A composite breeding target system for BNCT

Abstract

The application relates to the technical field of composite targets, and discloses a composite breeding target system for BNCT, which comprises a Be-Li composite target and a primary breeding system, the primary breeding system is located at the back of the Be-Li composite target, and the two form a composite target structure, wherein the primary breeding system comprises a uranium layer and an aluminum substrate layer, the uranium layer is attached to the aluminum substrate layer, the output efficiency and quality of neutrons can be effectively improved through optimization of a neutron generation and breeding process, thereby providing a more efficient neutron source for BNCT, the composite breeding target system for BNCT can improve the neutron yield after proton targeting, and can also make the neutron energy generated by the Li layer consistent with the neutron energy generated by the Be layer.

Description

Technical Field

[0001] This invention relates to the field of composite target technology, and in particular to a composite proliferation target system for BNCT. Background Technology

[0002] Cancer poses a serious threat to human health and is one of the most important issues in the world's medical field today. Radiotherapy, which uses the energy released by ionizing radiation to kill cancer cells, has become one of the effective means of treating cancer. Boron neutron capture therapy (BNCT) is a binary, targeted, and cellular-level precise radiotherapy method. Its principle is that boron-containing drugs specifically accumulate at the tumor site, and neutrons trigger the boron-10 nuclear fission reaction, releasing high-energy particles to selectively destroy cancer cells. Compared with traditional radiotherapy, BNCT has the advantage of cellular-level localized killing, and is especially suitable for invasive and recurrent tumors.

[0003] Neutron sources are the core of treatment, and the current mainstream approach is to shift from nuclear reactors to accelerators (AB-BNCT). According to the latest IAEA report, the hyperthermic neutron flux rate (0.5 eV~40 keV) for treatment needs to exceed 5 × 10⁸ cm⁻¹. -2 ·s -2 Achieving AB-BNCT is quite challenging; therefore, it is necessary to increase the neutron yield after proton bombardment to improve the hyperthermal neutron fluence at the exit beam. The most commonly used target material is Li or... 9 Be target, 7 Li has an extremely high neutron resonance cross section (580 mb) at 2.25 MeV. 9 For Be targets, the neutron yield increases continuously with the energy of the incident protons. 9 For Be-targeted targets, the incident proton energy decreases with increasing depth. When the proton energy is 2.5 MeV, the neutron yield per unit proton flux is much lower than at that energy. 7 Li yield. Currently common composite target systems include Be-Li composite targets and beam shaping devices for BNCT, because protons from... 9 The energy decreases continuously from the Be target to the Li target. If it is only a Be-Li composite target, the energy comes from... 9 The neutron energy from the Be target is much higher than that from the Li target. After both groups of neutrons pass through the beam shaping device (BSA) of BNCT, the neutrons from the Li target are absorbed, resulting in almost no improvement in the neutron fluence of the final exit window. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a composite proliferation target system for BNCT, which can increase the neutron yield after proton targeting, while simultaneously making the neutron energy generated by the Li layer and the neutron energy generated by the Be layer more consistent.

[0005] This invention provides a composite multiplication target system for BNCT, comprising: a Be-Li composite target and a primary multiplication system, wherein the primary multiplication system is located directly behind the Be-Li composite target, and the two form a composite target structure. The primary multiplication system includes a uranium layer and an aluminum substrate layer, with the uranium layer attached to the aluminum substrate layer. By optimizing the neutron generation and multiplication process, the output efficiency and quality of neutrons can be effectively improved, thereby providing a more efficient neutron source for BNCT.

[0006] Optionally, the uranium layer and the aluminum substrate layer form a uranium breeding layer, and a primary breeding system includes multiple uranium breeding layers.

[0007] Optionally, there are gaps between the multiple uranium breeding layers.

[0008] Optionally, it also includes a secondary propagation system, which includes... 9 Be ball, 9 The Be sphere is wrapped around the composite target structure. The design of the secondary multiplication system allows the system to adapt to proton beams and neutron sources of different energies, giving it high flexibility and applicability.

[0009] Optional, 9 The diameter of the Be sphere is obtained by simulating the incident proton energy using a Monte Carlo algorithm.

[0010] Optionally, the secondary proliferation system also includes a package containing 9 The Pb layer surrounding the Be sphere.

[0011] Optionally, the thickness of the Pb layer is obtained by simulating the incident proton energy using a Monte Carlo algorithm.

[0012] Optionally, the Be-Li composite target is fixed to the surfaces of a copper substrate and a vanadium substrate by coating, with the copper substrate in close contact with the Be-Li composite target.

[0013] Optionally, in the Be-Li composite target, the Be layer is located directly in front of the Li layer.

[0014] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art:

[0015] This invention provides a composite breeding target system for BNCT that fully combines the advantageous energy regions of Be and Li targets with proton reactions to increase neutron yield. At higher proton energies, the Be-proton reaction can produce a high neutron yield. As the proton penetration depth increases, the proton energy decreases, allowing the protons to enter the Li target. Utilizing the resonance cross-section of Li, a larger neutron yield is generated. A breeding system is placed directly behind the Be-Li composite target so that more protons can generate neutrons that undergo fission reactions with uranium, thus increasing the neutron yield. Since the reaction between protons and Be typically requires relatively high proton energies, [further details needed]. According to the law of conservation of energy, the released neutron energy is relatively high, requiring a thicker BSA to slow it down to the hyperthermal neutron energy region suitable for therapeutic use. However, the neutron energy released by the reaction of protons with Li near the resonance energy region is relatively low. After entering the BSA, it will be absorbed, greatly reducing the effect of the composite target in increasing yield. In contrast, the reaction of uranium with low-energy neutrons in a primary breeding system has a high fission reaction cross section, releasing neutrons with higher energy. After slowing down and shaping by the BSA, a large number of neutrons will still be retained for therapeutic use. Therefore, a primary breeding system can increase neutron yield while making the neutron energy produced by the Li layer more consistent with that produced by the Be layer. Attached Figure Description

[0016] Figure 1 A flowchart of a composite proliferation target system for BNCT provided in an embodiment of the present invention;

[0017] Figure 2 Provided for embodiments of the present invention 9 The (N, 2N) reaction cross section of Be;

[0018] Figure 3 Provided for embodiments of the present invention 206 The (N, 2N) reaction cross section of Pb;

[0019] Figure 4 Provided for embodiments of the present invention 207 The (N, 2N) reaction cross section of Pb;

[0020] Figure 5 Provided for embodiments of the present invention 208 The (N, 2N) reaction cross section of Pb;

[0021] Figure 6 This is a schematic diagram of the composite target structure provided in an embodiment of the present invention;

[0022] Figure 7 This is a schematic diagram of a composite proliferation target system for BNCT provided in an embodiment of the present invention;

[0023] Figure 8The proton flux of a composite proliferation target system (A) for BNCT provided in this embodiment of the invention is compared with that of a non-composite target system (B) and a pure Be target system without proliferation, wherein the proton energy is 14 MeV.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. Be-Li composite target; 10. Be layer; 11. Li layer; 2. Primary breeding system; 20. Uranium layer; 21. Aluminum substrate layer; 3. Secondary breeding system; 30. 9 Be sphere; 31, Pb layer; 4, copper substrate; 5, vanadium substrate. Detailed Implementation

[0026] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0027] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the technical solution of this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0028] Currently common composite target systems include Be-Li composite targets and beam shaping devices for BNCT, because protons from... 9 The energy decreases continuously from the Be target to the Li target. If it is only a Be-Li composite target, the energy comes from... 9 The neutron energy from the Be target is much higher than that from the Li target. After both groups of neutrons pass through the beam shaping device (BSA) of BNCT, the neutrons from the Li target are absorbed, resulting in almost no improvement in the neutron fluence of the final exit window.

[0029] Therefore, embodiments of the present invention provide a composite proliferation target system for BNCT, which can increase the neutron yield after proton targeting, while making the neutron energy generated by the Li layer and the neutron energy generated by the Be layer more consistent.

[0030] At least one embodiment of the present invention provides a composite proliferation target system for BNCT, comprising: a Be-Li composite target and a primary proliferation system, wherein the primary proliferation system is located directly behind the Be-Li composite target, and the two form a composite target structure, wherein the primary proliferation system comprises a uranium layer and an aluminum substrate layer, and the uranium layer is attached to the aluminum substrate layer.

[0031] The composite proliferation target system for BNCT provided in the above embodiments of the present invention fully combines the advantageous energy regions of the Be target and Li target with proton reactions to increase neutron yield. Through a single proliferation system, the neutron yield can be increased while making the neutron energy produced by the Li layer and the neutron energy produced by the Be layer more consistent.

[0032] The present invention will be described below through several specific embodiments. To keep the following description of the embodiments clear and concise, detailed descriptions of known functions and components may be omitted. When any component of an embodiment of the present invention appears in more than one drawing, the component may be represented by the same reference numerals in each drawing.

[0033] refer to Figure 1 , Figure 6 and Figure 7 , Figure 1 A flowchart of a composite proliferation target system for BNCT provided in an embodiment of the present invention. Figure 6 This is a schematic diagram of the composite target structure provided in an embodiment of the present invention. Figure 7 A schematic diagram of a composite proliferation target system for BNCT provided in an embodiment of the present invention is shown below. Figure 1 , Figure 6 and Figure 7 As shown, this embodiment of the invention provides a composite breeding target system for BNCT, including: a Be-Li composite target 1 and a primary breeding system 2. The Be-Li composite target 1 is one of the core components of the system, and its main function is to generate neutrons through the nuclear reaction of protons with the target material. The Be-Li composite target 1 is usually composed of beryllium (Be) and lithium (Li). These two materials have excellent performance in neutron production. Beryllium has a high neutron yield at higher proton energies, while lithium has a high neutron resonance cross section and a high neutron yield at a proton energy of about 2.25 MeV. By using these two materials in combination, the neutron production efficiency can be significantly improved. The primary breeding system 2 is located directly behind the Be-Li composite target 1, and its main function is to further breed and optimize the neutrons generated by the Be-Li composite target 1. The two form a composite target structure. The primary breeding system 2 includes a uranium layer 20 and an aluminum substrate layer 21. The uranium layer 20 is attached to the aluminum substrate layer 21. The uranium layer 20 is a key material for breeding neutrons, and is usually made of enriched uranium (such as...). 235U) As the breeding material, the uranium layer 20 generates more secondary neutrons through the fission reaction between neutrons and uranium nuclei, thereby achieving neutron breeding. The thickness and distribution of the uranium layer 20 are carefully designed to maximize the neutron breeding efficiency while avoiding excessive neutron loss. The aluminum substrate layer 21 serves as the supporting structure for the uranium layer 20, possessing not only good mechanical strength but also effectively reducing neutron absorption. The design of the aluminum substrate layer 21 takes into account thermal conduction and heat dissipation to ensure the stability of the system during high-power operation.

[0034] Uranium (especially) 235 Uranium (U) has a high fission reaction cross section, especially under low-energy neutron incidence. Uranium can release more secondary neutrons through fission reactions. These secondary neutrons have higher energies, and after moderation, a significant number can still be retained for therapeutic use. Therefore, the introduction of a uranium layer not only increases neutron yield but also makes the neutron energies produced by the Li target more consistent with those produced by the Be target, thus optimizing the neutron energy distribution. Neutrons produced by the Li target have lower energies and are easily absorbed after entering the moderation layer, leading to a decrease in neutron yield. By introducing a primary breeding system, the uranium layer can undergo fission reactions with low-energy neutrons, releasing higher-energy secondary neutrons. After moderation, a significant number of these secondary neutrons can still be retained for therapeutic use, thereby improving the overall efficiency of the system.

[0035] This invention provides a composite breeding target system for BNCT that fully combines the advantageous energy regions of Be and Li targets with proton reactions to increase neutron yield. At higher proton energies, the Be-proton reaction can produce a high neutron yield. As the proton penetration depth increases, the proton energy decreases, allowing the protons to enter the Li target. Utilizing the resonance cross-section of Li, a larger neutron yield is generated. A breeding system is placed directly behind the Be-Li composite target so that more protons can generate neutrons that undergo fission reactions with uranium, thus increasing the neutron yield. Since the reaction between protons and Be typically requires relatively high proton energies, [further details needed]. According to the law of conservation of energy, the released neutron energy is relatively high, requiring a thicker BSA to slow it down to the hyperthermal neutron energy region suitable for therapeutic use. However, the neutron energy released by the reaction of protons with Li near the resonance energy region is relatively low. After entering the BSA, it will be absorbed, greatly reducing the effect of the composite target in increasing yield. In contrast, the reaction of uranium with low-energy neutrons in a primary breeding system has a high fission reaction cross section, releasing neutrons with higher energy. After slowing down and shaping by the BSA, a large number of neutrons will still be retained for therapeutic use. Therefore, a primary breeding system can increase neutron yield while making the neutron energy produced by the Li layer more consistent with that produced by the Be layer.

[0036] Because uranium is attached to the aluminum substrate, the thicker the uranium layer... 235The higher the U concentration, the better the breeding effect. However, due to the high density of uranium, there are some problems if a thicker uranium layer is considered, such as the high mechanical requirements of the aluminum substrate and the uranium layer being prone to dripping.

[0037] Therefore, in the composite breeding target system for BNCT provided in this embodiment of the invention, the uranium layer 20 and the aluminum substrate layer 21 form a uranium breeding layer. The primary breeding system 2 includes multiple uranium breeding layers. This means that the thickness of the uranium layer 20 in each uranium breeding layer does not need to be too thick, thus eliminating the need for excessively high mechanical properties of the aluminum substrate and preventing uranium layer dripping. The primary breeding system 2 includes multiple uranium breeding layers. This design further improves the uniformity of neutron yield and energy distribution. The design of multiple uranium breeding layers has the following characteristics and advantages: multiple uranium breeding layers can fully utilize the energy of incident neutrons, producing more secondary neutrons through multiple fission reactions; each uranium breeding layer can breed the incident neutrons, from... This significantly improves the overall neutron yield of the system; the multi-layer uranium breeder layer, through layer-by-layer fission reaction, makes the energy distribution of neutrons more uniform, and each uranium breeder layer can regulate the neutron energy, so that the final output neutron energy is more suitable for the needs of BNCT treatment; the design of the multi-layer uranium breeder layer enables the system to achieve efficient neutron breeding in a limited space. This compact design not only reduces the size of the system, but also reduces the complexity and cost of the equipment; the aluminum substrate layer 21 in the multi-layer uranium breeder layer not only provides structural support, but also effectively conducts and dissipates heat. This design ensures the thermal stability of the system when operating at high power and avoids performance degradation or equipment damage due to overheating.

[0038] Working principle of multilayer uranium breeder layers: Neutron incidence and fission reaction: Incident neutrons first enter the first layer of uranium breeder layer and undergo fission reaction with uranium layer 20 to produce secondary neutrons. These secondary neutrons then enter the next layer of uranium breeder layer and continue to undergo fission reaction, thereby producing more neutrons; Layer-by-layer regulation of neutron energy: Each layer of uranium breeder layer can regulate the neutron energy. Through layer-by-layer fission reaction, the energy distribution of neutrons gradually becomes more uniform, so that the final output neutron energy is more suitable for the needs of BNCT treatment; Layer-by-layer increase in neutron yield: Multilayer uranium breeder layers significantly increase neutron yield through layer-by-layer fission reaction. Each layer of uranium breeder layer can breed incident neutrons, thereby greatly increasing the overall neutron yield of the system.

[0039] Refer again Figure 6 , Figure 6 The diagram shows a case with three uranium breeding layers. There are gaps between the multiple uranium breeding layers, and the interlayer spacing of the multiple uranium breeding layers is as small as possible to ensure that more neutrons from the target interact with uranium and are multiplied.

[0040] This invention provides a composite proliferation target system for BNCT, which, in addition to including a Be-Li composite target 1 and a primary proliferation system 2, also includes a secondary proliferation system 3. The secondary proliferation system 3 includes... 9 Be ball 30, 9 Encasing the composite target structure with Be spheres 30 further optimizes the neutron slowing and multiplication processes, thereby significantly improving the uniformity of the system's neutron yield and energy distribution. 9 The design of Be Sphere 30 fully utilizes the (N, 2N) reaction characteristics of beryllium (Be) at neutron energies above 3 MeV, as well as its advantages as a hyperthermal neutron moderator. It can moderate high-energy neutrons to the hyperthermal neutron energy range suitable for BNCT therapy (typically between 0.5 eV and 10 keV), thereby improving neutron utilization efficiency. The secondary multiplication system 3 can increase neutron yield through the (N, 2N) reaction and neutron reflection. 9 Be-ball 30 significantly improved the system's neutron yield; 9 The moderation function of Be Sphere 30 makes the energy distribution of neutrons more uniform, thus making it more suitable for the needs of BNCT therapy; 9 The low neutron absorption cross section and neutron reflection function of Be Sphere 30 reduce neutron loss, thereby improving the overall efficiency of the system.

[0041] refer to Figure 2 , Figure 2 Provided for embodiments of the present invention 9 The (N, 2N) reaction cross section of Be, such as Figure 2 As shown, the composite target structure is placed entirely within a container 9 In Be's ball, 9 Be exhibits a high (N, 2N) reaction cross section at neutron energies above 3 MeV, while 9 Be is a superthermal neutron moderator material, generally used to bombard Be targets with proton energies exceeding 8 MeV, a reaction threshold of 2.057 MeV, and a maximum neutron energy exceeding 6 MeV. It can moderate and multiply neutrons generated after one multiplication.

[0042] Specifically, 9 The diameter of Be sphere 30 was obtained by simulating the incident proton energy using a Monte Carlo algorithm. 9 The diameter of the Be sphere depends on the energy of the incident protons. It can be calculated based on Monte Carlo simulation software. The sphere with the highest total number of neutrons emitted from its surface is the optimal diameter.

[0043] Refer again Figure 6 The secondary proliferation system 3 also includes a package containing 9The Pb layer 31 surrounding the Be sphere 30 has multiple stable isotopes of Pb with high (N, 2N) reaction cross sections and a resonance energy of 300 keV. This not only rapidly reduces the neutron energy to about 1 MeV, but also increases the neutron yield.

[0044] refer to Figure 3 , Figure 4 and Figure 5 , Figure 3 Provided for embodiments of the present invention 206 The (N, 2N) reaction cross section of Pb Figure 4 Provided for embodiments of the present invention 207 The (N, 2N) reaction cross section of Pb Figure 5 Provided for embodiments of the present invention 208 The (N, 2N) reaction cross section of Pb, such as Figure 3 , Figure 4 and Figure 5 As shown, the secondary propagation system 3 utilizes 9 The resonance cross section and (N, 2N) reaction cross section of Be and Pb with neutrons further increase neutron yield and reduce neutron energy, thus reducing the difficulty, cost and size of the back-end BSA design. The present invention provides a composite breeding target system for BNCT, which is designed as a Be-Li composite target by calculating the appropriate thickness of Be and Li, and increases the neutron yield after proton bombardment by using neutrons of various breeding nuclides in the primary breeding system 2 and the secondary breeding system 3, and finally improves the neutron fluence rate of the exit window. For the Be target: (1) increase the incident proton energy and Be target thickness; (2) increase the incident proton beam intensity. For the Li target: increase the incident proton beam intensity. The composite breeding target system for BNCT provided by the present invention is compatible with existing methods to increase neutron yield, such as increasing proton beam intensity.

[0045] Specifically, the thickness of the Pb layer 31 is obtained by simulating the incident proton energy using Monte Carlo algorithms (such as MCNP and Geant4). Monte Carlo algorithms can accurately simulate the transport processes of protons and neutrons in materials, thus providing a scientific basis for the design of the Pb layer 31 thickness. The Pb layer thickness also depends on the incident proton energy. Based on the simulation results of Monte Carlo software, the optimal thickness is the one with the highest total number of neutrons emitted from the Pb surface. The thickness of the Pb layer 31 depends on the incident proton energy; protons with different energies interact with the Pb layer 31 in different ways, therefore, optimization design is required based on the specific proton energy range. For example:

[0046] For high-energy protons (e.g., tens of MeV), the Pb layer 31 needs to be designed to be thicker to fully absorb proton energy and reflect neutrons; for low-energy protons (e.g., a few MeV), the thickness of the Pb layer 31 can be appropriately reduced to avoid excessive neutron loss.

[0047] Optionally, the Be-Li composite target 1 is fixed to the surface of the copper substrate 4 and the vanadium substrate 5 by coating. The copper substrate 4 is in close contact with the Be-Li composite target 1. The Be-Li target adopts a composite structure with the first layer being Be and the second layer being Li. The coating is applied to the surface of the copper (Cu) and vanadium (V) substrates to dissipate heat and prevent the Li layer from blistering.

[0048] The copper substrate 4 is in close contact with the Be-Li composite target 1. Its main functions are to provide efficient heat dissipation and structural support: copper has excellent thermal conductivity, which can quickly conduct away the heat generated by the Be-Li composite target 1 during high-power operation, thereby avoiding performance degradation or damage caused by overheating of the target material; the copper substrate 4 provides stable mechanical support for the Be-Li composite target 1, ensuring the structural integrity of the target material under high-power operating conditions. The vanadium substrate 5 is located behind the copper substrate 4. Its main functions are to further dissipate heat and prevent blistering of the Li layer; vanadium has good thermal conductivity and high-temperature stability, and can work in synergy with the copper substrate 4 to further improve the heat dissipation efficiency of the system; the vanadium substrate 5 can effectively suppress the blistering phenomenon that may occur in the Li layer under high-temperature and high-power operating conditions, thereby ensuring the long-term stable operation of the Be-Li composite target 1.

[0049] Optionally, in the Be-Li composite target 1, the Be layer 10 is located directly in front of the Li layer 11.

[0050] Specific implementation plan:

[0051] The design of the composite proliferation target system is illustrated using a 14 MeV proton as an example:

[0052] (1) The thickness combination of Be and Li targets with the maximum neutron yield in the composite target was calculated using Monte Carlo software. The thickness of the Be target was 0.89 mm and the thickness of the Li target was 2 mm. 6 Li accounted for 7.5%. 7 Li accounted for 92.5%);

[0053] (2) The composite target is plated with Be in front and Li behind, on a 0.6 mm thick copper (Cu) substrate. A 2 mm thick vanadium (V) layer is placed immediately behind the copper. The use of Cu and V is to prevent blistering of the Li layer and for heat dissipation. Three U-layers are added behind the composite target and attached to the Al substrate. Each U layer is 0.5 mm thick (e.g., ...). Figure 6 (as shown)

[0054] (3) Place the above target structure in a radius of 15cm. 9 Be has a high neutron multiplication rate and can reduce neutron energy;

[0055] (4) In 9The outer layer of the Be sphere is placed inside a 5 cm thick Pb shell, resulting in a high neutron multiplication rate and a reduction in neutron energy (e.g., ...). Figure 7 (As shown).

[0056] according to Figure 8 It can be seen that the neutron energy spectrum of the Be-Li composite target system (A) is similar to that of the non-composite target system (B), but the neutron yield is increased by 12.8%. Compared with the pure Be target system without breeding, the neutron yield is increased by 11.2%, but the average neutron energy is significantly reduced, which can greatly reduce the design difficulty and cost of the back-end BSA.

[0057] The above inventions are merely a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A composite proliferation target system for BNCT, characterized in that, include: The Be-Li composite target (1) and the primary breeding system (2) are located directly behind the Be-Li composite target (1), forming a composite target structure. The primary breeding system (2) includes a uranium layer (20) and an aluminum substrate layer (21), with the uranium layer (20) attached to the aluminum substrate layer (21). The uranium layer (20) and the aluminum substrate layer (21) form a uranium breeding layer, and the primary breeding system (2) includes multiple uranium breeding layers; It also includes a secondary propagation system (3), which includes 9 Be ball (30), the 9 Be-sphere (30) is wrapped around the periphery of the composite target structure.

2. The composite proliferation target system for BNCT as described in claim 1, characterized in that, There are gaps between the multiple uranium breeding layers.

3. The composite proliferation target system for BNCT as described in claim 1, characterized in that, The 9 The diameter of the Be sphere (30) is obtained by simulating the incident proton energy using the Monte Carlo algorithm.

4. The composite proliferation target system for BNCT as described in claim 1, characterized in that, The secondary proliferation system (3) also includes a package containing the 9 The Pb layer (31) surrounding the Be sphere (30).

5. The composite proliferation target system for BNCT as described in claim 4, characterized in that, The thickness of the Pb layer (31) is obtained by simulating the incident proton energy using a Monte Carlo algorithm.

6. The composite proliferation target system for BNCT as described in claim 1, characterized in that, The Be-Li composite target (1) is fixed to the surfaces of the copper substrate (4) and the vanadium substrate (5) by coating, with the copper substrate (4) in close contact with the Be-Li composite target (1).

7. The composite proliferation target system for BNCT as described in claim 1, characterized in that, In the Be-Li composite target (1), the Be layer (10) is located directly in front of the Li layer (11).

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