Radionuclide production system, radionuclide production method, and accelerator system

Abstract

The present invention provides a radionuclide production system, a radionuclide production method, and an accelerator system with which a beam profile of radiation irradiated on a target can be monitored in real time using a destructive monitor, and with which appropriate irradiation on the target can be carried out according to the beam profile. The radionuclide production system comprises: an accelerator that accelerates charged particles; and a target that produces a radionuclide by nuclear reaction upon being irradiated with an accelerated charged particle beam or radiation generated by a charged particle beam. The radionuclide production system further comprises, behind targets (T205, T207) in the direction of advancement of the charged particle beam, destructive monitors (T206, T209) which are detectors for detecting radiation and which interact with the radiation. On the basis of a spatial distribution of intensity of the charged particle beam or radiation measured by the destructive monitors, the radionuclide production method produces a radionuclide while determining, as a beam profile at positions of the targets, at least one of a spatial distribution of intensity, a position of a beam center, and a beam spread.

Description

Radionuclide production system, radionuclide production method, and accelerator system

[0001] The present invention relates to a radionuclide production system, a radionuclide production method, and an accelerator system that monitor a beam profile using a destructive monitor.

[0002] As one type of cancer treatment, RI internal therapy using a radioisotope (RI) is known. RI internal therapy is a treatment in which a drug incorporating a radioactive nuclide is administered to accumulate in the affected tissue, and the affected tissue is directly irradiated with radiation emitted by the radioactive nuclide. As a radioactive nuclide used in RI internal therapy, alpha-ray emitting nuclides have attracted attention.

[0003] Alpha rays have a short range and a large amount of linear energy imparted, so they can selectively and effectively destroy only cancer cells without significantly damaging surrounding normal cells. Therefore, alpha-ray therapy using alpha-ray emitting nuclides is expected to have a higher therapeutic effect than beta-ray therapy, and its clinical application is being promoted.

[0004] Alpha-ray emitting nuclides include radium-223 (Ra-223), astatine-211 (At-211), and actinium-225 (Ac-225). Actinium-225 is a nuclide that rarely exists in nature. Conventionally, actinium-225 has been produced by the decay of thorium-229 (Th-229). Thorium-229 has been produced by the decay of uranium-233 (U-233). After being produced in thorium-229, actinium-225 is recovered by chemical separation methods, etc.

[0005] Traditionally, thorium-229 has been produced in nuclear facilities, but production is limited from the standpoint of nuclear material protection, making it increasingly scarce. There are concerns that the supply of therapeutic actinium-225 will be insufficient in the future. Therefore, in recent years, development of a process for producing actinium-225 using an accelerator has been underway. The following (1) to (3) are known methods for producing actinium-225 using an accelerator.

[0006] (1) ２２６ Ra(p, 2n)２２５ A method that utilizes the proton-neutron reaction of radium 226 (Ra-226), represented by Ac. (2) ２３２ Th(p,spall) ２２５ A method utilizing the spallation reaction of thorium-232 (Th-232), represented by Ac, with protons. (3) ２２６ Ra(γ, n) ２２５ A method utilizing the photon-neutron reaction represented by Ra followed by the conversion of Ra-225 to Ac-225 by beta decay.

[0007] Methods (1) and (2) have the problem of producing impurity nuclides that are difficult to separate from actinium-225. Impurity nuclides produced include actinium-226, which has a half-life of approximately 29 hours, and actinium-227, which has a half-life of approximately 22 years, in contrast to actinium-225, which has a half-life of approximately 10 days. Impurity nuclides pose problems in terms of safety during administration and the increase in radioactive waste. Furthermore, the need for a proton accelerator poses the problem of the accelerator becoming large.

[0008] Method (3) has the advantage of avoiding the generation of impurity nuclides because it uses a photonuclear reaction. However, the cross section of a photonuclear reaction is smaller than that of a proton-neutron reaction or a spallation reaction. Therefore, it is necessary to efficiently irradiate gamma rays onto the source material containing the source nuclides.

[0009] Actinium-225 is a radionuclide with a relatively short half-life. Radionuclides with short half-lives cannot be stockpiled until needed. Therefore, production capacity is required to supply the required amount without delay in response to demand. In order to secure the required amount at the required time, it is necessary to stabilize the production volume by the production system. It is necessary to ensure the nuclear reaction rate of the source nuclide and the yield of the radionuclide, and monitoring the beam profile is important in order to precisely irradiate the source material with radiation.

[0010] Patent Document 1 describes a duct for a radiation shield for irradiating a target with an electron beam from an electron accelerator. In this duct, transition radiation is observed with a camera to determine the spatial intensity distribution of the electron beam. The camera is disposed forward of the electron beam, closer to the electron source than the target, in the direction of electron beam propagation. The camera is disposed laterally with respect to the central axis of the electron beam, and observes the transition radiation reflected by a mirror from a direction approximately perpendicular to the beam.

[0011] Patent Document 2 describes a charged particle beam irradiation system including a charged particle generator, an accelerator, an irradiation unit that irradiates a target with a charged particle beam, and the like. This system includes an infrared camera that detects infrared rays emitted from the target in order to detect the irradiation position of the charged particle beam. The infrared camera is disposed forward of the target in the direction of travel of the charged particle beam, closer to the charged particle source than the target. The infrared camera is disposed laterally with respect to the central axis of the charged particle beam, and detects the beam from an angle inclined at 45°.

[0012] JP 2021-188904 A JP 2014-025908 A

[0013] Charged particles accelerated by an accelerator and radiation such as gamma rays generated by irradiating a target material with charged particles are highly directional, with their intensity increasing in the direction of travel of the beam accelerated by the accelerator. In the process of producing the target radioactive nuclide by nuclear transmutation of a source nuclide, there is a problem that the nuclear reaction rate of the source nuclide and the yield of the radioactive nuclide decrease when the source target is placed too far apart relative to the beam diameter or when the source target is displaced from the beam center.

[0014] In order to increase the nuclear reaction rate of the source nuclides and the yield of radioactive nuclides, it is important to accurately grasp the radiation beam profile and accurately align the source target with respect to the beam. In the direction perpendicular to the beam axis, it is desirable to limit the range of the source target with respect to the beam diameter. In addition, precise alignment of the source target with respect to the beam center is desirable. Since the beam diameter is typically on the order of several mm, it is necessary to precisely align the source target with respect to the beam center and keep it within a diameter range of several mm.

[0015] Conventionally, a method using a profile monitor such as a fluorescent screen is known as a method for measuring a beam profile. The profile monitor is installed in place of the target at the target's position before the target is irradiated with radiation. The beam position, shape, intensity, etc. are confirmed by irradiating the profile monitor. After the target is positioned based on the results of such measurements, the target is actually irradiated.

[0016] However, typical profile monitors are destructive monitors that interact with radiation. The profile monitor itself shields or scatters radiation, making it difficult to accurately measure the beam profile. Furthermore, because profile monitors are prone to deterioration and breakdown due to radiation, measurements must be performed while shielding them appropriately. Stable operation of destructive monitors in an irradiation environment is difficult, so they must be removed when irradiating the target with radiation.

[0017] Conventionally, the beam profile measured by a destructive monitor is acquired before the actual irradiation of the target, and is therefore used for target alignment under the assumption that it will remain constant until the actual irradiation of the target. The actual irradiation of the target is performed under the assumption that the previously measured beam profile has not changed.

[0018] However, the beam profile at the target can fluctuate even during irradiation. For example, in the process of producing radionuclides, when a raw target is irradiated for a long period of time, the area around the beam outlet can become very hot, which can cause fluctuations in the position of the beam center and the beam divergence from the beam center. Under these circumstances, there is a need for technology that can monitor the beam profile at the target in real time even during irradiation.

[0019] Therefore, an object of the present invention is to provide a radionuclide production system, a radionuclide production method, and an accelerator system that are capable of monitoring the beam profile of radiation irradiated to a target in real time using a destructive monitor, and that can appropriately irradiate the target according to the beam profile.

[0020] In order to solve the above problems, the radionuclide production system of the present invention is a radionuclide production system comprising an accelerator that accelerates charged particles, and a target that produces radionuclides through a nuclear reaction when irradiated with a charged particle beam accelerated by the accelerator or radiation generated by the charged particle beam, and further comprising a destructive monitor that detects radiation and interacts with the radiation, located behind the target in the direction of travel of the charged particle beam.

[0021] Further, a radionuclide production method according to the present invention is a radionuclide production method for producing a radionuclide using a radionuclide production system including an accelerator for accelerating charged particles and a target for producing a radionuclide by a nuclear reaction when irradiated with a charged particle beam accelerated by the accelerator or radiation generated by the charged particle beam, wherein the radionuclide production system includes a destructive monitor, which is a particle detector for detecting the charged particle beam behind the target in the direction of propagation of the charged particle beam and which interacts with the charged particle beam, and the radionuclide is produced while determining, as the beam profile at the position of the target, one or more of the spatial distribution of intensity of the charged particle beam or the radiation, the position of the beam center of the charged particle beam or the radiation, and the beam spread from the beam center of the charged particle beam or the radiation, based on the spatial distribution of intensity of the charged particle beam or the radiation measured by the destructive monitor.

[0022] Furthermore, the accelerator system according to the present invention is an accelerator system comprising an accelerator for accelerating charged particles, and a target irradiated with a charged particle beam accelerated by the accelerator or radiation generated by the charged particle beam, and further comprising a destructive monitor behind the target in the direction of travel of the charged particle beam, which is a particle detector for detecting the charged particle beam and interacts with the charged particle beam.

[0023] According to the present invention, it is possible to provide a radionuclide production system, a radionuclide production method, and an accelerator system that are capable of monitoring in real time the beam profile of radiation irradiated to a target using a destructive monitor and that can appropriately irradiate the target according to the beam profile.

[0024] FIG. 1 is a diagram showing an example of a radionuclide production system according to an embodiment of the present invention. FIG. 2 is a diagram showing an arrangement of destructive monitors in a radionuclide production system according to an embodiment of the present invention. FIG. 3 is a diagram showing an arrangement of destructive monitors in a conventional accelerator system. FIG. 4 is a flowchart showing an example of a method of operating a radionuclide production system according to an embodiment of the present invention. FIG. 5 is a diagram showing an example of a configuration for monitoring a beam profile. FIG. 6 is a diagram showing an example of a configuration for monitoring a beam profile. FIG. 7 is a diagram showing an example of a configuration for monitoring a beam profile.

[0025] Hereinafter, a radionuclide production system, a radionuclide production method, and an accelerator system according to an embodiment of the present invention will be described with reference to the drawings. In the following drawings, common components are designated by the same reference numerals, and duplicated explanations will be omitted.

[0026] Fig. 1 is a diagram showing an example of a radionuclide production system according to an embodiment of the present invention. As shown in Fig. 1, the radionuclide production system A100 according to this embodiment includes an accelerator A101 that accelerates and emits charged particles, an irradiation chamber A102 that irradiates a target with the accelerated charged particles, and a control device A103 that controls the equipment.

[0027] The radionuclide production system A100 is an apparatus that irradiates a source target containing a source nuclide with radiation to transmute the source nuclide through a nuclear reaction, thereby producing a predetermined radionuclide. The source target containing the source nuclide is held in a sample target system A135. The sample target system A135 is irradiated with radiation having an energy equal to or greater than the threshold for the nuclear reaction, thereby inducing a predetermined nuclear reaction in the source nuclide, thereby transmuting the source nuclide into a target radionuclide.

[0028] In the radionuclide production system A100, the radiation to be irradiated onto the raw material target is radiation generated by irradiating a radiation generation target with a charged particle beam accelerated by an accelerator A101. Depending on the type of radionuclide to be produced, the type of nuclear reaction to be used for nuclear transmutation, etc., it is also possible to use a charged particle beam accelerated by the accelerator A101 as the radiation to be irradiated onto the raw material target.

[0029] As the source nuclide, an appropriate type can be used depending on the type of radioactive nuclide to be produced, etc. As the nuclear reaction for nuclear transmuting the source nuclide, an appropriate nuclear reaction can be used depending on the type of radioactive nuclide to be produced, the type of source nuclide, the required energy, etc.

[0030] The radionuclide production system A100 is configured to use a photonuclear reaction caused by irradiation with gamma rays as a nuclear reaction for nuclear transmuting a raw material nuclide. The gamma rays are generated by irradiating a gamma ray generation target A134 with a charged particle beam accelerated by an accelerator A101. To generate the gamma rays, a heavy metal or the like is used as the gamma ray generation target A134, and bremsstrahlung caused by the incidence of the charged particle beam can be utilized.

[0031] The accelerator A101 accelerates charged particles to a predetermined energy band and emits them toward the irradiation chamber A102. In the radionuclide production system A100, the accelerator A101 is provided as an electron linear accelerator that accelerates electrons.

[0032] The accelerator A101 includes a charged particle source A111 that generates charged particles, an acceleration tube A114 that accelerates the charged particles to generate a focused charged particle beam, a vacuum pumping device A115 that draws a vacuum inside the transport path of the charged particle beam, a beam transport section A129 that transports the charged particle beam toward the extraction side, and a beam window A133 that emits the charged particle beam.

[0033] The charged particle source A111 can be configured as a three-electrode thermionic emission electron gun equipped with a cathode, an anode, and a control electrode, or an ion source that extracts ions from plasma generated in a high-frequency electric field. Appropriate types of charged particles can be used depending on the type of radioactive nuclide to be produced, the type of nuclear reaction used for nuclear transmutation, etc. In the radionuclide production system A100, after electrons are produced in the charged particle source A111, the accelerated electrons are irradiated onto the gamma ray generation target A134.

[0034] The solenoid A112 is installed on the exit side of the charged particle source A111. The solenoid A113 is installed on the entrance side of the acceleration structure A114. The magnetic fields generated by the solenoids A112 and A113 converge low-energy charged particles generated by the charged particle source A111 and efficiently transport them toward the acceleration structure A114. The solenoids A112 and A113 may be omitted if the charged particles are appropriately collimated.

[0035] The acceleration tube A114 forms an electric field acting on the charged particles, thereby accelerating the charged particles generated by the charged particle source A111. The acceleration tube A114 may accelerate the charged particles by applying a DC voltage or an AC voltage. The charged particles accelerated by the acceleration tube A114 are transported to the beam transport part A129.

[0036] The vacuum pumping device A115 prevents the diffusion and loss of the charged particle beam by evacuating the acceleration tube A114 and the beam transport part A129. Any number of vacuum pumping devices A115 can be provided at any suitable location.

[0037] The beam transport part A129 is formed by a plurality of electromagnet groups, a beam pipe A121, etc. The charged particles accelerated by the acceleration tube A114 are efficiently transported through the beam transport part A129, which forms HEBTs (High Energy Beam Transport lines), and then emitted from a beam window A133, which is an outlet for the charged particle beam, to irradiate a target.

[0038] 1, the beam transport part A129 is formed by a first focusing electromagnet group A116, a second focusing electromagnet group A122, a bending electromagnet group A123, and a third focusing electromagnet group A128. In the beam transport part A129, the shape and traveling direction of the charged particle beam are adjusted by adjusting the excitation amount of the electromagnets, thereby reducing losses due to diffusion and collision of the charged particles.

[0039] The focusing electromagnet groups A116, A122, and A128 are electromagnet groups that focus the charged particle beam toward the central axis, and are formed by a combination of steering electromagnets A117 and A120 and a plurality of quadrupole electromagnets A118 and A119, respectively.

[0040] The bending electromagnet group A123 is a group of electromagnets that deflects the charged particle beam in a predetermined direction, and is formed by a combination of bending electromagnets A124 and A127 and a plurality of quadrupole electromagnets A125 and A126.

[0041] The quadrupole electromagnets A118, A119, A125, and A126 each have two pairs of opposing coils and magnetic poles. The quadrupole electromagnets generate a magnetic field that cancels out misalignment in the vertical or horizontal direction relative to the beam axis within a plane perpendicular to the beam propagation direction, thereby focusing the charged particle beam in a predetermined direction. The vertically focusing quadrupole electromagnets diverge the beam in the horizontal direction, while the horizontally focusing quadrupole electromagnets diverge the beam in the vertical direction. However, by alternately arranging electromagnets that focus the beam in the vertical direction and electromagnets that focus the beam in the horizontal direction, a charged particle beam that is focused in both the vertical and horizontal directions can be obtained.

[0042] The steering electromagnets A117 and A120 are a type of bending electromagnet that generate a weak magnetic field in a direction perpendicular to the traveling direction of the charged particle beam, enabling fine adjustment of the traveling direction of the charged particle beam. The bending electromagnets A124 and A127 generate a strong magnetic field in a direction perpendicular to the traveling direction of the charged particle beam, changing the traveling direction of the charged particle beam.

[0043] The irradiation chamber A102 is a space where the accelerated charged particles are irradiated onto a target. In the radionuclide production system A100, the irradiation chamber A102 is equipped with a gamma ray generation target A134 that generates gamma rays when irradiated with a charged particle beam accelerated by the accelerator A101, and a sample target system A135 that holds a source target containing a source nuclide.

[0044] The irradiation chamber A102 houses a beam monitor A132 that measures the beam profile of the charged particle beam, a beam window A133 that emits the charged particle beam, a target A134 for generating gamma rays that is irradiated with the charged particle beam, a sample target system A135 that is irradiated with gamma rays, and a beam dump A136 that attenuates the charged particle beam.

[0045] The beam monitor A132 is a device for measuring the beam profile relating to the position, shape, intensity, etc. of the charged particle beam. The beam profile measured includes the position of the beam center, the beam spread from the beam center, and the spatial distribution of the beam intensity. An appropriate number of beam monitors A132 can be provided at appropriate locations. The beam monitor A132 can also be installed in the beam transport part A129 instead of or together with the irradiation chamber A102.

[0046] The beam monitor A132 may be a current monitor that detects the current of the charged particle beam using a current transformer, a beam position monitor that measures wall currents due to radiation-induced charges using multiple electrode pairs installed on the inner wall of the transport path and identifies the position of the beam center from the asymmetry of the density distribution of the wall current, or a beam profile monitor that measures the coordinate characteristics of the beam.

[0047] The beam profile monitor can be one based on various principles for measuring the spatial distribution of beam intensity, emittance, etc. For example, a screen-type monitor can be used, in which charged particles are incident on a fluorescent screen to generate fluorescence, and the fluorescence emission distribution is captured and analyzed by a camera, or a conductive material can be used to collect charged particles.

[0048] The beam window A133 is located on the exit side of the beam transport section A129, at the rear end of the charged particle transport path. The gamma ray generation target A134 is located behind the beam window A133 in the direction of travel of the charged particle beam. The sample target system A135 is located behind the gamma ray generation target A134 in the direction of travel of the charged particle beam. The beam dump A136 is located behind the sample target system A135 in the direction of travel of the charged particle beam.

[0049] The radionuclide production system A100 is configured to use a photonuclear reaction caused by irradiation with gamma rays as the nuclear reaction for nuclear transmuting the source nuclide. A charged particle beam accelerated by an accelerator A101 is irradiated onto a gamma ray generation target A134. The gamma ray generation target A134 emits gamma rays by bremsstrahlung caused by the charged particle beam. A sample target system A135 is irradiated with the gamma rays emitted by the gamma ray generation target A134.

[0050] Heavy metals with high atomic numbers, high densities, and high heat resistance can be used as the gamma ray generation target A134. Examples of materials for the gamma ray generation target A134 include gold (Au), mercury (Hg), platinum (Pt), tungsten (W), tantalum (Ta), lead (Pb), and bismuth (Bi).

[0051] Note that if a nuclear reaction such as a proton-neutron reaction caused by irradiation with charged particles or a nuclear spallation reaction is used as the nuclear reaction for nuclear transmuting the source nuclide, rather than a photonuclear reaction caused by irradiation with gamma rays, then it is not necessary to install the gamma ray generation target A134. A charged particle beam accelerated by the accelerator A101 can also be used for the sample target system A135.

[0052] The sample target system A135 is formed by a source target containing source nuclides, a container or substrate for holding the source target, etc. The source target can be a substance in an appropriate physical state or chemical form. The source target may be a solid such as a powder, a powder aggregate, a powder compact, or a bulk mass, or may be a liquid or semi-fluid such as a pure substance liquid, a solution, or a suspension. The sample target system A135 may be equipped with a cooling mechanism for removing heat from the source target, the container, the substrate, etc.

[0053] The beam dump A136 absorbs the charged particle beam that has passed through the sample target system A135 and prevents the charged particle beam from leaking to the outside. Examples of materials for the beam dump A136 include carbon and aluminum. The beam dump A136 may be cooled by water cooling, air cooling, or the like. Furthermore, when a fluid absorbent material that absorbs the charged particle beam is used, heat can be removed by dissipating heat from the absorbent material to the outside through heat exchange.

[0054] The irradiation chamber A102 is shielded from radiation to the outside by a shielding wall A130. The shielding wall A130 is made of a shielding material such as concrete, lead, or iron. The shielding wall A130 protects the accelerator A101 and other equipment from unnecessary radiation generated by the gamma ray generation target A134, the sample target system A135, etc.

[0055] Fig. 2 is a diagram showing the arrangement of destructive monitors in a radionuclide production system according to an embodiment of the present invention. Fig. 2 shows an example of the arrangement and structure of equipment for monitoring the beam profile for the gamma ray generation target A134 and the sample target system A135 in the radionuclide production system A100 shown in Fig. 1. As shown in Fig. 2, the radionuclide production system A100 according to this embodiment is equipped with destructive monitors (T206, T209, T214, T215) as detectors for detecting radiation.

[0056] 2, a beam window T201 is provided at the rear end of the transport path of the charged particle beam. The charged particle beam T202 travels through the inside of the beam pipe T204 along a beam axis T203, passes through the beam window T201, and is extracted to the outside. The beam axis T203 is an axis indicating the traveling direction of the charged particle beam T202, and corresponds to the position of the center of gravity of the intensity of the charged particle beam T202.

[0057] A gamma ray generation target T205 is installed behind the beam window T201 in the traveling direction of the charged particle beam T202. A target container T208 containing a raw material target T207 is installed behind the gamma ray generation target T205 in the traveling direction of the charged particle beam T202. A beam dump T222 is installed behind the target container T208. The gamma ray generation target T205 and the target container T208 can be installed using a fixing jig to prevent misalignment.

[0058] The target container T208 is placed horizontally so that the raw material target T207 contained therein is positioned at a position intersecting the beam axis T203. The raw material target T207 is contained on the bottom side of the target container T208. The beam axis T203 passes through the target container T208 along the longitudinal direction and is configured to irradiate the raw material target T207.

[0059] The charged particle beam T202 extracted outside the transport path is incident on the gamma-ray generation target T205, causing bremsstrahlung and emitting gamma rays. The gamma rays emitted from the gamma-ray generation target T205 are irradiated onto the source target T207, causing a photonuclear reaction of the source nuclide. The photonuclear reaction of the source nuclide converts the source nuclide into a predetermined product nuclide, thereby producing the desired radioactive nuclide.

[0060] In the radionuclide production system A100, while the raw material target T207 is irradiated with radiation, the beam profile relative to the target is monitored in real time. The beam profile refers to the geometric properties of the beam, such as the position, shape, and intensity. The beam profile can be expressed as a spatial distribution of the dose in a predetermined coordinate system orthogonal to the beam axis T203, with the coordinates, intensity, etc. as parameters.

[0061] In the radionuclide production system A100, the beam profile of radiation such as a charged particle beam T202 or gamma rays relative to a target is analyzed based on measurements by a destructive monitor. The destructive monitor is used to measure the spatial distribution of radiation intensity at a predetermined position in the traveling direction of the charged particle beam T202. The destructive monitor is a detector that detects radiation such as a charged particle beam or gamma rays, and refers to a detector that interacts with radiation.

[0062] As shown in FIG. 2, in the radionuclide production system A100, unlike conventional accelerator systems, the destructive monitors (T206, T209, T214, T215) are installed behind the targets (T205, T207) in the direction of travel of the charged particle beam T202 while the targets (T205, T207) are being irradiated with radiation.

[0063] Fig. 3 shows the arrangement of destructive monitors in a conventional accelerator system. Fig. 3 shows the arrangement of destructive monitors used to measure beam profiles in a conventional accelerator system and the surrounding structure. As shown in Fig. 3, destructive monitors (T217, T218, T221, T240) are widely used as detectors to detect radiation in conventional accelerator systems.

[0064] In FIG. 3, the destructive monitor is provided with fluorescent screens T217 and T221, which are light emitters that emit light when exposed to radiation, and photodetectors T218 and T240, which are photodetectors that detect the light emitted by the light emitters.

[0065] 3 shows the state before the target is irradiated with radiation. The fluorescent screens T217, T221 and the photodetectors T218, T240 are installed before the target is irradiated with radiation and are used to measure the beam profile. The fluorescent screens T217, T221 and the photodetectors T218, T240 are removed from their installed positions when the target is irradiated with radiation. The gamma ray generation target T205 and the raw material target T207 are installed in the positions where the fluorescent screens T217, T221 were installed.

[0066] 3, a first fluorescent screen T217 is installed on the front side, closer to the accelerator, in the traveling direction of the charged particle beam T202 parallel to the beam axis T203, and a second fluorescent screen T221 is installed on the rear side, farther from the accelerator.

[0067] In addition, as light detection units for detecting light emission, a first light detection device T218 for detecting light emission from the first fluorescent screen T217 and a second light detection device T240 for detecting light emission from the second fluorescent screen T221 are installed.

[0068] The first fluorescent screen T217 is installed inside the beam pipe T204 to detect the charged particle beam T202 extracted by the accelerator and is used to measure the beam profile of the charged particle beam T202 extracted by the accelerator.

[0069] The first fluorescent screen T217 emits luminescent light upon excitation by the radiation. The first fluorescent screen T217 generates a spatial distribution of the luminescent intensity of the luminescent light corresponding to the spatial distribution of the intensity of the charged particle beam T202 at the position where the first fluorescent screen T217 is installed. The luminescent light emitted by the first fluorescent screen T217 is detected by the first photodetector T218.

[0070] The second fluorescent screen T221 is installed at a position where a target is planned to be installed. The second fluorescent screen T221 is installed to detect the charged particle beam T202 and gamma rays at the target position. When irradiating the target with radiation, a raw material target T207 is installed at the target position. In addition, a gamma ray generation target T205 is installed in front of the raw material target T207. The second fluorescent screen T221 is used to measure the beam profile of the charged particle beam T202 and gamma rays at the target position.

[0071] The second fluorescent screen T221 emits luminescent light when excited by radiation. The second fluorescent screen T221 generates a spatial distribution of the luminescence intensity of the luminescent light in accordance with the spatial distribution of the intensity of the charged particle beam T202 or gamma rays at the installation position. The luminescent light emitted by the second fluorescent screen T221 is detected by the second photodetector T240.

[0072] The first photodetector T218 is installed in front of the beam window T201 in the traveling direction of the charged particle beam T202 parallel to the beam axis T203, and is installed inside the beam pipe T204. The first photodetector T218 is installed to the side of the beam axis T203 in a direction perpendicular to the beam axis T203, but not intersecting with the beam axis T203.

[0073] The second photodetector T240 is installed in front of the second fluorescent screen T221 installed at the target position in the traveling direction of the charged particle beam T202 parallel to the beam axis T203. The second photodetector T240 is installed to the side of the beam axis T203 in a direction perpendicular to the beam axis T203, but not intersecting the beam axis T203.

[0074] In the conventional accelerator system, the photodetectors T218 and T240 are configured to measure the light emitted from the fluorescent screens T217 and T221 reflected by the optical systems T219 and T220 from the front side in the traveling direction of the charged particle beam T202. The photodetectors T218 and T240 are shielded from the beam axis T203 by a shielding wall while enabling measurement of the fluorescent screens T217 and T221.

[0075] In conventional accelerator systems, the beam profile of the charged particle beam T202 is adjusted based on the measurement results of the photodetectors T218 and T240. Measurements and adjustments are repeated until an appropriate beam profile is obtained. The fluorescent screens T217 and T221 are removed after the beam profile is adjusted. The target T205 for gamma ray generation and the target container T208 containing the raw material target T207 are installed in the location of the second fluorescent screen T221 after measurements are performed by changing the position of the second fluorescent screen T221.

[0076] Generally, when using a destructive monitor to detect radiation, it is difficult to accurately measure the spatial distribution of radiation intensity because the device itself interacts with the radiation. The device itself interacts with the radiation, which can cause shielding or scattering of the radiation, affecting the measurement results. Furthermore, if a target is placed behind the destructive monitor, the radiation that interacts with the destructive monitor will be incident on the target. This results in a discrepancy between the measurement results of the destructive monitor and the actual beam profile.

[0077] Therefore, in conventional accelerator systems, after installing a destructive monitor to measure the beam profile, the destructive monitor is removed before irradiating the target. The actual irradiation of the target is carried out with the destructive monitor used for the measurement removed. Because the beam profile at the target position is measured in advance, it is assumed to be steady from the time of measurement by the destructive monitor until the actual irradiation of the target.

[0078] However, conventional methods have the problem of being unable to accurately determine the beam profile relative to the target. The beam profile at the target position is not necessarily constant, but may change over time. For example, when a charged particle beam is irradiated, the area around the beam outlet becomes very hot due to the thermal load. This increase in temperature can cause the beam profile to fluctuate. Conventional methods have the problem of being unable to accurately determine the beam profile in real time, making them unable to respond to changes over time.

[0079] Conventionally, non-destructive monitors that do not substantially interact with radiation have been known as radiation detectors, but non-destructive monitors often have special structures and pose problems in terms of cost and versatility.

[0080] In contrast, in the radionuclide production system A100, the beam profile for the target is monitored by measuring the spatial distribution of the radiation intensity at a predetermined position using a destructive monitor installed behind the target in the direction of travel of the charged particle beam while the target is being irradiated with radiation. This arrangement makes it possible to monitor the beam profile in real time while the target is being irradiated with radiation.

[0081] When the destructive monitor is installed behind the target, radiation that has interacted with the target may be detected. In the radionuclide production system A100, a beam profile for the target can be obtained by fitting an appropriate function corresponding to the spatial distribution of unit radiation to the measurement results measured by the destructive monitor.

[0082] In FIG. 2, the destructive monitor is provided with fluorescent screens T206 and T209, which are light emitters that emit light when exposed to radiation, and photodetectors T214 and T215, which are photodetectors that detect the light emitted by the light emitters.

[0083] 2, a first fluorescent screen T206 is installed in front of the charged particle beam T202, closer to the accelerator, in the direction of travel of the charged particle beam T202 parallel to the beam axis T203. A second fluorescent screen T209 is installed in the rear of the charged particle beam T202, farther from the accelerator. The second fluorescent screen T209 is disposed adjacent to the target container T208 and is integral with the target container T208.

[0084] In addition, as light detection units for detecting light emission, a first light detection device T214 for detecting light emission from the first fluorescent screen T206 and a second light detection device T215 for detecting light emission from the second fluorescent screen T209 are installed.

[0085] The fluorescent screens T206 and T209 are formed of light-emitting elements that emit light when exposed to radiation and that emit fluorescence when excited by radiation. The fluorescent screens T206 and T209 are provided as light-emitting element arrays in which a plurality of light-emitting elements are arranged in two axial directions perpendicular to the beam axis T203. The fluorescent screens T206 and T209 enable measurement of the spatial distribution of radiation intensity using the arrayed light-emitting elements.

[0086] The first fluorescent screen T206 is installed to detect the charged particle beam T202 at the position of the gamma-ray generation target T205. The first fluorescent screen T217 is used to measure the beam profile of the charged particle beam T202 with respect to the gamma-ray generation target T205. The first fluorescent screen T206 generates a spatial distribution of the emission intensity of emitted light according to the spatial distribution of the intensity of the charged particle beam T202 at the position of the gamma-ray generation target T205. The emission light emitted by the first fluorescent screen T206 is detected by the first photodetector T214.

[0087] The first fluorescent screen T206 is installed adjacent to the gamma ray generation target T205, behind the gamma ray generation target T205 and in front of the target container T208, in the traveling direction of the charged particle beam T202 parallel to the beam axis T203. The first fluorescent screen T206 is installed at the center of the beam axis T203 in a direction perpendicular to the beam axis T203. With this arrangement, the spatial distribution of the intensity of the charged particle beam T202 at the position of the gamma ray generation target T205 can be measured with high accuracy.

[0088] The second fluorescent screen T209 is installed to detect the charged particle beam T202 and gamma rays at the position of the raw target T207. The second fluorescent screen T209 is used to measure the beam profile of the charged particle beam T202 and gamma rays relative to the raw target T207. The second fluorescent screen T209 generates a spatial distribution of the emission intensity of the emitted light in accordance with the spatial distribution of the intensity of the charged particle beam T202 and gamma rays at the position of the raw target T207. The emitted light emitted by the second fluorescent screen T209 is detected by the second photodetector T215.

[0089] The second fluorescent screen T209 is installed adjacent to the target container T208 behind the target container T208 in the direction of travel of the charged particle beam T202 parallel to the beam axis T203. The second fluorescent screen T209 is installed at the center of the beam axis T203 in a direction perpendicular to the beam axis T203. With this arrangement, the spatial distribution of the intensity of the charged particle beam T202 and gamma rays at the position of the raw material target T207 can be measured with high accuracy.

[0090] The fluorescent screens T206 and T209 can be made of an appropriate illuminant, taking into consideration the luminous intensity, response speed, durability, etc. As the illuminant, a substance that emits light of an appropriate wavelength, such as visible light or infrared light, can be used. A specific example of the illuminant is YAlO ３ , YGaO ３ , GdAlO ３ , GdGaO ３ , LuAlO ３ , GaAlO ３ Examples of the ceramic include ceramics obtained by doping these with Y, Gd, or Lu, beryllium oxide (BeO), Ce:YAG, Ce:LuAG, and Ce:YAP.

[0091] The light emitter is preferably a substance that is excited by the charged particle beam T202. Since the spatial distribution of the intensity of gamma rays emitted from the gamma ray generation target T205 depends on the spatial distribution of the intensity of the charged particle beam T202 incident on the gamma ray generation target T205, the beam profile for the target container T208 can be evaluated based on the measurement result of the spatial distribution of the intensity of the charged particle beam T202.

[0092] The illuminants of the fluorescent screens T206 and T209 are preferably substances that emit visible light. A substance that emits visible light makes it easy to check the emitted light, facilitating maintenance. Furthermore, a substance that emits visible light allows the use of illuminants used in optical devices, etc., making it easier to obtain the illuminants.

[0093] The photodetectors T214 and T215 detect the spatial distribution of the emission intensity of the fluorescent screens T206 and T209, which corresponds to the spatial distribution of the intensity of the charged particle beam T202. Methods for detecting the spatial distribution of the emission intensity include a method of actually measuring using an array of light-receiving elements, a method of capturing an emission image of the fluorescent screens T206 and T209 and determining the intensity for each pixel by image processing, and the like.

[0094] The photodetectors T214 and T215 can be formed of a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a streak camera, a photodiode, a photomultiplier tube, etc. The detection elements of the photodetectors T214 and T215 are provided in an array structure arranged in two axial directions perpendicular to the beam axis T203.

[0095] The photodetectors T214 and T215 may include, in addition to a light-receiving element that detects the emitted light, an optical mechanism that adjusts the intensity and wavelength of the emitted light, an optical filter, etc. Examples of the optical mechanism include an image intensifier that photoelectrically converts the received light to multiply electrons and then performs inverse photoelectric conversion to form an image, a mechanical shutter that limits the exposure time, and an ND filter (Neutral Density Filter) that suppresses the amount of exposure. As the optical filter, a wavelength filter that corresponds to the wavelength of the emitted light can be used to increase the S / N ratio.

[0096] The first photodetector T214 is installed behind the gamma ray generation target T205 in the direction of travel of the charged particle beam T202. The second photodetector T215 is installed behind the target container T208 in the direction of travel of the charged particle beam T202. These photodetectors T214 and T215 are installed on the side of the beam axis T203 in a direction perpendicular to the beam axis T203, but not intersecting the beam axis T203.

[0097] The photodetectors T214 and T215 are configured to monitor the fluorescent screens T206 and T209 from behind. When the fluorescent screens T206 and T209 are installed behind the targets, it is preferable to monitor the fluorescent screens T206 and T209 from behind. This configuration makes it less likely that the emitted light will be blocked by the target or the like.

[0098] A first optical axis T212 from the first fluorescent screen T206 is formed with respect to the first photodetector T214 by using the optical system 210. The first optical axis T212 extends from the rear surface of the first fluorescent screen T206 rearward in the traveling direction of the charged particle beam T202 and laterally in a direction perpendicular to the beam axis T203. The first optical axis T212 is reflected by the optical system 210 and reaches the first photodetector T214.

[0099] A second optical axis T213 from the second fluorescent screen T209 is formed for the second photodetector T215 by using the optical system T211. The second optical axis T213 extends from the rear surface of the second fluorescent screen T209 rearward in the traveling direction of the charged particle beam T202 and laterally in a direction perpendicular to the beam axis T203. The second optical axis T213 is reflected by the optical system T211 and reaches the second photodetector T215.

[0100] The photodetectors T214 and T215 are shielded from the beam axis T203 by a shielding wall, while allowing measurement of the light emitted from the fluorescent screens T206 and T209. The shielding wall can be made of a shielding material such as concrete, lead, or iron. Alternatively, a transparent shielding material such as lead glass can be used to block radiation while allowing measurement of the light emitted.

[0101] In general, the photodetectors T214 and T215 tend to have low radiation resistance because they are formed using semiconductor components. When exposed to high doses of radiation, radiation damage such as soft errors and hard errors occurs, and their lifespan is significantly shortened. In contrast, bending the optical axes T212 and T213 using reflection makes it difficult for radiation to directly strike the photodetectors T214 and T215, making it easier to shield the radiation, thereby protecting the photodetectors T214 and T215 from radiation.

[0102] 2, the optical systems T211 and T213 are formed as optical mirrors, but they may be formed of any suitable optical components as long as they transmit the emitted light to the photodetectors T214 and T215 and form an image. The optical systems T211 and T213 may be formed of a single optical component or multiple optical components. Examples of optical components include optical mirrors, optical lenses, optical diaphragms, and optical filters.

[0103] 2, one fluorescent screen T206 and one fluorescent screen T209 are installed behind the gamma-ray generation target T205 and the other behind the target container T208, but the fluorescent screens T206 and T209 and the photodetectors T214 and T215 may be installed behind either one of the targets. Furthermore, any number of fluorescent screens T206 and T209 may be installed at any appropriate location as long as they are behind the gamma-ray generation target T205, which is the target onto which the charged particle beam T202 first strikes.

[0104] The photodetectors T214 and T215 are provided so as to be able to transmit the measurement results of the spatial distribution of the luminous intensity of the fluorescent screens T206 and T209 to the controller T216. The measurement results of the spatial distribution of the luminous intensity of the fluorescent screens T206 and T209 can be transmitted to the controller T216 at appropriate time intervals while the target is being irradiated with radiation.

[0105] The controller T216 is provided, for example, as a control computer for monitoring the beam profile. The controller T216 can be connected to a central control computer via a bus so that signals can be transmitted and received between them. The central control computer is provided for integrated control of the accelerator A101, the beam transport part A129, etc.

[0106] The radionuclide production system A100 can have a function of analyzing a beam profile for the gamma ray generation target T205 and a function as a numerical analysis unit that analyzes a beam profile for the raw material target T207. The function as the numerical analysis unit may be provided by the controller T216, the central control computer, or another computer connected to the central control computer.

[0107] The beam profile for each target is determined by function fitting using a preset function. In function fitting, the spatial distribution of radiation intensity, such as charged particles or gamma rays, at the target position is expressed by a combination of preset functions or by the preset function itself. The validity of the function fitting can be confirmed by comparing the measurement results measured by multiple destructive monitors with the results determined by function fitting and evaluating the correlation between them.

[0108] The radionuclide production system A100 may also have a function of controlling radiation irradiation based on the beam profile determined by analysis, or a function of adjusting the beam profile based on the beam profile determined by analysis. These functions may be provided by the controller T216, the central control computer, or another computer connected to the central control computer.

[0109] The irradiation of radiation can be controlled by controlling the accelerator A 101. The control of the irradiation of radiation can include control of continuation of irradiation of the charged particle beam, control of stopping irradiation of the charged particle beam, etc., depending on whether the beam profile is appropriate during irradiation of the charged particle beam.

[0110] The beam profile can be adjusted by controlling the accelerator A101, the beam transport part A129, etc. The beam profile can be adjusted by adjusting the irradiation direction of the charged particle beam, adjusting the operation parameters of the accelerator A101, etc. The irradiation direction of the charged particle beam can be adjusted, for example, by adjusting the steering electromagnet. The operation parameters of the accelerator A101 can be adjusted by adjusting the radio frequency phase, radio frequency amplitude, etc.

[0111] In the arrangement and structure of the equipment shown in FIG. 2, irradiation of a target with radiation and measurement of the spatial distribution of radiation intensity are carried out as follows.

[0112] The charged particle beam T202 passes through the beam window T201, is extracted to the outside, and is incident on the gamma-ray generation target T205, where it generates bremsstrahlung radiation and emits gamma rays. The gamma rays emitted from the gamma-ray generation target T205 are irradiated onto the raw material target T207, causing a photonuclear reaction of the raw material nuclides. The target radioactive nuclides are then recovered from the raw material target T207 in which the product nuclides have been generated.

[0113] A portion of the charged particle beam T202 is extracted through the beam window T201, passes through the gamma ray generation target T205, and is incident on the first fluorescent screen T206. The first fluorescent screen T206 emits luminescent light of a predetermined emission wavelength when luminescent materials excited by the incidence of the charged particle beam T202 return to their ground state. Since the luminescent intensity depends on the fluence, the first fluorescent screen T206 generates a spatial distribution of luminescent intensity corresponding to the spatial distribution of the intensity of the charged particle beam T202.

[0114] The emitted light from the first fluorescent screen T206 travels along an optical axis T212, and after being redirected by the optical system T210, is detected by a first photodetector T214. A measurement signal from the first photodetector T214 is transmitted to a controller T216. The first fluorescent screen T206 and the first photodetector T214 measure the spatial distribution of the intensity of the charged particle beam T202 at the position of the first fluorescent screen T206.

[0115] Furthermore, a portion of the charged particle beam T202 and a portion of the gamma rays emitted from the gamma ray generation target T205 pass through the target container T208 and are incident on the second fluorescent screen T209. The second fluorescent screen T209 emits luminescent light of a predetermined emission wavelength when a luminescent material excited by the incidence of the charged particle beam T202 or the gamma rays returns to its ground state. Since the luminescent intensity depends on the fluence, the second fluorescent screen T209 generates a spatial distribution of luminescent intensity corresponding to the spatial distribution of the intensity of the charged particle beam T202 or the gamma rays.

[0116] The emitted light from the second fluorescent screen T209 travels along the optical axis T213, and after being changed in direction by the optical system T211, is detected by the second photodetector T215. A measurement signal from the second photodetector T215 is transmitted to a controller T216. The second fluorescent screen T209 and the second photodetector T215 measure the spatial distribution of the intensity of the charged particle beam T202 or gamma rays at the position of the second fluorescent screen T209.

[0117] Upon receiving the measurement results from the photodetectors T214 and T215, the controller T216 stores the measurement result data in a storage device. The numerical analysis unit executes function fitting processing to obtain the beam profile at the target position based on the measurement results measured by the destructive monitors transmitted from the photodetectors T214 and T215.

[0118] The function fitting process to obtain the beam profile at the target position can be performed using any function corresponding to the spatial distribution of a charged particle, which is a unit radiation, or any function corresponding to the spatial distribution of a unit gamma ray, which is a unit radiation. The validity of the set function can be evaluated by collecting multiple measurement results measured by destructive monitors and performing multiple regression analysis of the correlation between the measurement results measured by the multiple destructive monitors and the results obtained by the function fitting process.

[0119] The beam profile can be obtained as a spatial distribution on a plane perpendicular to the beam axis T203. Therefore, any coordinate system can be set on the plane perpendicular to the beam axis T203. As a function used in the function fitting process, a function corresponding to any coordinate system can be used.

[0120] The function used in the function fitting process can be assumed to follow any statistical distribution with respect to the spatial distribution of charged particles, which are unit radiation, or the spatial distribution of unit gamma rays, which are unit radiation. Furthermore, the spatial distribution of the luminous intensity of the emitted light can be assumed to follow any order. For example, the spatial distribution of the intensity of unit radiation can be treated as a Gaussian distribution. Furthermore, the spatial distribution of the luminous intensity of the emitted light can be treated as following a first-order reaction to the incident radiation.

[0121] For example, in a direction perpendicular to the beam axis T203, an X-axis and a Y-axis can be set as two mutually perpendicular axes, and coordinates (x, y) can be set as coordinates on this plane. In such a coordinate system, if the spatial distribution of the intensity of unit radiation follows a Gaussian distribution, the following formula (1) can be used as a function f that represents the correlation between the spatial distribution of the luminous intensity of the emitted light and the spatial distribution of the intensity of the radiation.

[0122] f(x,y) =C1×exp[-((x-C2) ２ +(y-C3) ２ ) / (2 x C4 ２ ) )]+C5 (1) where C1 to C5 each represent an unknown quantity.

[0123] By the function fitting process using Equation (1), the position x of the beam center is obtained as the beam profile. Ｇ = (C2, C3) and the beam spread σ from the beam center σ = C4 can be obtained.

[0124] Furthermore, in the function fitting process, if there is no symmetry with respect to two mutually orthogonal axes, function fitting can be performed for each axis. For example, suppose the spatial distribution of emission intensity is measured on a predetermined pixel plane orthogonal to the beam axis. If a matrix of i × j pixels is arranged on such a pixel plane, the emission intensity F(i, j) for each pixel is measured.

[0125] For the light emission intensity F(i,j) of each pixel, the anisotropy can be smoothed by calculating the cumulative intensity in the direction of the pixel array. For example, Fx(i) = Σ_j F(i,j) or Fy(j) = Σ_i F(i,j) can be calculated. As a function f representing the correlation, the following formulas (2) and (3) can be used for each direction of the pixel array.

[0126] fx(x)=D1×exp[-(x-D2) ２ / (2 x D3 ２ )]+D4...(2) fy(y)=E1×exp[-(y-E2) ２ / (2 x E3 ２ ) )]+E4 (3) where D1 to D4 and E1 to E4 respectively represent unknown quantities in the formulas (2) and (3).

[0127] By the function fitting process using equations (2) and (3), the position of the beam center x Ｇ = (D2, E2), and the beam spread in the x-axis direction from the beam center σ ｘ = D3 and the beam spread in the y-axis direction from the beam center σｘ =E3 can be found.

[0128] In the function fitting process, any other coordinate system or analysis along any axis may be used. The spatial distribution of the intensity of the unit ray may be assumed to follow any type of distribution model other than Gaussian distribution. In general, the position x of the beam center is Ｇ can be calculated as the first moment (product moment) of the emission intensity. The beam divergence σ from the beam center can be calculated as the second moment (product moment) of the emission intensity.

[0129] 2, fluorescent screens T206 and T209 are installed behind the targets (T205 and T207) in the direction of travel of the charged particle beam T202. The fluorescent screens T206 and T209 emit luminescent light when the charged particle beam T202 or gamma rays are incident on them. However, the spatial distribution of the luminescent intensity of the fluorescent screens T206 and T209 does not accurately reflect the spatial distribution of the intensity of the charged particle beam T202 incident on the gamma ray generation target T205 or the spatial distribution of the intensity of the gamma rays incident on the raw material target T207.

[0130] What is actually detected by the fluorescent screens T206 and T209 is radiation that has been scattered or partially blocked by the gamma-ray generation target T205 and the raw material target T207. Therefore, the spatial distribution of the light intensity due to the emission of the fluorescent screens T206 and T209 has a wider beam diameter and a lower intensity than the spatial distribution of the intensity of the radiation incident on the gamma-ray generation target T205 and the raw material target T207.

[0131] On the other hand, if the arrangement of the structures of the gamma-ray generation target T205 and the raw material target T207 can be considered symmetrical with respect to the beam axis, the scattering by the structures can also be considered uniform with respect to the beam axis. Therefore, the center of gravity of the spatial distribution of the luminescence intensity of the fluorescent screens T206 and T209 can be considered to coincide with the center of gravity of the spatial distribution of the intensity of the radiation incident on the gamma-ray generation target T205 and the raw material target T207.

[0132] After the function fitting process, it is preferable to evaluate the correlation between the measurement results measured by the multiple destructive monitors and the result of the radiation beam profile for the target obtained by the function fitting process. The evaluation of the correlation can be performed using numerical analysis with a calculation system that simulates a radionuclide production system.

[0133] When using the results of a simulation using numerical analysis, the validity of the correlation between the measurement results measured by the destructive monitor and the results obtained by the function fitting process can be confirmed by comparing the measurement results of the spatial distribution of the intensity of the charged particle beam T202 measured by the destructive monitor with the analysis results of the spatial distribution of the intensity of the charged particle beam T202 analyzed by numerical analysis, or by comparing the state of the charged particle beam based on the measurement results with the state of the charged particle beam based on the analysis results.

[0134] Simulations using numerical analysis can be performed using the Monte Carlo method. A calculation system for performing the numerical analysis is constructed that simulates the materials, geometric shapes, geometric arrangement, etc. of the components that make up the system. By performing multiple simulations using parameters such as the position, shape, and intensity of the radiation relative to the target, data on the spatial distribution of the intensity of the radiation incident on the destructive monitor can be collected. This makes it possible to evaluate the correlation between the measurement results obtained by the destructive monitor and the results obtained by function fitting processing.

[0135] By comparing the data showing this correlation with the measurement results from the destructive monitor and extrapolating the measurement results to the correlation, the radiation beam profile at the target can be estimated. Monte Carlo simulations enable highly accurate estimation of the radiation beam profile at the target even when there are asymmetric structures in the radiation path or when the radiation is scattered non-uniformly.

[0136] When using the results of a simulation based on numerical analysis, it is necessary to verify the validity of the simulation results by comparing the results with actual measurements. The comparison between the analysis results and actual measurements can be performed using various matching algorithms. For the comparison, evaluation of the sum of squared differences (SSD) or cross-correlation analysis using a cross-correlation function can be used.

[0137] For example, when comparing analytical results with actual measurement results, the analytical results and actual measurement results are each normalized using a maximum value or the like, and the sum of squared differences between the normalized results is calculated. The analytical result with the smallest calculated sum of squared differences or the analytical result with a sum of squared differences equal to or less than a threshold value is determined to be an accurate analytical result and can be used to estimate the beam profile.

[0138] The measurement results from the destructive monitor can also be expanded using basis functions, with the analysis results from the simulation as the basis functions. By performing such basis function expansion, it is possible to evaluate the intermediate state of the simulation and to estimate the intermediate beam profile for the target. This allows for a reduction in the number of simulation trials and the required time.

[0139] For example, the emission intensity F(i, j) for each pixel can be expressed by the following formula (4) by basis function expansion using the intensity φk(i, j) of the radiation incident on the destructive monitor, which is obtained as an analysis result from a simulation, as the basis function.

[0140] F(i, j) = Σ_k^N wk φk(i, j) (4) where, in equation (4), k represents the number of simulations (k = 1, 2, ... N), and wk represents the expansion coefficient for φk. wk indicates the degree of linear combination between basis functions, and is a value corresponding to the similarity of the images. Since the right-hand side of equation (4) is a matrix product, wk can be obtained by multiplying both sides of equation (4) by a generalized matrix.

[0141] When comparing analysis results with actual measurement results, a process for limiting the feature quantities of the analysis results or actual measurement results in advance may be performed. The process for limiting the feature quantities may involve dimensionality reduction using principal component analysis or the like, or feature extraction using machine learning or the like. Furthermore, various machine learning, clustering techniques, extraction algorithms, and the like may be used to search for and extract highly interpretable results from among multiple analysis results or multiple actual measurement results.

[0142] Fig. 4 is a flowchart showing an example of a method for operating a radionuclide production system according to an embodiment of the present invention. Fig. 4 shows an example of an operation for determining a beam profile in the radionuclide production system A100. As the destructive monitor, a case where the fluorescent screens T206 and T209 and the photodetectors T214 and T215 shown in Fig. 3 are used is exemplified.

[0143] In the radionuclide production system A100, a beam profile at a target position can be determined based on the spatial distribution of the intensity of the charged particle beam or radiation measured by the destructive monitor during radionuclide production. The beam profile can determine one or more of the spatial distribution of the intensity of the charged particle beam or radiation at the target position, the position of the beam center of the charged particle beam or radiation at the target position, and the beam spread from the beam center of the charged particle beam or radiation at the target position.

[0144] When measuring the beam profile of a target, first, the center position, angle, and range of imaging by the photodetectors T214 and T215 are adjusted (step S101). When imaging the fluorescent screens T206 and T209, the field of view and angle of view are adjusted by adjusting the positions and orientations of the photodetectors T214 and T215.

[0145] Next, the focus, exposure time, and light intensity of the photodetectors T214 and T215 are adjusted (step S102). When photographing the fluorescent screens T206 and T209, the exposure conditions are adjusted by adjusting the alignment of the optical systems T211 and T213 and the exposure parts of the photodetectors T214 and T215, such as the shutters and filters.

[0146] Adjustments to the photodetectors T214 and T215 and alignment of the optical systems T211 and T213 may be performed manually, but are preferably performed remotely. If adjustments are performed during irradiation, the work will be performed under high radiation doses. Furthermore, when adjusting the light intensity, it is necessary to irradiate the charged particle beam T202 on a trial basis. Therefore, it is preferable to perform remote operation using a manipulator, robot arm, or the like, utilizing a stepping motor or an actuator operated by compressed air.

[0147] Next, positional correspondence is established between the pixels of the photodetectors T214 and T215 and the imaging areas of the fluorescent screens T206 and T209 (step S103). For example, markers or the like are attached to reference positions in the imaging areas of the fluorescent screens T206 and T209. Using these markers as indices, the pixels forming the pixel space and the imaging areas are associated with each other. The association may be a one-to-one correspondence, or, if there is an axis of symmetry, multiple markers may be associated to create a correspondence in pixel spaces with different dimensions. Markers can also be attached to singular points such as the four corners of the imaging area, and local coordinates can also be associated.

[0148] Next, irradiation of the target with the charged particle beam T202 is started (step S104). Irradiation of the gamma ray generation target T205 with the charged particle beam T202 and irradiation of the raw material target T207 with gamma rays are started, and radiation is also started to be incident on the fluorescent screens T206 and T209.

[0149] Adjustments to the photodetectors T214 and T215 and alignment of the optical systems T211 and T213 are preferably performed before irradiation with the charged particle beam T202, but may be performed during or after irradiation with the charged particle beam T202. On the other hand, adjustments to the fluorescent screens T206 and T209 are preferably performed periodically during irradiation with the charged particle beam T202. This is because the fluorescent screens T206 and T209 may deteriorate due to irradiation with radiation, causing the emission intensity to change over time.

[0150] Next, the photodetectors T214 and T215 wait for the input of a trigger signal for detecting the emitted light (step S105). When detecting the emitted light from the fluorescent screens T206 and T209, the photodetectors T214 and T215 may be continuously exposed to light, but it is preferable to expose them intermittently in response to a trigger signal in order to respond to changes in the emitted light over time.

[0151] Next, exposure of the photodetectors T214 and T215 is started (step S106). For example, the photodetectors T214 and T215 are exposed in response to input of a trigger signal, and the spatial distribution of the emission intensity is measured for a predetermined exposure time.

[0152] Subsequently, the data of the measurement results measured by the photodetectors T214 and T215 are transmitted (step S107). The measurement results of the spatial distribution of the luminescence intensity are transmitted to a controller T216 or a computer having a function as a numerical analysis unit such as a central control computer.

[0153] Next, the measurement results of the spatial distribution of the emission intensity are image-processed to create a histogram showing the beam profile relative to the target (step S108). The numerical analysis unit performs function fitting processing on the measurement results measured by the destructive monitor. As the histogram, for example, a graph showing the relationship between the position in a direction perpendicular to the traveling direction of the charged particle beam and the emission intensity can be created.

[0154] Next, the beam profile at the target position is calculated by the position x of the beam center. Ｇ In the function fitting process, the position of the beam center x is calculated for the position of the gamma ray generation target T205 and the position of the raw material target T207. Ｇ Before the function fitting process, noise removal by filtering or dimensionality reduction by principal component analysis or the like may be performed.

[0155] Next, it is determined whether the error in the function fitting process is within an allowable range (step S110). For example, the mean squared error (MSE) or the like is calculated between the measurement results measured by multiple destructive monitors and the analysis results obtained by the function fitting process, and it can be determined whether the calculated value exceeds a predetermined threshold. The validity of the function fitting can be confirmed by evaluating the error.

[0156] If the result of the determination is that the error in the function fitting process is not within the allowable range (step S110; NO), the process proceeds to step S115. On the other hand, if the result of the determination is that the error in the function fitting process is within the allowable range (step S110; YES), the process proceeds to step S111.

[0157] Next, the position x of the beam center Ｇ It is determined whether the positional deviation of the beam center x from the reference position is within the allowable range (step S111). For example, the positional deviation of the beam center x from the position of the center of gravity of the intensity of the charged particle beam T202 can be evaluated. Ｇ It can be determined whether the difference in distance between the target position and the reference position exceeds a predetermined threshold value.

[0158] If the determination result shows that the positional deviation is not within the allowable range (step S111; NO), the process proceeds to step S115. On the other hand, if the determination result shows that the positional deviation is within the allowable range (step S111; YES), the process proceeds to step S112.

[0159] Next, it is determined whether the beam divergence σ relative to the beam center is within an allowable range (step S112). For example, it can be determined whether the beam divergence σ obtained by analysis exceeds a predetermined threshold value.

[0160] If the result of the determination is that the beam spread is not within the allowable range (step S112; NO), the process proceeds to step S115. On the other hand, if the result of the determination is that the beam spread is within the allowable range (step S112; YES), the process proceeds to step S113.

[0161] As a result of the determination, if the error in the function fitting process is not within the allowable range (step S110; NO), if the positional deviation is not within the allowable range (step S111; NO), or if the beam spread is not within the allowable range (step S112; NO), an alarm signal for issuing an alarm is sent (step S115).The visual or audio alarm can warn the operator that the beam profile is abnormal.

[0162] Next, a beam irradiation stop signal is sent to stop the irradiation of the charged particle beam T202 (step S116). If there is a problem with the compatibility of the beam profile with the target or if there is an abnormality in the state of the charged particle beam T202, the operation of the accelerator A101 is stopped by sending the beam irradiation stop signal.

[0163] Instead of stopping the operation of the accelerator A101 with a beam irradiation stop signal, the charged particle beam T202 may be attenuated. After the beam intensity is reduced to a safe level, the beam profile relative to the target may be readjusted. Because an unnecessary beam irradiation stop signal may be sent due to momentary noise, the robustness of the system may be improved by using a moving average filter or median filter that responds to time changes.

[0164] Next, it is determined whether or not to continue monitoring the beam profile for the target (step S113). The monitoring of the beam profile can be terminated appropriately depending on the operation of the accelerator A101, the stability of the charged particle beam T202, and the like.

[0165] If the determination result is that the monitoring of the beam profile is to be continued (step S113; YES), the process returns to step S105. On the other hand, if the determination result is that the monitoring of the beam profile is not to be continued (step S113; NO), the process proceeds to step S114.

[0166] If the result of the determination is that the beam profile monitoring will not continue (step S113; NO) or if a beam irradiation stop signal is sent (step S116), the settings and logs related to the monitoring of the beam profile for the target are saved (step S114). Thereafter, the beam profile monitoring process ends.

[0167] 4 shows an interlock function that stops the irradiation of the charged particle beam according to the beam profile, but the control may be such that only the beam profile is adjusted or data is recorded without stopping the irradiation of the charged particle beam. Furthermore, the control may be such that the operation parameters of the accelerator are adjusted based on the beam profile. From the viewpoint of avoiding a serious accident, it is preferable to start the adjustment of the operation parameters of the accelerator after the beam intensity of the charged particle beam is sufficiently reduced.

[0168] According to this radionuclide production system A100, the beam profile at the target position is determined by analysis based on the measurement results from a destructive monitor installed behind the target in the direction of travel of the charged particle beam. Since the analysis result of the beam profile at the target position is based on the measurement results measured behind the target, the influence of the destructive monitor can be avoided. Therefore, the beam profile of the radiation irradiated to the target can be monitored in real time using the destructive monitor, and appropriate irradiation of the target can be performed according to the beam profile.

[0169] After the beam profile at the target position is determined, the equipment can be controlled and the beam profile adjusted appropriately, thereby improving the yield of the desired radioactive nuclide. Furthermore, after the beam profile has been adjusted appropriately, the accelerator can be operated with its operating parameters fixed. By fixing the current of the electromagnet that focuses or deflects the charged particle beam, as well as the accelerator's operating parameters, the desired radioactive nuclide can be produced stably.

[0170] Furthermore, since the beam profile at the target position is calculated in real time, it is possible to appropriately respond to changes in the beam profile over time. Unlike conventional methods, it is not necessary to assume that the beam profile at the target position remains constant from the time of measurement by the destructive monitor to the time of actual irradiation of the target. This makes it possible to avoid situations such as a shortage of the production amount of the target radionuclide after continued irradiation for a long period of time. This therefore improves the reliability of the supply of radionuclides.

[0171] Furthermore, when a photonuclear reaction caused by irradiation with gamma rays is used as the nuclear reaction for nuclear transmuting the source nuclides, the beam profile for the gamma-ray generating target can be accurately determined, and the source target can be irradiated with highly accurate gamma rays. While it is desirable that the charged particle beam irradiated to the gamma-ray generating target is not affected by the destructive monitor, the charged particle beam that has passed through the gamma-ray generating target is unnecessary. Therefore, even if a destructive monitor is installed behind the gamma-ray generating target, it can avoid affecting the gamma rays irradiated to the source target. Because the gamma rays emitted by the gamma-ray generating target have high penetrating power, the effects of shielding and scattering by the destructive monitor are small.

[0172] Furthermore, unlike non-destructive monitors, the use of destructive monitors for beam profile monitoring reduces restrictions on the monitor structure and measurement principle, making it possible to monitor the beam profile at low cost.

[0173] Furthermore, if a destructive monitor is installed behind the target in the direction of travel of the charged particle beam, it is easy to secure a location for the destructive monitor. Destructive monitors such as photodetectors not only affect the charged particle beam, but also have the risk of the device itself being deteriorated by radiation. Therefore, they must be placed in a location where they are not directly hit by the charged particle beam and must be shielded from radiation from the surroundings. If a destructive monitor is installed inside the beam pipe, a special structure must be provided in the beam pipe. In contrast, if a destructive monitor is installed behind the target, there is no need to modify the surrounding area of ​​the beam pipe.

[0174] Furthermore, the radionuclide production system A100 can appropriately adjust the beam profile at the target position, so that after the beam profile is adjusted, the accelerator can be operated with fixed operating parameters. By fixing the current of the electromagnet that converges or deflects the charged particle beam, the accelerator operating parameters, etc., the target radionuclide can be stably produced.

[0175] Furthermore, the radionuclide production system A100 can adjust the beam profile in real time, eliminating the need for adjustments prior to irradiating the target with radiation. Conventional beam profile adjustments require the installation and removal of targets. Because work during irradiation is limited, the work takes time. Furthermore, manual work poses a risk of worker exposure. There are many tasks for which automation is not appropriate and manual work is more effective. For example, manual work is required when the target is made of a material that is vulnerable to impacts, such as glass, when robust fixation of the target is required, or when connecting cooling pipes to cool the target. In contrast, the radionuclide production system A100 can reduce the number of charged particle beam irradiations, thereby reducing worker exposure.

[0176] Fig. 5 is a diagram showing an example of a configuration for monitoring a beam profile. Fig. 5 shows an example of the arrangement and structure of equipment for monitoring the beam profile for the gamma ray generation target A134 and the sample target system A135 in the radionuclide production system A100 shown in Fig. 1. As shown in Fig. 5, the target container T208 containing the raw material target T207 can also be installed in a vertical orientation such that the longitudinal direction of the target container T208 is perpendicular to the beam axis T203.

[0177] The target container T208 is installed vertically so that the raw material target T207 contained therein is positioned at a position intersecting the beam axis T203. The raw material target T207 is contained at the bottom side of the target container T208 along the short side of the target container T208. The sidewall of the target container T208 can be thin. The beam axis T203 passes through the target container T208 along the short side and is configured to irradiate the raw material target T207.

[0178] By installing the target container T208 vertically in this manner, the distance that the charged particle beam T202 passes through the target container T208 can be shortened. This reduces the shielding and scattering of the charged particle beam T202 in front of the second fluorescent screen T209. This allows for more accurate measurement using the second fluorescent screen T209. Furthermore, the thermal load on the target container T208 can be reduced. This reduces the cooling performance requirements for the cooling mechanism used to remove heat from the target container T208. Furthermore, since disturbances caused by temperature increases in the target container T208 are prevented, changes in the beam profile of the target container T208 over time can be suppressed.

[0179] 5, a first fluorescent screen T206 is installed in front of the charged particle beam T202, closer to the accelerator, in the direction of travel of the charged particle beam T202 parallel to the beam axis T203. A second fluorescent screen T209 is installed in the rear of the charged particle beam T202, farther from the accelerator. The second fluorescent screen T209 is disposed separately from the target container T208 and spaced apart from the target container T208.

[0180] By disposing the destructive monitor separately from the target in this manner, the degree of freedom in the size, shape, structure, etc. of the destructive monitor can be increased. For example, even if the target container T208 is small, it becomes easy to install a large second fluorescent screen T209. Furthermore, it is not necessary to process the shape of the second fluorescent screen T209 to match the shape of the target container T208. Furthermore, when the target container T208 is discarded, the second fluorescent screen T209 is not discarded at the same time, so it can be reused.

[0181] When the second fluorescent screen T209 is disposed at a distance from the target container T208, the beam profile is determined at a position distant from the raw material target T207. In such a case, the spatial distribution of the intensity of the charged particle beam T202 at the position of the raw material target T207 and the position of the beam center at the position of the raw material target T207 can be determined with high accuracy by interpolation using the measurement results from the first fluorescent screen T206 and the measurement results from the second fluorescent screen T209.

[0182] Fig. 6 is a diagram showing an example of a configuration for monitoring a beam profile. Fig. 6 shows an example of the arrangement and structure of equipment for monitoring the beam profile for the gamma ray generation target A134 and the sample target system A135 in the radionuclide production system A100 shown in Fig. 1. As shown in Fig. 6, the destructive monitor may also include a Faraday cup T241 made of a conductive material that collects the charged particle beam as a current, and a current sensor T244 that is a current measuring unit that measures the current due to the charged particle beam. In addition, an optical fiber T228 may be used to transmit the luminescent light emitted by the fluorescent screen.

[0183] The Faraday cup T241 converts the charged particle beam into an electric current, enabling measurement of the intensity of the charged particle beam. The Faraday cup T241 is installed to detect the charged particle beam T202 and gamma rays at the position of the raw material target T207. The Faraday cup T241 is used to measure the beam profile of the charged particle beam T202 relative to the raw material target T207.

[0184] The Faraday cup T241 is installed behind the target container T208 in the traveling direction of the charged particle beam T202, which is parallel to the beam axis T203. The Faraday cup T241 is installed at the center of the beam axis T203 in a direction perpendicular to the beam axis T203.

[0185] The Faraday cup T241 includes a cup-shaped inner electrode made of a conductive material and a cup-shaped outer electrode made of a conductive material that surrounds the inner electrode. The outer electrode is electrically connected to a bias electrode T243. The inner electrode is electrically connected to a current sensor T244. The inner electrode and the outer electrode are electrically insulated from each other by an insulating material.

[0186] The Faraday cups T241 may be arranged in an array in a direction perpendicular to the beam axis T203 of the charged particle beam, may be scanned in a direction perpendicular to the beam axis T203 of the charged particle beam, or may be provided with a slit that divides the charged particle beam in a direction perpendicular to the beam axis T203 of the charged particle beam. With such a configuration, the spatial distribution of the intensity of the charged particle beam T202 at the position of the raw material target T207 can be measured.

[0187] The Faraday cup T241 may also be provided with a grid T242 at its cup-shaped opening. A high voltage can be applied to the grid T242 from a bias electrode T243. Applying a high voltage to the grid T242 can prevent the capture of charged particles with unnecessary energy. Limiting the energy of the charged particles to be detected makes it possible to obtain a more accurate profile.

[0188] By using such a Faraday cup T241, the spatial distribution of the intensity of the charged particle beam T202 can be directly measured without photoelectric conversion, as is the case when a fluorescent screen is used. While a fluorescent screen can be used to determine the spatial distribution of relative intensity, the Faraday cup T241 can obtain a current value that indicates absolute intensity. Furthermore, the Faraday cup T241 has higher radiation resistance than photodetectors such as image sensors, enabling accurate measurements even under high radiation doses.

[0189] The optical fiber T228 is provided to transmit the luminescent light emitted by the first fluorescent screen T206 to the first photodetector T214. The optical fiber T228 is connected between the optical fiber head T226 and the optical fiber connector T227.

[0190] The optical fiber head T226 is installed adjacent to the gamma ray generation target T205, behind the gamma ray generation target T205 and in front of the target container T208, in the traveling direction of the charged particle beam T202 parallel to the beam axis T203. The optical fiber connector T227 is installed at a position where it can be detected by the photodetector T214, which is spaced apart from the beam axis T203.

[0191] The optical fiber T228 may be a single fiber or a fiber bundle of multiple fibers. The optical fiber head T226 and the optical fiber connector T227 may have functions such as an optical lens, an optical aperture, and an optical filter in order to collect, converge, collimate, etc. the emitted light.

[0192] When such an optical fiber T228 is used, the optical axis is not limited to a linear shape, which increases the degree of freedom in the location where the photodetector T214 is installed and the structure for shielding the photodetector T214. When the optical axis is linear, as shown in Figure 2, bending the transmission path of the emitted light increases the number of optical components, which limits the location where the photodetector T214 is installed and the location where the shielding material is installed. In contrast, when the optical fiber T228 is used, the degree of freedom in the installation location is increased and the number of optical components is reduced, which improves the soundness against radiation degradation and the maintainability of the equipment.

[0193] Furthermore, by using such an optical fiber T228, it is possible to detect at an appropriate position the luminescence light emitted by the fluorescent screen T206. Because the optical fiber head T226 can be easily made compact, it is possible to appropriately measure the spatial distribution of the luminescence intensity of the fluorescent screen T206 even when the space around the fluorescent screen T206 is narrow.

[0194] In addition, in the configuration shown in Figure 2, the optical fiber T228 may be provided to transmit the luminescent light emitted by the first fluorescent screen T206 to the first photodetector T214, or to transmit the luminescent light emitted by the second fluorescent screen T209 to the second photodetector T215.

[0195] Fig. 7 is a diagram showing an example of a configuration for monitoring a beam profile. Fig. 7 shows an example of the arrangement and structure of equipment for irradiating a sample target system A135 with a charged particle beam and monitoring the beam profile for the sample target system A135 in the radionuclide production system A100 shown in Fig. 1 without installing a gamma ray generation target A134. As shown in Fig. 7, when a raw material target T207 is irradiated with a charged particle beam T202 to produce a radionuclide, it is also possible to obtain only the beam profile for the raw material target T207. In addition, the destructive monitor may also be provided with a heating element T230 that generates heat upon incidence of radiation and a temperature sensor T231 that is a temperature measurement unit that measures the temperature of the heating element T230.

[0196] When a nuclear reaction such as a proton-neutron reaction or a spallation reaction is used as the nuclear reaction for transmuting the source nuclide, an ion beam accelerated by an accelerator can be used as the charged particle beam T202 to irradiate the source target T207. The beam profile of the ion beam with respect to the source target T207 can be monitored by a destructive monitor installed behind the source target T207 in the direction of travel of the ion beam.

[0197] The heating element T230 is installed to detect the charged particle beam T202 at the position of the raw material target T207. The heating element T230 is used to measure the beam profile of the charged particle beam T202 with respect to the raw material target T207. The heating element T230 generates a spatial distribution of temperature due to heat generation in accordance with the spatial distribution of the intensity of the charged particle beam T202 at the position of the raw material target T207. The temperature of the heating element T230 is detected by a temperature sensor T231.

[0198] The heating element T230 is installed adjacent to the target container T208 behind the target container T208 in the direction of travel of the charged particle beam T202 parallel to the beam axis T203. The heating element T230 is installed at the center of the beam axis T203 in a direction perpendicular to the beam axis T203. With this arrangement, the spatial distribution of the intensity of the charged particle beam T202 at the position of the raw material target T207 can be measured with high accuracy.

[0199] The heating element T230 can be made of an appropriate material taking into consideration the absorbed dose, response speed, specific heat, durability, etc. Examples of the heating element T230 include metals such as iron, copper, lead, tin, aluminum, magnesium, titanium, and silicon, alloys of these metals, carbon materials such as graphite, and ceramics. The heating element T230 may be divided into cells by a heat insulating material in a direction perpendicular to the beam axis T203.

[0200] The temperature sensor T231 detects the spatial distribution of the temperature of the heating element T230, which corresponds to the spatial distribution of the intensity of the charged particle beam T202. Methods for detecting the spatial distribution of the temperature include a method of actually measuring using detection elements arranged in an array, and a method of capturing an image of infrared rays emitted from the heating element T230 and determining the intensity for each pixel by image processing.

[0201] The temperature sensor T231 can be formed by an infrared thermography camera, a radiation temperature sensor, a thermocouple-type temperature sensor, a resistance temperature sensor, etc. The detection elements of the temperature sensor T231 are arranged in an array in two axial directions perpendicular to the beam axis T203. The temperature sensor T231 can also be configured to have multiple channels and perform detection for each cell of the heating element T230.

[0202] The temperature sensor T231 is installed behind the target container T208 in the traveling direction of the charged particle beam T202. The temperature sensor T231 is installed on the central side intersecting with the beam axis T203 in a direction perpendicular to the beam axis T203, but may be installed on the side not intersecting with the beam axis T203.

[0203] By using such a heating element T230 and temperature sensor T231, the spatial distribution of the intensity of the charged particle beam T202 can be measured by utilizing the heat generated by absorption of the charged particle beam T202. When using the heating element T230, the measured intensity and distribution can be adjusted depending on the absorption cross section and specific heat of the material. Furthermore, the heating element T230 has higher radiation resistance than photodetectors such as image sensors, enabling accurate measurement even under high doses. Because the heating element T230 has the effect of attenuating radiation, it is possible to omit the installation of the beam dump 222 or to perform detection using a beam dump equipped with a detection element.

[0204] Fig. 8 is a diagram showing an example of a configuration for monitoring a beam profile. Fig. 8 shows an example of the arrangement and structure of equipment for irradiating a sample target system A135 with a charged particle beam and monitoring the beam profile for the sample target system A135 in the radionuclide production system A100 shown in Fig. 1 without installing a gamma ray generation target A134. As shown in Fig. 8, when a raw material target T207 is irradiated with a charged particle beam T202 to produce a radionuclide, it is also possible to determine only the beam profile for the raw material target T207. In addition, a destructive monitor can detect the charged particle beam T202 deflected from the beam axis T203.

[0205] 8, a deflection magnet T246 is installed behind the gamma ray generation target T205 and in front of the raw material target T207 in the traveling direction of the electron beam T202. As a destructive monitor, a fluorescent screen T247, which is a light emitter that emits light when exposed to radiation, and a photodetector T248, which is a photodetector that detects the light emitted by the light emitter, are installed.

[0206] The deflection magnet T246 generates a static magnetic field in a predetermined direction, and deflects the charged particle beam T202 extracted from the beam window T201 in a direction different from the beam axis T203 at the time of extraction. The deflection magnet T246 can be formed by an electromagnet such as a solenoid, a permanent magnet, or the like. The angle of deflection by the deflection magnet T246 is preferably small within a range in which the charged particle beam T202 does not enter the target container T208. This is because the beam profile may change significantly due to deflection.

[0207] The fluorescent screen T247 is installed behind the gamma ray generation target T205 in the traveling direction of the charged particle beam T202, which is parallel to the beam axis T203 at the time of extraction. The fluorescent screen T247 is installed to the side of the charged particle beam T202, in a direction perpendicular to the beam axis T203 at the time of extraction, but not intersecting with the beam axis T203. The fluorescent screen T247 is installed at a position intersecting with the beam axis T203 after deflection by the deflection magnet T246. The fluorescent screen T247 measures the spatial distribution of the intensity of the charged particle beam T202 deflected by the deflection magnet T246.

[0208] The photodetector T248 is installed behind the gamma ray generation target T205 and the target container T208 in the traveling direction of the charged particle beam T202. The photodetector T248 is installed to the side so as not to intersect with the beam axis T203 at the time of extraction or after deflection. The photodetector T248 is shielded by a shielding wall between it and the beam axis T203 at the time of extraction or after deflection, while enabling measurement of the light emission from the fluorescent screen T247.

[0209] By using such a bending magnet T246, the spatial distribution of the intensity of the charged particle beam T202 that has passed through the gamma ray generation target T205 can be measured without being affected by shielding or scattering by the target container T208. Therefore, the beam profile for the target container T208 can be determined with high accuracy. In addition, the thermal load on the target container T208 by the charged particle beam T202 can be reduced. Therefore, the robustness of the radionuclide production system A100 can be improved.

[0210] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the present invention. For example, the present invention is not necessarily limited to those having all of the configurations of the above-described embodiments. It is possible to replace part of the configuration of an embodiment with another configuration, add part of the configuration of an embodiment to another form, or omit part of the configuration of an embodiment.

[0211] For example, the destructive monitor installed behind the target is provided in a radionuclide production system that produces radionuclides, but the destructive monitor may also be provided in an accelerator system. The accelerator system includes an accelerator that accelerates charged particles and a target that is irradiated with a charged particle beam accelerated by the accelerator or radiation generated by the charged particle beam, and the destructive monitor can be provided behind the target in the traveling direction of the charged particle beam. Any suitable target for testing, measurement, etc. can be installed as the target.

[0212] 6, a Faraday cup is provided as the destructive monitor, but the destructive monitor can be any combination of a suitable conductive material that is conductive and collects the charged particle beam as a current, and a current measuring unit such as a current sensor that measures the current, as long as it can measure radiation such as a charged particle beam or gamma rays as a current, etc. The conductive material can be provided in any suitable shape and size, such as a wire, mesh, rod, plate, or foil.

[0213] A100 Radionuclide production system A101 Accelerator A102 Irradiation chamber A103 Control device A111 Charged particle source A112 Solenoid A113 Solenoid A114 Accelerator tube A115 Vacuum pumping device A116 First focusing magnet group A117 Steering magnet A118 Quadrupole magnet A119 Quadrupole magnet A120 Steering magnet A121 Beam pipe A122 Second focusing magnet group A123 Bending magnet group A124 Bending magnet A125 Quadrupole magnet A126 Quadrupole magnet A127 Bending magnet A128 Third focusing magnet group A129 Beam transport section A130 Shielding wall A132 Beam monitor A133 Beam window A134 Target for gamma-ray generation A135 Sample target system A136 Beam dump T201 Beam window T202 Charged particle beam T203 Beam axis T204 Beam pipe T205 Target for gamma-ray generation T206 Fluorescent screen (destructive monitor) T207 Raw material target T208 Target container T209 Fluorescent screen (destructive monitor) T214 Photodetector (photodetector section / destructive monitor) T215 Photodetector (photodetector section / destructive monitor) T217 Fluorescent screen (destructive monitor) T218 Photodetector (photodetector section / destructive monitor) T221 Fluorescent screen (destructive monitor) T222 Beam dump T226 Optical fiber head T227 Optical fiber connector T228 Optical fiber T230 Heating element T231 Temperature sensor (temperature measurement part) T240 Photodetector (destructive monitor) T241 Faraday cup T242 Grid T244 Current sensor (current measurement part) T246 Deflection magnet T247 Fluorescent screen (photodetector part / destructive monitor) T248 Photodetector (destructive monitor)

Claims

1. A radionuclide production system comprising: an accelerator for accelerating charged particles; and a target for producing radioactive nuclides through a nuclear reaction when irradiated with a charged particle beam accelerated by the accelerator or radiation generated by the charged particle beam, the radionuclide production system comprising a detector for detecting the charged particle beam or the radiation, the detector being a destructive monitor that interacts with the charged particle beam or the radiation, located behind the target in the direction of propagation of the charged particle beam.

2. A radionuclide manufacturing system as described in claim 1, wherein the targets are a gamma ray generating target that generates gamma rays by irradiating the charged particle beam accelerated by the accelerator, and a raw material target that produces the radionuclide by irradiating the gamma rays, and the destructive monitor is provided behind the gamma ray generating target and behind the raw material target in the direction of travel of the charged particle beam.

3. A radionuclide production system as described in claim 1 or claim 2, wherein the destructive monitor comprises an illuminant that emits light upon incidence of the charged particle beam or radiation, and a light detection unit that detects the emission.

4. A radionuclide production system as described in claim 1 or 2, wherein the destructive monitor comprises a conductive material that collects the charged particle beam as a current, and a current measuring unit that measures the current.

5. A radionuclide production system as described in claim 1 or claim 2, wherein the destructive monitor comprises a heating element that generates heat upon incidence of the charged particle beam or the radiation, and a temperature measuring unit that measures the temperature of the heating element.

6. A radionuclide production system as described in claim 3, wherein the light emitter is a light emitter array in which a plurality of the light emitters are arranged, and the light detection unit detects the spatial distribution of the light intensity due to the light emission.

7. A radionuclide production system according to claim 3, wherein the illuminant is a substance that emits visible light.

8. A radionuclide production system as claimed in claim 1 or 2, wherein the destructive monitor is disposed adjacent to the target as an integral part of the target.

9. A radionuclide production system as claimed in claim 1 or 2, wherein the destructive monitor is disposed separately from the target.

10. A radionuclide production system as defined in claim 1 or 2, comprising a numerical analysis unit which numerically analyzes the beam profile of the charged particle beam or radiation relative to the target, wherein the numerical analysis unit determines, based on the spatial distribution of intensity of the charged particle beam or radiation measured by the destructive monitor, one or more of the following as the beam profile at the target position: the spatial distribution of intensity of the charged particle beam or radiation at the target position, the position of the beam center of the charged particle beam or radiation at the target position, and the beam spread from the beam center of the charged particle beam or radiation at the target position.

11. A radionuclide production method for producing a radionuclide using a radionuclide production system comprising: an accelerator for accelerating charged particles; and a target for producing a radionuclide through a nuclear reaction by irradiating the target with a charged particle beam accelerated by the accelerator or with radiation generated by the charged particle beam, wherein the radionuclide production system comprises a destructive monitor which is a particle detector for detecting the charged particle beam or the radiation, behind the target in the traveling direction of the charged particle beam, and which interacts with the charged particle beam or the radiation, and based on the spatial distribution of the intensity of the charged particle beam or the radiation measured by the destructive monitor, the radionuclide production method determines, as the beam profile at the position of the target, one or more of the spatial distribution of the intensity of the charged particle beam or the radiation, the position of the beam center of the charged particle beam or the radiation, and the beam spread from the beam center of the charged particle beam or the radiation.

12. A method for producing a radionuclide as described in claim 11, wherein the beam profile at the position of the target is determined by a function fitting process that expresses the spatial distribution of the intensity of the charged particle beam or the radiation at the position of the target by a combination of preset functions or by a preset function itself, and a correlation between the measurement results measured by a plurality of the destructive monitors and the results determined by the function fitting process is evaluated.

13. A radionuclide production method as claimed in claim 12, wherein the evaluation of the correlation is carried out by utilizing numerical analysis using a calculation system simulating the radionuclide production system, and a comparison is made between the measurement results measured by the destructive monitor and the analysis results obtained by the numerical analysis, or a comparison is made between the state of the charged particle beam based on the measurement results and the state of the charged particle beam based on the analysis results.

14. A method for producing a radionuclide as described in claim 11, comprising the steps of continuing irradiation of the charged particle beam, stopping irradiation of the charged particle beam, adjusting the irradiation direction of the charged particle beam, or adjusting operating parameters of the accelerator, based on the determined beam profile.

15. An accelerator system comprising an accelerator for accelerating charged particles, and a target irradiated with a charged particle beam accelerated by the accelerator or radiation generated by the charged particle beam, the accelerator system comprising a particle detector for detecting the charged particle beam, located behind the target in the direction of propagation of the charged particle beam, the particle detector comprising a destructive monitor that interacts with the charged particle beam.

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