum generator to maintain the vacuum level in the vacuum chamber 10. This makes it possible to create a vacuum in the vacuum chamber 10.

[0039] In addition, for example, if a vacuum solenoid valve is provided between the vacuum exhaust pipe 101 and the vacuum generator, the vacuum control unit 501 may close the vacuum solenoid valve to maintain the vacuum level of the vacuum chamber 10 when the vacuum level falls below a threshold. There are no particular limitations on the vacuum level of the vacuum chamber 10, but for example, 0.1 × 10⁻⁶ -2 Pa~10.0×10 -2 It is preferably within the range of Pa, 0.1 × 10 -2 Pa~5.0×10 -2 It is even more preferable if it is within the range of Pa.

[0040] Next, once the vacuum control unit 501 has created a vacuum in the vacuum chamber 10, the magnetic field control unit 502 of the control device 17 applies a magnetic field using the upper and lower electromagnets 11a and 11b (Figure 6: S102).

[0041] Here, there are no particular limitations on the method by which the magnetic field control unit 502 applies the magnetic field. For example, the magnetic field control unit 502 supplies power to the upper and lower electromagnets 11a and 11b that are in motion, so as to correspond to a preset magnetic field distribution, thereby applying a magnetic field in the vertical direction of the vacuum chamber 10.

[0042] Furthermore, if a predetermined magnetic field sensor is installed inside the vacuum chamber 10, the magnetic field control unit 502 obtains the magnetic flux density inside the vacuum chamber 10 from the magnetic field sensor and determines whether the magnetic flux density is above a predetermined threshold. If the magnetic flux density is below the threshold, the magnetic field control unit 502 supplies power to the upper and lower electromagnets 11a and 11b to increase the magnetic flux density. On the other hand, if the magnetic flux density is above the threshold, the magnetic field control unit 502 stabilizes the power supply to the upper and lower electromagnets 11a and 11b to maintain the magnetic flux density of the vacuum chamber 10. This allows the magnetic field to be controlled in the vacuum chamber 10. There are no particular limitations on the magnetic flux density of the vacuum chamber 10, but it is preferably in the range of 10mT to 100mT, and more preferably in the range of 10mT to 50mT.

[0043] Next, when the magnetic field control unit 502 applies a magnetic field, the supply control unit 503 of the control device 17 supplies hydrogen gas to the pair of gas supply pipes 15a and 15b (Figure 6: S103).

[0044] Here, there are no particular limitations on the method by which the supply control unit 503 supplies hydrogen gas. For example, a pair of gas supply pipes 15a and 15b are connected to a pre-installed hydrogen gas cylinder (not shown), and a gas solenoid valve is provided between the pair of gas supply pipes 15a and 15b and the hydrogen gas cylinder. The supply control unit 503 opens the gas solenoid valve, connects the pair of gas supply pipes 15a and 15b to the hydrogen gas cylinder, and supplies hydrogen gas from the hydrogen gas cylinder to the pair of gas supply pipes 15a and 15b. Then, through the pair of gas supply pipes 15a and 15b, the hydrogen gas is supplied to the cylindrical section 12 from the tip portions 15a1 and 15b1 of the pair of gas supply pipes 15a and 15b.

[0045] Furthermore, if a predetermined gas sensor is installed inside the pair of gas supply pipes 15a and 15b, the supply control unit 503 obtains the gas concentration from the gas sensor and determines whether the gas concentration exceeds a predetermined threshold. If the gas concentration is below the threshold, the supply control unit 503 opens the gas solenoid valve further to increase the gas concentration. On the other hand, if the gas concentration exceeds the threshold, the supply control unit 503 restricts the opening of the gas solenoid valve to maintain the gas concentration. This allows the amount of hydrogen gas supplied to the cylindrical section 12 to be controlled. Note that the gas sensor may detect gas pressure or gas flow rate in addition to gas concentration. There are no particular limitations on the amount of hydrogen gas supplied, but it is preferably in the range of 10cc / min to 100cc / min, and more preferably in the range of 10cc / min to 50cc / min.

[0046] Next, when the supply control unit 503 supplies hydrogen gas, the high-pressure control unit 504 of the control device 17 applies high pressure between the pair of electrode sections 14a and 14b to generate protons inside the cylindrical section 12 (Figure 6: S104).

[0047] Here, there are no particular limitations on the method by which the high-voltage control unit 504 applies high voltage. For example, a predetermined high-voltage power supply is electrically connected to a pair of electrode sections 14a and 14b, and a predetermined switch is provided between the pair of electrode sections 14a and 14b and the high-voltage power supply. The high-voltage control unit 504 electrically connects the pair of electrode sections 14a and 14b to the high-voltage power supply by electrically connecting the switch, and applies the high voltage of the high-voltage power supply to the pair of electrode sections 14a and 14b.

[0048] Here, when high pressure is applied to the pair of electrode sections 14a and 14b, as shown in Figure 7, the pair of electrode sections 14a and 14b are rapidly heated (ignited), and thermionic electrons are emitted into the cylindrical section 12. On the other hand, as described above, since the cylindrical section 12 is filled with hydrogen gas, the inside of the cylindrical section 12 becomes a plasma state with hydrogen gas and thermionic electrons, and the hydrogen gas and thermionic electrons react to generate protons inside the cylindrical section 12.

[0049] Furthermore, since the inside of the cylindrical portion 12 becomes a plasma state, for example, cooling pipes (not shown) may be provided in advance at both ends 12d, 12e in the longitudinal direction of the cylindrical portion 12 or on the outer circumference of the cylindrical portion 12, and the cylindrical portion 12 and the pair of electrode portions 14a, 14b may be cooled by passing water through the cooling pipes.

[0050] Furthermore, if a predetermined voltage sensor is provided inside the cylindrical portion 12, the high-voltage control unit 504 acquires the voltage value from the voltage sensor and determines whether the voltage value is above a predetermined threshold. If the voltage value is below the threshold, the high-voltage control unit 504 increases the voltage of the high-voltage power supply to raise the voltage value. On the other hand, if the voltage value is above the threshold, the high-voltage control unit 504 lowers the voltage of the high-voltage power supply to maintain the voltage value. This allows the voltage applied to the cylindrical portion 12 to be controlled. There are no particular limitations on the voltage value of the applied high voltage, but it is preferably in the range of -0.2kV to -3.0kV, and more preferably in the range of -0.4kV to -1.6kV. There are no particular limitations on the arc current value in this case, but it is preferably in the range of 0.1A to 1.0A.

[0051] Next, when the high-voltage control unit 504 applies high voltage, the extraction control unit 505 of the control device 17 applies a negative charge to the extraction electrode 16 to extract the generated proton beam (Figure 6: S105).

[0052] Here, there are no particular limitations on the method by which the extraction control unit 505 applies a negative charge. For example, the extraction electrode 16 may have a predetermined negative charge electrode electrically connected to it, and a positive charge electrode electrically connected to another location. A predetermined switch may be provided between the extraction electrode 16 and the negative charge electrode. The extraction control unit 505 electrically connects the extraction electrode 16 and the negative charge electrode by electrically connecting the switch, thereby applying a negative charge to the extraction electrode 16.

[0053] As shown in Figure 7, the multi-holes 13 of the cylindrical section 12 and the extraction electrode 16 are positioned opposite each other with a predetermined extraction interval d. As a result, protons generated inside the cylindrical section 12 pass through the multi-holes 13, form a beam, and are extracted to the extraction electrode 16. This allows the generated proton beam to be extracted. In particular, because the aperture ratio is increased by the multi-holes 13, a large amount of generated protons can be extracted.

[0054] Here, the holding portion 18, for example, has the multi-holes 13 of the cylindrical portion 12 tilted at a predetermined angle α, and the extraction electrode 16 is applied with a negative charge to the multi-holes 13 of the cylindrical portion 12 at a predetermined distance d. Furthermore, the upper and lower electromagnets 11a and 11b apply a magnetic field to the vacuum chamber 10 for the protons to rotate. In this case, as shown in Figure 8, the extracted beam of protons can be rotated outward from near the center of the vacuum chamber 10, and finally extracted as a beam of protons.

[0055] In this invention, compared to the conventional technology, the cylindrical portion 12 is provided with multi-holes 13, which allows for the emission of a large number of protons from the cylindrical portion 12 to form a proton beam. Therefore, by optimizing the proton extraction method, this invention makes it possible to generate a high-current proton beam at low energy.

[0056] Furthermore, in the above description, for example, the generated positive ions (protons) were rotated as a beam and extracted. However, if, for example, there is no holding unit 18 and there are no plans to accelerate protons in the vacuum chamber 10, then a large amount of positive ions can simply be extracted from the extraction hole 16a of the extraction electrode 16. Also, there are no particular limitations on the extraction voltage, but it is preferable that it be in the range of 1kV to 20kV. Similarly, there are no particular limitations on the extraction current, but it is preferable that it be in the range of 1mA to 20mA.

[0057] Furthermore, as described above, in S103, the supply control unit 503 supplied hydrogen gas and the high-pressure control unit 504 applied high pressure. However, the procedure is not limited to this. For example, the high-pressure control unit 504 may apply high pressure first, and then the supply control unit 503 may supply hydrogen gas, reversing the order. In this case, the high-pressure control unit 504 applies high pressure between the pair of electrode sections 14a and 14b, and then the supply control unit 503 supplies hydrogen gas to generate protons inside the cylindrical section 12. [Examples]

[0058] Examples and comparative examples of the present invention will be described below in detail, but the application of the present invention is not limited to these examples.

[0059] <Manufacturing of high-voltage, high-density PIG ion sources> Based on Figure 1-3, a high-voltage, high-density PIG ion source was manufactured as Example 1. As shown in Figure 9, in Example 1 of the high-voltage, high-density PIG ion source 1, a cylindrical part 12, a multi-hole 13, a pair of electrode parts 14a and 14b, a pair of gas supply pipes 15a and 15b, and a holding part 18 can be seen. By placing this in a vacuum chamber 10 and electrically connecting each control unit of the control device 17, the high-voltage, high-density PIG ion source 1 can be operated.

[0060] Next, the vacuum control unit 501 created a vacuum in the vacuum chamber 10. Here, the vacuum level was, for example, 3.2 × 10⁻⁶. -2 The vacuum level was Pa. If the magnetic field control unit 502 were to apply a magnetic field, the vacuum level would be 1.6 × 10⁻⁶. -2The pressure was Pa. Next, the supply control unit 503 supplied hydrogen gas at a predetermined gas flow rate. The gas flow rate was, for example, 30 cc / min. Then, the high-pressure control unit 504 applied high pressure. Here, the applied voltage (arc voltage) was -1.2 kV. The arc current at this time is assumed to be, for example, 0.4 A. As a result, the inside of the cylindrical part 12 became a plasma state with hydrogen gas and thermionic electrons, and the hydrogen gas and thermionic electrons reacted to generate protons inside the cylindrical part 12. Here, as shown in Figure 10A, it can be understood that plasma is generated in the high-voltage, high-density PIG ion source inside the vacuum chamber 10.

[0061] Then, the extraction control unit 505 extracted the generated proton beam by applying a negative charge to the extraction electrode 16 within a predetermined extraction voltage range. For the extracted protons, the magnitude of the extraction current relative to the extraction voltage was confirmed by measuring the extraction current as shown in Figure 10B.

[0062] As a result, as shown in Figure 11, it is understood that when the extraction voltage is, for example, 2kV, the extraction current is 10mA. Here, conventionally, an extraction voltage of 10kV and an extraction current of 10mA are common, and it is understood that in Example 1, surprisingly, it was possible to obtain an extraction current five times that of the normal value. In other words, a large number of protons were successfully extracted. Thus, it has been found that in the present invention, by optimizing the extraction method of positive ions, it is possible to extract a large current at a low energy.

[0063] Thus, because the present invention makes it possible to extract a large current with low energy, it can be applied to a variety of devices such as particle accelerators used in radiation therapy, ion implanters, mass spectrometers, sputtering equipment, surface modification equipment, material processing equipment, thin film formation equipment, analytical equipment, measuring equipment, semiconductor manufacturing equipment, environmental application equipment, energy application equipment, and bio-application equipment.

[0064] Now, in the particle accelerator using the high-voltage, high-density PIG ion source 1 according to the first embodiment described above, an experimental vacuum chamber 10 was explained. Next, for example, in the particle accelerator using the high-voltage, high-density PIG ion source 1 according to the second embodiment, an actual accelerator will be assumed and explained.

[0065] In the high-voltage, high-density PIG ion source 1 according to the second embodiment, as shown in Figures 12-14, it comprises an acceleration chamber 10, upper and lower electromagnets 11a and 11b, a cylindrical section 12, a multi-hole 13, a pair of electrode sections 14a and 14b, a pair of gas supply pipes 15a and 15b, an extraction electrode 16, a control device 17, and a holding section 18.

[0066] In the particle accelerator according to the second embodiment, a pair of accelerating electrodes 103 (D-electrodes) are further provided inside the accelerating chamber 10 to accelerate protons. The pair of accelerating electrodes are electrically connected to a high-frequency power supply, and the high-frequency electric field of the pair of accelerating electrodes can accelerate protons. In addition, a pair of auxiliary electrodes 104 are provided near the outer circumference of the multi-hole 13 of the cylindrical section 12 to assist in the acceleration of protons.

[0067] Furthermore, a septum electrode 19 is provided near the outer periphery of the acceleration chamber 10, along the orbit of the proton beam, and a voltage is applied to the proton beam to separate it from the orbit inside the acceleration chamber 10. Also, near the outer periphery of the acceleration chamber 10, a deflector 20 is provided after the septum electrode 19, along the orbit of the proton beam, to align the separated proton beam's orbit with the outside.

[0068] In the particle accelerator according to the second embodiment, as shown in Figure 14, extraction electrodes 16 are provided opposite the multi-holes 13 of the cylindrical section 12, similar to the above, and a large number of protons can be emitted from the cylindrical section 12 to form a proton beam. [Industrial applicability]

[0069] As described above, the high-voltage, high-density PIG ion source and ion extraction method according to the present invention are useful in a wide range of industrial fields, including medical accelerators, radiation therapy devices, radioisotope production devices, and various beam application devices. By optimizing the positive ion extraction method, it is an effective high-voltage, high-density PIG ion source and ion extraction method that can extract large currents at low energy. [Explanation of Symbols]

[0070] 1. High-voltage, high-density PIG ion source 10 Vacuum chamber 11a, 11b Upper and lower electromagnets 12 Cylindrical section 13 Multi-hole 14a, 14b Pair of electrode sections 15a, 15b A pair of gas supply pipes 16 Extraction electrode 17 Control device 18 Holding part 501 Vacuum Control Unit 502 Magnetic Field Control Unit 503 Supply Control Unit 504 High-voltage control unit 505 Drawer Control Unit

Claims

1. A vacuum chamber and Upper and lower electromagnets are provided outside the vacuum chamber in the vertical direction and generate a magnetic field in the vertical direction of the vacuum chamber, A cylindrical portion whose longitudinal direction is aligned with the vertical direction of the vacuum chamber, A multi-hole structure is formed by arranging multiple holes along the longitudinal direction of the cylindrical portion on one longitudinal side of the cylindrical portion, A pair of electrode portions are provided at both ends in the longitudinal direction of the cylindrical portion, A pair of gas supply pipes are provided at both ends in the longitudinal direction of the cylindrical portion, Displaced inside the vacuum chamber at a predetermined interval from the multi-holes, the extraction electrode has an extraction hole facing the multi-holes, A vacuum control unit that brings the vacuum chamber into a vacuum state, A magnetic field control unit that applies a magnetic field using the upper and lower electromagnets, The gas supply pipe is supplied with a supply control unit that supplies gas of ionizable molecules, A high-pressure control unit that applies high pressure between the electrode portions to generate positive ions inside the cylindrical portion, An extraction control unit that extracts the generated positive ions by applying a negative charge to the extraction electrode, A high-voltage, high-density PIG ion source equipped with these features.

2. The cylindrical portion has tapered surfaces at both ends in the longitudinal direction, and a planar shape extending from the tapered surface to the longitudinal direction. The multi-hole configuration is achieved by arranging the plurality of holes in the planar shape of the cylindrical portion with predetermined spacings between them. The high-voltage, high-density PIG ion source according to claim 1.

3. The arrangement of the aforementioned multiple holes includes any of the following: staggered, in series, or in two rows. The high-voltage, high-density PIG ion source according to claim 1.

4. A vacuum chamber and Upper and lower electromagnets are provided outside the vacuum chamber in the vertical direction and generate a magnetic field in the vertical direction of the vacuum chamber, A cylindrical portion whose longitudinal direction is aligned with the vertical direction of the vacuum chamber, A multi-hole structure is formed by arranging multiple holes along the longitudinal direction of the cylindrical portion on one longitudinal side of the cylindrical portion, A pair of electrode portions are provided at both ends in the longitudinal direction of the cylindrical portion, A pair of gas supply pipes are provided at both ends in the longitudinal direction of the cylindrical portion, Displaced inside the vacuum chamber at a predetermined interval from the multi-holes, the extraction electrode has an extraction hole facing the multi-holes, A method for extracting ions from a high-voltage, high-density PIG ion source, comprising: A vacuum control process to bring the vacuum chamber into a vacuum state, A magnetic field control step in which a magnetic field is applied by the upper and lower electromagnets, A supply control step for supplying a gas of ionizable molecules to the gas supply pipe, A high-pressure control step involves applying high pressure between the electrode portions to generate positive ions inside the cylindrical portion, An extraction control step is performed to extract the generated positive ions by applying a negative charge to the extraction electrode, An ion extraction method comprising [a specific feature].

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