Dual seal structure for accelerator irradiation of radium-226 targets

Abstract

The application discloses a double sealing structure of an accelerator irradiation radium-226 target, which comprises a target body, an inner end face of which is provided with a radium-226 groove, an indium wire groove and an annular welding area from inside to outside in sequence; radium-226 material is arranged in the radium-226 groove, high-purity indium wire is arranged in the indium wire groove, and aluminum foil is arranged above the indium wire; and a compression end cover is combined on the upper end of the target body and locked by a screw. When the compression end cover is pressed, the indium wire is plastically deformed to fill the groove and compress the aluminum foil, thereby forming an inside cold compression seal; the outer edge of the aluminum foil is fixed with the annular welding area by laser welding, thereby forming an outside welding seal, and a radial series double-redundancy seal is formed. The radium-226 decay produces gaseous radon, which is prone to leakage, and the application of the complementary functions of the cold compression seal and the welding seal completely solves the problem of equipment pollution and personnel radiation injury caused by the leakage of the gaseous radon, and has the advantages of high sealing reliability, adaptability to target shooting conditions and strong engineering feasibility.

Description

Technical Field

[0001] This invention belongs to the field of medical radioisotope production technology, specifically relating to a double-sealed structure for an accelerator irradiated radium-226 target. Background Technology

[0002] Actinium-225 (Ac-225) is a radioactive medical isotope with great potential in the field of targeted alpha therapy. Its preparation is based on radium-226 (Ac-225). 226 Radium-226 is produced using accelerators as the target material: either radium-226 can be bombarded with proton accelerators to directly generate actinium-225 via (p,2n) nuclear reactions; or radium-226 can be bombarded with bremsstrahlung gamma rays generated by electron accelerators to generate radium-225 via (γ,n) nuclear reactions, followed by indirect radium-225 decay. Radium-226 itself decays, and its decay product, radon-222, is a gaseous radioactive substance. Leakage of radon-222 would pose significant health hazards to operators; therefore, both preparation routes have strict requirements for the sealing performance of the radium-226 target.

[0003] In existing technologies, when preparing radioactive isotopes using accelerators, solid radioactive targets are typically placed directly within the accelerator target chamber for irradiation. While accelerator equipment and the hall housing the accelerator are equipped with radiation shielding structures, this type of shielding primarily protects against external irradiation by charged particles and gamma rays, and cannot prevent the diffusion and escape of gaseous radioactive materials. For most solid targets, their decay products are solid substances; even without additional sealing, radioactive material leakage is unlikely. Operational protection can be achieved solely through the shielding of the accelerator body and the hall.

[0004] However, radium-226 targets pose unique risks: radon, generated from the decay of radium-226, is a gaseous radioactive product with strong permeability and diffusion. During long-term irradiation in accelerators, the increased internal temperature and pressure of the target further exacerbate the leakage and diffusion of radon. This risk is prevalent in the process of preparing actinium-225 using proton and electron accelerators: radon can enter the accelerator cavity, causing radioactive contamination of the accelerator equipment and beam lines, increasing the difficulty and cost of radiation protection for subsequent maintenance and repair; furthermore, radon can penetrate conventional radiation shielding structures and diffuse into the working environment, causing internal radiation damage to operators upon inhalation, severely harming their health.

[0005] Currently, in the process of preparing actinium-225 by bombarding radium-226 targets with accelerators, there is a lack of reliable sealing and encapsulation solutions for radium targets. It is difficult to effectively contain the radon gas generated by the decay of radium-226. The equipment pollution and personnel radiation damage caused by radon gas leakage have become technical problems that urgently need to be solved in the implementation of this process. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art by proposing a sealing structure for bombarding radium-226 targets with an accelerator. The purpose is to solve the problem that existing radium-226 targets lack an effective sealing structure, and that radon gas generated by radium-226 decay is prone to leakage, causing equipment pollution and radiation damage to personnel.

[0007] To solve its technical problems, the present invention proposes the following technical solutions:

[0008] A dual-sealing structure for an accelerator irradiation radium-226 target includes a target cavity body, a high-purity metal foil, a high-purity metal wire, a clamping end cap, and a locking component. The clamping end cap has a proton injection through-hole at its center, and the locking component is used to lock and fix the clamping end cap to the target cavity body. The dual-sealing structure employs a radially tandem redundant layout of "inner indium wire cold-press sealing + outer welding sealing" to address the high risk of radon gas leakage. Along the radial direction on the upper end face of the target body, a radium-226 groove, a metal wire groove, and an annular welding area are sequentially provided from the inside to the outside. The radium-226 groove is a circular radium-226 groove located at the center of the target body, used to hold radium-226 material. The metal wire groove is an annular groove located outside the radium-226 groove, used to hold a high-purity metal wire, including a high-purity indium wire. The annular welding area is an annular area located around the outer ring of the metal wire groove, used to weld and fix the target body and the metal foil. The upper surface of the target body has, from bottom to top, the following components arranged vertically: a first layer of circular radium-226 grooves embedded below the upper surface of the target body; a second layer of annular metal wire grooves embedded below the upper surface of the target body and high-purity indium wires arranged within the annular metal wire grooves; a third layer of circular metal foil covering the high-purity indium wires, the diameter of which is larger than the outer diameter of the high-purity indium wires; a fourth layer of pressure end cap arranged on the circular metal foil, which covers the upper end of the target cavity body; a through hole is provided in the middle for proton beam irradiation, and the pressure end cap is locked and fixed to the target body by screws; when the pressure end cap is locked downward by the locking member, pressure is transmitted to the metal foil, the metal foil further compresses the high-purity indium wires, the high-purity indium wires deform under pressure, fill the internal space of the metal wire grooves, and the metal foil sinks down, achieving the first seal; the outer edge of the metal foil is fixed to the annular welding area by welding, forming the second seal.

[0009] Furthermore, the compression ratio of the high-purity indium wire is 30% to 45%, which ensures that the indium wire is fully deformed to compress the metal and fill the micro gaps, while avoiding excessive material compression and overflow from the groove; the joint of the high-purity indium wire adopts a 45° bevel butt joint, which increases the contact area at the joint and helps to ensure the continuity of the circumferential seal.

[0010] Furthermore, the high-purity metal wire is any one of indium wire, tin wire, lead wire, gold wire, or silver wire. All of the above metals have good room temperature plasticity and can undergo plastic flow under axial pressure. On the one hand, it presses the irradiation window downward to make it fit tightly against the end face of the target cavity. On the other hand, the micro-concavity and groove contour of the filler surface achieves cold-pressed airtight sealing.

[0011] Furthermore, the cross-section of the metal wire groove is rectangular, and the diameter of the high-purity indium wire is greater than the depth of the metal wire groove. The diameter of the high-purity indium wire ensures that the metal wire can be fully compressed when the target cover is locked, generating sufficient plastic deformation to compress the irradiated metal.

[0012] Furthermore, the metal is high-purity aluminum, and the thickness of the high-purity aluminum is 100μm to 1500μm; the purity of the high-purity aluminum is that the high-purity metal foil is of high-purity aluminum grade, with a purity ≥99.999%; the circumferential dimension of the high-purity aluminum is consistent with the outer diameter of the annular welding area, and the diameter of the high-purity aluminum is larger than the diameter of the high-purity indium wire; a continuous annular weld is formed along the annular welding shoulder by laser welding process, fusing and fixing the high-purity aluminum with the target cavity body to form a second independent seal on the outside.

[0013] Furthermore, the inner diameter of the through hole in the middle of the clamping end cap is the same as the diameter of the radium-226 groove;

[0014] Furthermore, the radium-226 groove is a universal accommodating structure, suitable for radium-226 powder tablets, radium-226 electroplated thin films, and radium-226 wet evaporation preparation forms.

[0015] Furthermore, the clamping force of the high-purity indium wire acts directly on the edge of the material, forming a tightly fitting sealing strip between the material and the end face of the target cavity, blocking the path for radon gas to escape from the edge of the material.

[0016] Furthermore, the pressing area of ​​the pressing end cap corresponds to the position of the metal wire groove, so that the pressing force is concentrated on the top of the high-purity indium wire.

[0017] Furthermore, after the outer edge of the high-purity aluminum ring is fixed and sealed to the annular welding area by welding, the high-purity indium wire is then deformed by being pressed down by the pressing end cap, that is, welding is performed first and then pressing is performed.

[0018] Advantages and effects of the present invention

[0019] 1. Dual-layer redundant sealing significantly solves the radon gas leakage problem and improves protective safety. This invention addresses the issue of gaseous radon gas generated by the decay of radium-226 targets, which conventional shielding structures cannot prevent from diffused and escape. It employs a radially tandem redundant layout of "inner indium wire cold-pressed seal + outer welded seal." The inner indium wire undergoes plastic deformation under pressure, filling the grooves and microscopic gaps in the aluminum foil to form the first airtight barrier; the outer welded seal fuses the aluminum foil to the target body, forming the second independent seal. The two seals are independent and serve as backups for each other. Even if one seal fails, the other can still effectively confine the radon gas, significantly reducing the risk of radon gas leakage into the accelerator cavity and working environment, effectively protecting the health of operators and the safety of the site. It is applicable to both proton accelerators and electron accelerators for the preparation of actinium-225.

[0020] 2. High sealing reliability, adaptable to irradiation conditions. In this invention, the indium wire compression ratio is controlled at 30%–45%, which can fully plastically deform and compress the aluminum foil to fill microscopic gaps, while avoiding excessive material extrusion. The indium wire joint adopts a 45° beveled butt joint to increase the contact area and ensure the continuity of the seal in the circumferential direction. At the same time, the aluminum foil uses 5N grade high-purity aluminum (thickness 100μm–1500μm, which can be optimized according to the incident particle energy), and laser welding forms a continuous annular weld, ensuring that the sealing structure maintains stable and reliable performance under long-term irradiation conditions such as proton beam irradiation, thermal effects, and mechanical vibration, and will not fail due to environmental changes.

[0021] 3. The structure is compact and rationally laid out, with strong engineering feasibility. This invention features a radium-226 groove, an indium wire groove, and an annular welding area arranged radially along the upper surface of the target body. Each component is layered and clearly positioned. During assembly, the outer ring is welded first, followed by the inner ring, resulting in a rational process sequence that facilitates engineering implementation. A through-hole of the same diameter as the radium-226 groove is opened in the center of the clamping end cap. This ensures smooth irradiation of the target by the particle beam and concentrates the clamping force on the indium wire groove area, improving sealing efficiency. Furthermore, the overall structure does not increase the volume of the target, making it suitable for the limited space of an accelerator target chamber.

[0022] 4. Material selection balances sealing performance and nuclear purity requirements. Indium wire and its alternatives (tin, lead, gold, silver) possess excellent room-temperature plasticity, allowing them to flow and fill microscopic irregularities under axial pressure, achieving cold-pressed airtight seals. Furthermore, these materials exhibit short half-lives or low radioactive hazards from their activation products under low- to medium-energy particle irradiation, facilitating subsequent target processing. High-purity aluminum foil prevents the introduction of impurities that could affect the quality of actinium-225 products. Its ductility, combined with the deformation of the indium wire, ensures a tight first seal, comprehensively improving the overall performance of the sealing system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the double-sealing structure of the present invention;

[0024] Figure 2 This is a schematic diagram of the double-sealing structure of the present invention;

[0025] Figure 3 This is an exploded view of the double-sealing structure of the present invention. Detailed Implementation Innovation of this invention

[0026] 1. A dual-sealing architecture for radon gas protection of radium-226 targets is proposed for the first time. The problem solved: It fills the technological gap in the process of preparing actinium-225 using accelerator bombardment of radium-226 targets, lacking an effective sealing and encapsulation solution for the gaseous radon gas decaying from radium-226. It innovatively combines "inner indium wire cold-press sealing" with "outer welding sealing," employing a radially tandem redundant layout. From the inside out, radium-226 target material grooves, metal wire grooves, and an annular welding area are sequentially arranged on the upper surface of the target body. This provides a dedicated gaseous product sealing solution for highly radioactive radium targets, reliably sealing the previously uncontainable gaseous radon gas inside the target with a dual barrier. It is applicable to both proton accelerator direct preparation of actinium-225 and electron accelerator indirect preparation of actinium-225.

[0027] 2. The two sealing layers complement each other, providing redundancy. This addresses the problem that radon gas leakage can occur if a single sealing method fails, causing equipment contamination and personnel injury. The inner indium wire undergoes plastic deformation under pressure from the end cap, filling the grooves and microscopic gaps in the aluminum foil to form the first cold-pressed seal. The outer aluminum foil edge is welded to the target body, forming the second independent seal. The two seals are independent and undependent. Even if one seal experiences partial failure due to irradiation, thermal stress, or mechanical vibration, the other seal can still independently maintain airtightness, significantly improving the fault tolerance and long-term reliability of the sealing system.

[0028] 3. Precise optimization of sealing parameters and process sequence. Problems solved: Insufficient indium wire compression leads to poor sealing, while excessive compression may cause extrusion of grooves and failure; improper welding and tightening sequence also affects sealing quality. The indium wire compression ratio is limited to 30%–45%, and the indium wire joints are butt-jointed at a 45° angle to increase the contact area; the aluminum foil thickness is selected from 100μm to 1500μm (which can be optimized according to the incident particle energy), with a purity of 5N grade (≥99.999%); the process employs a specific assembly sequence of welding the outer ring first, then tightening the inner ring of indium wire. This ensures that the indium wire is fully deformed to fill the microscopic gaps without overflowing, the weld is continuous and dense, the aluminum foil is firmly fused to the target, and the sealing performance is stable and reliable under particle irradiation and thermal cycling conditions.

[0029] 4. The structure is highly compatible with the target space, ensuring high engineering feasibility. The problem solved: Accelerator target chamber space is limited, and the sealing structure must achieve effective encapsulation without altering the basic shape of the target and irradiation conditions. The target end face is layered with functional areas (radium-226 groove → metal wire groove → welding area). A through-hole is opened in the center of the clamping end cap, with the diameter matching the inner diameter of the radium-226 groove, and the clamping area is concentrated at the location of the indium wire groove. The indium wire material can be expanded to include metals with room-temperature plasticity such as tin, lead, gold, and silver. The particle beam can irradiate the target material without obstruction, and the clamping force is precisely transmitted to the sealing area. The structure is compact, does not increase the extra volume of the target, facilitates engineering assembly and mass production, and the material selection takes into account both nuclear purity and the convenience of subsequent waste target disposal. Design principle of the invention

[0030] I. The Special Nature of the Problem: Gaseous Radon is the Core Contradiction. The radium-226 target targeted in this invention differs from most solid radioactive targets in that its decay product, radon-222, is a gaseous radioactive substance. In conventional accelerator isotope preparation processes, the decay products of most targets are solid. Even without additional sealing, the decay products are confined within the target matrix. The accelerator's vacuum cavity and hall shielding structure effectively prevent radioactive material leakage, meeting operational protection requirements. However, gases differ from solids. Radon possesses extremely strong migration and penetration capabilities, capable of penetrating microscopic gaps that conventional radiation shielding structures cannot cover, escaping along the assembly gaps between the target and the target cavity. Once leaked, radon will contaminate the accelerator's high-frequency cavity, vacuum pipelines, and other precision components, significantly increasing the difficulty and cost of radiation protection for equipment maintenance. Furthermore, radon can penetrate conventional radiation shielding walls, diffuse into the working environment, and cause severe internal radiation damage if inhaled by personnel.

[0031] This presents a fundamental challenge: solids can be "enclosed," but gases must be "sealed off." For gases, external shielding is insufficient; absolute airtightness must be achieved at the sealing interface of the target itself. In other words, the target itself must possess one or more reliable airtight barriers to cut off all escape paths of radon gas at the source. This problem is prevalent in both the direct proton accelerator preparation of actinium-225 and the indirect electron accelerator preparation of actinium-225.

[0032] II. Limitations of Single Sealing Methods. For sealing gaseous media, two common technical approaches exist in the current industrial field: Cold-press sealing (e.g., indium, lead, and other soft metal gaskets): This relies on the plastic deformation of the soft metal under axial pressure to fill the microscopic irregularities of the sealing interface, forming a physical contact airtight barrier. Its advantages include simple operation, no need for high temperatures, and no damage to adjacent components; however, its disadvantages include the potential for stress relaxation or creep in the soft metal after long-term exposure to radiation, thermal cycling, and mechanical vibration, leading to a decrease in the sealing specific pressure and a potential risk of long-term failure. Welded sealing (e.g., laser welding, electron beam welding): This involves fusing the base material with the cover material to form a metallurgical bond, resulting in a permanent seal with strong resistance to radiation and aging. Its disadvantages include the potential thermal impact of welding heat input on the target material or sealing interface, and the inability to adjust the weld once formed; if there are pre-weld assembly deviations or post-weld defects, they are difficult to remedy. It is evident that both sealing methods have their advantages and disadvantages, and relying solely on either one is insufficient to provide long-term, foolproof sealing protection for gaseous radon under the harsh conditions of strong radiation, high heat, and vibration during accelerator target firing.

[0033] III. Design Logic of the Combined Scheme: Functional Complementarity Rather Than Simple Superposition. The core design principle of this invention lies in combining cold-press sealing and welded sealing in a functionally complementary manner, supported by strict material and dimensional parameters, to achieve a synergistic effect of 1+1>2. Specifically:

[0034] The first step—indium wire cold-press sealing—solves the problem of "microscopic leakage paths." An annular metal wire groove is created on the end face of the target, containing a high-purity indium wire, which is then covered with a high-purity aluminum foil. Axial pressure is applied by a pressing end cap. The indium wire undergoes sufficient plastic deformation at a compression ratio of 30%–45%, pressing the aluminum foil downwards to ensure a tight fit with the target cavity end face. Simultaneously, it flows and fills the microscopic irregularities and groove contours on the aluminum foil surface, forming a continuous, dense contact seal. This seal rapidly establishes an initial airtight barrier, blocking the microscopic channels through which radon gas escapes from the edges of the aluminum foil, thus fulfilling the primary sealing function.

[0035] The second layer—the welded seal—addresses the issue of "long-term reliability." In the annular welding area outside the metal wire groove, the outer edge of the aluminum foil is fused and fixed to the target body, forming a continuous metallurgically bonded sealing band. This seal is pressure-independent and unaffected by material creep relaxation, maintaining stable airtightness under irradiation and thermal cycling. Its function is to provide a permanent backup barrier for the sealing system; even if the inner indium wire experiences stress relaxation due to long-term operation, the outer weld can still independently seal against radon gas. The two seals employ a radially tandem redundant layout—when gas escapes from the central radium-226 groove, it must successively overcome both the indium wire sealing band and the welded sealing band. They serve as backups for each other and do not interfere with each other; if one fails, the other can still function independently, achieving high fault tolerance in the sealing system.

[0036] IV. Precise matching of materials and dimensions is a prerequisite for the combination to be effective. It is particularly important to note that the combination of the two sealing methods is not a simple patchwork; precise matching of material properties and dimensional parameters is the technical prerequisite for the synergistic effect of the above combination: Matching the indium wire diameter and the groove size: The indium wire diameter must be greater than the groove depth to ensure that the indium wire is fully compressed when the end cap is tightened, generating sufficient plastic deformation to compress the aluminum foil and fill the gap. A compression ratio of 30%–45% ensures sufficient deformation while preventing excessive material extrusion into the groove, which could lead to seal failure. A 45° beveled butt joint of the indium wire: This increases the contact area of ​​the joint, avoids the formation of a through-flow leakage channel in the circumferential direction, and ensures the continuity of the sealing strip at the joint. High purity and thickness range of aluminum foil: 5N grade (≥99.999%) high-purity aluminum is selected to avoid introducing impurities that could affect the nuclear purity of Actinium-225. The thickness ranges from 100μm to 1500μm (optimizable based on incident particle energy), ensuring sufficient mechanical strength to withstand clamping force and irradiation thermal stress, while also allowing for appropriate shrinkage with the deformation of the indium wire, achieving a tight fit. The "weld-then-press" process sequence: Laser welding of the outer ring is completed first, followed by pressing down the inner ring of indium wire with the clamping end cap. This sequence ensures that the welding heat input does not affect the sealing state of the already pressed indium wire, and the post-weld clamping of the indium wire compensates for any minor stress deformation that may exist in the weld. These two processes complement each other in terms of time.

[0037] V. Conclusion: In summary, the design principle of this invention can be summarized as follows: Addressing the unique challenge of gaseous radon gas generated by radium-226 decay, which cannot be protected by external shielding, this invention abandons the single sealing approach and adopts a complementary combination scheme of "cold-press sealing for immediate barrier establishment + welded sealing for long-term independent backup." Supported by systematic optimization of key parameters such as indium wire compression ratio, joint type, aluminum foil purity and thickness, and assembly sequence, the two seals are spatially redundant, functionally complementary, and process-independent, ultimately achieving absolute sealing of gaseous radon gas. This fundamentally solves the unique technical challenge of gaseous radioactive leakage in the accelerator process for preparing actinium-225, distinguishing it from other solid target preparation processes. The essence of this design principle is the purposeful and precisely parameter-matched combination and adaptation of two known sealing methods to the specific physical characteristics of gaseous radon gas (small molecules, strong permeability, unconstrained by conventional shielding), thus forming a new, non-obvious technical solution, a typical example of a combined invention.

[0038] Based on the above principles, this invention designs a double-sealed structure for an accelerator irradiation radium-226 target, such as... Figure 1 , Figure 2 , Figure 3As shown, the target body includes a target cavity body, a high-purity metal wire, a high-purity metal foil, a clamping end cap, and a locking component. The clamping end cap has a proton injection through-hole at its center, and the locking component is used to lock and fix the clamping end cap to the target cavity body. The key feature is that the dual-sealing structure adopts a radially tandem redundant layout of "inner indium wire cold-press sealing + outer welding sealing" to solve the problem of high radon gas leakage risk. Along the radial direction on the upper end face of the target body, a radium-226 groove, a metal wire groove, and an annular welding area are sequentially provided from the inside to the outside. The radium-226 groove is a circular radium-226 groove located at the center of the target body, used to place radium-226 material. The metal wire groove is an annular groove located outside the radium-226 groove, used to place a high-purity metal wire, including a high-purity indium wire. The annular welding area is an annular area located on the outer ring of the metal wire groove, used to weld and fix the target body and the metal foil. The upper end face of the target body... Along the vertical direction, from bottom to top, are arranged the following: a first layer of circular radium-226 grooves embedded below the upper surface of the target body; a second layer of annular metal wire grooves embedded below the upper surface of the target body and high-purity indium wires arranged within the annular metal wire grooves; a third layer of circular metal foil covering the high-purity indium wires, the diameter of which is larger than the outer diameter of the high-purity indium wires; a fourth layer of clamping end cap arranged on the circular metal foil, which is fitted onto the upper end of the target cavity body; a through hole is provided in the middle for proton beam irradiation, and the clamping end cap is locked and fixed to the target body by screws; when the clamping end cap is locked downward by the locking member, the pressure is transmitted to the metal foil, the metal foil further compresses the high-purity indium wires, the high-purity indium wires deform under pressure, fill the internal space of the metal wire grooves, and the metal foil sinks down accordingly, achieving the first seal; the outer edge of the metal foil is fixed to the annular welding area by welding, forming the second seal.

[0039] Furthermore, the compression ratio of the high-purity indium wire is 30% to 45%, which ensures that the indium wire is fully deformed to compress the metal and fill the micro gaps, while avoiding excessive material compression and overflow from the groove; the joint of the high-purity indium wire adopts a 45° bevel butt joint, which increases the contact area at the joint and helps to ensure the continuity of the circumferential seal.

[0040] Furthermore, the high-purity metal wire is any one of indium wire, tin wire, lead wire, gold wire, or silver wire. All of the above metals have good room temperature plasticity and can undergo plastic flow under axial pressure. On the one hand, it presses the irradiation window downward to make it fit tightly against the end face of the target cavity. On the other hand, the micro-concavity and groove contour of the filler surface achieves cold-pressed airtight sealing.

[0041] Furthermore, the cross-section of the metal wire groove is rectangular, and the diameter of the high-purity indium wire is greater than the depth of the metal wire groove. The diameter of the high-purity indium wire ensures that the metal wire can be fully compressed when the target cover is locked, generating sufficient plastic deformation to compress the irradiated metal.

[0042] Furthermore, the high-purity metal foil is high-purity aluminum, and the thickness of the high-purity aluminum is 100μm to 1500μm; the purity of the high-purity aluminum is 5N grade, with a purity ≥99.999%; the circumferential dimension of the high-purity aluminum is consistent with the outer diameter of the annular welding area, and the diameter of the high-purity aluminum is larger than the diameter of the high-purity indium wire; a continuous annular weld is formed along the annular welding shoulder by laser welding process, fusing and fixing the high-purity aluminum with the target cavity body to form a second independent seal on the outside.

[0043] Furthermore, the inner diameter of the through hole in the middle of the clamping end cap is the same as the diameter of the radium-226 groove;

[0044] Furthermore, the radium-226 groove is a universal accommodating structure, suitable for radium-226 powder tablets, radium-226 electroplated thin films, and radium-226 wet evaporation preparation forms.

[0045] Furthermore, the clamping force of the high-purity indium wire acts directly on the edge of the material, forming a tightly fitting sealing strip between the material and the end face of the target cavity, blocking the path for radon gas to escape from the edge of the material.

[0046] Furthermore, the pressing area of ​​the pressing end cap corresponds to the position of the metal wire groove, so that the pressing force is concentrated on the top of the high-purity indium wire.

[0047] Furthermore, after the outer edge of the high-purity aluminum ring is fixed and sealed to the annular welding area by welding, the high-purity indium wire is then deformed by being pressed down by the pressing end cap, that is, welding is performed first and then pressing is performed.

[0048] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A double-sealed structure for an accelerator irradiation radium-226 target, comprising a target cavity body, a high-purity metal foil, a high-purity metal wire, a clamping end cap, and a locking component, wherein the clamping end cap has a proton injection through-hole at its center, and the locking component is used to lock and fix the clamping end cap to the target cavity body; characterized in that, This dual-sealing structure employs a radially tandem redundant layout of "inner indium wire cold-press sealing + outer welding sealing" to address the high risk of radon gas leakage. Along the radial direction on the upper surface of the target body, from the inside out, are sequentially arranged a radium-226 groove, a metal wire groove, and an annular welding area. The radium-226 groove is a circular radium-226 groove located at the center of the target body, used to hold radium-226 material. The metal wire groove is an annular groove located outside the radium-226 groove, used to hold a high-purity metal wire, including high-purity indium wire. The annular welding area is an annular area located around the outer ring of the metal wire groove, used to weld and fix the target body and the metal foil. Along the vertical direction on the upper surface of the target body, from bottom to top, are sequentially arranged a first layer of circular radium-226 embedded below the upper surface of the target body. 26 grooves; a second layer of annular metal wire grooves embedded below the upper end face of the target body and high-purity indium wires arranged within the annular metal wire grooves; a third layer of circular metal foil covering the high-purity indium wires, the diameter of which is larger than the outer diameter of the high-purity indium wires; a fourth layer of clamping end caps arranged on the circular metal foils, which are fitted onto the upper end of the target cavity body; a through hole is provided in the middle for proton beam irradiation, and the clamping end caps are locked and fixed to the target body by screws; when the clamping end caps are locked downwards by the locking member, pressure is transmitted to the metal, the metal foil further compresses the high-purity indium wires, the high-purity indium wires deform under pressure, fill the internal space of the metal wire grooves, and the metal foil sinks down accordingly, achieving the first seal; the outer edge of the metal foil is fixed to the annular welding area by welding, forming the second seal.

2. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 1, characterized in that: The high-purity indium wire has a compression ratio of 30% to 45%, which ensures that the indium wire is fully deformed to compress the metal and fill the micro gaps, while avoiding excessive material compression and overflow from the groove. The joint of the high-purity indium wire adopts a 45° bevel joint, which increases the contact area at the joint and helps to ensure the continuity of the circumferential seal.

3. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 1, characterized in that: The high-purity metal wire is any one of indium wire, tin wire, lead wire, gold wire, or silver wire. All of the above metals have good room temperature plasticity and can undergo plastic flow under axial pressure. On the one hand, it presses the irradiation window downward to make it fit tightly against the end face of the target cavity. On the other hand, the micro-concavity and groove contour of the filler surface achieves cold-pressed airtight sealing.

4. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 1, characterized in that: The cross-section of the metal wire groove is rectangular, and the diameter of the high-purity indium wire is greater than the depth of the metal wire groove. The diameter of the high-purity indium wire ensures that the metal wire can be fully compressed when the target cover is locked, generating sufficient plastic deformation to compress the irradiated metal.

5. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 1, characterized in that: The high-purity metal foil is high-purity aluminum with a thickness of 100μm to 1500μm; the purity of the high-purity aluminum is 5N grade, with a purity ≥99.999%; the circumferential dimension of the high-purity aluminum is consistent with the outer diameter of the annular welding area, and the diameter of the high-purity aluminum is larger than the diameter of the high-purity indium wire; a continuous annular weld is formed along the annular welding shoulder by laser welding process, fusing and fixing the high-purity aluminum to the target cavity body to form a second independent seal on the outside.

6. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 1, characterized in that: The inner diameter of the through hole in the middle of the clamping end cap is the same as the diameter of the radium-226 groove.

7. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 1, characterized in that: The radium-226 groove is a universal accommodating structure, suitable for radium-226 powder tablets, radium-226 electroplated thin films, and radium-226 wet evaporation preparation.

8. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 1, characterized in that: The clamping force of the high-purity indium wire acts directly on the edge of the material, forming a tight-fitting sealing strip between the material and the end face of the target cavity, blocking the path for radon gas to escape from the edge of the material.

9. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 1, characterized in that: The clamping area of ​​the clamping end cap corresponds to the position of the metal wire groove, so that the clamping force is concentrated on the top of the high-purity indium wire.

10. The double-sealed structure of an accelerator irradiation radium-226 target according to claim 5, characterized in that: After the outer edge of the high-purity aluminum ring is fixed and sealed to the annular welding area by welding, the high-purity indium wire is then deformed by being pressed down by the pressing end cap, that is, welding is done first and then pressing.

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