A high gradient vacuum insulator and a method of manufacturing the same

Abstract

The application provides a high-gradient vacuum insulator and a preparation method thereof, and aims at solving the technical problems that the poor air tightness of the existing high-gradient vacuum insulator leads to poor voltage resistance stability and poor operation stability of a high-voltage device, and the high-voltage device is difficult to meet the requirement of vacuum insulation strength. The insulator comprises a columnar insulator body with a vacuum cavity and a plurality of equalizing rings. A plurality of parallel and concentric ring grooves are formed on the outer wall of the insulator body in the circumferential direction, and the axial spacing of adjacent ring grooves is equal. The shape and size of the ring grooves are matched with the shape and size of the equalizing rings, respectively. The plurality of equalizing rings are embedded in the plurality of ring grooves, respectively, and the outer surface of the equalizing ring is flush with the outer surface of the insulator body. The preparation method comprises the following steps: processing the insulator body; processing the ring grooves on the outer wall of the insulator body; pouring the metal liquid in the mold to prepare the equalizing ring; and processing the final high-gradient vacuum insulator.

Description

Technical Field

[0001] This invention relates to a vacuum insulator, specifically to a high-gradient vacuum insulator and its preparation method. Background Technology

[0002] According to the paper "Improvement of surface flashover in vacuum" published in *High Voltage* in March 2020 and "Process of Surface Flashover in Vacuum Under Nanosecond Pulse" published in *IEEE Transactions on Plasmas Science* in January 2010, the ultra-high operating voltages in vacuum pulsed power systems such as high-energy particle accelerators, Z-pinch, and high-power lasers impose stringent withstand voltage requirements on insulators. However, the interface between the vacuum and the insulator is a weak point in withstand voltage, prone to surface breakdown under high voltage. The breakdown voltage is generally much lower than the bulk breakdown voltage of insulating materials of the same thickness and the breakdown voltage of vacuum. This low vacuum surface withstand voltage performance restricts the withstand voltage capability of high-voltage vacuum equipment, limiting the development of high-power, miniaturized, and high-reliability pulsed power systems, and has become a bottleneck problem for pulsed power systems.

[0003] To address the aforementioned issues, extensive research has been conducted on surface flashover phenomena, leading to the development of explanatory theories, such as the secondary electron avalanche model. Based on this, high-gradient insulators (HGIs) have been designed. High-gradient insulators are characterized by alternating layers of insulating and conductive metal. The conductive metal layers act as voltage equalization rings, ensuring a uniform voltage distribution across the insulator surface and reducing local electric field distortion. Furthermore, based on the relationship between insulator thickness *d* and flashover electric field intensity *E*, i.e., *E = k / d*... 1 / 2Reducing the insulator thickness *d* can increase the flashover electric field strength *E*, meaning that thinner insulators can achieve a higher flashover voltage per unit distance. Multilayer high-gradient insulators, by transforming a single thick insulator into a structure of multiple thin insulators connected in series, can effectively improve the electric field breakdown strength of the entire insulator structure. Based on the "High gradient insulator technology for the dielectric wall accelerator" published in the April 1995 issue of *Proc of PAC*, Lawrence Livermore National Laboratory in the United States used high-gradient insulation technology to obtain small-sized HGI samples with a maximum insulation strength of approximately 32 MV / m at a pulse width of 100 ms. The Institute of Electrical Engineering, Chinese Academy of Sciences, has also conducted related research on high-gradient insulators. Based on the vacuum surface flashover characteristics of micro-layer insulators under nanosecond pulses published in the November 2009 issue of *High Power Laser and Particle Beams*, they obtained a withstand voltage exceeding 15 MV / m. The Institute of Fluid Physics, China Academy of Engineering Physics, in its article "Development of High-Gradient Insulators for Dielectric Wall Accelerators" published in the same journal, obtained a withstand voltage of 16.1 MV / m. However, these technologies are currently not practically applicable due to complex manufacturing processes, numerous uncertainties, unstable product performance, and limitations to small-sized insulators.

[0004] At present, in large-scale pulse power systems, multi-layer high-gradient vacuum insulators are mainly produced by separately preparing multiple metal equalizing rings and polymer insulating rings, stacking them alternately, and then heating and curing the metal equalizing rings and insulating rings under mechanical pressure. Figure 1 This diagram illustrates the structure of a conventional high-gradient vacuum insulator, comprising multiple insulating rings 01 and equalizing rings 02. The inner and outer diameters of the equalizing rings 02 are identical to those of the insulating rings 01. The equalizing rings 02 and insulating rings 01 are stacked alternately to form a columnar structure with a vacuum cavity 010. To maintain the vacuum environment inside the insulator, it needs to maintain high airtightness, which places high precision requirements on the manufacturing process. However, due to the significant difference in thermal expansion coefficients between the metal equalizing rings and the polymer insulating rings, it is difficult for them to fit tightly together, easily leading to air gaps and leakage. This contradicts the high airtightness requirement of high-gradient insulators, resulting in reduced withstand voltage stability and operational stability of high-voltage devices. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of poor withstand voltage stability and poor operational stability of high-voltage devices caused by poor air tightness of existing high-gradient vacuum insulators, as well as the difficulty in meeting the vacuum insulation strength requirements of high-voltage devices, and to provide a high-gradient vacuum insulator and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-gradient vacuum insulator, which is special in that:

[0008] It includes a cylindrical insulator body with a vacuum cavity and multiple equalizing rings; the outer wall of the insulator body is provided with multiple parallel and concentric annular grooves along the circumference, and the axial spacing between adjacent annular grooves is equal; the shape and size of the annular grooves are adapted to the shape and size of the equalizing rings, and the multiple equalizing rings are respectively embedded in the multiple annular grooves, and the outer surface of the equalizing rings is flush with the outer surface of the insulator body.

[0009] Furthermore, the axis of the annular groove coincides with the axis of the insulator body.

[0010] Furthermore, the axial width of the annular groove is 0.5mm to 5mm, the radial depth is 0.5 to 0.8 times the wall thickness of the insulator body, and the axial spacing between adjacent annular grooves is 1 to 5 times the axial width of the annular groove.

[0011] Furthermore, the axial width of the annular groove is 3 mm, the radial depth is 0.75 times the wall thickness of the insulator body, and the axial spacing between adjacent annular grooves is 4 times the axial width of the annular groove.

[0012] Furthermore, the equalizing ring is an alloy composed of low-melting-point metals, and the melting point of the equalizing ring is 90℃~150℃.

[0013] Furthermore, the insulator body is made of nylon, polystyrene, polyimide, polymethyl methacrylate, epoxy resin, polyphenylene sulfide, or ceramic.

[0014] The equalizing ring is an alloy composed of Bi, Sn, Pb, and In.

[0015] Meanwhile, this invention provides a method for preparing the above-mentioned high-gradient vacuum insulator, which is characterized by including the following steps:

[0016] Step 1: Process the insulator body according to the preset insulator sample dimensions;

[0017] Step 2: Machining multiple parallel and concentric annular grooves along the circumferential direction on the outer wall of the obtained insulator body, with equal axial spacing between adjacent annular grooves, and the distance between the bottom of the annular groove and the inner wall of the insulator body being consistent with that of the insulator sample; cleaning and drying.

[0018] Step 3: Place the insulator body processed in Step 2 into the corresponding mold. The mold is a cylindrical structure with an inner diameter 5-10 mm larger than the outer diameter of the insulator body.

[0019] In the vacuum chamber of the sealed insulator body, the low melting point metal used for the equalizing ring is melted in a vacuum environment and poured into the gap between the ring groove and the mold, and then cooled and solidified.

[0020] Step 4: Remove the formed high-gradient vacuum insulator from the mold, treat surface defects, and form the final high-gradient vacuum insulator.

[0021] Further, step 1 specifically involves: processing the insulator body according to the preset insulator sample size, wherein the outer diameter of the insulator body is 1mm to 3mm thicker than the outer diameter of the insulator sample.

[0022] Furthermore, in step 2, multiple parallel and concentric annular grooves are machined circumferentially on the outer wall of the obtained insulator body using laser or mechanical processing methods;

[0023] In step 3, rubber plugs are used to seal both ends of the vacuum cavity of the insulator body.

[0024] Further, step 4 specifically involves: removing the formed high-gradient vacuum insulator from the mold, and using mechanical processing to remove the residual metal on the surface of the insulator and the excess thickness of the insulator body to form the final high-gradient vacuum insulator.

[0025] The beneficial effects of this invention are:

[0026] 1. This invention provides a high-gradient vacuum insulator, wherein the design of the equalizing ring embedded in the ring groove can eliminate the gas permeation interface between the metal and the insulating material, thereby achieving the isolation of external gas, ensuring that the vacuum system of the high-voltage device has high airtightness, and maintaining a high vacuum degree during operation. This solves the common dilemma that insulators have high permeability due to poor assembly, making it difficult to obtain an ideal vacuum degree.

[0027] 2. This invention provides a method for preparing a high-gradient vacuum insulator. The insulator body is an integral structure, and the equalizing ring is generated in situ through casting a low-melting-point metal into the annular groove of the insulator body. This method is simple to implement and produces a high-precision insulator, avoiding random errors introduced by complex manufacturing processes, high machining precision requirements, and multi-layer stacking assembly. The equalizing ring in this invention is generated in situ through casting a low-melting-point metal into the annular groove, ensuring a tight bond with the groove and eliminating internal pores. This effectively avoids the problem of insulation material breakdown caused by pores, improving the operational stability of high-voltage devices and the withstand voltage stability of the insulator, and meeting the vacuum insulation strength requirements of high-voltage devices. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of an existing high-gradient vacuum insulator;

[0029] Figure 1In the diagram, 01-insulating ring, 010-vacuum cavity, 02-equalizing ring;

[0030] Figure 2 This is a schematic diagram of the structure of an embodiment of a high-gradient vacuum insulator according to the present invention;

[0031] Figure 2 In the middle, 1-insulator body, 10-vacuum cavity, 11-ring groove, 2-equalizing ring;

[0032] Figure 3 This is a flowchart of a method for preparing a high-gradient vacuum insulator according to the present invention;

[0033] Figure 4 This is a schematic diagram of the structural changes during the fabrication process of a high-gradient vacuum insulator according to the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] like Figure 2 As shown, a high-gradient vacuum insulator includes a cylindrical insulator body 1 with a vacuum cavity 10 and multiple equalizing rings 2. Specifically, the outer wall of the insulator body 1 has multiple parallel and concentric annular grooves 11 circumferentially formed. The axial width of the annular grooves 11 is 0.5 mm to 5 mm, and the radial depth is 0.5 to 0.8 times the wall thickness of the insulator body 1. These grooves are capable of supporting the equalizing rings 2 to provide a uniform electric field. The axis of the annular grooves 11 coincides with the axis of the insulator body 1. The axial spacing between adjacent annular grooves 11 is equal and is 1 to 5 times the axial width of the annular grooves 11. The shape and size of the annular grooves 11 are adapted to the shape and size of the equalizing rings 2. The multiple equalizing rings 2 are respectively embedded in the multiple annular grooves 11, and the outer surface of the equalizing rings 2 is flush with the outer surface of the insulator body 1. The equalizing ring 2 is an alloy composed of Bi, Sn, Pb, and In. The melting point of the equalizing ring 2 is 90℃~150℃, which is at least 10℃ lower than the glass transition temperature of the insulator body 1. The insulator body 1 is made of nylon, polystyrene, polyimide, polymethyl methacrylate, epoxy resin, polyphenylene sulfide, or ceramic. In this embodiment, the axial width of the annular groove 11 is 3mm, the radial depth is 0.75 times the wall thickness of the insulator body 1, and the axial spacing between adjacent annular grooves 11 is 4 times the axial width of the annular groove 11. The insulator body 1 is made of polyphenylene sulfide.

[0037] like Figure 3 , Figure 4 As shown, the specific steps of the preparation method of the high-gradient vacuum insulator in this embodiment are as follows:

[0038] Step 1: Based on the preset insulator sample size, polyphenylene sulfide is used as the material of the insulator body 1. It is machined into an insulator body 1 with an inner diameter of 240mm, an outer diameter of 321mm, and an axial length of 60mm. The outer diameter of the insulator body 1 is 1mm thicker than the outer diameter of the insulator sample.

[0039] Step 2: Using machining, multiple parallel and concentric annular grooves 11 are machined along the circumferential direction on the outer wall of the obtained insulator body 1. The axial spacing of adjacent annular grooves 11 is equal, the axial width of the annular groove 11 is 3mm, the radial depth is 30.5mm, the axial spacing of adjacent annular grooves 11 is 12mm, and the distance between the bottom of the annular groove 11 and the inner wall of the insulator body 1 is consistent with that of the insulator sample. Clean and dry.

[0040] Step 3: Place the insulator body 1 processed in Step 2 into a cylindrical mold with an inner diameter of 330 mm, fix it in the center position using a clamp, seal both ends of the vacuum cavity 10 of the insulator body 1 with rubber plugs to prevent metal from entering the inner surface of the vacuum cavity 10, and then melt the low melting point metals Bi, Sn, Pb and In used for the equalizing ring 2 when the vacuum degree is below 10 Pa, pour them into the gap between the ring groove 11 and the mold, and cool and solidify to form the shape.

[0041] The reason for using liquid metal to cast the equalizing ring 2 in this step is that the metal has poor elasticity and cannot be embedded into the insulator body 1 after processing. Therefore, it is necessary to use flowing liquid metal to fill the ring groove 11 to prepare the embedded equalizing ring 2 in situ. The reason for using low-melting-point metal is that common polymer materials have poor heat resistance and will soften and deform at high temperatures. In addition, increasing the outer diameter of the insulator body 1 in step 1 allows for the addition of more liquid metal in this step to compensate for the shrinkage of the liquid metal during the cooling and solidification process, and also provides processing redundancy for the removal of excess metal later.

[0042] Step 4: Remove the formed high-gradient vacuum insulator from the mold and remove the residual metal on the surface of the insulator and the excess thickness of the insulator body 1 by mechanical processing to form the final high-gradient vacuum insulator. The inner diameter of the insulator body 1 is 240mm, the outer diameter is 320mm, and the axial length is 60mm. The inner diameter of the equalizing ring 2 is 260mm, the outer diameter is 320mm, and the thickness is 3mm. The axial distance between adjacent equalizing rings 2 is 12mm.

[0043] Example 2

[0044] The high-gradient vacuum insulator and its preparation method in this embodiment are the same as those in Embodiment 1, except that:

[0045] The axial width of the annular groove 11 of the high gradient vacuum insulator is 0.5 mm, the radial depth is 0.5 times the wall thickness of the insulator body 1, the axial spacing between adjacent annular grooves 11 is 5 times the axial width of the annular groove 11, and the material of the insulator body 1 is polystyrene.

[0046] In step 1, the insulator body 1 is made of polystyrene and has an outer diameter of 323 mm. The outer diameter of the insulator body 1 is 3 mm thicker than the outer diameter of the insulator sample.

[0047] In step 2, laser processing is used. The axial width of the annular groove 11 is 0.5 mm, the radial depth is 21.5 mm, and the axial distance between adjacent annular grooves 11 is 2.5 mm.

[0048] In step 4, the inner diameter of the equalizing ring 2 of the final high-gradient vacuum insulator is 280 mm, the thickness is 0.5 mm, and the axial spacing between adjacent equalizing rings 2 is 2.5 mm.

[0049] Example 3

[0050] The high-gradient vacuum insulator and its preparation method in this embodiment are the same as those in Embodiment 1, except that:

[0051] The annular groove 11 of the high gradient vacuum insulator has an axial width of 1.5 mm, a radial depth of 0.8 times the wall thickness of the insulator body 1, and an axial spacing between adjacent annular grooves 11 that is 1 times the axial width of the annular groove 11. The insulator body 1 is made of polyimide.

[0052] In step 1, the insulator body 1 is made of polyimide and has an outer diameter of 322 mm. The outer diameter of the insulator body 1 is 2 mm thicker than the outer diameter of the insulator sample.

[0053] In step 2, the axial width of the annular groove 11 is 1.5 mm, the radial depth is 33 mm, and the axial distance between adjacent annular grooves 11 is 1.5 mm.

[0054] In step 4, the inner diameter of the equalizing ring 2 of the final high-gradient vacuum insulator is 256 mm, the thickness is 1.5 mm, and the axial spacing between adjacent equalizing rings 2 is 1.5 mm.

[0055] Example 4

[0056] The high-gradient vacuum insulator and its preparation method in this embodiment are the same as those in Embodiment 3, except that:

[0057] The axial width of the annular groove 11 of the high gradient vacuum insulator is 5mm, the axial spacing between adjacent annular grooves 11 is 1 times the axial width of the annular groove 11, and the material of the insulator body 1 is nylon.

[0058] In step 1, the insulator body 1 is made of nylon;

[0059] In step 2, the axial width of the annular groove 11 is 5mm, and the axial spacing between adjacent annular grooves 11 is 5mm.

[0060] In step 4, the thickness of the equalizing ring 2 of the final high-gradient vacuum insulator is 5mm, and the axial spacing between adjacent equalizing rings 2 is 5mm.

[0061] The high-gradient vacuum insulators obtained in Examples 1 to 4, as well as existing high-gradient vacuum insulators, were subjected to breakdown voltage dispersion tests and on-site operation tests. The test results show that the withstand voltage stability of the high-gradient vacuum insulator of the present invention is significantly improved, the surface breakdown voltage dispersion is reduced by more than 30%, and the operational stability of the high-voltage device is also significantly improved, which can meet the requirements of the high-voltage device for vacuum insulation strength. At the same time, the use of this insulator can reduce the installation difficulty and significantly reduce the time required for vacuuming the device and the pumping power required to maintain the vacuum state, enabling the device to quickly enter the working state.

[0062] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-gradient vacuum insulator, characterized in that: The insulator includes a columnar insulator body (1) with a vacuum cavity (10) and multiple equalizing rings (2); the outer wall of the insulator body (1) is provided with multiple parallel and concentric annular grooves (11) along the circumferential direction, and the axial spacing between adjacent annular grooves (11) is equal; the shape and size of the annular grooves (11) are adapted to the shape and size of the equalizing rings (2), and the multiple equalizing rings (2) are respectively embedded in the multiple annular grooves (11), and the outer surface of the equalizing rings (2) is flush with the outer surface of the insulator body (1); The axial width of the annular groove (11) is 0.5mm~5mm, the radial depth is 0.5~0.8 times the wall thickness of the insulator body (1), and the axial spacing between adjacent annular grooves (11) is 1~5 times the axial width of the annular groove (11).

2. The high-gradient vacuum insulator according to claim 1, characterized in that: The axis of the annular groove (11) coincides with the axis of the insulator body (1).

3. The high-gradient vacuum insulator according to claim 1, characterized in that: The axial width of the annular groove (11) is 3 mm, the radial depth is 0.75 times the wall thickness of the insulator body (1), and the axial spacing between adjacent annular grooves (11) is 4 times the axial width of the annular groove (11).

4. The high-gradient vacuum insulator according to claim 3, characterized in that: The equalizing ring (2) is an alloy composed of low-melting-point metals, and the melting point of the equalizing ring (2) is 90℃~150℃.

5. A high-gradient vacuum insulator according to claim 4, characterized in that: The insulator body (1) is made of nylon, polystyrene, polyimide, polymethyl methacrylate, epoxy resin, polyphenylene sulfide or ceramic. The equalizing ring (2) is an alloy composed of Bi, Sn, Pb and In.

6. A method for preparing a high-gradient vacuum insulator according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Process the insulator body according to the preset insulator sample size (1); Step 2: Process multiple parallel and concentric annular grooves (11) along the circumferential direction on the outer wall of the obtained insulator body (1). The axial spacing of adjacent annular grooves (11) is equal. The distance between the bottom of the annular groove (11) and the inner wall of the insulator body (1) is consistent with that of the insulator sample. Clean and dry. Step 3: Place the insulator body (1) processed in step 2 into the corresponding mold. The mold is a cylindrical structure with an inner diameter 5-10 mm larger than the outer diameter of the insulator body (1). In the vacuum chamber (10) of the sealed insulator body (1), the low melting point metal used in the equalizing ring (2) is melted and poured into the gap between the ring groove (11) and the mold in a vacuum environment, and then cooled and solidified. Step 4: Remove the formed high-gradient vacuum insulator from the mold, treat surface defects, and form the final high-gradient vacuum insulator.

7. The method for preparing a high-gradient vacuum insulator according to claim 6, characterized in that: Step 1 is as follows: The insulator body (1) is processed according to the preset insulator sample size. The outer diameter of the insulator body (1) is 1mm to 3mm thicker than the outer diameter of the insulator sample.

8. The method for preparing a high-gradient vacuum insulator according to claim 7, characterized in that: In step 2, multiple parallel and concentric annular grooves (11) are machined circumferentially on the outer wall of the obtained insulator body (1) using laser or mechanical processing. In step 3, rubber plugs are used to seal both ends of the vacuum cavity (10) of the insulator body (1).

9. The method for preparing a high-gradient vacuum insulator according to claim 8, characterized in that: Step 4 specifically involves removing the formed high-gradient vacuum insulator from the mold and using mechanical processing to remove the residual metal on the surface of the insulator and the excess thickness of the insulator body (1) to form the final high-gradient vacuum insulator.

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