A method for improving the neutron source yield of proton accelerator

Abstract

The present invention relates to a method for increasing the neutron source yield of a proton accelerator, comprising the following steps: constructing a double-layer target chamber, including a tritium gas target chamber and a helium gas target chamber, wherein a lithium target is fixedly installed in the helium gas target chamber; filling the tritium gas target chamber with tritium gas until a set tritium gas target chamber pressure is reached; filling the helium gas target chamber with helium gas until a set helium gas target chamber pressure is reached; and injecting protons into the double-layer target chamber through a proton injection main pipe. The method provided by the present invention can increase the neutron yield below 1 MeV obtained by the accelerator neutron source by more than 95% compared to traditional methods, effectively utilizing beam time, increasing neutron flux, reducing the proportion of environmental background, and improving experimental results. The method provided by the present invention can eliminate interference from neutrons with energies above 1 MeV, which can reduce interference from other reactions for nuclear physics experimental measurements. For boron neutron therapy accelerators, the low neutron energy makes it easy to moderate and shield, which can reduce additional shielding measures.

Description

Technical Field

[0001] The invention belongs to the technical field of proton accelerator neutron sources, and in particular relates to a method for improving the yield of a proton accelerator neutron source. Background Art

[0002] Common accelerators can accelerate a variety of particles and produce neutrons through a variety of reaction channels. They offer greater tunability in neutron intensity and energy spectrum than reactor-based and isotope-based neutron sources, and are easier to build and maintain than reactor-based and spallation-based neutron sources. Neutron energies below 1 MeV are of particular interest in reactor design, boron neutron therapy, capture, and fission cross-section measurements. Producing neutrons of the required intensity and energy requires not only the performance of the accelerator itself but also neutron target design, a key factor in generating the desired neutrons.

[0003] Common ways to produce accelerator neutron sources are: 7 Li(p,n), 9 Be(p,n), T(p,n) 3 He, 9 Be(d,n), 13 C(d,n), T(d,n) 4 He and D(d,n) 3 He et al., among them 7 The Li(p,n) reaction has the advantages of high neutron yield, low reaction threshold energy, and low average neutron energy, and is a commonly used channel for producing low-energy neutrons. 7 The threshold energy of the Li(p,n) reaction is 1.88MeV. When the proton energy is lower than 1.88MeV, no neutrons will be produced, which will cause a certain degree of beam waste. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for improving the neutron source yield of a proton accelerator, which can improve the low-energy neutron yield on the proton accelerator, save beam time, and can be widely used in proton accelerators for boron neutron therapy.

[0005] To achieve the above objectives, the present invention adopts a technical solution: a method for increasing the neutron source yield of a proton accelerator, comprising the following steps:

[0006] S1. constructing a double-layer target chamber and fixedly connecting the double-layer target chamber to a proton injection main pipe;

[0007] The double-layer target chamber includes a tritium gas target chamber and a helium gas target chamber, the first end of the helium gas target chamber is fixedly connected to the adapter of the proton injection main pipe, and the first end of the tritium gas target chamber is fixedly connected to the second end of the helium gas target chamber;

[0008] A lithium target is fixedly installed in the helium gas target chamber;

[0009] S2, filling the tritium gas target chamber with tritium gas until the set tritium gas target chamber pressure is reached; filling the helium gas target chamber with helium gas until the set helium gas target chamber pressure is reached;

[0010] S3. Protons are incident into the double-layer target chamber through the proton injection main pipe.

[0011] Furthermore, a rubber and indium sealing ring is used to seal the first end of the helium gas target chamber and the adapter of the proton injection main pipe;

[0012] The first end of the tritium gas target chamber and the second end of the helium gas target chamber are sealed and connected by using rubber and indium sealing rings.

[0013] Furthermore, the first end of the tritium gas target chamber is sealed with molybdenum foil, rubber and indium sealing ring;

[0014] The first end of the helium gas target chamber is sealed by using molybdenum foil, rubber and an indium sealing ring.

[0015] Furthermore, a tantalum tube is fixedly arranged on the inner wall of the tritium gas target chamber.

[0016] Furthermore, a gold stopper is installed at the second end of the tritium gas target chamber.

[0017] Furthermore, step S1 includes the following specific steps:

[0018] S11, placing the tritium gas target chamber, the helium gas target chamber, the adapter of the proton injection main pipeline, and the sealed lithium target into a glove box, and then setting the glove box to an argon gas environment;

[0019] S12. In a glove box, a lithium target is installed at the second end of the helium gas target chamber, a first end of the helium gas target chamber is fixedly connected to an adapter of a proton injection main pipe of a proton accelerator, and a first end of the tritium gas target chamber is fixedly connected to a second end of the helium gas target chamber; and the first end of the helium gas target chamber and the first end of the tritium gas target chamber are sealed to obtain the double-layer target chamber.

[0020] S13. Take the double-layer target chamber out of the glove box and securely connect it to the proton injection main pipe.

[0021] Furthermore, before step S2, the following steps are also included:

[0022] The tritium gas target chamber is evacuated, and the helium gas target chamber is evacuated.

[0023] Furthermore, the energy of the protons incident into the double-layer target chamber through the proton injection main pipe is 2.7 MeV.

[0024] Furthermore, step S3 includes the following specific steps:

[0025] S31, protons incident into the double-layer target chamber through the proton injection main pipe are incident on the lithium target;

[0026] S32. The protons that pass through the lithium target are incident again on the tritium gas target formed by the tritium gas in the tritium gas target chamber.

[0027] Furthermore, the thickness of the lithium target is set to 0.14 mm;

[0028] The thickness of the tritium gas target is set to 4.5 cm.

[0029] The beneficial effects of the present invention are as follows: a method for improving the neutron source yield of a proton accelerator provided by the present invention is adopted, and the method comprises the following steps: constructing a double-layer target chamber, and fixedly connecting the double-layer target chamber to a proton injection main pipe; the double-layer target chamber comprises a tritium gas target chamber and a helium gas target chamber, and a lithium target is fixedly installed in the helium gas target chamber; filling tritium gas into the tritium gas target chamber until a set tritium gas target chamber pressure is reached; filling helium gas into the helium gas target chamber until a set helium gas target chamber pressure is reached; and injecting protons into the double-layer target chamber through the proton injection main pipe. The method can improve the neutron yield below 1 MeV obtained by the accelerator neutron source by more than 95% compared with a traditional method, effectively utilize beam time, improve neutron flux, reduce the proportion of environmental background, and improve experimental effect. The method provided by the present invention eliminates the interference of neutrons with energy above 1MeV, which can reduce the interference of other reactions for nuclear physics experimental measurements; for boron neutron therapy accelerators, the neutrons have low energy and are easy to moderate and shield, which can reduce additional shielding measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of a method for improving the neutron source yield of a proton accelerator according to an embodiment of the present invention.

[0031] Figure 2 The embodiment of the present invention is described 7 A plot of the Li(p,n) reaction cross section as a function of incident proton energy.

[0032] Figure 3 is T(p,n) described in the embodiment of the present invention 4 A graph showing the He reaction cross section as a function of incident proton energy.

[0033] Figure 4 This is a 0° neutron energy distribution diagram generated by 2.7 MeV protons incident on a thick lithium target according to an embodiment of the present invention.

[0034] Figure 5This is a 0° neutron energy distribution diagram generated by 1.8 MeV protons incident on a thick tritium target according to an embodiment of the present invention.

[0035] Figure 6 This is a 0° angle neutron energy distribution diagram generated by 2.7 MeV protons incident on a thick lithium target + a thick tritium target according to an embodiment of the present invention.

[0036] Figure 7 Schematic diagram of the double-layer target chamber structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be further clearly and completely described below in conjunction with the drawings and examples. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0038] The inventors found through analysis that 7 The threshold energy of Li(p,n) reaction is 1.88MeV. Protons with energy below this threshold energy cannot react with lithium target to produce neutrons. Through research, the inventors found that T(p,n) 3 He reactions can also produce low-energy neutrons, and T(p,n) 3 The threshold energy of He reaction is 1.02MeV. 7 The threshold energy of the Li(p,n) reaction is low and the yield is high. Therefore, based on this principle, the present invention designs a double-layer target consisting of a lithium target and a tritium target, which can significantly increase the yield of low-energy neutrons with an energy below 1MeV and save beam time. 7 The Li(p,n) reaction cross section changes with the incident proton energy as shown in the figure Figure 2 As shown, T(p,n) 3 The He reaction cross section changes with the incident proton energy as shown in the figure Figure 3 (The nuclear reaction cross section is a physical quantity that indicates the probability of a specific nuclear reaction occurring between the incident particle and the target nucleus.)

[0039] During the implementation of the present invention, the inventors discovered that when the proton energy is higher than 2.7 MeV, the generated neutron energy is higher than 1 MeV, which is not easy to moderate and is prone to other interfering reactions. Therefore, in this embodiment, we selected the proton energy of the incident proton to be 2.7 MeV, and performed simulation calculations. The 0° angle neutron energy distribution (i.e., neutron energy spectrum) generated by the 2.7 MeV proton incident on the thick lithium target is as follows: Figure 4 As shown. Figure 4It can be seen that when the proton energy is 2.7MeV, the upper limit of the neutron energy generated by p+Li (p particles react when incident on the lithium target) is about 1MeV. As the proton incidence depth in the lithium target increases, the proton energy gradually decreases. When the incidence depth reaches 0.14mm, the proton energy decreases to about 1.8MeV, and no new neutrons are generated. Therefore, the thickness of the lithium target used in this embodiment is set to 0.14mm.

[0040] And T(p,n) 3 The threshold energy of He reaction is 1.02MeV, and 1.8MeV protons can react with thick tritium targets to generate T(p,n) 3 The energy of the neutrons produced by the He reaction is just below 1 MeV. As the proton's penetration depth in the tritium target increases, the energy gradually decreases. When the penetration depth reaches 4.5 cm, the proton energy decreases to about 1 MeV, and no new neutrons are produced. The energy distribution of the 0° neutrons produced by the 1.8 MeV proton incident on the thick tritium target is as follows: Figure 5 shown.

[0041] Based on the above principles and analysis, the inventors proposed a method for improving the neutron source yield of a proton accelerator: designing the target assembly as a double-layer target chamber consisting of a tritium gas chamber and a helium gas chamber. Protons first enter the helium gas chamber, where a lithium target is placed. The lithium target is set to a thickness of approximately 0.14 mm, reducing the proton energy from 2.7 MeV to 1.8 MeV, fully utilizing the proton neutron-producing energy range of 1.88 to 2.7 MeV. The protons are then incident on an adjacent 4.5 cm long tritium target, effectively utilizing the proton energy range of 1.0 to 1.8 MeV. This method not only maintains neutron energy below 1 MeV but also significantly improves neutron yield, effectively utilizing beam time and increasing neutron yield, with significant scientific research value and social benefits.

[0042] like Figures 1 to 7 As shown, an embodiment of the present invention provides a method for improving the neutron source yield of a proton accelerator, the method comprising the following steps:

[0043] S1. constructing a double-layer target chamber and fixedly connecting the double-layer target chamber to a proton injection main pipe;

[0044] The double-layer target chamber includes a tritium gas target chamber 1 and a helium gas target chamber 7. The first end of the helium gas target chamber 7 is fixedly connected to the adapter of the proton injection main pipe of the proton accelerator, and the first end of the tritium gas target chamber 1 is fixedly connected to the second end of the helium gas target chamber 7.

[0045] In the constructed double-layer target chamber, the tritium gas target chamber 1 and the helium gas target chamber 7 are both sealed target chambers.

[0046] Specifically, a lithium target 3 is fixedly installed in the helium gas target chamber 7 , and the second end of the helium gas target chamber 7 is the end of the helium gas target chamber 7 along the proton incident direction.

[0047] Specifically, the first end of the helium gas target chamber 7 is fixedly connected to the adapter of the proton injection main pipe of the proton accelerator by means of threaded connection, snap connection, etc. The first end of the tritium gas target chamber 1 is fixedly connected to the second end of the helium gas target chamber 7 by means of threaded connection, snap connection, etc.

[0048] Specifically, a rubber and indium sealing ring 5 is used to seal the first end of the helium gas target chamber 7 and the adapter of the proton injection main pipe of the proton accelerator; a rubber and indium sealing ring 5 is used to seal the first end of the tritium gas target chamber 1 and the second end of the helium gas target chamber 7.

[0049] The first end of the tritium gas target chamber 1 is sealed with a molybdenum foil 4, a rubber and an indium sealing ring 5. The specific sealing method is: under the compression of the second end of the helium gas target chamber 7, the rubber and the indium sealing ring 5, the molybdenum foil 4 is sealed and connected to the first end of the tritium gas target chamber 1; thereby, the tritium gas target chamber 1 and the helium gas target chamber 7 are separated by the molybdenum foil 4.

[0050] The first end of the helium gas target chamber 7 is sealed with a molybdenum foil 4, a rubber and an indium sealing ring 5. The specific sealing method is as follows: under the compression of the adapter, rubber and indium sealing ring 5 of the proton injection main pipe of the proton accelerator, the molybdenum foil 4 is sealed and connected to the first end of the tritium gas target chamber 1; thereby, the helium gas target chamber 7 is separated from the proton injection main pipe of the proton accelerator by the molybdenum foil 4.

[0051] Optionally, a tantalum tube 2 is fixedly provided on the inner wall of the tritium gas target chamber 1 to reduce the influence of scattered protons.

[0052] In a specific embodiment, a gold barrier 6 is installed at the second end of the tritium gas target chamber 1 to absorb excess energy protons to reduce the background generated by excess energy protons. The second end of the tritium gas target chamber 1 is the end of the tritium gas target chamber 1 along the proton incidence direction.

[0053] Specifically, the process of installing the lithium target in the double-layer target chamber is performed in a glove box. Step S1 includes the following specific steps:

[0054] S11, placing the tritium gas target chamber 1, the helium gas target chamber 7, the adapter of the proton injection main pipe, and the lithium target with a sealed package into a glove box, and then setting the glove box to an argon gas environment to prevent oxidation of the lithium target 3;

[0055] S12. Unpacking the lithium target 3 in the glove box, installing the lithium target 3 at the second end of the helium gas target chamber 7, and fixing the first end of the helium gas target chamber 7 to the adapter of the proton injection main pipe of the proton accelerator, and fixing the first end of the tritium gas target chamber 1 to the second end of the helium gas target chamber 7; and sealing the first end of the helium gas target chamber 7 with a molybdenum foil 4, a rubber and an indium sealing ring 5, and sealing the first end of the tritium gas target chamber 1 with a molybdenum foil 4, a rubber and an indium sealing ring 5, to obtain the double-layer target chamber;

[0056] S13, taking the double-layer target chamber out of the glove box and fixedly connecting it to the proton injection main pipe of the proton accelerator.

[0057] S2. Filling tritium gas into the tritium gas target chamber 1 through the gas filling line of the tritium gas pipeline 8 until the set pressure of the tritium gas target chamber 1 is reached; filling helium gas into the helium gas target chamber 7 through the gas filling line of the helium gas pipeline 9 until the set pressure of the helium gas target chamber 7 is reached;

[0058] Before step S2, the following steps are also included: evacuating the tritium gas target chamber 1 and evacuating the helium gas target chamber 7 to ensure the purity of the gases inside the two target chambers.

[0059] Optionally, the tritium target chamber 1 is set at a pressure of 4 atmospheres, while the helium target chamber 7 is set at a pressure of 3 atmospheres to ensure pressure balance and stability within the dual-layer target chamber. Furthermore, the helium environment within the helium target chamber 7 prevents oxidation of the lithium target 3. Furthermore, the dual-layer target chamber not only allows for the compartmentalization of different targets but also reduces the risk of tritium gas leakage.

[0060] S3. The protons emitted by the proton accelerator are incident into the double-layer target chamber through the proton injection main pipe.

[0061] Optionally, the energy of the protons incident into the double-layer target chamber through the proton injection main pipe is 2.7 MeV.

[0062] Specifically, step S3 includes the following steps:

[0063] S31, protons incident into the double-layer target chamber through the proton injection main pipe are vertically incident on the lithium target 3;

[0064] S32 , the protons that have passed through the lithium target 3 are incident again on the tritium gas target formed by the tritium gas in the tritium gas target chamber 1 .

[0065] In a specific embodiment, the thickness of the lithium target 3 is set to about 0.14 mm, which can reduce the energy of protons from 2.7 MeV to 1.8 MeV, making full use of the neutron-producing energy range of protons from 1.88 to 2.7 MeV.

[0066] In step S32, the protons that have passed through the lithium target 3 pass through the molybdenum foil 4 and are then incident on the tritium gas target formed by the tritium gas in the tritium gas target chamber 1. The molybdenum foil 4 is a molybdenum foil with a thickness of microns, which allows the incident protons to pass through easily, and the loss of proton energy during the process of passing through the molybdenum foil 4 is negligible.

[0067] In a specific embodiment, the thickness of the tritium gas target is set to about 4.5 cm, which can reduce the energy of protons from 1.8 MeV to 1.0 MeV, effectively utilizing the energy range of protons from 1.0 to 1.8.

[0068] The method provided in this embodiment can not only keep the neutron energy below 1MeV to meet the needs of various application fields, but also significantly improve the neutron yield (neutron flux): Figure 6 As shown in the 0° angle neutron energy distribution diagram produced by 2.7MeV protons incident on thick lithium target + thick tritium target, it can be seen that the neutron flux is increased by about 98% (if the energy loss part of the proton incidence process is taken into account, the neutron flux is increased by more than 95%), which effectively utilizes the beam time and increases the neutron yield, with significant scientific research value and social benefits.

[0069] By using the method for improving the neutron source yield of a proton accelerator provided in this embodiment, the neutron yield below 1 MeV obtained is increased by more than 95% compared with the traditional method, saving beam time and improving the utilization efficiency of the accelerator, which is of great significance for completing the corresponding experimental tasks. Moreover, if applied to the proton accelerator required for boron neutron therapy in medicine, the neutron yield can be improved, resulting in better social and economic benefits.

[0070] The methods described herein are not limited to the specific embodiments described. The above embodiments are merely illustrative of the present invention, and the present invention may also be implemented in other specific ways or in other specific forms without departing from the gist or essential characteristics of the present invention. Therefore, the embodiments described herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is to be determined by the appended claims, and any variations that are equivalent to the intent and scope of the claims are intended to be within the scope of the present invention.

Claims

1. A method for increasing the neutron source yield of a proton accelerator, characterized in that: The steps include: S1. constructing a double-layer target chamber and fixedly connecting the double-layer target chamber to a proton injection main pipe; The double-layer target chamber includes a tritium gas target chamber and a helium gas target chamber, the first end of the helium gas target chamber is fixedly connected to the adapter of the proton injection main pipe, and the first end of the tritium gas target chamber is fixedly connected to the second end of the helium gas target chamber; A lithium target is fixedly installed in the helium gas target chamber; S2, filling tritium gas into the tritium gas target chamber until the set tritium gas target chamber pressure is reached; filling helium gas into the helium gas target chamber until the set helium gas target chamber pressure is reached; S3. Protons are incident into the double-layer target chamber through the proton injection main pipe.

2. The method for improving the neutron source yield of a proton accelerator according to claim 1, characterized in that: The first end of the helium gas target chamber and the adapter of the proton injection main pipe are sealed and connected by using rubber and indium sealing rings; The first end of the tritium gas target chamber and the second end of the helium gas target chamber are sealed and connected by using rubber and indium sealing rings.

3. The method for improving the neutron source yield of a proton accelerator according to claim 1, characterized in that: The first end of the tritium gas target chamber is sealed with molybdenum foil, rubber and indium sealing ring; The first end of the helium gas target chamber is sealed by using molybdenum foil, rubber and an indium sealing ring.

4. The method for improving the neutron source yield of a proton accelerator according to claim 1, characterized in that: A tantalum tube is fixedly arranged on the inner wall of the tritium gas target chamber.

5. The method for improving the neutron source yield of a proton accelerator according to claim 1, characterized in that: A gold stopper is installed at the second end of the tritium gas target chamber.

6. A method for improving the neutron source yield of a proton accelerator according to any one of claims 1 to 5, characterized in that: The step S1 includes the following specific steps: S11, placing the tritium gas target chamber, the helium gas target chamber, the adapter of the proton injection main pipeline, and the sealed lithium target into a glove box, and then setting the glove box to an argon gas environment; S12. In a glove box, a lithium target is installed at the second end of the helium gas target chamber, a first end of the helium gas target chamber is fixedly connected to an adapter of a proton injection main pipe of a proton accelerator, and a first end of the tritium gas target chamber is fixedly connected to a second end of the helium gas target chamber; and the first end of the helium gas target chamber and the first end of the tritium gas target chamber are sealed to obtain the double-layer target chamber. S13. Take the double-layer target chamber out of the glove box and securely connect it to the proton injection main pipe.

7. The method for improving the neutron source yield of a proton accelerator according to claim 6, characterized in that: Before step S2, the method further includes the following steps: The tritium gas target chamber is evacuated, and the helium gas target chamber is evacuated.

8. The method for improving the neutron source yield of a proton accelerator according to claim 6, characterized in that: The energy of the protons incident into the double-layer target chamber through the proton injection main pipe is 2.7 MeV.

9. The method for improving the neutron source yield of a proton accelerator according to claim 6, characterized in that: The step S3 includes the following specific steps: S31, protons incident into the double-layer target chamber through the proton injection main pipe are incident on the lithium target; S32. The protons that pass through the lithium target are incident again on the tritium gas target formed by the tritium gas in the tritium gas target chamber.

10. The method for improving the neutron source yield of a proton accelerator according to claim 9, characterized in that: The thickness of the lithium target is set to 0.14 mm; The thickness of the tritium gas target is set to 4.5 cm.

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