Fast neutron imaging detection system and applications thereof

Abstract

The application provides a fast neutron imaging detection system and application thereof. The system comprises: a shielding shell provided with a fast neutron incident window; an integrated liquid flash capillary array arranged in the shielding shell and comprising an array substrate, a liquid scintillator, a first sealing member and a second sealing member; the array substrate comprises a straight zone and a tapered zone which are integrally formed; the straight zone is composed of a plurality of capillaries with parallel axes; the tapered zone is formed by gradually shrinking the plurality of capillaries with parallel axes; the first sealing member is embedded in the fast neutron incident window; a photoelectric detection assembly is arranged in the shielding shell, and an input window of the photoelectric detection assembly is tightly attached to and connected with the second sealing member; an image output terminal is arranged outside the shielding shell; and the photoelectric detection assembly is externally connected with the image output terminal through a data line. The technical problem to be solved is how to provide a fast neutron imaging detection system, improve the light transmission efficiency and imaging quality of the system, simplify assembly, reduce the volume of the whole machine and improve the running stability of the system.

Description

Technical Field

[0001] This invention relates to the field of fast neutron detection technology, and in particular to a fast neutron imaging detection system and its applications. Background Technology

[0002] In physical processes such as laser-driven inertial confinement fusion and Z-Pinch-driven inertial confinement fusion, the 14MeV fast neutrons released by the fusion nuclear reaction have strong penetrating power. Their spatial distribution can reflect information such as the size, shape, and uniformity of the fuel implosion compression zone. Therefore, fast neutron imaging systems are usually used to diagnose the fusion process.

[0003] Currently, the core detection structure of fast neutron imaging systems based on liquid scintillator capillary arrays commonly employs a combination of parallel liquid scintillator capillary arrays and optical cones. The liquid scintillator capillary array is a capillary array filled with liquid scintillator, with one end encapsulated in glass and the other in an optical fiber panel, used to convert fast neutrons into visible light signals. The optical cone is a gradually contracting array of glass fibers; its large-aperture end is coupled to the end face of the optical fiber panel of the liquid scintillator capillary array, while its small-aperture end is used to converge and transmit the visible light signal to the subsequent photodetector, ensuring efficient transmission of the optical signal to the detector for imaging.

[0004] However, this split structure of "liquid scintillation capillary array + light cone" has many inherent defects: First, as an independent component, the light cone requires precise sub-micron alignment and installation with the liquid scintillation capillary array, which significantly increases the assembly difficulty and production cost of the system. Second, the unavoidable assembly gap between the light cone and the liquid scintillation capillary array can cause leakage and scattering of some visible light signals during transmission, reducing the transmission efficiency of the light signal and thus affecting the detection sensitivity and imaging quality of the imaging system. Third, when the parallel liquid scintillation capillary array is coupled with the light cone, the pixel arrangement of the two cannot be strictly one-to-one, resulting in a significant loss of spatial resolution during the coupling process. Fourth, the independent light cone component is susceptible to external factors such as vibration and impact, which can cause relative positional shifts with the liquid scintillation capillary array, affecting the stability and service life of the system and increasing the maintenance cost of the equipment. Summary of the Invention

[0005] The main objective of this invention is to provide a fast neutron imaging detection system and its application. The technical problem to be solved is how to provide a fast neutron imaging detection system that improves its optical transmission efficiency and imaging quality, simplifies assembly, reduces the overall size of the system, and improves the stability of system operation.

[0006] The objective of this invention and the technical problem it solves are achieved through the following technical solution. A fast neutron imaging detection system according to this invention includes: The shielding shell has a fast neutron incident window at one end; An integrated liquid scintillator capillary array is housed within a shielding housing. The integrated liquid scintillator capillary array includes an array substrate, a liquid scintillator, a first seal, and a second seal. The array substrate comprises an integrally formed straight region and a conical region. The straight region is composed of multiple capillaries with parallel axes. The conical region is formed by the gradual contraction of the multiple parallel capillaries, with each capillary extending seamlessly and continuously from the straight region to the conical region and contracting synchronously. The liquid scintillator fills the internal channels of each capillary, and the refractive index of the liquid scintillator is higher than that of the capillaries. The first seal is located at the end of the straight region to seal the liquid scintillator and allow fast neutrons to enter. The second seal is located at the end of the conical region to seal the liquid scintillator and allow optical signal output. The first seal is embedded within the fast neutron incident window. A photoelectric detection component is disposed within a shielded housing; the photoelectric detection component includes an input window; the input window is tightly fitted to and docked with the second sealing element; the photoelectric detection component is used to collect and process optical signals; An image output terminal is located outside the shielding housing; the photoelectric detection component is externally connected to the image output terminal via a data cable; the image output terminal is used to output fast neutron imaging images.

[0007] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0008] Preferably, in the fast neutron imaging detection system, the shielding shell has a double-layer structure, with the outer layer being a lead material with a thickness greater than 5 cm and the inner layer being a boron-containing polyethylene material with a thickness greater than 10 cm.

[0009] Preferably, in the fast neutron imaging detection system, the size of the fast neutron incident window matches the cross-sectional size of the straight region.

[0010] Preferably, in the fast neutron imaging detection system, the inner diameter of a single capillary in the straight region is 20 μm to 500 μm, and the length is ≥10 cm.

[0011] Preferably, in the fast neutron imaging detection system, the shrinkage ratio of the cone region is greater than 1 and less than 10.

[0012] Preferably, in the fast neutron imaging detection system, the capillary material is glass; the integrated liquid scintillator capillary array further includes a light-absorbing layer disposed between adjacent capillaries; the hydrogen atom content of the liquid scintillator is ≥4×10⁻⁶. 22 pcs / cm 3 .

[0013] Preferably, in the fast neutron imaging detection system, the photoelectric detection component is an ICCD camera with gated function. The ICCD camera is equipped with a signal processing unit, the single pixel size is smaller than the center distance of the capillary aperture at the conical end, and the gated accuracy is better than 2ns.

[0014] Preferably, in the fast neutron imaging detection system, the input window is a second fiber optic panel; the second sealing element is a first fiber optic panel; the size of the second fiber optic panel is not smaller than the size of the first fiber optic panel, and the two are bonded together with optical adhesive with a bonding gap ≤0.1mm.

[0015] The objective of this invention and the technical problem it solves are achieved through the following technical solution. A fast neutron imaging method according to this invention, implemented using the aforementioned fast neutron imaging detection system, includes the following steps: S1 fast neutrons pass through the first seal embedded in the incident window of the shielded shell and enter the straight region of the integrated liquid scintillator array. S2 fast neutrons elastically collide with hydrogen atoms in the liquid scintillator in the straight region to produce recoil protons, which excite the scintillator to generate visible light signals; the visible light is transmitted through total internal reflection in the capillary. S3 visible light is transmitted along the capillary to the conical region, and after being converged by the gradually contracting capillary, it is output from the second seal at the end of the conical region; S4 visible light enters the photoelectric detection component through the docked input window, is converted into an electrical signal, and after signal processing, is transmitted to the image output terminal to generate a fast neutron imaging image.

[0016] The objective of this invention and the technical problem it solves are achieved through the following technical solution: An application of the aforementioned fast neutron imaging detection system in inertial confinement fusion diagnostics, according to this invention.

[0017] By employing the above technical solution, the fast neutron imaging detection system and its application proposed in this invention have the following beneficial effects: The fast neutron imaging detection system and its application proposed in this invention adopt an integrated liquid scintillator capillary array with straight and conical regions molded in one piece, eliminating the need for separate optical cone components. This completely eliminates the assembly gap and pixel misalignment problems caused by separate coupling, reduces optical signal leakage and scattering loss, and eliminates resolution loss. At the same time, it eliminates the need for high-precision alignment between the optical cone and the array, simplifying the assembly process and reducing production costs. The integrated optical path makes the overall structure more compact and less susceptible to component displacement due to vibration, significantly improving the system's imaging stability.

[0018] Furthermore, this system is equipped with a double-layer shielding shell, which can isolate external stray neutrons and gamma-ray interference, effectively improving the imaging signal-to-noise ratio; and with an incident window of the corresponding size, it can completely receive all incident fast neutron signals.

[0019] Furthermore, by limiting the inner diameter, length, and conical contraction range of the capillary, the free path characteristics of high-energy fast neutrons can be adapted to avoid crosstalk between channels and ensure basic imaging resolution; adapting to transparent materials ensures total internal reflection transmission of light within the capillary and reduces light loss within the channel.

[0020] Furthermore, by using a gated ICCD as a photoelectric detection component, it is possible to accurately acquire transient nuclear reaction signals, and smaller pixel size avoids coupling resolution loss; the fiber optic panels at both ends are tightly bonded with optical adhesive, which greatly reduces interface light leakage and further improves optical transmission efficiency.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the fast neutron imaging detection system of the present invention, wherein 1-integrated liquid scintillator array, 2-photoelectric detection component, 21-input window, 3-shielding shell, 31-inner layer of shielding shell, 32-outer layer of shielding shell, 4-image output terminal, 5-data line; Figure 2 This is a schematic diagram of the integrated liquid scintillator capillary array arrangement structure in the fast neutron imaging detection system of the present invention; wherein, 11-first sealing element, 12-second sealing element, 13-array substrate, 131-straight region, 132-conical region, 14-liquid scintillator, 15-capillary, 16-light absorption layer, 17-edge region. Detailed Implementation

[0023] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following detailed description, in conjunction with preferred embodiments, provides a fast neutron imaging detection system and its application according to the present invention, including its specific implementation and effects. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, the results of one or more embodiments can be combined in any suitable manner. These embodiments are provided to make the invention thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​described in these embodiments should be interpreted as merely exemplary and not as limiting.

[0024] This invention proposes a fast neutron imaging detection system, as shown in the attached figure. Figure 1 and attached Figure 2 As shown, it includes an integrated liquid scintillation capillary array 1, a photodetector component 2, a shielding housing 3, and an image output terminal 4. The integrated liquid scintillation capillary array and the photodetector component are both housed within the shielding housing; the image output terminal is located outside the shielding housing and is used to output fast neutron imaging images. A fast neutron incident window is provided at one end of the shielding housing. The integrated liquid scintillation capillary array includes a first sealing element 11 and a second sealing element 12. The photodetector component includes an input window 21 for acquiring and processing optical signals. The first sealing element is embedded within the fast neutron incident window; the input window is tightly fitted to and docked with the second sealing element; the photodetector component is externally connected to the image output terminal via a data cable 5.

[0025] In the above technical solution, the integrated liquid scintillation capillary array is the most critical structural component. Besides the first and second sealing elements, it also includes an array substrate 13. The array substrate is a monolithically formed structure, comprising a connected straight region 131 and a conical region 132. The straight region consists of multiple parallel capillaries 15, used to receive fast neutrons and convert them into visible light signals. The conical region is formed by the gradual contraction of the same set of capillaries. Each capillary extends seamlessly and continuously from the straight region to the conical region and contracts synchronously, ensuring a one-to-one correspondence and continuous co-origin of the capillary channels in the straight and conical regions, without segmented docking structures. This allows for the convergence and conduction of the visible light signals generated in the straight region, directly transmitting them to the photoelectric detection module. Liquid scintillators 14 are filled within the internal channels of each capillary. The refractive index of the liquid scintillators is higher than that of the capillaries. The first sealing element is assembled at the end of the straight section to seal the liquid scintillators and allow fast neutrons to be incident into the liquid scintillator capillary array. The second sealing element is assembled at the end of the conical section to seal the liquid scintillators and allow optical signal output. Fast neutrons incident on and bombard the liquid scintillators to generate fluorescence. The generated fluorescence signal is transmitted along the capillary channel and then sequentially through the second sealing element and the input window to the photodetector assembly. The photodetector assembly collects and processes the optical signal, and then outputs the detection result to the image output terminal via a data line.

[0026] In some specific embodiments of the present invention, a light-absorbing layer 16 is preferably provided between adjacent capillaries in the array substrate; the visible light transmittance of the light-absorbing layer glass at a thickness of 0.4 mm is ≤1%. This light-absorbing layer glass can efficiently absorb crosstalk light between capillaries.

[0027] In some specific embodiments of the present invention, a solid glass edging region 17 is preferably formed around the outer periphery of the array substrate. The softening point temperature of the glass in this edging region is lower than that of the capillary wall material and the light-absorbing layer glass. Its function is to homogenize the pressure during melting and pressing, homogenize the tensile force during drawing, and provide mechanical strength.

[0028] In some specific embodiments of the present invention, the inner diameter of a single capillary in the straight region is preferably 20 μm to 500 μm and the length is ≥10 cm. This setting is because the detection target is a parallel fast neutron beam. The free path of high-energy fast neutrons is about 10 cm. Fast neutrons have strong penetrating power. If the length of the parallel capillary is short, the fast neutrons will penetrate multiple capillary tubes in the conical region, resulting in a decrease in resolution.

[0029] In some specific embodiments of the present invention, the cross-section of the array substrate is preferably a circular, tightly packed structure, and the cross-sectional size is set according to the imaging field of view requirements to ensure that the incident fast neutron signal can be fully received while ensuring the spatial resolution of the signal conversion.

[0030] In some specific embodiments of the present invention, the shrinkage ratio of the tapered region is preferably greater than 1 and less than 10. Tapered fibers inevitably suffer from light transmission loss; if the shrinkage ratio is too high, the light transmission loss will be excessive, and it will be detrimental to the fabrication process.

[0031] In some specific embodiments of the present invention, it is preferred that the cross-sectional size of the end of the conical region is not less than the size of the input window of the photoelectric detection component, so as to improve the utilization rate of light signal and imaging resolution.

[0032] In some specific embodiments of the present invention, the capillary material is preferably glass to ensure that the visible light signal can be transmitted by total internal reflection in the capillary, thereby reducing the loss of the light signal.

[0033] In some specific embodiments of the present invention, the liquid scintillator is preferably a hydrogen-containing scintillator liquid with a hydrogen atom content ≥ 4 × 10⁻⁶. 22 pcs / cm 3 This ensures that fast neutrons collide elastically with hydrogen atoms in the liquid scintillator to generate a sufficient number of recoil protons, which are then efficiently converted into visible light signals.

[0034] In some specific embodiments of the present invention, the first sealing element is preferably glass, and the second sealing element is an optical fiber panel.

[0035] In some specific embodiments of the present invention, the above-mentioned integrated liquid scintillation capillary array is prepared according to the following steps: First, the glass preform tube is drawn twice to obtain secondary multifilaments. After the secondary multifilaments are arranged and shaped, they are melted, pressed, rolled, and cut to obtain the first blank segment. The first blank segment includes multiple capillary tubes with parallel axes. The process from the glass preform tube to the first blank segment can refer to conventional processes in the field, and the present invention does not specifically limit it.

[0036] In some specific embodiments of the present invention, the preparation of secondary multifilaments specifically includes steps such as glass material preparation, preform preparation, and capillary drawing. Detailed explanations are as follows: In the first preform of the liquid scintillation capillary array of the present invention, a light-absorbing glass layer is preferably provided between adjacent glass preforms, and a solid glass layer is wrapped around the outermost layer as an edge-sealing area during the secondary multifilament arrangement. The glass preforms are processed into capillaries, hence the material is also called capillary glass.

[0037] When preparing the glass materials, it is preferable that the softening points of the capillary glass, the light-absorbing layer glass, and the solid glass in the edge region have a gradient. This gradient setting helps the light-absorbing layer glass soften and fuse first during drawing, even before the solid glass in the edge region is added, while the inner wall glass still maintains its circular shape. After adding the solid glass in the edge region, during capillary pressing, the edge region material softens and fuses first, while the array region capillary still maintains its circular shape, overcoming the problem of capillary deformation under high temperature. However, the softening point gradient of the above-mentioned glass should not be too large, especially the softening point of the edge glass should not be too low, otherwise it will cause the edge region to separate from the array region during subsequent tapering. Preferably, the softening point of the light-absorbing layer glass is 30°C to 60°C lower than that of the capillary glass, and the softening point of the solid glass in the edge region is 20°C to 40°C lower than that of the light-absorbing layer glass.

[0038] In some specific embodiments of the present invention, the capillary glass is processed into a glass tube with a circular cross-section, preferably with a wall thickness of 2-4 mm and an inner diameter of 20-50 mm. The light-absorbing layer is made of light-absorbing glass, which is first processed into a glass tube with a circular cross-section, preferably with an inner diameter 0.5-1 mm larger than the outer diameter of the capillary glass tube and a wall thickness of 1-3 mm; then the light-absorbing glass tube is nested around the capillary glass tube to form a pre-fabricated tube, thereby enabling it to absorb crosstalk light in all directions at 360°.

[0039] In some specific embodiments of the present invention, the solid glass in the edge area is first processed into a glass rod with a regular hexagonal cross-section, preferably with a side-to-side distance of 20~50mm; then the glass rod is drawn into an edge-bound glass monofilament, preferably with a side-to-side distance of 0.5~2mm.

[0040] Regarding the selection of the aforementioned rod size, excessively thin dimensions will result in low material utilization, while excessively thick dimensions will lead to a large temperature difference between the center and periphery of the rod during drawing, resulting in poor uniformity of the capillary pore size. The wall thickness is set to ensure that the final capillary has the necessary strength, while not reducing the detection efficiency due to excessive wall thickness and low duty cycle.

[0041] In some specific embodiments of the present invention, capillary drawing is performed in two stages. The first stage involves drawing a pre-formed tube to obtain multiple circular primary multifilaments, preferably with a cross-sectional diameter of 0.5-2 mm. If the diameter of the primary multifilaments is too small, the subsequent bar arrangement operation will be more difficult; however, if the diameter is too large, the diameter accuracy during drawing will be difficult to control, resulting in significant deviations and more gaps during subsequent bar arrangement. Then, the obtained primary multifilaments are hexagonally stacked to obtain multifilament rods with a hexagonal cross-section. Preferably, the distance between opposite sides of the multifilament rod is 15-50 mm to meet the requirements for material utilization and temperature homogenization. A second stage of drawing is then performed, i.e., drawing the arranged multifilament rods to obtain secondary multifilaments. Preferably, the distance between opposite sides of the cross-section of the secondary multifilament is 0.5-2 mm to meet the requirements for accuracy control and subsequent array arrangement. After the two stages of drawing, the inner diameter of a single capillary within the obtained secondary multifilament is preferably 20 μm-500 μm.

[0042] In some specific embodiments of the present invention, preparing the secondary multifilament into a first blank specifically includes steps such as array arrangement, melting and pressing, rounding, and cutting. Detailed explanations are as follows: Hexagonal multifilaments and edge-sealing glass monofilaments are arranged at fixed lengths to form a hexagonal blank segment, preferably 300-500 mm in length. This length is designed to ensure sufficient straightness while forming a tapered region. The central part of the array consists of a capillary bundle with an approximately circular cross-section, forming the array region. Multiple layers of edge-sealing glass monofilaments surround this array, forming the edge-sealing region, preferably 5-20 mm thick. The edge-sealing region softens the glass during melting and pressing to homogenize stress and protects the channel area during tapering. If the edge-sealing region is too thin, the homogenization effect during melting and pressing will be ineffective, or it may crack under the clamping force during tapering. If it is too thick, unnecessary material waste will occur. The array is arranged in a regular hexagonal shape to ensure compatibility with the shape of conventional melting and pressing molds.

[0043] The arranged array is loaded into a melting and pressing mold and melted at high temperature to form a blank. Generally, the melting and pressing temperature is set higher than the softening point of the light-absorbing layer glass and lower than the softening point of the capillary glass. This is because at this melting and pressing temperature, the light-absorbing layer glass is already in a softened state while the capillary glass is still not softened, so that the capillaries can still maintain their circular structure while being fused together by the light-absorbing layer glass.

[0044] The blank segment with the above-mentioned cross-section is rounded and cut. The six corners of the edge area are removed, and the two ends of the blank segment are cut flat to form the first blank segment with a circular cross-section, so that the heat and force are more uniformly transferred during the subsequent tapering process.

[0045] The second step is tapering, which involves inserting the first billet into a zoned temperature-controlled heating furnace, aligning the billet axis with the furnace axis, continuously introducing protective gas into the capillary, and simultaneously applying tension along the billet axis to both ends to draw it, thereby obtaining a second billet with a straight zone and a pre-formed conical zone. The zoned temperature-controlled heating furnace includes three temperature zones: a high-temperature zone in the center and secondary high-temperature zones at both ends.

[0046] The tapering step described above is a key step in the integral forming of the straight and tapered regions of this invention. In some specific embodiments of this invention, the tapering process is implemented using specially designed tapering equipment.

[0047] Specifically, the tapering device is a horizontal structure, including a zoned temperature-controlled heating furnace. The heating furnace has two opposing openings for the blank segments to be inserted into the furnace during installation. Along the stretching axis of the blank, the heating furnace has at least a central high-temperature zone and secondary high-temperature zones on both sides of the high-temperature zone. This three-zone temperature configuration ensures that the middle of the first blank segment softens while the two ends remain unsoftened, so that only the central specific area narrows when tension is applied, while the radial dimensions at both ends remain unchanged. In the central region, the degree of softening of the glass varies at different locations, thus making the radial dimension of the central narrowing area gradually change.

[0048] The tapered device also includes two clamping members, symmetrically arranged on the outside of the two openings of the heating furnace, for clamping the billet segment passing through the heating furnace so that its axis coincides with the axis of the heating furnace.

[0049] The tapered device also includes a lead screw assembly, which is connected to two clamping members via a column; the lead screw can drive the two clamping members to translate towards or away from each other; when the two clamping members move away from each other in coordination with the lead screw, a pulling force can be applied to the clamped blank segment to reduce its diameter in the middle.

[0050] The tapering device also includes a gas supply assembly, comprising a gas cylinder, a gas supply pipeline, and a hollow sealing element. The sealing element is fitted inside the clamping element, with one side conforming to the clamping element and the other side conforming to the edge area of ​​the billet end cap to ensure an airtight seal between the billet and the clamping element. One end of the gas supply pipeline is connected to the gas cylinder, and the other end passes through the sealing element. The sealing element is tightly fitted against the outer wall of the gas supply pipeline to ensure an airtight seal. This is used to fill the capillary tube of the billet with gas to provide internal air pressure support for the array area, thereby ensuring the shape of the capillary tube is maintained. The tapering process specifically includes the following steps: A. The first billet segment is passed through a zone-controlled temperature heating furnace, ensuring that the axis of the first billet segment coincides with the axis of the heating furnace to guarantee uniform heating in all radial directions during heating. Both ends of the first billet segment are fixed to two adjustable clamping members. Hollow sealing elements are installed within the clamping members, which hold and fix the billet segment at both ends. The sealing elements are tightly fitted against the edge area of ​​the billet segment's end face, thus preventing gas exchange between the array area and the external environment. The edge area is solid, providing sufficient mechanical strength for clamping and sealing operations. The array area is hollow. The other end of the sealing element is connected to a gas supply line to a gas cylinder. The gas supply line passes through the sealing element and is tightly fitted against it to maintain airtightness. Since the purpose of gas filling is to support the shape, to avoid interaction between the gas and the glass, the gas used in this invention is preferably an inert gas such as nitrogen or argon.

[0051] B. The central region of the first billet is placed in the high-temperature zone, with the temperature set 20-50°C above the softening point of the capillary glass. The remaining regions of the first billet are placed in the secondary high-temperature zones on both sides and outside the furnace, with the secondary high-temperature zones set 50-150°C below the softening point of the capillary glass. Nitrogen or argon gas is introduced into the array area and reaches the capillary. The high-temperature zone temperature setting at this stage is to create a low-viscosity zone in the center of the first billet, facilitating tapering during the drawing process. If the high-temperature zone temperature is set too low, tapering will be difficult or take too long; if it is set too high, the glass will be too fluid, making it difficult to control the regularity of the tapered shape. The secondary high-temperature zone temperature setting is to allow the portion of the first billet near the center to complete the transition from the straight zone to the tapered zone. The side of the secondary high-temperature zone closer to the high-temperature zone forms a transition zone through the thermal radiation of the high-temperature zone, while the side farther from the high-temperature zone ensures the stability of the straight zone. If the secondary high-temperature zone temperature is set too low, a temperature drop may cause severe abrupt changes in the cone shape; if it is set too high, the stability of the straight zone cannot be guaranteed.

[0052] C. The movement of the lead screw assembly causes the two clamping parts to translate in opposite directions, causing the portion of the first blank section in the high-temperature zone to thin under tension. At high temperature, the gas inside the capillary expands, providing strong support for the capillary and ensuring that it maintains its round structure during deformation. As the two clamping parts move in opposite directions, the thinned blank section moves to the secondary high-temperature zone for cooling and solidification, resulting in a second blank section with a straight region and a pre-formed conical region. After tapering, the shrinkage ratio at the thinnest part of the cone is preferably greater than 1 and less than 10.

[0053] The third step is end-face processing. Specifically, after the second blank is removed from the clamping device, a cutting machine is used to cut along the radial cross-section of the second blank at both ends and the narrowest point in the middle, forming a flat surface. After cutting, each second blank becomes two cut pieces with one straight end and one tapered end. The cutting surface is perpendicular to the capillary axis, facilitating subsequent end-face encapsulation of lenses or fiber optic panels. Water is used as the coolant during cutting to facilitate subsequent cleaning. The cut pieces are then ultrasonically cleaned and dried to remove glass debris or cutting fluid impurities that entered the capillary during end-face processing, resulting in the third blank.

[0054] The fourth step is filling the liquid flash, which involves filling the array area of ​​the third billet section with liquid flash under the action of a peristaltic pump. Both the straight and conical areas are filled with liquid flash.

[0055] Finally, there is the encapsulation process, which involves using optical adhesive to seal the straight section end with glass and the tapered section end with an optical fiber panel. In other words, the first sealing element is assembled at the end of the straight section and the second sealing element is assembled at the end of the tapered section.

[0056] In some specific embodiments of the present invention, a solid glass edging region is preferably formed around the outer periphery of the array substrate. The softening point temperature of the glass in this edging region is lower than that of the capillary wall material and the light-absorbing layer glass. Its function is to homogenize the pressure during melting and pressing, homogenize the tensile force during drawing, and provide mechanical strength.

[0057] In some specific embodiments of the present invention, the shielding shell has a double-layer structure, with the outer layer being lead material with a thickness of >5cm and the inner layer being boron-containing polyethylene material with a thickness of >10cm; this arrangement is to enable it to better shield external stray neutrons and gamma rays, avoid them interfering with the normal operation of the system, and ensure that the imaging has a high signal-to-noise ratio.

[0058] In some specific embodiments of the present invention, a fast neutron incident window is provided at one end of the shielding shell, the size of which matches the cross-sectional size of the straight region of the integrated liquid scintillator array, to ensure that all incident fast neutrons can be received by the straight region.

[0059] In some specific embodiments of the present invention, the photoelectric detection component is an ICCD camera with gated function, and the single pixel size is smaller than the center distance of the capillary aperture at the conical end, thereby avoiding coupling resolution loss; the gated function has an accuracy better than 2ns, enabling it to achieve nanosecond or even picosecond level exposure, thereby enabling rapid capture of physical processes such as nuclear reactions.

[0060] In some specific embodiments of the present invention, the input window is a second optical fiber panel; the second sealing member is a first optical fiber panel; the size of the second optical fiber panel is not smaller than the size of the first optical fiber panel, and the two are bonded together with optical adhesive, with a bonding gap ≤0.1mm; the purpose of this technical arrangement is to avoid optical signal leakage at the junction and further improve the optical signal transmission efficiency. The signal processing module in the ICCD camera is used to collect and normalize the electrical signal and convert it into a digital signal, and to perform noise reduction, enhancement, and other processing on the digital signal to output a clear fast neutron imaging image.

[0061] This invention also proposes a fast neutron imaging method, implemented using the aforementioned fast neutron imaging detection system, comprising the following steps: S1 fast neutrons pass through the fast neutron incident window of the shielding shell and are injected into the straight region of the integrated liquid scintillation capillary array through the first seal embedded inside the incident window. S2 fast neutrons collide elastically with hydrogen atoms in a high-hydrogen-content liquid scintillator in the straight region, producing recoil protons. The recoil protons excite the scintillator to generate a visible light signal. Because the refractive index of the liquid scintillator is higher than that of the capillary material, the visible light undergoes total internal reflection within the capillary wall and is transmitted downstream. S3 visible light is transmitted along parallel capillaries to an integrally formed conical region, and after being converged and collected by a gradually shrinking capillary bundle, it is output from the second seal (first optical fiber panel) at the end of the conical region. S4 visible light is input into the ICCD camera through the second fiber optic panel bonded with optical adhesive. The camera's built-in signal processing unit converts the optical signal into a weak electrical signal, and then performs amplification, filtering and shaping, analog-to-digital conversion, image noise reduction and reconstruction processing in sequence. Finally, it is transmitted to the external image output terminal via a data cable to output a complete fast neutron imaging image.

[0062] The present invention also proposes an application of the aforementioned fast neutron imaging detection system in the diagnosis of inertial confinement fusion, specifically, the system is used for the spatial distribution diagnosis of 14MeV fast neutrons in laser-driven and Z-Pinch-driven inertial confinement fusion devices.

[0063] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0064] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0065] Example 1 This embodiment is a fast neutron imaging system based on an integrated liquid scintillation capillary array, including an integrated liquid scintillation capillary array, an ICCD camera with a second fiber optic panel, and a shielded shell composed of a lead shielding layer and a boron-containing polyethylene shielding layer. The integrated liquid scintillation capillary array and the ICCD camera with the second fiber optic panel are both encapsulated in the shielded shell, with only the quartz glass window of the liquid scintillation capillary array exposed. The first fiber optic panel of the liquid scintillation capillary array is in close contact with the second fiber optic panel of the ICCD camera, and the ICCD camera is connected to the computer via a data cable.

[0066] The integrated liquid scintillator capillary array is a single-piece structure. The capillary walls are made of glass with a refractive index of 1.5, and light-absorbing glass is contained between the capillary walls. Along the fast neutron incident direction, it includes a straight region and a conical region, seamlessly connected. Both the straight and conical regions are filled with a liquid scintillator, which is a hydrogen-containing scintillator liquid with a hydrogen atom content of 5.43 × 10⁻⁶. 22 pcs / cm 3 The refractive index of the liquid scintillator is 1.57.

[0067] The straight region is a parallel capillary array structure, with the capillary cross-section being a circular hexagonal close-packed structure. The inner diameter of a single capillary is 100 μm, the length is 11 cm, the center-to-center distance between adjacent capillary tubes is 120 μm, and the cross-section of the array is a circle with a diameter of 100 mm; the end of the straight region away from the conical region is sealed with quartz glass.

[0068] The conical region is a gradually shrinking capillary array structure. Its input end is seamlessly connected to the output end of the straight region. The cross-sectional dimensions of the input end are the same as those of the straight region. Each capillary gradually shrinks from the input end to the output end. The length of the shrinking region is 60mm. The cross-section at the output end is a circle with a diameter of 30mm. The average inner diameter of the capillary at the output end is 30μm, and the average center distance between adjacent capillary tubes is 36μm. The output end of the conical region is sealed with an optical fiber panel.

[0069] The ICCD camera has a single pixel size of 13μm×13μm. Its second fiber optic panel at the light-receiving end has a circular cross-section with a diameter of 40mm. It is tightly fitted to the output end of the fiber optic panel of the integrated liquid scintillator array, with a fitting gap of 0.05mm.

[0070] The shielding shell is made of an outer lead layer and an inner boron-containing polyethylene neutron shielding material. The lead shielding layer is 6cm thick and the boron-containing polyethylene shielding layer is 11cm thick. The shielding shell has a 100mm diameter hollow circle. The quartz glass of the integrated liquid scintillator capillary array is inserted in the hollow to become a fast neutron incident window.

[0071] The specific work process is as follows: 1) Fast neutrons pass through the quartz glass fast neutron incident window on the shielding shell and are incident into the straight region of the integrated liquid scintillator array; 2) Fast neutrons collide elastically with hydrogen atoms in the liquid scintillator in the straight region, producing recoil protons. The recoil protons interact with the scintillator solute in the liquid scintillator, converting the energy of the fast neutrons into visible light signals. 3) Visible light signals are transmitted to the conical region through total internal reflection in the parallel capillaries in the straight region. The tapered capillary array in the conical region converges and conducts the visible light signals, so that the light signals are precisely matched to the second fiber optic panel of the light receiving end of the ICCD camera. 4) The ICCD camera acquires visible light signals within 10ns, converts them into weak electrical signals, and after amplification, filtering and shaping, and conversion into digital signals, the image processing unit performs noise reduction, enhancement, reconstruction and other processing, and finally presents a clear fast neutron imaging image on the computer.

[0072] The technical features in the claims and / or specification of this invention can be combined, and the combination is not limited to the combinations obtained through reference in the claims. Technical solutions obtained by combining the technical features in the claims and / or specification are also within the scope of protection of this invention.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A fast neutron imaging detection system, characterized in that, include: The shielding shell has a fast neutron incident window at one end; An integrated liquid scintillation capillary array is housed within a shielded housing; The integrated liquid scintillator capillary array includes an array substrate, a liquid scintillator, a first seal, and a second seal. The array substrate includes an integrally formed straight region and a conical region. The straight region is composed of multiple capillaries with parallel axes. The conical region is formed by the gradual contraction of the multiple parallel capillaries, with each capillary extending seamlessly and continuously from the straight region to the conical region and contracting synchronously. The liquid scintillator fills the internal channels of each capillary, and the refractive index of the liquid scintillator is higher than that of the capillaries. The first seal is disposed at the end of the straight region to seal the liquid scintillator and allow fast neutrons to enter. The second seal is disposed at the end of the conical region to seal the liquid scintillator and allow optical signal output. The first seal is embedded in the fast neutron incident window. A photoelectric detection component is disposed within a shielded housing; the photoelectric detection component includes an input window; the input window is tightly fitted to and docked with the second sealing element; the photoelectric detection component is used to collect and process optical signals; An image output terminal is located outside the shielding housing; the photoelectric detection component is externally connected to the image output terminal via a data cable; the image output terminal is used to output fast neutron imaging images.

2. The fast neutron imaging detection system according to claim 1, characterized in that, The shielding shell has a double-layer structure, with the outer layer being lead material with a thickness greater than 5cm and the inner layer being boron-containing polyethylene material with a thickness greater than 10cm.

3. The fast neutron imaging detection system according to claim 1, characterized in that, The size of the fast neutron incident window matches the cross-sectional size of the straight region.

4. The fast neutron imaging detection system according to claim 1, characterized in that, The inner diameter of a single capillary in the straight region is 20μm~500μm, and the length is ≥10cm.

5. The fast neutron imaging detection system according to claim 1, characterized in that, The contraction ratio of the conical region is greater than 1 and less than 10.

6. The fast neutron imaging detection system according to claim 1, characterized in that, The capillary material is glass; the integrated liquid scintillator array further includes a light-absorbing layer disposed between adjacent capillaries; the hydrogen atom content of the liquid scintillator is ≥4×10⁻⁶. 22 pcs / cm 3 .

7. The fast neutron imaging detection system according to claim 1, characterized in that, The photoelectric detection component is an ICCD camera with gating function. The ICCD camera is equipped with a signal processing unit, and the single pixel size is smaller than the center distance of the capillary hole at the conical end. The gating accuracy is better than 2ns.

8. The fast neutron imaging detection system according to claim 7, characterized in that, The input window is a second fiber optic panel; the second sealing element is a first fiber optic panel; the size of the second fiber optic panel is not smaller than the size of the first fiber optic panel, and the two are bonded together with optical adhesive with a bonding gap of ≤0.1mm.

9. A fast neutron imaging method, implemented using the fast neutron imaging detection system according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1 fast neutrons pass through the first seal embedded in the incident window of the shielded shell and enter the straight region of the integrated liquid scintillator array. S2 fast neutrons elastically collide with hydrogen atoms in the liquid scintillator in the straight region to produce recoil protons, which excite the scintillator to generate visible light signals; the visible light is transmitted through total internal reflection in the capillary. S3 visible light is transmitted along the capillary to the conical region, and after being converged by the gradually contracting capillary, it is output from the second seal at the end of the conical region; S4 visible light enters the photoelectric detection component through the docked input window, is converted into an electrical signal, and after signal processing, is transmitted to the image output terminal to generate a fast neutron imaging image.

10. An application of the fast neutron imaging detection system according to any one of claims 1 to 8 in the diagnosis of inertial confinement fusion.

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