A neutron source target body structure for improved energy resolution

Abstract

The utility model relates to a nuclear physics technical field, it is a kind of neutron source target body structure of promoting energy resolution;The structure includes tungsten target, cooling layer, slowing layer, shielding layer and neutron hole, tungsten target adopts 6cm thin target design, reduces neutron multiple scattering, makes 100keV below neutron energy resolution higher than 0.1%, 1MeV neutron reaches 0.3%.Cooling layer and slowing layer add boron-containing material, reduce gamma ray generation, improve experimental data accuracy.Target body is distributed with multiple neutron hole around, forms stereoscopic extraction system, supports multiple experiments in parallel, improves utilization efficiency.Shielding layer adopts low carbon steel and concrete combination, reduces radiation dose;This design makes the equivalent slowing length standard deviation of whole neutron energy area less than 5cm, promotes energy resolution and experimental precision.

Description

Technical Field

[0001] This invention relates to the field of nuclear physics, specifically to a neutron source target structure that improves energy resolution. Background Technology

[0002] Spallation neutron sources are an indispensable tool in nuclear physics research and many cutting-edge scientific fields. They generate neutrons by bombarding heavy metal targets with high-energy proton beams and are widely used in materials structure analysis, biomolecular research, condensed matter physics exploration, and many other areas.

[0003] However, the target design of traditional spallation neutron sources has certain limitations. Typically, the target adopts a relatively thick structure, which causes neutrons to undergo multiple scatterings within the target, making the direction and energy distribution of neutrons complex and increasing the uncertainty of neutron flight distance. This, in turn, severely reduces the energy resolution of the neutron source device. The insufficient energy resolution greatly limits its application in high-precision neutron experimental research. For example, in experiments that require precise measurement of neutron energy distribution, traditional target structures are difficult to meet the experimental requirements.

[0004] In addition, traditional target designs need improvement in terms of radiation protection. Spallation processes generate a large amount of secondary radiation such as gamma rays, and the high gamma ray background can interfere with the experimental environment and pose a potential threat to the safety of experimental personnel. Therefore, how to reduce multiple scattering of neutrons in the target while ensuring neutron yield, improve energy resolution, and effectively control radiation dose has become a key issue that urgently needs to be addressed in the field of spallation neutron source technology. Summary of the Invention

[0005] To address the aforementioned issues, this invention aims to provide a neutron source target structure that improves energy resolution. It is suitable for spallation neutron source devices, effectively enhancing the energy resolution of neutron sources while meeting radiation protection requirements, thus providing crucial support for high-precision neutron experimental research.

[0006] The technical solution adopted in this utility model is: a neutron source target structure for improving energy resolution, including: a tungsten target, a cooling layer, a moderation layer, a shielding layer and a neutron channel, wherein the tungsten target has dimensions of 7cm wide × 7cm high × 6cm thick and adopts a thin target design for receiving proton beam bombardment provided by an accelerator.

[0007] The cooling layer is located on the outside of the tungsten target as the first layer, and includes a 2cm thick layer of boron-containing water (1.25% boron content) in the forward direction and a 1.5cm thick layer of water in the side direction, which is used to cool the target and moderate the neutrons to a certain extent.

[0008] The moderation layer is located outside the cooling layer and uses boron-containing water (1.25% boron content) with a radius of 50 cm to moderate and broaden the neutron energy spectrum to the thermal neutron energy region.

[0009] The aforementioned shielding layer is located outside the moderating layer and uses low-carbon steel and concrete as shielding materials. The low-carbon steel is located inside the shielding material near the target and has a thickness of 4m. The outer concrete layer has a thickness of 2m and is used for radiation protection and shielding of the target.

[0010] The aforementioned neutron channels are provided in several forms, with the ends of the neutron channels connected to the experimental terminal. Their layout and size must match the terminal equipment.

[0011] The tungsten target is 6 cm thick. This thin target design significantly reduces the multiple scattering process of neutrons within the target body, thereby improving the energy resolution of the neutron source device.

[0012] The boron-containing water in both the cooling layer and the moderation layer contains 1.25% boron, which reduces the gamma-ray background through the boron neutron capture process.

[0013] The shielding layer adopts a design combining low-carbon steel and concrete, with the low-carbon steel being 4m thick and the outer concrete layer being 2m thick, in order to reduce the radiation dose and meet the radiation protection safety requirements.

[0014] The system comprises five neutron channels distributed around the target, covering key directions such as forward and lateral directions, forming a three-dimensional neutron extraction system to support the parallel execution of multiple types of experiments.

[0015] The neutron source target structure with improved energy resolution exhibits a standard deviation of less than 5 cm for the equivalent moderation length at different neutron energies. Combined with the flight distance corresponding to the first neutron channel, the relative error of the flight distance is less than 2.5 × 10⁻⁶. -4 This significantly improves the energy resolution of the device.

[0016] This invention provides a neutron source target structure that improves energy resolution. Through unique structural design and material selection, it achieves several significant beneficial effects: This invention employs a thin-target design, controlling the tungsten target thickness within a reasonable range (e.g., 6 cm). While ensuring a high neutron yield, it significantly reduces the multiple scattering process of neutrons within the target body, effectively lowering the uncertainty of neutron flight distance. Calculations show that for experimental terminals at specific flight distances (e.g., 200 m), the energy resolution for neutrons below 100 keV is higher than 0.1%, and the energy resolution for 1 MeV neutrons reaches 0.3%, achieving world-leading levels and meeting the stringent requirements of high-precision neutron experimental research.

[0017] In this invention, boron-containing materials (1.25% boron content) are cleverly incorporated into the cooling layer and the moderation layer. Utilizing boron's neutron-trapping properties, the generation of gamma rays is significantly reduced while neutrons are moderated. This helps to improve the neutron / gamma flux ratio at the experimental terminal, reduces gamma ray interference with experimental measurements, and thus improves the accuracy and reliability of experimental data.

[0018] In this invention, multiple neutron channels are distributed around the target, forming a three-dimensional neutron extraction system. These channels can extract neutrons from different directions; the forward channels preferentially extract high-energy neutrons, while the lateral channels extract sufficiently slowed thermal neutrons. Simultaneously, a collimation design ensures that the spatial distribution of the neutron beam meets the requirements of the experimental terminals. This design allows the ends of the five neutron channels to be connected to different experimental terminals (such as high-precision detector calibration terminals, fundamental physics research terminals, imaging devices, etc.), supporting the parallel execution of multiple types of experiments and significantly improving the utilization efficiency of the neutron source.

[0019] This invention employs a shielding layer design combining low-carbon steel and concrete. The low-carbon steel is located inside the shielding material near the target, providing excellent shielding against high-energy neutrons and gamma rays; the outer concrete layer primarily shields against low-energy neutrons. This dual-shielding structure effectively reduces the radiation dose from proton beams and other radiating particles penetrating the target, lowering the radiation dose below a safe threshold (e.g., <1 μSv / h).

[0020] Under the design scheme of this utility model, the standard deviation of the equivalent moderation length in the entire neutron energy region is less than 5 cm. Combined with the flight distance corresponding to a specific neutron channel, the relative error of the flight distance is extremely small (e.g., less than 2.5 × 10⁻⁶). -4 This further improves the energy resolution and experimental accuracy of the device, providing strong support for high-precision neutron experimental research. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural diagram of the high-precision wide-spectrum target structure of the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the high-precision wide-spectrum target structure of the present invention; Figure 3 This is a schematic diagram of the standard deviation of the equivalent slowing length corresponding to different neutron energies in this invention.

[0022] The attached diagram is described as follows: 1-Tungsten target, 2-Cooling layer, 3-Moderizing layer, 4-Shielding layer, 5-Neutron channel, 51-First neutron channel. Detailed Implementation

[0023] This invention proposes a high-precision, wide-spectrum neutron source target structure, aiming to reduce multiple scattering effects of neutrons within the target by optimizing the target design, thereby improving the energy resolution of the neutron source device and meeting radiation protection requirements. Figure 1-3 As shown, where Figure 1 and 2 This is a schematic diagram of the high-precision wide-spectrum target structure design. The diagram clearly marks the position and structure of the tungsten target 1, cooling layer 2, moderation layer 3, shielding layer 4, and neutron channel 5, which is used to understand the overall layout and function of each part of the present invention. Figure 2 The figure shows the standard deviation of the equivalent moderation length for different neutron energies. It visually demonstrates that under the design scheme of this invention, the standard deviation of the equivalent moderation length in the entire neutron energy region is less than 5 cm, proving the effectiveness of this invention in improving the energy resolution of neutron source devices. Figure 3 This is a schematic diagram of the overall structure of the target station. The specific implementation of the present invention is detailed below with reference to embodiments: Example: This high-precision wide-spectrum neutron source target system mainly consists of a tungsten target 1, a cooling layer 2, a moderation layer 3, a shielding layer 4, and a neutron channel 5, etc. A schematic diagram of the specific structure is shown below. Figure 1 As shown, it includes: Tungsten target 1: Dimensions: 7cm (width) × 7cm (height) × 6cm (thickness).

[0024] Design features: A thin target design is employed, with the 6cm thickness aligned with the direction of the proton beam. This design significantly reduces the multiple scattering process of neutrons within the target, substantially improving the energy resolution of the neutron source device.

[0025] Function: Receives proton beams from an accelerator to bombard the neutrons and generate spallation neutrons.

[0026] Cooling layer 2: Location: Located on the first layer outside the tungsten target.

[0027] Structure: It consists of a 2cm thick layer of boron-containing water (1.25% boron content) in the forward direction and a 1.5cm thick layer of water in the lateral direction.

[0028] Functions: Cools the target and moderates neutrons to some extent. Simultaneously, boron in the boron-containing water reduces the gamma-ray background through neutron capture.

[0029] Moderation layer 3: Location: Located on the outside of the cooling layer.

[0030] Structure: Use boron-containing water with a radius of 50cm (boron content 1.25%).

[0031] Function: To slow down and broaden the neutron energy spectrum into the thermal neutron energy region, further reducing the gamma-ray background.

[0032] Shielding layer 4: Location: Located outside the moderating layer.

[0033] Structure: Low-carbon steel and concrete are used as shielding materials. The low-carbon steel is located inside the shielding material near the target and is 4m thick. The outer concrete layer is 2m thick.

[0034] Function: Radiation protection and shielding of the target, reducing radiation dose and ensuring radiation safety.

[0035] Neutron Channel 5: Location: Five neutron channels are distributed around the target. Structure: Neutrons generated by the spallation neutron source are emitted in all directions. Multiple channels are set up to allow neutrons from different directions to be emitted, thereby improving neutron utilization. Five channels cover key directions such as the forward and lateral directions of the target, forming a three-dimensional neutron extraction system.

[0036] Function: Neutron channel 5 plays a crucial role in the neutron source device, guiding neutrons generated by the target to the experimental terminal. Neutron channel 5 provides a directional transport path for the neutrons, ensuring their efficient entry from the target region into the subsequent moderation and shielding layers, ultimately reaching the experimental terminal. This process must maintain the directionality and intensity of the neutron beam to meet the experiment's neutron flux requirements. The experimental terminal is connected at its end, and its layout and dimensions must match the terminal equipment to ensure the collimation and spatial distribution of the neutron beam meet experimental requirements. The layout of the five channels allows for the simultaneous execution of multiple types of experiments.

[0037] The working principle of the high-precision wide-spectrum target system in this embodiment is as follows: Proton beam bombardment: A proton beam with a beam size of 3.5cm × 3.5cm and an energy of 600MeV, provided by the accelerator, directly bombards the tungsten target 1, producing high-energy neutrons through a spallation reaction. The neutrons are emitted in all directions, forming an initial neutron field.

[0038] Neutron moderation and cooling: The generated neutrons are first scattered multiple times within the tungsten target 1, with some neutrons experiencing a decrease in energy. Subsequently, they enter the cooling layer 2, where the neutron energy further decays under the combined moderation effect of boron-containing water and the water layer. Simultaneously, the target body is cooled due to heat exchange. During this stage, the neutron energy spectrum begins to transition towards the intermediate energy region.

[0039] Neutron spectral broadening and directional transport: Neutrons passing through cooling layer 2 enter moderation layer 3 and are moderated to the thermal neutron energy region (energy ≤ 0.025 eV) through elastic / inelastic scattering in boron-containing water. Five neutron channels are distributed in a solid angle around the target, extracting neutrons in different directions, including forward and lateral. All five channels extract white-light neutrons with a wide energy range, with the forward channel extracting more high-energy neutrons and the lateral channel extracting more thermal neutrons. The channel length combined with the equivalent moderation length ensures that the neutron energy resolution of the experimental terminal meets the requirements. Through the collimation design of the channel cross-section, the spatial distribution of the neutron beam meets the needs of the experimental terminal.

[0040] Multi-experiment terminal adaptation: The ends of the five neutron channels are connected to different experimental terminals (such as high-precision detector calibration terminals, basic physics research terminals, imaging devices, etc.), supporting the parallel execution of multiple types of experiments.

[0041] Radiation protection and safety control: Neutrons that do not enter the channel, protons that penetrate the tungsten target, and other radiation particles enter the shielding layer 4. Under the dual action of low-carbon steel and concrete, the radiation dose is reduced to below the safety threshold (e.g., <1μSv / h), ensuring the safety of experimental personnel and the environment.

[0042] This embodiment employs a 6cm thick thin target design, which significantly reduces the multiple scattering process of neutrons within the target body and substantially improves the energy resolution of the neutron source device. Calculations show that for the experimental terminal corresponding to the first neutron channel 51 with a flight distance of 200m, the energy resolution of neutrons below 100keV is higher than 0.1%, and the energy resolution of 1MeV neutrons is 0.3%, reaching a world-leading level.

[0043] from Figure 3 The flight distance error can be observed; the standard deviation of the equivalent slowing length across the entire neutron energy region is less than 5 cm. Combined with the 200 m flight distance corresponding to the first neutron channel 51, the relative error of the flight distance is less than 2.5 × 10⁻⁶. -4 This will greatly improve the energy resolution of the device. For the portion of the proton beam that penetrates the tungsten target 1, a shielding layer 4 combining low-carbon steel and concrete is designed to effectively reduce the radiation dose and ensure radiation safety.

[0044] In summary, this invention achieves high energy resolution and radiation protection effects required for high-precision neutron experimental research by optimizing the design of the target thickness, cooling layer, moderation layer, and shielding layer.

Claims

1. A neutron source target structure for improving energy resolution, characterized in that, include: The tungsten target (1), cooling layer (2), moderation layer (3), shielding layer (4) and neutron channel (5) are used. The tungsten target (1) has a size of 7cm wide × 7cm high × 6cm thick and adopts a thin target design to receive proton beam bombardment provided by the accelerator.

2. The neutron source target structure for improving energy resolution according to claim 1, characterized in that, The cooling layer (2) is located on the outside of the tungsten target as the first layer, and includes a 2cm thick layer of boron-containing water in the front and a 1.5cm thick layer of water in the side, which is used to cool the target and slow down the neutrons to a certain extent.

3. The neutron source target structure for improving energy resolution according to claim 1, characterized in that, The moderation layer (3) is located outside the cooling layer and uses boron-containing water with a radius of 50 cm to moderate and broaden the neutron energy spectrum to the thermal neutron energy region.

4. The neutron source target structure for improving energy resolution according to claim 1, characterized in that, The shielding layer (4) is located outside the moderating layer. Low carbon steel and concrete are used as shielding materials. The low carbon steel is located inside the shielding material near the target and has a thickness of 4m. The outer concrete layer has a thickness of 2m and is used for radiation protection and shielding of the target.

5. The neutron source target structure for improving energy resolution according to claim 1, characterized in that, The neutron channel (5) is provided in several parts, and the end of the neutron channel is connected to the experimental terminal. Its layout and size must match the terminal equipment.

6. The neutron source target structure for improving energy resolution according to claim 1, characterized in that, The shielding layer (4) adopts a design scheme combining low-carbon steel and concrete, wherein the thickness of the low-carbon steel is 4m and the thickness of the outer concrete layer is 2m, in order to reduce the radiation dose and meet the radiation protection safety requirements.

7. The neutron source target structure for improving energy resolution according to claim 1, characterized in that, The number of neutron channels (5) is five, distributed around the target, covering the key directions of forward and lateral, forming a three-dimensional neutron extraction system.

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