Target, radioisotope production apparatus, target substrate, and radioisotope production method

Abstract

To provide a target that extends the travel distance of a charged particle beam relative to that in the case of using a conventional inclined target.SOLUTION: A target (40) used in a radioisotope production apparatus (10), wherein the target (40) comprises a target substrate (41), a target layer (42) containing a target material and covering a part of the surface of the target substrate (41), and a plurality of protrusions (42a) having at least a part of the target layer (42) raised.SELECTED DRAWING: Figure 4B

Description

[Technical Field]

[0001] The present disclosure relates to targets, radioisotope generation devices, target substrates, and methods for radioisotope generation. [Background technology]

[0002] Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are widely used diagnostic methods for visualizing tumors, blood flow, etc. using short-lived radioisotopes (RI).

[0003] The desired RI is produced by a nuclear reaction between a charged particle beam accelerated to a certain energy and a target material. Targets have long been known to have problems with heat generation and heat removal, and to address these problems, tilted targets, whose main surface is tilted relative to the charged particle beam, are used. The tilted target increases the irradiation area of ​​the charged particle beam and can reduce the density of the charged particle beam in the irradiation region. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Re-tabled publication 2019 / 189022 [Non-patent literature]

[0005] [Non-Patent Document 1] Standardized High Current Solid Targets for Cyclotron Production of Diagnostic and Therapeutic Radionuclides, IAEA TRS432 (2004) [Non-patent document 2] IAEA RADIOISOTOPES AND RADIOPHARMACEUTICALS REPORTS No. 1 Cyclotron Produced Radionuclides: Emerging Positron Emitters for Medical Applications: 64Cu and 124I, IAEA (2016) [Non-patent document 3] Bong Hwan Hong et al., THE PERFORMANCE OF DOUBLE-GRID O-18 WATER TARGET FOR FDG PRODUCTION Proceedings of EPAC 2006 Summary of the Invention [Problem to be solved by the invention]

[0006] It is known that the amount of RI generated can be increased by decreasing the tilt angle of the tilted target and increasing the thickness of the target layer, but in reality there are limits to both. When using a target layer with a specified tilt angle and thickness, there is a need for a technology that can extend the range of the charged particle beam compared to conventional tilted targets.

[0007] One aspect of the present disclosure aims to provide a target, a radioisotope generation device, a target substrate, and a radioisotope generation method that increase the range of a charged particle beam compared to when using conventional tilted targets. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, a target according to one aspect of the present disclosure is a target used in a radioisotope generating device, and comprises a target substrate, a target layer containing a target material and covering a portion of the surface of the target substrate, and a plurality of protrusions that protrude at least a portion of the target layer.

[0009] In order to solve the above-mentioned problems, a radioisotope generation device according to one aspect of the present disclosure is a radioisotope generation device that generates radioisotopes, and includes: a particle accelerator that emits a charged particle beam; a target substrate; a target layer that contains a target material and covers a portion of the surface of the target substrate; and a target that includes a plurality of protrusions that protrude at least a portion of the target layer.

[0010] In order to solve the above-mentioned problems, a target substrate according to one embodiment of the present disclosure is a target substrate in which a target layer containing a target material is laminated on a partial region of the surface, thereby forming a target together with the target layer, and a plurality of folded plate-shaped protrusions are provided on at least a portion of the partial region.

[0011] In order to solve the above-mentioned problems, a radioisotope generation method according to one embodiment of the present disclosure is a radioisotope generation method in a radioisotope generation device, which includes preparing a target layer containing a target material and having a plurality of protrusions, at least some of which include an inclined region that is inclined with respect to a first main surface, which is a physical plane or a virtual plane, and irradiating the target layer with a charged particle beam. [Effects of the Invention]

[0012] According to one aspect of the present disclosure, it is possible to provide a target, a radioisotope production device, a target substrate, and a radioisotope production method that increase the range of a charged particle beam compared to when a conventional tilted target is used. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram for explaining an outline of the manufacturing cycle of a radiopharmaceutical. [Figure 2] FIG. 1 is a diagram illustrating the configuration of a general radioisotope generating device. [Figure 3A] 1 is a diagram showing a state in which a charged particle beam is incident on a main surface of a target substrate at an inclination angle θ1. [Figure 3B]FIG. 3B is a cross-sectional view taken along the line AA' in FIG. 3A. [Figure 4A] 1 is a cross-sectional view of a main portion of a target according to the present disclosure. [Figure 4B] FIG. 1 is a perspective view of a target according to the present disclosure, illustrating how a charged particle beam is incident on the target. [Figure 4C] 1 is a diagram for explaining the range of a charged particle beam incident on a target according to the present disclosure. [Figure 5] 1 is a photograph showing an example of a target according to the present disclosure. [Figure 6] FIG. 1 shows the energy range that maximizes the utilization of the 64Ni(p,n)64Cu reaction cross section. [Figure 7] The produced nuclides, production reaction formulas, and thermal properties of the target material are shown. [Figure 8] FIG. 1 is a cross-sectional view of a target model used in comparative verification. [Figure 9] FIG. 10 is a diagram for explaining that model conditions are aligned. [Figure 10A] 1 shows a contour plot of a target according to the present disclosure. [Figure 10B] A contour diagram of a flat target is shown. [Figure 11] These graphs can be said to be for quantitatively evaluating the temperature analysis results of the target model and the flat target shown in FIGS. 10A and 10B. [Figure 12A] 1 shows a contour plot of a target according to the present disclosure. [Figure 12B] A contour diagram of a flat target is shown. [Figure 13] FIG. 1 is a cross-sectional view of a target according to one embodiment of the present disclosure. [Figure 14] FIG. 1 is a cross-sectional view of a target according to one embodiment of the present disclosure. [Figure 15] FIG. 1 is a cross-sectional view of a target according to one embodiment of the present disclosure. [Figure 16] FIG. 1 is a cross-sectional view of a target according to one embodiment of the present disclosure. [Figure 17] FIG. 1 is a cross-sectional view of a target according to one embodiment of the present disclosure. [Figure 18] 1 is a flowchart of a radioisotope production method according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, the target and the like according to the present disclosure will be described with reference to the drawings.

[0015] [Radiopharmaceuticals (Outline of the manufacturing cycle)] Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are widely used diagnostic methods for visualizing tumors or blood flow using short-lived radioisotopes (RI). 64 Cu and other radioisotopes have attracted attention as therapeutic agents (radiopharmaceuticals) with high therapeutic effects due to the Auger electron emission that accompanies orbital electron capture in their decay forms, and innovative research and preclinical studies are being conducted. RIs are mass-produced not only in research institutions and hospitals but also on a commercial basis, and technological advances in their generation methods and mass-production methods are progressing daily.

[0016] Figure 1 is a diagram for explaining an overview of the manufacturing cycle of a radiopharmaceutical. Figure 1 shows S1 to S8 as the main steps. The radiopharmaceutical is supplied to a research institute, hospital, etc. after passing through S1 to S8.

[0017] In step S1, a high-energy charged particle beam generated by a radioisotope generator is irradiated onto a target (target material) to produce RI suitable for radiopharmaceuticals. This process will be described later with reference to Figure 2.

[0018] In S2, RI is produced in bulk, including target melting and chemical processing.

[0019] In S3, the obtained RI is compounded, diluted and adjusted, and aseptically filled to prepare a formulation.

[0020] In S4, the medicines obtained in S3 are packaged.

[0021] In S5, the packaged pharmaceuticals are shipped. Radioactive pharmaceuticals have a short half-life and their effectiveness tends to decrease over time. Therefore, the pharmaceuticals are shipped while taking into consideration weather and / or traffic conditions so that they arrive by the delivery date specified by the customer. In this way, the cycle of S1 to S5 circulates.

[0022] In S6, the target material from step S2 is recovered and purified so that it can be reused.

[0023] In S7, the target material obtained is electrodeposited onto a target substrate. The target obtained in S7 is provided to S1.

[0024] In S8, quality testing and release determination are carried out to check whether there are any quality problems with the preparation obtained in S3.

[0025] [Overall configuration of charged particle irradiation device] Next, a description will be given of the schematic configuration of the radioisotope generating device described with reference to S1 in Fig. 1. Fig. 2 is a configuration diagram of a general radioisotope generating device.

[0026] 2, a radioisotope generator 10 produces RI using an accelerator that generates a high-energy charged particle beam. The radioisotope generator 10 includes, for example, a main body 1, an ion source 2, a distribution electromagnet 3, a focusing lens 4, and a target station 5.

[0027] For example, a cyclotron, a synchrotron, or a linear accelerator is used as the apparatus main body 1. The apparatus main body 1 emits particles such as protons, deuterons, or helium nuclei supplied from an ion source 2 as a charged particle beam.

[0028] In the device main body 1, the type of particle, acceleration energy, irradiation current value, and / or irradiation time are appropriately set according to the type of target or its thickness in order to produce the desired RI with high purity and high yield through a nuclear reaction.

[0029] The distribution electromagnet 3 distributes the irradiation course of the charged particle beam emitted from the main body 1 of the apparatus.

[0030] The converging lens 4 converges the charged particle beam incident from the distributing electromagnet 3 toward an irradiation area on a target provided in a target station 5 .

[0031] The target station 5 includes a target to be irradiated with the charged particle beam, a target fixing portion for fixing the target, and the like.

[0032] 〔target〕 Next, the target according to the present disclosure will be described. For ease of understanding, the tilted target will be described first with reference to Figures 3A and 3B, and then the target according to the present disclosure will be described with reference to Figures 4A to 4C, etc.

[0033] [Sloped target] The desired RI is produced by a nuclear reaction between a charged particle beam accelerated to a certain energy and a target material. A typical target includes a metal target substrate with a flat main surface and a target layer formed by stacking target material on the main surface of the target substrate. To mass-produce RI using such a target, methods include (1) increasing the amount of charged particle beam and (2) maximizing the amount of target material within the effective range for nuclear reaction to occur. However, (1) and (2) above can increase the heat generation of the target, potentially causing scattering of the target material or damage to the target. Therefore, heat removal from the target is also a challenge.

[0034] To address the problem of target heat generation and heat removal, a method of irradiating a charged particle beam obliquely onto the main surface of a target substrate is known. FIG. 3A is a diagram showing how a charged particle beam is incident on the main surface of the target substrate at an oblique angle θ1. FIG. 3B is a cross-sectional view taken along line A-A' in FIG. 3A. As shown in FIG. 3A, an oblique target 30 includes a target substrate 31 and a target layer 32 stacked on a main surface 31F of the target substrate 31. The target layer 32 has a thickness t.

[0035] In the tilted target 30, the irradiation area of ​​the charged particle beam becomes elliptical depending on the tilt angle θ1 of the propagation direction of the charged particle beam with respect to the main surface 31F. This increases the irradiation area of ​​the charged particle beam compared to when the charged particle beam is incident perpendicularly to the main surface 31F. The target layer 32 is provided in an area that encompasses the irradiation area depending on the assumed tilt angle θ1. The tilt angle θ1 can also be considered as the incident angle of the charged particle beam with respect to the main surface 31F. When the thickness of the target layer 32 is thinner than the penetration depth of the charged particle beam into the target layer 32, the tilted target 30 can increase the range of the charged particle beam in the target layer 32 compared to a perpendicular target.

[0036] Furthermore, the tilted target 30 can reduce the density of the charged particle beam in the irradiation region as the irradiation area of ​​the charged particle beam increases. Therefore, the tilted target 30 reduces the amount of heat generated per unit area in the irradiation region. Furthermore, the tilted target 30 enhances the heat removal effect of the target layer 32 as the irradiation area increases.

[0037] The effect of widening the irradiation area obtained by the tilted target 30 (hereinafter referred to as the "tilt effect") is proportional to "1 / sinθ1," which increases as the tilt angle θ1 decreases. Conventionally, tilt angles such as θ1=6° and θ1=15° are known. At θ1=6°, 1 / sinθ1=9.6, resulting in a tilt effect of 9.6 times.

[0038] However, the tilted target 30 has a longer target substrate 31 than a perpendicular target. For example, when θ1=6°, the tilt effect is 9.6 (=1 / sinθ1), so the target substrate 31 must be 9.6 times longer than in the case of perpendicular incidence, which leads to an increase in the size of the device.

[0039] Furthermore, compared to a vertical target, the tilted target 30 requires more accurate adjustment of the propagation direction and irradiation position of the charged particle beam. Assume that the trajectory of the charged particle beam deviates by approximately 1 mm in the case of a vertical target. If a deviation of the same magnitude were to occur in the tilted target 30, the deviation would be 1 / sinθ1 (9.6 mm at θ1 = 6°), increasing the risk of the beam hitting an unintended area. For these reasons, a value of approximately θ1 = 6° is considered the lower limit for stable RI generation.

[0040] Furthermore, when forming the target layer 32 on the main surface 31F of the target substrate 31, the time required to form the target layer 32 is roughly proportional to the thickness of the target layer 32. Furthermore, making the target layer 32 too thick can exacerbate heat problems. In general, the thicker the target layer (electrodeposited layer), the more likely it is that problems with the quality of the target layer, such as cracks or lifting, will occur. A thick target layer not only increases the amount of heat generated internally, but cracks or lifting also hinder heat transfer to the target substrate, which acts as a heat sink, compounding the heat problem.

[0041] Furthermore, it is attracting attention in theranostics, a new medical technology that integrates treatment and diagnosis. 64 Cu etc. is the raw material target material ( 64 For these reasons, it is difficult to increase the thickness of the target layer 32 excessively, even if it is to increase the range of the charged particle beam.

[0042] As described above, it is known that the amount of RI generated can be increased by reducing the tilt angle θ1 and increasing the thickness of the target layer 32, but in reality there are limits to both.

[0043] [Target according to the present disclosure] Next, a target 40 according to the present disclosure will be described with reference to Figures 4A to 4C. Figure 4A is a cross-sectional view of a main part of the target 40. Figure 4B is a perspective view of the target 40, illustrating how a charged particle beam is incident on the target 40. Figure 4C is a diagram for explaining the range of the charged particle beam incident on the target 40.

[0044] 4A and 4B show XYZ coordinates. The XY plane corresponds to a first main surface 42F, which will be described later. The Y axis corresponds to the direction in which a target layer protrusion 52a (or an inclined region 43), which will be described later, extends. The Z axis corresponds to the direction perpendicular to the XY plane.

[0045] Referring to FIG. 4A, the target 40 includes a target substrate 41 and a target layer 42 (with a thickness t) stacked on the surface of the target substrate 41.

[0046] The target substrate 41 is made of a metal material, and the material is selected from the viewpoints of mechanical strength, thermal properties such as thermal conductivity, or resistance to the solvent used in dissolving the target. The target substrate 41 is attached to a target fixing portion (not shown) provided in the target station by a fixing means such as bolts.

[0047] A target substrate protrusion 41a having a folded plate shape is provided in at least a portion of a region of the target substrate 41. Generally, a folded plate shape refers to a structure having a three-dimensional shape formed by folding a flat plate (or sheet, etc.). A folded plate shape has creases, with the angle changing at the folded portion. The target substrate protrusion 41a is not formed by folding the target substrate 41, but is formed by depositing material constituting the target substrate protrusion 41a on the surface of the target substrate 41. Therefore, the fact that the target substrate protrusion 41a has a folded plate shape means that the shape is a folded plate when the outer edge of the target substrate protrusion 41a, which defines the shape of the target substrate protrusion 41a, is considered. In the example of FIG. 4A, the cross section of the target substrate protrusion 41a in the XZ plane is triangular (or approximately triangular), and the apex angle is 2·θ2.

[0048] The target layer 42 generates RI in the irradiated area by being irradiated with a charged particle beam such as protons, deuterons, alpha particles, or 3He. 64 Ni, 89 Y, 100 Mo, 89 Y2O3, 65 The target layer 42 may be a metal such as Cu. 64 Cu, 89 Zr, 99 mTc, 65 Produces RI such as Zn.

[0049] The target layer 42 contains the target material and covers a portion of the surface of the target substrate 41. The target substrate 41 and the target layer 42 containing the target material are stacked on a partial region of the surface, thereby constituting the target 40 together with the target layer 42. The target layer 42 is also laminated on the surface of the target substrate protrusion 41a. As a result, the target 40 has a target layer protrusion 42a, which is at least a portion of the target layer 42 that protrudes. The target 40 may have only one target layer protrusion 42a, but the following description will be given assuming that the target 40 has multiple target layer protrusions 42a. Only one target layer protrusion 42a is shown in FIG. 4A.

[0050] If the same amount of RI is to be produced using multiple target layer protrusions 42a as using one target layer protrusion 42a, the size of the single target layer protrusion 42a will be larger. This poses a problem in that the ancillary equipment, such as a vacuum chamber, used in the radioisotope production device will also be larger. In this regard, the target 40 has the advantage that, by having multiple target layer protrusions 42a, the conventional radioisotope production device can be used as is simply by replacing the conventional target with the target 40.

[0051] The target layer 42 has a first main surface 42F that is a physical plane. The outer edge shape that defines the outer shape of the target layer protrusion 42a has a triangular (or approximately triangular) cross section in the XZ plane, and includes an inclined region 43 that is inclined with respect to the first main surface 42F.

[0052] Next, for ease of understanding, an example of the target 40 is shown in Fig. 5. Fig. 5 is a photograph showing an example of a target 50 according to the present disclosure.

[0053] The target 50 includes a target layer 52 that contains a target material and covers a portion of the surface of a target substrate (not shown), and a plurality of target layer protrusions 52a that protrude from at least a portion of the target layer 52. A valley 54 is formed between two adjacent target layer protrusions 52a. With the above configuration, the target layer 52 (or the target 40) can be considered to have a first main surface 52F that is an imaginary plane that contacts the bottoms of the plurality of valleys 54.

[0054] Each of the target layer protrusions 52a includes an inclined region 53 that is inclined with respect to the first main surface 52F. The inclined region 53 may be formed in at least a portion of each of the target layer protrusions 52a.

[0055] Each of the plurality of inclined regions 53 extends parallel to a predetermined direction (Y-axis direction) within the in-plane direction of the first main surface 52F. Some of the plurality of inclined regions 53 do not necessarily have to extend parallel to the predetermined direction (Y-axis direction).

[0056] The width of each of the plurality of target layer protrusions 52a narrows toward the tip. Only some of the plurality of target layer protrusions 52a may be formed so that the width narrows toward the tip.

[0057] The multiple target layer protrusions 52a are arranged at a predetermined pitch from one another. In the example shown in Fig. 5, the tops of the multiple target layer protrusions 52a are spaced apart by 1.26 mm. The tops of the multiple target layer protrusions 52a may be arranged at different pitches from one another. Only some of the multiple target layer protrusions 52a may be arranged at a predetermined pitch from one another.

[0058] Each of the plurality of target layer protrusions 52a is formed in a folded plate shape. Only some of the plurality of target layer protrusions 52a may be formed in a folded plate shape. The folded plate shape can also be expressed as a corrugated plate shape in which peaks and valleys are alternately arranged.

[0059] For ease of understanding, the target 50 according to the present disclosure has been described above with reference to Fig. 5. Next, the fact that the range of a charged particle beam incident on the target according to the present disclosure is increased will be described with reference to Figs. 4A to 4C.

[0060] 4A, the target substrate protrusion 41a is formed in a folded plate shape, with its width narrowing toward the tip. The cross section of the target substrate protrusion 41a in the XZ plane is triangular (or approximately triangular), with an apex angle of 2·θ2. The target layer 42 is also laminated on the surface of the target substrate protrusion 41a.

[0061] 4B, the target 40 is positioned so that the charged particle beam is incident in an oblique direction with respect to the surface of the inclined region 43 and in a direction inclined with respect to a predetermined direction within the in-plane direction of the first main surface 42F (not shown). Here, the predetermined direction refers to the Y-axis direction in which the inclined region 43 extends. In this case, referring to FIG. 4C, the beam path of the charged particle beam incident on the target 40 is expressed by the following equation:

[0062] Beam Path=t / (sinθ1·sinθ2)···(1) In equation (1), t represents the thickness of the target layer protrusion 42a, θ1 represents the angle at which the charged particle beam is incident on the surface of the inclined region 43, and θ2 represents the value obtained by dividing the apex angle of the target substrate protrusion 41a by 2.

[0063] [Tilt effect] In formula (1), it is assumed that θ1 and θ2 are each 15 degrees. In this case, the tilt effect obtained in the target 40 is the tilt effect (1 / sinθ1) obtained by a conventional tilt target multiplied by sinθ2. Specifically, when θ1 = θ2 = 15°, the tilt effect obtained in the target 40 is 1 / (sinθ1·sinθ2) = approximately 15 times. This means that, for example, 64 In the production of Cu, an electrodeposited film thickness of 30 μm effectively becomes 450 μm.

[0064] The target 40 can achieve a tilt effect that is 1.56 times greater than that of a conventional tilted target (θ1 = 6°). Specifically, the tilt effect of a conventional tilted target (θ1 = 6°) is 1 / sinθ1 = 9.6. Furthermore, when θ1 and θ2 are each 15 degrees, the tilt effect of the target 40 is 1 / (sinθ1 · sinθ2) = 14.9. Therefore, the target 40 can achieve a tilt effect that is 1.56 times greater (= 14.9 / 9.6 = 1.56) than that of a conventional tilted target (θ1 = 6°). At a tilt angle of 15°, beam control is relatively easy, and the entire target can be configured compactly. Therefore, a tilt angle of 15° promotes effective use of expensive target materials.

[0065] In this way, the target 40 extends the range of the charged particle beam by utilizing the inclination of the target layer protrusions 52a (inclined regions 43) formed by microfabrication technology, in addition to the oblique incidence of the charged particle beam employed in the conventional inclined target 30. This method can be said to be a technical concept different from the expansion of the irradiation area by a beam deflection system such as a conventional beam scanner or wobbling magnet system.

[0066] Another effect of the gradient effect is that the effective thickness of the target 40 can be increased even with a thin target layer. Since there is an inverse proportionality between the thickness of the target layer and the quality of the electrodeposition, the target 40 can stably provide a higher quality target layer with excellent uniformity, adhesion, and smoothness.

[0067] Furthermore, because the electrodeposition time of the target layer is proportional to the surface area of ​​the target layer, target 40 can significantly reduce the electrodeposition time of the target layer compared to conventional tilted targets. In addition, because the dissolution time of the target layer depends on the thickness of the target layer, target 40 can also significantly reduce the dissolution time of the target layer compared to conventional tilted targets.

[0068] [Effective use of gradient effect and reaction cross section] As explained above, it is known that the amount of RI generated can be increased by reducing the tilt angle of the tilted target and increasing the thickness of the target layer, but in reality there are limits to both.

[0069] Therefore, a method is required to obtain the maximum range of the charged particle beam in a thinner target layer, and one way to effectively generate RI is to make the most of the reaction cross section. This is explained using Figure 6.

[0070] Figure 6 shows 64 Ni(p, n) 64 This figure shows the energy range that maximizes the use of the Cu reaction cross section. The horizontal axis shows the incident energy (MeV) of the particle accelerator. The vertical axis shows the reaction cross section (mb).

[0071] Attention in theranostics 64 For example, Cu is a very expensive target material, so it is most effective for clinical use or commercial production. 64 To produce Cu, it is desirable to maximize the reaction cross section (mb). As shown in Figure 6, the range of 16 MeV to 5 MeV covers a highly reactive range. Specifically, 16 MeV is an economically significant incident energy that can be irradiated with a small cyclotron. Energy below 5 MeV hardly contributes to the reaction and is transferred to the target substrate as a heat sink.

[0072] Target 40 is the most efficient 64 The range of nuclear reaction cross section that can produce Cu (16 MeV to 5 MeV) is utilized to the maximum extent, and the effective thickness is increased by the gradient effect while the thickness of the target layer is thin. 64 The generation of Cu has been explained as an example, but the same can be said for other RIs.

[0073] In this way, the target 40 can obtain a high tilting effect while fully utilizing the reaction cross section. This effect is similar to that of any other solid target, and can be optimized by appropriately setting the film thickness of the target layer and the energy of the charged particle beam.

[0074] 4A to 4C, θ1 and θ2 are each described as being 15 degrees. However, θ1 and θ2 are not limited to 15 degrees. The combination of θ1 and θ2 can be appropriately selected depending on the target substrate material (e.g., Cu, Ag, Au) used, the characteristics or cost of the target material, the purpose of the radioisotope generation apparatus 10, etc.

[0075] [Verification of fever] As explained above, the target according to the present disclosure can make full use of the reaction cross section, while increasing the range of the charged particle beam by the tilting effect, compared to when a conventional tilted target is used.

[0076] In solid targets, the target substrate on which the target material (target layer) is deposited by electrodeposition or the like can be selected from materials that have thermal properties such as mechanical strength or thermal conductivity, or resistance to solvents used in dissolving the target. However, there is no room for choice when it comes to the target material and reaction products. Therefore, we examine whether thermal problems, such as loss of the target material and / or the produced nuclides due to dissolution and / or evaporation, can occur with the targets disclosed herein.

[0077] Figure 7 shows the thermal properties of the produced nuclides, the production reaction formula, and the target material. The items listed in Figure 7, from left to right, are the produced nuclides, the production reaction formula, the melting point of the target material, the melting point of the produced nuclides, and the thermal conductivity of the target material. As shown in Figure 7, the melting points of many of the produced nuclides and target materials are 300°C to 500°C or lower. Therefore, a comparison and verification of thermal issues will be conducted between the target according to the present disclosure and a conventional flat target, particularly in the temperature range above 300°C.

[0078] [Verification using a thermal fluid analysis model] 8 is a cross-sectional view of a target model used in the comparative verification. Target model 80 includes a target substrate 81 and a target layer 82 provided on target substrate 81. A cooling unit 83 that circulates a refrigerant (cooling water in this model) for cooling target substrate 81 is provided on the back side of target substrate 81.

[0079] The model conditions are as follows:

[0080] (Model conditions) Software used: Simcenter Femap Thermal / Flow v2021.2 θ1, θ2: both 15° Charged particle (proton) beam shape: Gaussian distribution with a half-width of 10 mm Heat load: 4kW (250μA in 16MeV proton beam dose, exceeding the maximum value of 200μA confirmed in public literature) ·Cooling water: 30L / min (25℃) Target audience for this disclosure: 64 Ni layer (30 μm thick at the protrusion) Target audience of the flat target for comparison: 64 Ni layer (thickness 116 μm) Target substrate: Silver Furthermore, the model conditions for the target according to the present disclosure and the conventional flat target are made as consistent as possible. This will be explained with reference to Fig. 9. Fig. 9 is a diagram for explaining the consistency of the model conditions.

[0081] In Figure 9, the left side of line segment L shows target model 80 corresponding to the present disclosure, and the right side of line segment L shows flat plate target 90 corresponding to a conventional flat plate target. The surface that forms the boundary between target substrate 81 (target substrate 91) and cooling section 83 is defined as boundary surface 83F. In target model 80, the distance from the tip of target layer protrusion 82a to boundary surface 83F (the distance indicated by A-A' in the figure) is defined as X1. In flat plate target 90, the distance from the surface of target layer 92 to boundary surface 83F (the distance indicated by B-B' in the figure) is defined as X2.

[0082] According to Fourier's law, when a temperature gradient exists in an object, in a steady state, the greater the distance between the heat-generating surface and the cooling surface, the smaller the heat flux. In this model, X1 > X2, and the distance between the heat-generating surface and the cooling surface of the target model 80 is greater than that of the flat target 90.

[0083] Therefore, in order to make the conditions as uniform as possible when comparing and examining the target model 80 and the flat target 90, the shape of the cooling part 83 and the conditions of the cooling water circulating in the cooling part 83 were set to be the same. In addition, the upper surface of the flat target 90 was placed at position P, which was the center of the height of the target layer protrusion 82a.

[0084] 10A and 10B show contour diagrams of the temperature analysis results. A contour diagram is a method for visualizing three-dimensional analysis results, in which points with the same value are connected and color-coded according to the value. FIG. 10A shows a contour diagram of a target model 80. FIG. 10B shows a contour diagram of a flat target 90.

[0085] Furthermore, a graph comparing the area ratios of temperature zones in 50°C increments based on Figures 10A and 10B is shown in Figure 11. Figure 11 shows the areas by temperature zone based on the contour diagrams of Figures 10A and 10B. Figure 11 can be said to be a graph for quantitatively evaluating the temperature analysis results of target model 80 shown in Figure 10A and flat target 90 shown in Figure 10B.

[0086] In Figure 11, "this disclosure" corresponds to target model 80, and "flat target" corresponds to flat target 90. Figure 11 shows that under an extremely high charged particle beam load of 4 kW, the area ratios of the two are considered to be approximately equivalent at temperatures below 300°C, which is below the melting points of many solid target nuclides. On the other hand, in the temperature range above 300°C, target model 80 has a lower area ratio than flat target 90, and the results show that it has superior heat removal capability to flat target 90.

[0087] The reason for focusing on 300°C is that, as explained with reference to FIG. 7, the melting points of many of the generated nuclides and target materials are 300°C to 500°C or less, and therefore a target with excellent heat removal capability in the temperature range exceeding 300°C is required.

[0088] Next, the results of comparing the target model 80 and the flat target 90 in terms of heat transfer density will be explained with reference to Figures 12A and 12B. Figure 12A shows a contour diagram of the target model 80. Figure 12B shows a contour diagram of the flat target 90.

[0089] For target model 80, the heat transfer rate per unit area of ​​the target layer (nickel layer) is qr, the temperature difference between the surface of the nickel layer and the back surface of the nickel layer (the boundary surface with the target substrate) is ΔTr, and the thickness of the nickel layer is Δxr. In this case, Δxr = 30 μm, and from Figure 12A, ΔTr = 14°C is obtained.

[0090] Furthermore, for the flat target 90, the heat transfer rate per unit area of ​​the target layer (nickel layer) is qp, the temperature difference between the surface of the nickel layer and the back surface of the nickel layer (the boundary surface with the target substrate) is ΔTp, and the thickness of the nickel layer is Δxp. In this case, Δxp = 116 μm, and from Figure 12B, ΔTr = 117°C is obtained.

[0091] From the above, the ratio between qr of the target model 80 and qp of the flat target 90 is calculated as "0.46" by the following formula (2).

[0092] qr / qp=(ΔTr / Δxr) / (ΔTp / Δxp)··(2) This means that the target model 80 has approximately twice the heat transfer density in the target layer compared to the planar target 90. In other words, this means that the irradiation dose can be increased to twice the incident beam amount (number of incident charged particles), and therefore suggests that twice the yield can be obtained. The small amount of heat generated in the target layer is extremely advantageous for the target material and the produced nuclides, whose melting point and boiling point (vapor pressure) cannot be selected. In other words, the target model 80 makes it possible to efficiently produce radioisotopes while avoiding the issue of heat generation in the target layer.

[0093] Based on the above verification, the target according to the present disclosure can achieve various effects, such as (1) providing a means for making the most efficient use of target materials, which are very expensive raw materials; (2) providing a target layer of higher quality with excellent uniformity, adhesion, and smoothness, and thinner than conventional flat targets; (3) enabling the miniaturization of target systems; (4) facilitating the control of charged particle beams; and (5) providing a new means for mass-producing RIs.

[0094] [Variation 1] The target according to the present disclosure employs a folded-plate target layer and target substrate, thereby increasing structural strength and enabling the realization of a more excellent cooling surface structure than conventional targets. This allows for a variety of shapes, thicknesses, and cooling surface shapes of the target substrate. Examples of such shapes are described with reference to FIGS. 13 to 15.

[0095] FIG. 13 is a cross-sectional view of a target 130 according to an aspect of the present disclosure. The target 130 includes a target substrate 131 and a target layer 132 laminated on the target substrate 131. On the back side of the target substrate 131, a cooling unit 133 for circulating a refrigerant (such as cooling water) for cooling the target substrate 131 is provided. The target substrate 131 is integrally formed with a plurality of cooling fins 131a extending into the interior of the cooling unit 133. Each of the plurality of cooling fins 131a is formed with a width a and a length b1. Grooves are formed between the plurality of cooling fins 131a. By circulating the refrigerant through the grooves as well, the target substrate 131 is cooled through the plurality of cooling fins 131a.

[0096] FIG. 14 is a cross-sectional view of a target 140 according to an aspect of the present disclosure. The target 140 includes a target substrate 141 and a target layer 142 laminated on the target substrate 141. On the back side of the target substrate 141, a cooling unit 143 for circulating a refrigerant (such as cooling water) for cooling the target substrate 141 is provided. The target substrate 141 is integrally formed with a plurality of cooling fins 141a extending into the interior of the cooling unit 143. Each of the plurality of cooling fins 141a is formed with a width a and a length b2. Grooves are formed between the plurality of cooling fins 141a. By circulating the refrigerant through the grooves as well, the target substrate 141 is cooled through the plurality of cooling fins 141a.

[0097] As shown in the figure, the cooling fin 141a (FIG. 14) is longer than the cooling fin 131a (FIG. 13) (b1 < b2). Therefore, when various conditions (such as the incident energy of the charged particle beam) are made the same, the target layer 142 cools faster than the target layer 132.

[0098] Thus, the target of the present disclosure can vary the shape of the cooling fins (such as the ratio of a, b1, b2) in various ways.

[0099] 15 is a cross-sectional view of a target according to one embodiment of the present disclosure. A target 150 according to the present disclosure includes a target substrate 151 and a target layer 152 stacked on the target substrate 151. A cooling unit 153 that circulates a refrigerant (such as cooling water) for cooling the target substrate 151 is provided on the back side of the target substrate 151. The target substrate 151 is formed in a folded plate shape. Furthermore, the inside of the folded plate part of the target substrate 151 is hollow, and this hollow space serves as part of the cooling unit 153. The shape of the target substrate 151, which can be described as a corrugated thin plate, is achieved by increasing the structural strength of the folded plate-shaped target substrate 151, and a more excellent cooling surface structure than conventional structures can be provided.

[0100] [Variation 2] In the target according to the present disclosure, the target layer has a first main surface that is a physical or virtual plane, and each of the plurality of protrusions includes at least a portion of an inclined region that is inclined with respect to the first main surface. An example of this will be described with reference to FIG.

[0101] 16 is a cross-sectional view of a target 160 according to one embodiment of the present disclosure. The target 160 includes a target substrate 161 and a target layer 162 stacked on the surface of the target substrate 161. A target substrate protrusion 161a is provided on at least a portion of a partial region of the target substrate 161. The target substrate protrusion 161a is composed of a vertical protrusion 161a1 extending in the Z-axis direction and an inclined protrusion 161a2 connected to the vertical protrusion 161a1 and having a triangular (or approximately triangular) cross section in the XZ plane.

[0102] The target layer 162 is also stacked on the surface of the target substrate protrusion 161a. As a result, the target 160 has a target layer protrusion 162a, which is at least a portion of the target layer 162 that protrudes. In the region of the target layer protrusion 162a stacked on the inclined protrusion 161a2, an inclined region 163 that is inclined with respect to the first main surface 162F is formed. Note that, because the vertical protrusion 161a1 extends in the Z-axis, no inclined region is formed in the target layer protrusion 162a stacked on the vertical protrusion 161a1.

[0103] In this way, the target 160 may be realized by a configuration including an inclined region 163 inclined with respect to the first main surface 162F in at least a portion of the target layer protrusion portion 162a, and in this case, the inclined region 163 may be understood to correspond to the inclined region 43 (Figure 4A).

[0104] [Variation 3] 17 is a cross-sectional view of a target 170 according to one embodiment of the present disclosure. The target 170 includes a target substrate 171 and a target layer 172 stacked on the surface of the target substrate 171. The target 170 differs from the target 40 (FIG. 5) in that it includes multiple target layer protrusions 172a extending in the Y-axis direction. The multiple target layer protrusions 172a are arranged at a pitch of L1 in the X-axis direction and at a pitch of L2 in the Y-axis direction.

[0105] 17 shows only four target layer protrusions 172a, more target layer protrusions 172a may be provided at a pitch of L1 in the X-axis direction and at a pitch of L2 in the Y-axis direction. Also, only some of the multiple target layer protrusions 172a may be provided at a predetermined pitch from one another.

[0106] Finally, in the above description, the particle accelerator has been described as emitting a charged particle beam in a direction oblique to the surface of the inclined region inclined with respect to the first main surface and in a direction inclined with respect to the predetermined direction, but when RIs are produced on a relatively small scale, for example, the particle accelerator may emit a charged particle beam in a direction perpendicular to the first main surface.

[0107] [Radioisotope production method] Next, a radioisotope production method according to the present disclosure will be described with reference to Fig. 18. Fig. 18 is a flowchart of the radioisotope production method according to the present disclosure.

[0108] In S180, a target layer is prepared, which includes a target material and has a plurality of protrusions at least partly including an inclined region inclined with respect to a first main surface which is a physical plane or a virtual plane.

[0109] In S182, the target layer is irradiated with a charged particle beam.

[0110] According to the above configuration, the charged particle beam is emitted in an oblique direction relative to the surface of the inclined region and in a direction inclined relative to a predetermined direction, thereby making it possible to extend the range of the charged particle beam compared to when a conventional inclined target is used.

[0111] 〔summary〕 The target according to aspect 1 of the present disclosure comprises a target substrate, a target layer containing a target material and covering a portion of the surface of the target substrate, and a plurality of protrusions that protrude from at least a portion of the target layer.

[0112] According to the above configuration, the target according to the first aspect of the present disclosure can irradiate the charged particle beam onto multiple protrusions in addition to the oblique incidence of the charged particle beam employed in conventional tilted targets. As a result, the target according to the first aspect of the present disclosure can extend the range of the charged particle beam passing through the multiple protrusions. This effect can be achieved without increasing the thickness of the target layer at the multiple protrusions.

[0113] Furthermore, according to the above configuration, the target according to the first aspect of the present disclosure has a wider range for adjusting the incident angle of the charged particle beam onto the plurality of protrusions so that the range of the charged particle beam is longer than that when a conventional flat target layer is used. Therefore, the target according to the first aspect of the present disclosure also makes it possible to make the range of the charged particle beam incident on the plurality of protrusions longer than that of the conventional target, even when the charged particle beam is incident in a direction perpendicular to the main surface of the target substrate.

[0114] A target according to aspect 2 of the present disclosure is the same as that of aspect 1, except that the target layer has a first main surface that is a physical plane or a virtual plane, and each of the plurality of protrusions includes at least a portion of an inclined region that is inclined with respect to the first main surface.

[0115] According to the above configuration, the target according to the second aspect of the present disclosure can irradiate the inclined region with a charged particle beam in addition to the oblique incidence of the charged particle beam employed in conventional inclined targets. As a result, the target according to the second aspect of the present disclosure can extend the range of the charged particle beam passing through the inclined region. This effect can be achieved without increasing the thickness of the target layer in the inclined region.

[0116] A target according to a third aspect of the present disclosure is the target of the second aspect, wherein the inclined region extends parallel to a predetermined direction among the in-plane directions of the first main surface.

[0117] According to the above configuration, the target according to the third aspect of the present disclosure allows easy adjustment of the irradiation direction of the charged particle beam with respect to the inclined region, and makes it easy to lengthen the range of the charged particle beam passing through the inclined region.

[0118] A target according to a fourth aspect of the present disclosure is the target of any one of the first to third aspects, wherein the width of each of the plurality of protrusions narrows toward the tip.

[0119] According to the above configuration, the target according to the fourth aspect of the present disclosure can achieve both the advantage of ease of forming (processing) the multiple protrusions and the advantage of being able to extend the range of the charged particle beam.

[0120] A target according to a fifth aspect of the present disclosure is the target of any one of the first to fourth aspects, wherein the plurality of protrusions are provided at a predetermined pitch from one another.

[0121] According to the above configuration, the target according to the fifth aspect of the present disclosure can achieve both the advantage of ease of forming (processing) the multiple protrusions and the advantage of being able to extend the range of the charged particle beam.

[0122] A target according to a sixth aspect of the present disclosure is the target of any one of the first to fifth aspects, wherein each of the plurality of protrusions is provided in a folded plate shape.

[0123] According to the above configuration, the target according to the sixth aspect of the present disclosure can achieve both the advantage of ease of forming (processing) the multiple protrusions and the advantage of being able to extend the range of the charged particle beam. Furthermore, the target according to the sixth aspect of the present disclosure has an increased structural strength due to the adoption of a folded plate shape, and various shapes can be adopted, such as the shape and thickness of the target substrate or the shape of the cooling surface.

[0124] A target according to a seventh aspect of the present disclosure is the target of the second or third aspect, wherein the first main surface is inclined with respect to a charged particle beam emitted from a particle accelerator of the radioisotope production device.

[0125] According to the above configuration, the target according to the seventh aspect of the present disclosure can increase the range of the charged particle beam passing through the inclined region compared to when a conventional inclined target is used.

[0126] A radioisotope generation apparatus according to an eighth aspect of the present disclosure includes a particle accelerator that emits a charged particle beam, a target substrate, and a target including a target layer containing a target material and covering a portion of the surface of the target substrate, and at least a plurality of protrusions provided on the target layer.

[0127] According to the above configuration, the radioisotope generation device according to the eighth aspect of the present disclosure can irradiate the charged particle beam onto multiple protrusions in addition to the oblique incidence of the charged particle beam employed in conventional tilted targets. This allows the radioisotope generation device according to the eighth aspect of the present disclosure to extend the range of the charged particle beam passing through the multiple protrusions. This effect can be achieved without increasing the thickness of the target layer at the multiple protrusions.

[0128] A radioisotope generation device according to aspect 9 of the present disclosure is the same as that of aspect 8, except that the target layer has a first main surface which is a physical plane or a virtual plane, the plurality of protrusions extend parallel to a predetermined in-plane direction of the first main surface, and the particle accelerator emits the charged particle beam in an oblique direction relative to the surface of an inclined region provided on the plurality of protrusions which is inclined with respect to the first main surface, and in a direction inclined with respect to the predetermined direction.

[0129] According to the above configuration, the radioisotope generation apparatus according to the ninth aspect of the present disclosure can increase the range of the charged particle beam passing through the inclined region compared to the case where a conventional inclined target is used.

[0130] The target substrate according to aspect 10 of the present disclosure is a target substrate in which a target layer containing a target material is laminated on a partial region of the surface, thereby constituting a target together with the target layer, and a plurality of folded plate-shaped protrusions are provided on at least a portion of the partial region.

[0131] According to the above configuration, the target substrate according to aspect 10 of the present disclosure can have a plurality of folded plate-shaped protrusions on the target layer by electrodepositing the target layer on the plurality of folded plate-shaped protrusions.

[0132] As a result, the target substrate according to the tenth aspect of the present disclosure can irradiate the charged particle beam onto multiple folded-plate-shaped protrusions provided on the target layer, in addition to the oblique incidence of the charged particle beam employed in conventional tilted targets. Therefore, the target substrate according to the tenth aspect of the present disclosure can extend the range of the charged particle beam passing through the multiple folded-plate-shaped protrusions provided on the target layer. This effect can be achieved without increasing the thickness of the target layer.

[0133] Furthermore, the target substrate according to the tenth aspect of the present disclosure has a folded plate shape, which increases its structural strength, and various shapes can be adopted for the shape, thickness, or cooling surface of the target substrate.

[0134] A radioisotope production method according to aspect 11 of the present disclosure includes preparing a target layer containing a target material and having a plurality of protrusions, at least some of which include an inclined region inclined with respect to a first main surface, which is a physical plane or a virtual plane, and irradiating the target layer with a charged particle beam.

[0135] According to the above configuration, the range of the charged particle beam passing through the inclined region can be increased compared to when a conventional inclined target is used, without increasing the thickness of the target layer in the inclined region.

[0136] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the disclosed technical means are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the disclosed technical means. [Explanation of symbols]

[0137] 10 Radioisotope generator 40, 130, 140, 150, 160, 170 targets 41, 81, 131, 141, 151, 161, 171 Target board 42, 52, 82, 132, 142, 152, 162, 172 Target demographic 41a, 161a Target substrate protrusion 42a, 52a, 82a, 162a, 172a Target layer protrusions 42F, 52F, 162F 1st main surface 43, 53, 163 slope area 54 Valley 80 Target Model 83, 133, 143, 153 Cooling section 83F Boundary surface 131a, 141a Cooling fins 161a1 Vertical protrusion 161a2 Slanted protrusion

Claims

1. A target for use in a radioisotope generating device, comprising: A target substrate; a target layer containing a target material and covering a portion of the surface of the target substrate; A target comprising: a plurality of protrusions formed by protruding at least a portion of the target layer.

2. The target layer has a first main surface that is a physical plane or a virtual plane, The target according to claim 1 , wherein each of the plurality of protrusions includes at least a portion of an inclined region that is inclined with respect to the first main surface.

3. The target according to claim 2 , wherein the inclined region extends parallel to a predetermined direction among in-plane directions of the first main surface.

4. The target according to claim 1 or 2, wherein each of the plurality of protrusions has a width that narrows toward a tip thereof.

5. The target according to claim 1 or 2, wherein the plurality of protrusions are provided at a predetermined pitch from one another.

6. The target according to claim 1 or 2, wherein each of the plurality of protrusions is provided in a folded plate shape.

7. The target according to claim 2 or 3, wherein the first main surface is inclined with respect to the charged particle beam emitted from a particle accelerator of the radioisotope production device.

8. A radioisotope generating device for generating a radioisotope, comprising: a particle accelerator that emits a charged particle beam; A radioisotope generating device comprising: a target substrate; a target layer containing a target material and covering a portion of the surface of the target substrate; and a target including a plurality of protrusions that protrude from at least a portion of the target layer.

9. The target layer has a first main surface that is a physical plane or a virtual plane, the plurality of protrusions extend parallel to a predetermined direction in the in-plane direction of the first main surface, 9. The radioisotope generating device according to claim 8, wherein the particle accelerator emits the charged particle beam in an oblique direction with respect to a surface of an inclined region inclined with respect to the first main surface, the inclined region being provided on the plurality of protrusions, and in a direction inclined with respect to the predetermined direction.

10. A target substrate having a target layer including a target material laminated on a partial area of ​​a surface thereof, and constituting a target together with the target layer, The target substrate has a plurality of folded plate-shaped protrusions provided on at least a portion of the partial region.

11. A method for producing radioisotopes in a radioisotope production device, comprising: preparing a target layer containing a target material and having a plurality of protrusions at least partly including an inclined region inclined with respect to a first main surface which is a physical plane or a virtual plane; A method for producing radioisotopes, comprising irradiating the target layer with a charged particle beam.

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