A composite parabolic focusing target and its preparation process

Abstract

The present invention provides a compound parabolic focusing target and its preparation process, the target comprising: a compound parabolic target shell, the inner surface of which is an axisymmetric shell formed by rotating a parabola 180 degrees along a central axis, the shell being cut off by a curved surface along the extension line of the parabola to ensure that the laser focus point is located outside the laser output port; a vertical target stand for supporting the compound parabolic target shell and vertically fixing the compound parabolic target shell. Precision machining technology is used to manufacture the metal shell, and the parabolic shell is prepared by combining precision turning technology, thick metal electroplating technology, and dual-mode corrosion technology; and high-precision 3D printing technology is used to complete the manufacture of its vertical target stand. The design of the compound parabolic focusing target allows the laser to enter from the target shell inlet and, after at most one reflection, be focused on one point through the laser output port, effectively reducing the laser power required for fusion ignition.

Description

Technical Field

[0001] The present invention relates to a target in the field of inertial confinement fusion, and in particular to a composite parabolic focusing target and a preparation process thereof. Background Art

[0002] In laser fusion ignition devices, a combination of a metal cone and a polymer ablation layer is often used to enhance the laser ignition energy. A typical example is the conical target type mentioned by Zhang Jie et al. in June 2020 (patent number: CN111681783 A). This target type pushes the fuel layer through the ablation layer and uses a tapered conical structure to achieve energy enhancement. Therefore, the assembly process has extremely high requirements for micro-nano processing technology and the output is very low. On the other hand, due to the particularity of fusion, the elemental composition of the ablation layer and the fuel layer is strictly restricted. Therefore, the range of material selection is very small and the cost of each fusion ignition target is extremely high.

[0003] In a broad application area, compound parabolic concentrators are mainly used for the efficient collection of sunlight. Their manufacturing substrate is mainly based on polymethyl methacrylate (PMMA) (take the article "Fabrication of high-performance luminescent solar concentrators using N-doped carbondots / PMMA mixed matrix slab" published by Gong et al. in 2018 as an example). However, PMMA has strong absorption of light. In order to enhance the light reflectivity of PMMA, a layer of metal is often deposited on the surface of PMMA. In addition, as mentioned in the article "Surface Construction and Optical Analysis of a New Circular Absorber Solar Compound Parabolic Concentrator" by Chen Fei et al. in 2019, compound parabolic concentrators are often used at the macro level, and are rarely processed and manufactured at the micro-nano level. Summary of the Invention

[0004] In response to the defects in the prior art, the purpose of the present invention is to provide a compound parabolic focusing target type and preparation process, which can reduce the alignment error between the laser and the target, greatly reduce the process difficulty and processing cost, increase the reliability of the laser ignition device, and improve the success rate of laser ignition.

[0005] A first aspect of the present invention provides a compound parabolic focusing target, comprising:

[0006] The inner surface of the composite parabolic target shell is an axisymmetric shell formed by rotating the parabola 180 degrees along the central axis. The shell is cut by a curved surface along the extended line of the parabola to ensure that the laser focus is located outside the laser output port.

[0007] The vertical target stand is used to support the compound parabolic target shell and vertically fix the compound parabolic target shell.

[0008] Optionally, the compound parabolic target shell, wherein the parabola equation is y=x 2 / 30.

[0009] Optionally, the vertical target stand includes: an upper annular body; a lower annular body located directly below the upper annular body; the diameter of the lower annular body is larger than that of the upper annular body; and a support beam connecting the upper annular body and the lower annular body.

[0010] Optionally, the centers of the upper annular body and the lower annular body are on the same vertical line, one end of the compound parabolic target shell passes through the upper annular body and reaches the plane where the lower annular body is located, and the inner surfaces of the upper annular body and the lower annular body are fitted with the outer surface of the compound parabolic target shell to ensure that the compound parabolic target shell is vertical.

[0011] Optionally, the upper annular body of the vertical target mount is provided with a notch structure with adjustable diameter to enable the fixing of compound parabolic target shells of different diameters. Without requiring the lower annular body of the vertical target mount to be coplanar with the laser output port, compound parabolic target shells of different lengths can be fixed.

[0012] A second aspect of the present invention provides a process for preparing a compound parabolic focusing target, comprising:

[0013] The target base is turned out by fine machining process and has a parabolic shape;

[0014] A thick layer of metal is electroplated on the tip of the target base, and the target shape and size required are cut using a finishing process;

[0015] The tip of the target base is removed and placed in a release liquid, and the final composite parabolic target shell is released by dynamic corrosion and static corrosion.

[0016] The taken-out compound parabolic target shell is placed on the vertical target stand and fixed with liquid glue to complete the assembly.

[0017] Optionally, the target base is composed of a substrate and a tip located on the substrate, and the target base is made of a conductive material, preferably a metal material.

[0018] Optionally, before electroplating a thick metal layer on the tip of the target base, the process also includes: first coating a seed layer on the tip. Depending on the characteristics of the electroplated metal, the tip of the target base itself can serve as a seed layer, and the electroplating material and the seed layer material cannot be the same.

[0019] Optionally, the vertical target stand and the compound parabolic target shell are connected by gluing heterogeneous materials, including:

[0020] Use a clamp to place the compound parabolic target shell into the vertical target stand;

[0021] Dip a small amount of curing glue onto the annular body on the vertical target stand to achieve a fixed connection between the composite parabolic target shell and the vertical target stand.

[0022] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0023] Compared with the conical target, the composite parabolic focusing target of the present invention can reduce the influence of the alignment error between the laser and the target and improve the laser efficiency; and can simplify the preparation method, reduce the processing cost and improve the output.

[0024] Compared with the compound parabolic concentrator widely used in sunlight collectors, the preparation process of the compound parabolic concentrating target type of the present invention realizes the miniaturization and metallization of the compound parabolic concentrating principle, increases the light reflectivity of the material, and can effectively improve the laser transmission efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0026] Figure 1 This is an overall diagram of a compound parabolic focusing target according to a preferred embodiment of the present invention;

[0027] Figure 2 This is a diagram of a target stand of the compound parabolic focusing target type of Example 1;

[0028] Figure 3 This is a process flow chart for preparing the composite parabolic focusing target of Example 1;

[0029] The marks in the figure respectively represent: compound parabolic focusing target laser output port 11, compound parabolic focusing target laser input port 12, compound parabolic target shell parabola 13, upper annular body 21, support beam 22, lower annular body 23, and target frame upper end diameter adjustable port 24. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0031] In the description of the present invention, it is necessary to understand that the orientation and positional relationships indicated by terms such as "upper" and "lower" are based on the orientation and positional relationships shown in the accompanying drawings, and are only used to facilitate the description of the present invention and its implementation methods. It does not indicate that the parts involved must have the specific orientation and position combination, and therefore cannot be understood as a limitation on the present invention.

[0032] Figure 1 This is an overall diagram of a compound parabolic focusing target according to a preferred embodiment of the present invention.

[0033] Reference Figure 1 As shown, this embodiment provides a compound parabolic focusing target, including: a compound parabolic target shell and a vertical target stand, wherein the inner surface of the compound parabolic target shell is an axisymmetric shell formed by rotating a parabola 180° along the central axis, and the shell is cut by a curved surface along the extension line of the parabola to ensure that the laser focus point is located outside the laser output port; the vertical target stand is used to support the compound parabolic target shell and fix the compound parabolic target shell vertically.

[0034] In some embodiments, the composite parabolic target shell is designed by truncating the curved surface along the extended line of the parabola to ensure that the laser focus is located outside the laser output port. The parabola equation includes the generalized parabola equation definition, preferably y = x 2 / 30. Figure 1 As shown, the overall shape of the compound parabolic target shell is a shape similar to a bullet head.

[0035] The compound parabolic focusing target in the above embodiment of the present invention can reduce the impact of laser and target alignment errors, improve laser efficiency, and is easy to prepare, which can reduce processing costs and increase output. It is a key component in solar energy collection, wireless communications, biomedicine and defense research, or any application that requires a focused divergent light source.

[0036] Figure 2 This is a diagram of the target stand of the compound parabolic focusing target type of Example 1.

[0037] Reference Figure 2 As shown, the vertical target stand is a frame structure that can vertically fix a compound parabolic target shell. In some embodiments, the vertical target stand includes: an upper annular body 21, a lower annular body 23, and a support beam 22. The upper annular body 21 and the lower annular body 23 are arranged vertically, with the lower annular body 23 located directly below the upper annular body 21 and having a larger diameter than the upper annular body 21. The support beam 22 connects the upper annular body 21 and the lower annular body 23, thereby connecting them into a single integrated target stand.

[0038] Specifically, such as Figure 1 、 2As shown, in some embodiments, the centers of the upper annular body 21 and the lower annular body 23 are on the same vertical line. One end of the compound parabolic target shell passes through the upper annular body 21 and reaches the plane of the lower annular body 23. The inner surfaces of the upper annular body 21 and the lower annular body 23 are aligned with the outer surface of the compound parabolic target shell (the parabola 13 of the compound parabolic target shell), ensuring that the compound parabolic target shell is vertical. There are multiple support beams 22, each of which has one end connected to the outer side of the upper annular body 21 and the other end connected to the inner side of the lower annular body 23. Multiple support beams 22 can be arranged in equal parts around the upper annular body 21 and the lower annular body 23. Preferably, the number of support beams 22 is an even number, so that they are symmetrical while being equally spaced, thereby improving the stability of the vertical fixed support.

[0039] In order to adapt to different target shells, in some embodiments, the upper annular body 21 of the vertical target holder is provided with a notch structure with adjustable diameter to achieve the fixation of compound parabolic target shells of different diameters. In the case where the lower annular body 23 of the vertical target holder is not required to be coplanar with the laser output port, the fixation of compound parabolic target shells of different lengths can be achieved. For details, refer to Figure 1 、 2 As shown, the gap structure is a gap set in the upper annular body 21, which cuts the annular shape of the upper annular body 21 to form a gap. The gap can be one or two, and other numbers can be set according to the actual situation of the target shell. Figure 2 In the illustrated embodiment, there are two notches, symmetrically arranged about the circumference of the upper annular body 21. This allows for convenient adjustment of the diameter of the upper annular body 21 to accommodate various target shell supports. However, the diameter of the upper annular body 21 should preferably not exceed the diameter of the lower annular body 23 to avoid unstable support.

[0040] In order to achieve a better and more stable connection between the upper annular body 21, the lower annular body 23 and the support beam 22, and better match the composite parabolic target shell, refer to Figure 1 、 2As shown, the upper annular body 21 includes an upper surface and a lower surface, wherein the diameter of the upper surface is greater than the diameter of the lower surface, that is, the upper annular body 21 formed by the upper and lower surfaces generally has an inverted truncated cone shape, so that the outer side surface of the upper annular body 21 is an arc-shaped inclined surface (inverted cone) with a large upper end diameter and a small lower end diameter. Through this configuration of the upper annular body 21, the inverted truncated cone can better fit the composite parabolic target shell placed therein, thereby achieving more stable support. The lower annular body 23 is a flat annular ring, and the lower surface can be placed stably to ensure the stability of the target after installation. A support beam 22 is provided on the upper surface. Corresponding to the structure of the above-mentioned upper annular body 21 and lower annular body 23, and the diameter of the upper annular body 21 is smaller than the diameter of the lower annular body 23, the support beam 22 connecting the two is inclined between the two. Therefore, the upper end of the support beam 22 connected to the upper annular body 21 is set as an inclined surface, which matches the arc inclined surface shape of the outer side of the upper annular body 21. The lower end of the support beam 22 connected to the upper annular body 21 is also an inclined surface, which is designed to match the flat upper surface of the lower annular body 23 in the inclined support.

[0041] The above-described embodiment of the present invention utilizes a composite parabolic target shell of a specific shape, which is stably supported by an upper annular body 21, a lower annular body 23, and a support beam 22. This facilitates the composite parabolic focusing target to effectively collect and concentrate distant light sources, ensuring a certain acceptance angle. In addition to absorbing the energy of direct radiation, all input laser light within the opening angle of the laser input port can be directly output to the laser output port. Furthermore, targets can overlap. Since geometrically all light entering the composite parabolic focusing target can pass through the laser output port in a single bounce, this reduces laser-target alignment errors, increases the maximum focusing power of the laser, and improves the environmental adaptability of laser ignition, thereby increasing the success rate.

[0042] Figure 3 This is a process flow chart for preparing the compound parabolic focusing target of Example 1.

[0043] Reference Figure 3 As shown, this embodiment provides a preparation process of the compound parabolic focusing target type in any of the above embodiments, which specifically includes the following steps:

[0044] S1. The target base is turned out by a finishing process, and the target base is parabolic in shape;

[0045] S2. Electroplating a thick layer of metal on the tip of the target base by electroplating, and cutting the target into the desired shape and size using a finishing process;

[0046] S3. Remove the tip of the target base and place it in the release liquid, and perform dynamic corrosion and static corrosion to release the final composite parabolic target shell;

[0047] S4. Place the removed composite parabolic target shell on the vertical target stand and fix it with liquid glue to complete the assembly.

[0048] As mentioned above Figure 1 、 2 As shown, the vertical target mount prepared in this embodiment has the inner surfaces of the upper and lower annular bodies 23 aligned with the outer surface of the composite parabolic target shell, ensuring the shell's verticality. A notch with adjustable diameter is designed at the upper annular ring of the target mount to accommodate different parabolic shell lengths and diameters. The target mount can be made of any material capable of supporting a parabolic shell and can be processed by lathing, casting, or 3D printing. Preferably, 3D printing is used, and the material used is a polymer, more preferably epoxy resin.

[0049] In the above embodiments, the target base is composed of a base and a tip, and the target base can be made of metal or other conductive materials.

[0050] In some embodiments, before S2, i.e., before electroplating, a seed layer is first applied to the tip. Depending on the characteristics of the electroplated metal, the target base tip itself can serve as the seed layer, or a layer of gold can be deposited or sputtered on the tip as the seed layer before subsequent electroplating. For example, if the tip is made of copper, the seed layer can be copper, or a layer of gold can be first formed as the seed layer before electroplating.

[0051] In the above-mentioned embodiment, the finishing process includes a multi-degree-of-freedom cutting method, and the desired shape includes a flat tip, whose side is a portion of a parabola, a target length of 0.2-2 mm, a laser output diameter of 10-200 μm, and a laser input diameter of 0.1-1 mm. For example, in a specific embodiment, the target length can be preferably 750 μm and the laser output diameter can be 30 μm. In order to meet the application requirements of laser fusion ignition, the embodiment of the present invention optimizes the application materials (micro-nanostructured gold material) and scale of the composite parabolic concentrator, proposes a micron-scale rotating body composite parabolic target type and its micro-nano processing technology, and realizes the laser fusion ignition application without an ablation layer while utilizing the advantages of the composite parabola focusing.

[0052] In the above-mentioned embodiments, dynamic etching involves relative motion between the removed base tip and the release liquid, primarily including one or more of rotation of the base tip and stirring of the release liquid. Static etching involves the base tip and the release liquid remaining stationary relative to each other. The release method can be one or more of dynamic and static etching, and the order can be adjusted. Preferably, dynamic etching is performed first, followed by static etching. The release liquid is a solution that can corrode the base tip material but not the composite parabolic target shell material.

[0053] In the above embodiment, the vertical target holder serves as a support for the composite parabolic target shell. The connection between the two is achieved by gluing heterogeneous materials. First, the composite parabolic target shell is placed into the target holder using a clamp. A small amount of curing glue is then applied to the annular body 21 on the target holder to securely connect the composite parabolic target shell and the target holder, completing the fabrication of the composite parabolic focusing target. The curing glue is preferably UV-curing glue.

[0054] In order to better understand the above technical solution, a specific example is provided below. However, it should be understood that the following example is not intended to limit the present invention.

[0055] In this embodiment, a preparation process for a compound parabolic focusing target is provided, in which a parabolic shell is prepared by a precision turning method, a shell layer is formed by electroplating, a dynamic and static dual-mode corrosion method is used to release the compound parabolic target shell, and a target holder is prepared by 3D printing technology, and finally the compound parabolic focusing target is assembled.

[0056] like Figure 3 As shown in Figure (a), a rough machining technique is first used to create a metal substrate, which serves as the sacrificial layer for the composite parabolic focusing support base and the initial cylindrical target shell tip. In one preferred embodiment, the metal substrate is made of copper. Then, a finishing turning technique is used to cut the composite parabolic base tip. This parabolic shape determines the final composite parabolic target shell's inner surface shape.

[0057] like Figure 3 As shown in (b), a layer of composite parabolic focusing shell material is deposited on the tip of the metal substrate by electroplating process, and the deposition thickness is greater than the required thickness. As a preferred embodiment, the target material is gold.

[0058] like Figure 3 As shown in (c), the outer surface of the composite parabolic focusing target is precisely machined, and the target shell meets the required thickness. While machining the outer parabola, a pre-fractured concave ring is cut at the root of the metal base tip, and the metal base tip is then removed with pliers.

[0059] like Figure 3 As shown in (e), a custom vacuum pipette is used to fix the composite parabolic target shell to the stirrer. The beaker is filled with the release liquid and placed on the magnetic stirrer. The release liquid is stirred by the magnetic stirrer. The vacuum pipette rotates counterclockwise at a speed of 100 rpm / min, and the magnetic stirrer rotates clockwise at a speed of 300 rpm / min. The purpose of using double stirring is to accelerate the corrosion rate. The composite parabolic target shell is then placed in the new release liquid and allowed to stand for 1 minute. Figure 3As shown in (f), unreacted impurities on the inner surface of the shell are allowed to continue reacting, and then the composite parabolic target shell is removed from the release liquid. In a preferred embodiment, the release liquid is a nitric acid solution. After the sacrificial layer is released, the composite parabolic target shell is removed and dried on a hot plate to remove moisture from the inner and outer surfaces.

[0060] like Figure 3 As shown in (g), the composite parabolic target shell is placed in a 3D-printed target stand made of a polymer material, preferably epoxy resin. The inner surface of the target stand's upper annular body 21 is bonded to the outer surface of the target shell (the parabola 13 of the composite parabolic target shell). The composite parabolic focusing target laser output port 11 and the lower surface of the target stand's lower annular body 23 are coplanar. The design of the upper annular body 21 and the lower annular body 23 mechanically ensure that the target shell is perpendicular to the plane. UV glue is then dripped onto the upper surface 21. After the glue has penetrated the gap between the composite parabolic target shell and the target stand, the UV glue is cured with ultraviolet light to form the final composite parabolic focusing target.

[0061] As can be seen from the above preferred embodiments, the present invention designs a parabolic focusing target (which can be micron-sized), which is divided into a composite parabolic target shell and a corresponding vertical target stand. Precision machining processes are used to manufacture the metal shell, increasing the target's mechanical strength and reflection efficiency. The parabolic shell is prepared by combining precision turning technology, thick metal electroplating technology, and dual-mode etching technology. High-precision 3D printing technology is used to complete the production of its vertical target stand. The target stand uses a double concentric ring and parabolic bonding method to achieve vertical assembly of the target shell, and a diameter-adjustable ring is used to pre-fix the target shell and improve the adaptability of the target stand. The target shell and the target stand are connected using liquid glue to achieve target assembly. The design of this composite parabolic focusing target allows the laser to enter from the target shell's incident port and, after at most one reflection, be focused at a point through the laser output port. This design not only reduces the alignment error between the laser and the target, but also reduces the laser ignition energy required for laser fusion ignition, effectively reducing the laser power required for fusion ignition.

[0062] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A process for preparing a compound parabolic focusing target, characterized in that: The compound parabolic focusing target type includes: The inner surface of the composite parabolic target shell is an axisymmetric shell formed by rotating the parabola 180 degrees along the central axis. The shell is cut by a curved surface along the extended line of the parabola to ensure that the laser focus is located outside the laser output port. A vertical target stand, used to support the compound parabolic target shell and vertically fix the compound parabolic target shell; The preparation process comprises: The target base is turned out by fine machining process and has a parabolic shape; A thick layer of metal is electroplated on the tip of the target base, and the target shape and size required are cut using a finishing process; The tip of the target base is removed and placed in a release liquid, and the final composite parabolic target shell is released by dynamic corrosion and static corrosion. Place the removed composite parabolic target shell on the vertical target stand and fix it with liquid glue to complete the assembly; in: The target base is composed of a base and a tip located on the base, and the target base is made of a conductive material; Before the target base tip is electroplated with a thick layer of metal, it also includes: First, a seed layer is applied to the tip. Depending on the characteristics of the electroplated metal, the target base tip itself can serve as the seed layer, and the electroplating material and the seed layer material cannot be the same. The target base includes a flat tip, the side of which is a part of a parabola, the target base has a length of 0.2-2 mm, a diameter of the laser output port is 10-200 μm, and a diameter of the laser input port is 0.1-1 mm; The release liquid is a solution that can corrode the tip material of the base.

2. The process for preparing a compound parabolic focusing target according to claim 1, characterized in that: The target base material is a metal material.

3. The process for preparing a compound parabolic focusing target according to claim 1, characterized in that: The finishing process cutting includes a multi-degree-of-freedom cutting method.

4. The process for preparing a compound parabolic focusing target according to claim 1, characterized in that: The dynamic corrosion and static corrosion methods are performed to release the final composite parabolic target shell, wherein: The dynamic corrosion is a relative movement between the removed base tip and the release liquid, including one or more of rotation of the base tip and stirring of the release liquid; The static corrosion is when the tip of the base and the released liquid are relatively still; Dynamic and static corrosion sequences are adjustable.

5. The process for preparing a compound parabolic focusing target according to claim 1, characterized in that: The vertical target stand and the compound parabolic target shell are connected by gluing heterogeneous materials, including: Use a clamp to place the compound parabolic target shell into the vertical target stand; Dip a small amount of curing glue onto the annular body on the vertical target stand to achieve a fixed connection between the composite parabolic target shell and the vertical target stand.

6. The process for preparing a compound parabolic focusing target according to claim 1, characterized in that: The composite parabolic target shell, wherein the parabolic equation is y=x 2 / 30.

7. The process for preparing a compound parabolic focusing target according to claim 1, characterized in that: The vertical target frame comprises: Upper torus; a lower annular body located directly below the upper annular body, wherein the diameter of the lower annular body is larger than that of the upper annular body; A support beam connects the upper annular body and the lower annular body.

8. The process for preparing a compound parabolic focusing target according to claim 7, characterized in that: The centers of the upper and lower annular bodies are on the same vertical line, one end of the compound parabolic target shell passes through the upper annular body and reaches the plane where the lower annular body is located, and the inner surfaces of the upper and lower annular bodies are in contact with the outer surface of the compound parabolic target shell to ensure that the compound parabolic target shell is vertical.

9. The process for preparing a compound parabolic focusing target according to claim 7, characterized in that: The upper annular body of the vertical target mount is provided with a notch structure with adjustable diameter to achieve the fixation of the compound parabolic target shells of different diameters. Without requiring the lower annular body of the vertical target mount to be coplanar with the laser output port, the fixation of compound parabolic target shells of different lengths can be achieved.

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