An integrally sealed electron curtain accelerator

Abstract

This invention relates to electron curtain accelerators, particularly a fully sealed electron curtain accelerator. The fully sealed electron curtain accelerator of this invention includes: a fully sealed vacuum chamber and a cathode assembly installed inside the vacuum chamber. The vacuum chamber comprises a cylindrical cavity, an electron beam window assembly, an end-capping plate assembly, an end-flange assembly, and a high-voltage connector assembly. The cylindrical cavity, the electron beam window assembly, the end-capping plate assembly, the end-flange assembly, and the high-voltage connector assembly are welded together to form a fully sealed vacuum structure. The fully sealed electron curtain accelerator of this invention can achieve a 10 kW exhaust temperature through high-temperature baking in the temperature range of 250°C to 600°C. ‑7 High vacuum state at the Pa level.

Description

Technical Field

[0001] This invention relates to the field of electron accelerators, and more specifically to an integrally sealed electron curtain accelerator. Background Technology

[0002] Electron accelerators are widely used in irradiation processing, including material modification, irradiation crosslinking, irradiation sterilization, irradiation curing, irradiation degradation, irradiation disinfection, irradiation preservation, and irradiation breeding. Most of these applications directly utilize electron beams for irradiation processing. Electron curtain accelerators are one of the main types, producing electron beams with relatively low energy, typically 150kV to 300kV, but with high efficiency, high power, and small size. They are the primary equipment for applications such as irradiation curing, irradiation disinfection, and irradiation sterilization. Electron accelerators used for irradiation processing generally consist of four parts: electron beam generation, electron beam acceleration, electron beam extraction, and vacuum environment acquisition. The electron curtain accelerator is a type of high-voltage accelerator. Its main body is a stainless steel cylindrical vacuum acceleration chamber. The cathode assembly is placed at the center of the vacuum acceleration chamber. The cathode assembly generates electron emission along a certain length of its axis, forming a rain curtain-like pattern, hence the name electron curtain accelerator.

[0003] In an electron curtain accelerator, the electron beam is primarily generated by producing free electrons at the cathode, commonly through filament heating. To direct the free electrons, a grid is typically included. The cathode and grid are collectively called the cathode-grid assembly, located at the center of the accelerator. The accelerator uses a high-voltage electric field to accelerate the electron beam, energizing it. For ease of implementation, a negative high voltage is usually applied to the cathode-grid assembly from the outer shell, creating a high-voltage electric field between the assembly and the shell. This requires a device to guide the high voltage from the outside through the shell to the internal cathode-grid assembly, commonly known as a high-voltage connector. For high-energy electron beams used in irradiation processing, they also need to pass through the shell and enter the atmosphere. This is achieved using an electron beam extraction device primarily composed of a very thin titanium film. Electron beam generation and acceleration must occur in a vacuum environment to prevent cathode burnout, high-voltage arcing, and electron loss due to collisions with gas molecules during acceleration. Therefore, the electron curtain accelerator must also be a sealed vacuum chamber. Generally, the higher the vacuum level, the more stable the operation of the accelerator. The most significant technical challenges are high-voltage feeding, electron beam extraction, and high-vacuum sealing.

[0004] In terms of existing technology, in order to achieve connection with internationally accepted high-voltage cable plugs while meeting vacuum sealing requirements, the structure of high-voltage connectors is very complex. For example, Chinese patent publication number CN104735896A discloses that the high-voltage connector includes a complex oil tank structure. The external high-voltage power supply is first connected to the oil tank through a conventional cable. The oil tank is sealed and isolated from the vacuum chamber. At the same time, it needs to be insulated from the high voltage of the chamber while introducing the high voltage from the oil tank into the vacuum chamber through the lead terminals. The structure is complex and the volume is large. In the current technology, for electron beam extraction, to achieve a vacuum seal between the 10-50µm thick titanium film and the accelerator cavity, a complex mechanical pressure sealing structure using flanges and elastic materials is typically employed. For example, Chinese patent CN110337172A discloses a titanium window assembly, and Chinese patents CN214279901U and CN215299173U disclose extraction windows. These typically require two thick flanges, with sealing grooves and a ring of fastening bolts on the flanges. This results in a large volume, heavy weight, and poor vacuum sealing performance due to mechanical pressure sealing, which is detrimental to the high-power, long-term stable operation of electron curtain accelerators. In terms of vacuum sealing, electron curtain accelerators have numerous openings in the accelerator vacuum cavity to achieve functions such as filament assembly, filament power supply and high-voltage introduction, and electron beam extraction. This complex structure requires numerous sealing surfaces to achieve vacuum sealing, and different locations are sealed using mechanical pressure with different elastic materials such as rubber rings, rubber gaskets, and copper rings. It is difficult to achieve a sealing effect exceeding the requirements of a true vacuum. In terms of existing technology, regarding vacuum realization, electronic curtain accelerators are complex in structure and large in size, and the sealing methods of many sealing surfaces are complicated. For example, the sealing of titanium windows and other positions uses organic elastic materials such as rubber rings, which are not suitable for high-temperature baking and exhaust above 250 degrees Celsius. Electronic curtain accelerators can only achieve and maintain a high vacuum state by evacuating for a long time through a vacuum unit containing mechanical pumps and molecular pumps. This is an open vacuum solution. For example, Chinese patent publication number CN215299173U discloses a vacuum pump. The accelerator vacuum chamber is connected to an external vacuum pump through vacuum pipes and flanges. When using the system, the auxiliary equipment cost is high, the maintenance is complicated, and the ease of use is poor.

[0005] Therefore, an innovative technology is needed to better solve the technical challenges of high-voltage feeding, electron beam extraction, vacuum sealing, and ultra-high vacuum realization in electron curtain accelerators. This technology should enable a new type of integrated sealed electron curtain accelerator that features low vacuum sealing leakage rate, high long-term reliability, suitability for high-temperature baking to achieve ultra-high vacuum, small size, light weight, and ease of maintenance and use. Summary of the Invention

[0006] One objective of this invention is to provide an innovative technical solution that better addresses the challenges of high-voltage feed, electron beam extraction, vacuum sealing, and ultra-high vacuum achievement in electron curtain accelerators. Furthermore, it provides a novel integrated sealed electron curtain accelerator with low vacuum sealing leakage rate, high long-term reliability, suitability for high-temperature baking to achieve ultra-high vacuum, and small size, light weight, and ease of maintenance and use.

[0007] The present invention provides an integrally sealed electron curtain accelerator with low vacuum sealing leakage rate, high long-term reliability, suitable for high-temperature baking to achieve ultra-high vacuum state, and small size, light weight, easy maintenance and use.

[0008] The integrally sealed electron curtain accelerator of the present invention includes: an integrally sealed vacuum chamber and a cathode assembly installed inside the vacuum chamber, wherein the vacuum chamber includes a cylindrical cavity, an electron beam window assembly, an end sealing plate assembly, an end flange assembly, and a high-voltage connector assembly. The cylindrical cavity, the electron beam window assembly, the end sealing plate assembly, the end flange assembly, and the high-voltage connector assembly are welded together to form a vacuum structure, and the interior of the vacuum structure is the integrally sealed vacuum chamber.

[0009] In one embodiment, the cylindrical cavity has a first opening parallel to its axis on its side, and a second opening and a third opening at each end of the cylindrical cavity; the electron beam window assembly is welded to the first opening of the cylindrical cavity via a first welding position, forming a vacuum-sealed connection with the cylindrical cavity; the end cap assembly is welded to the second opening of the cylindrical cavity via a second welding position, forming a vacuum-sealed connection with the cylindrical cavity; the outer edge of the end flange assembly is welded to the third opening of the cylindrical cavity via a third welding position, forming a vacuum-sealed connection with the cylindrical cavity; the end flange assembly has a mounting hole in its middle, and one end of the high-voltage connector assembly is welded to the mounting hole of the end flange assembly via a fourth welding position, forming a vacuum-sealed connection with the end flange assembly; the cylindrical cavity is made of one of copper, aluminum, iron, or stainless steel.

[0010] In one embodiment, the electron beam window assembly includes an electron beam window frame and a titanium film. The electron beam window frame and the titanium film are welded together to form a vacuum-sealed assembly. The electron beam window frame is made of stainless steel, and the titanium film is made of titanium with a thickness of 10µm to 50µm. The electron beam window assembly is welded to a first opening of a cylindrical cavity at a first welding position, sealing the first opening on the side of the cylindrical cavity and forming a vacuum-sealed connection.

[0011] In one embodiment, the end-sealing plate assembly is located at one end of the cylindrical cavity, sealing the second opening of the cylindrical cavity and achieving a vacuum-sealed connection with the cylindrical cavity. The end-sealing plate assembly is made of one of the following metals: copper, aluminum, iron, or stainless steel.

[0012] In one embodiment, the high-voltage connector assembly includes: a ceramic insulator, a first metal welding ring welded to one end of the ceramic insulator, a second metal welding ring welded to the other end of the ceramic insulator, a first lead terminal, a second lead terminal, and a third lead terminal mounted on the second metal welding ring, and small ceramic insulators that electrically insulate the three lead terminals from the second metal welding ring respectively; the components of the high-voltage connector assembly are connected by welding to form a vacuum-sealed assembly.

[0013] In one embodiment, the end flange assembly is made of one of the following metals: copper, aluminum, iron, or stainless steel. The end flange assembly has a mounting hole in its center, surrounded by a ring of threaded blind bolt holes. The end flange assembly achieves a vacuum seal by welding to the third opening of the vacuum chamber at a third welding position, thus sealing the third opening of the cylindrical cavity. The mounting hole in the center of the end flange assembly is welded to the first metal welding ring of the high-voltage connector assembly to achieve a vacuum seal connection. The bolt holes are used for the installation and connection of external high-voltage cables.

[0014] In one embodiment, the end sealing plate assembly and / or end flange assembly can also be integrally formed with the cylindrical cavity, which can also achieve the working effect of vacuum sealing and baking exhaust of the vacuum cavity described in this invention.

[0015] In one embodiment, the high-voltage connector assembly further includes a conical mounting surface disposed on the ceramic insulator. The end flange assembly has threaded holes, and the connection between bolts and the threaded holes ensures that the conical surface of the high-voltage cable head is tightly fitted with the conical mounting surface, achieving pressure resistance.

[0016] In one embodiment, the system further includes an exhaust pipe, which comprises a welded transition piece and a flange. The welded transition piece is located at the end where the exhaust pipe connects to the vacuum chamber. The welded transition piece is made of stainless steel and welds the exhaust pipe and the vacuum chamber together to achieve a vacuum seal. The flange has a through hole in the middle that connects to the inner hole of the exhaust pipe, allowing it to connect to a vacuum pipe for venting the vacuum chamber. The exhaust pipe is located on the vacuum chamber and is welded to the vacuum chamber at a fifth welding position to achieve a vacuum seal.

[0017] In one embodiment, the system further includes an exhaust pipe comprising a welded transition piece and a flange. The welded transition piece is located at the end of the exhaust pipe where it connects to the end cap assembly. The welded transition piece is made of stainless steel and welds the exhaust pipe and the end cap assembly together to achieve a vacuum seal. The flange has a through hole in the center that connects to the inner hole of the exhaust pipe, allowing it to connect to a vacuum pipe for venting the vacuum chamber. The exhaust pipe is located on the end cap assembly of the vacuum chamber and is welded to the end cap assembly at a fifth welding position to achieve a vacuum seal.

[0018] In one embodiment, an ion pump is also included, which is disposed on the vacuum chamber and is welded to the vacuum chamber via a sixth welding position to achieve a vacuum seal.

[0019] In one embodiment, an ion pump is also included, which is disposed on the end cap assembly of the vacuum chamber and is welded to the end cap assembly via a sixth welding position to achieve a vacuum seal.

[0020] In one embodiment, the end flange assembly includes a first flange, a second flange, a sealing copper ring, and bolts. The first flange and the second flange are arranged opposite to each other. Both the first flange and the second flange have mounting holes in their middle portions for mounting a high-voltage connector assembly. The first metal welding ring of the high-voltage connector assembly is welded to a fourth welding position located at the edge of the mounting hole of the second flange to achieve a vacuum-sealed connection. Both the first flange and the second flange have opposing metal sealing blades for pressing the sealing copper ring. Both the first flange and the second flange have non-metallic sealing blade sides. The non-metallic sealing blade side of the first flange is welded to the cylindrical cavity through a third welding position to achieve a vacuum-sealed connection. The non-metallic sealing blade side of the second flange has threaded holes for installing and connecting high-voltage cables.

[0021] In one embodiment, the cathode assembly inside the vacuum chamber includes a filament cathode, a grid, a support, and an electron reflection structure. The cathode assembly is fixed to the high-voltage connector assembly via the support and electron emission structure, and the two ends of the filament cathode and the grid are electrically connected to the three lead terminals of the high-voltage connector assembly. Attached Figure Description

[0022] Figure 1 This is a cross-sectional schematic diagram of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0023] Figure 2 This is a cross-sectional schematic diagram of the electron beam window assembly in an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0024] Figure 3 This is a cross-sectional schematic diagram of the high-voltage connector assembly and a schematic diagram of the high-voltage cable plug of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0025] Figure 4 This is a cross-sectional schematic diagram of the end flange assembly and high-voltage connector assembly of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram of the end sealing plate assembly of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0027] Figure 6 This is a cross-sectional schematic diagram of the end flange assembly and a schematic diagram of the high-voltage connector and cathode assembly of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0028] Figure 7 This is a schematic diagram of the overall structure of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0029] The attached figures are labeled as follows: 1: Cylindrical cavity; 2: Electron beam window assembly; 3: End cap assembly; 4: End flange assembly; 5: High voltage connector assembly; 6: Negative grid assembly; 7: Exhaust pipe; 8: Ion pump; 9: Negative grid support structure; 100: Vacuum cavity; 11: First welding position; 12: Second welding position; 13: Third welding position; 14: Fourth welding position; 15: Fifth welding position; 16: Sixth welding position; 21: Electron beam window frame; 22: Titanium film; 23: Titanium film support; 24: Mounting structure; 31: First vacuum extraction hole; 32: Second vacuum extraction hole; 40: Bolt hole; 41: First flange; 411: Mounting hole; 412: Metal sealing blade; 413: Bolt hole; 42: Second flange; 421: Mounting hole; 422: Metal sealing blade; 423: Bolt hole; 43: Sealing copper ring; 44: Bolt; 51: Ceramic insulator; 52: First metal welded ring; 53: Second metal welded ring; 54: Small ceramic insulator; 55: First lead terminal; 56: Second lead terminal; 57: Third lead terminal; 58: Conical mounting surface; 61: Filament cathode; 62: Grid; 63: Support and electron reflection structure; 71: Welded transition piece; 72: Oxygen-free copper tube; 73: Metal flange; a: Cone angle; L: Ceramic insulator length; E: Electron beam current. Detailed Implementation

[0030] Hereinafter, embodiments of the invention are described with reference to the accompanying drawings. The following detailed description and drawings are provided to exemplify the principles of the invention, which is not limited to the described preferred embodiments; the scope of the invention is defined by the claims. The invention is now described in detail with reference to exemplary embodiments, some of which are illustrated in the accompanying drawings. The following description is made with reference to the accompanying drawings, and unless otherwise indicated, the same reference numerals in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all aspects of the invention. Rather, these embodiments are merely examples of systems and methods related to various aspects of the invention as covered in the appended claims.

[0031] Below, refer to Figures 1 to 3 A completely sealed electron curtain accelerator according to an embodiment of the present invention is described. Figure 1 This is a cross-sectional schematic diagram of an integrally sealed electron curtain accelerator according to an embodiment of the present invention. Figure 2 This is a schematic cross-sectional view of the electron beam window assembly of an integrally sealed electron curtain accelerator according to an embodiment of the present invention; Figure 3 This is a cross-sectional schematic diagram of the high-voltage connector assembly of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0032] like Figure 1 As shown, the integrally sealed electron curtain accelerator according to an embodiment of the present invention includes an integrally sealed vacuum chamber 100 and a cathode grating assembly 6 installed in the middle position inside the vacuum chamber 100. The vacuum chamber 100 is an integrally sealed vacuum structure formed by welding a cylindrical chamber 1, an electron beam window assembly 2, an end sealing plate assembly 3, an end flange assembly 4, and a high-voltage connector assembly 5. The cylindrical chamber 1 is a cylindrical structure with openings at both ends, and an opening parallel to the axis on the side of the cylinder. The electron beam window assembly 2 is a vacuum seal component welded together from multiple parts. The electron beam window assembly 2 is connected to the cylindrical side opening of the cylindrical chamber 1 by welding at a first welding position 11, forming a vacuum-sealed connection with the cylindrical chamber 1. The end sealing plate assembly 3 is connected to one end opening of the cylindrical chamber 1 by welding at a second welding position 12, forming a vacuum-sealed connection with the cylindrical chamber 1. The end flange assembly 4 has an opening in the middle. Its outer edge is welded to the other end opening of the cylindrical cavity 1 via a third welding position 13, forming a vacuum-sealed connection. The high-voltage connector assembly 5 is a multi-part vacuum-sealed component welded together. One end of the high-voltage connector assembly 5 is welded to the middle opening of the end flange assembly 4 via a fourth welding position 14, forming a vacuum-sealed connection. The female gate assembly 6 is fixed to the other end of the high-voltage connector assembly 5 and is located within the cylindrical cavity 1.

[0033] In summary, the cylindrical cavity 1, electron beam window assembly 2, end sealing plate assembly 3, end flange assembly 4, and high-voltage connector assembly 5 are welded together to form an integrated vacuum-sealed vacuum cavity 100. This entirely welded sealing structure provides excellent sealing performance, extremely low leakage rate, and high reliability. Furthermore, the welded sealing structure can withstand high-temperature baking above 250°C. Therefore, the vacuum cavity 100 can be rapidly vented through high-temperature baking to achieve a high vacuum state and maintain this high vacuum state for extended periods, enabling the electron curtain accelerator to operate stably for long periods.

[0034] According to an embodiment of the present invention, the cylindrical cavity 1 is cylindrical and is the main structural component of the electron curtain accelerator. It is made of metal materials such as copper, aluminum, iron, stainless steel, etc. Stainless steel is preferred, usually considering suitability for vacuum, structural strength, machinability and economy.

[0035] like Figure 2 As shown, the electron beam window assembly 2 of the integrally sealed electron curtain accelerator according to an embodiment of the present invention is located on the side of the cylindrical cavity 1, including an electron beam window frame 21 and a titanium film 22 welded to the electron beam window frame 21. The electron beam window frame 21 is connected to the cylindrical side opening of the cylindrical cavity 1 by welding at a first welding position 11, sealing the side opening of the cylindrical cavity 1 and forming a vacuum-sealed connection with the cylindrical cavity 1 at the first welding position 11. The electron beam window frame 21 is made of metal, such as copper, aluminum, iron, stainless steel, etc., and stainless steel is preferred, generally considering suitability for vacuum, structural strength, machinability, and economy. The titanium film 22 is a titanium foil with a thickness of 10 μm to 50 μm. The welding connection technology between the titanium film 22 and the electron beam window frame 21 is described in Chinese patent application document CN202211542605.4, and will not be detailed here. The titanium film 22 and the electron beam window frame 21 constitute a vacuum-sealed assembly. In an exemplary embodiment, the electron beam window assembly 2 further includes a titanium film support 23 located on the vacuum side of the titanium film 22. When the area of ​​the titanium film 22 is large, it provides structural strength support to the titanium film 22, facilitating the titanium film 22 to resist atmospheric pressure without rupture. Correspondingly, the cylindrical cavity 1 is designed with an installation structure 24 on the vacuum side for positioning and installing the titanium film support 23.

[0036] According to an embodiment of the present invention, the end sealing plate assembly 3 is located at one end of the cylindrical cavity 1 and is made of a metal material, such as copper, aluminum, iron, stainless steel, etc. Stainless steel is preferred, generally considering suitability for vacuum, structural strength, machinability, and economy. The end sealing plate assembly 3 is welded to the cylindrical cavity 1 through a second welding position 12, sealing the end opening of the cylindrical cavity 1, and achieving a vacuum-sealed connection at the second welding position 12.

[0037] According to an embodiment of the present invention, the end flange assembly 4 is located at the other end of the cylindrical cavity 1 and is made of a metal material, such as copper, aluminum, iron, stainless steel, etc. Stainless steel is preferred, generally considering suitability for vacuum, structural strength, machinability, and economy. The end flange assembly 4 is welded to the cylindrical cavity 1 through a third welding position 13, sealing the end opening of the cylindrical cavity 1, and achieving a vacuum-sealed connection at the third welding position 13.

[0038] like Figure 3 As shown, the high-voltage connector assembly 5 of the integrally sealed electron curtain accelerator according to an embodiment of the present invention includes a ceramic insulator 51, a first metal welding ring 52 welded to one end of the ceramic insulator 51, a second metal welding ring 53 welded to the other end of the ceramic insulator 51, and a first lead terminal 55, a second lead terminal 56, and a third lead terminal 57 mounted on the second metal welding ring 53, as well as small ceramic insulators 54 that electrically insulate the first lead terminal 55, the second lead terminal 56, and the third lead terminal 57 from the second metal welding ring 53, respectively. All components are connected by welding and achieve a vacuum seal. The ceramic insulator 51 and the small ceramic insulator 54 are made of ceramic material, which has excellent insulation performance; typically, a length of 100mm can easily achieve a withstand voltage of over 200kV. The first metal welding ring 52, the second metal welding ring 53, the first lead terminal 55, the second lead terminal 56, and the third lead terminal 57 are made of Kovar alloy. Kovar alloy has a coefficient of thermal expansion very close to that of ceramic. After they are welded together, they have the same coefficient of thermal expansion under various temperature changes without affecting the vacuum sealing effect of the weld. Vacuum sealing welding of ceramic and metal is an existing technology. Usually, the ceramic parts to be welded are first metallized, and then brazed with the metal. The brazing temperature is usually higher than 600°C. Therefore, the high-voltage connector assembly 5 can withstand high-temperature baking from 250°C to 600°C.

[0039] According to an embodiment of the present invention, a mounting hole is formed in the center of the end flange assembly 4, and a high-voltage connector assembly 5 is disposed within the mounting hole of the end flange assembly 4. The high-voltage connector assembly 5 is welded to the end flange assembly 4 through a fourth welding position 14, sealing the mounting hole in the center of the end flange assembly 4, and achieving a vacuum-sealed connection at the fourth welding position 14. In an exemplary embodiment, the first metal welding ring 52 of the high-voltage connector assembly 5 is welded to the edge of the mounting hole of the end flange assembly 4 by argon arc welding or laser welding.

[0040] According to an embodiment of the present invention, a vacuum cavity 100, comprising a cylindrical cavity 1, an electron beam window assembly 2, an end sealing plate assembly 3, an end flange assembly 4, and a high-voltage connector assembly 5, is made of metal (including alloys) or ceramic and is vacuum-sealed entirely by welding. It features excellent vacuum sealing performance, low leakage rate, and high long-term reliability. Furthermore, it can withstand high-temperature baking at a temperature range of 250°C to 600°C to achieve a vacuum rating of 10. -7 The high vacuum state at the Pa level is beneficial for the long-term stable operation of the electron curtain accelerator composed of the vacuum chamber 100 and the negative grid assembly 6, significantly reducing the need for vacuum maintenance. Moreover, by avoiding the combination of vacuum sealing structures formed by multiple "large flanges + rubber rings" and "knife flanges + copper rings" required by existing technologies, this invention is more characterized by simplified structure, small size, and light weight.

[0041] Below, refer to Figure 4 The integrally sealed electron curtain accelerator according to different embodiments of the present invention is further described. Figure 4 This is a cross-sectional schematic diagram of the end flange assembly and high-voltage connector assembly of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0042] like Figure 4As shown, in the integrally sealed electron curtain accelerator according to an embodiment of the present invention, the end flange assembly 4 and the high-voltage connector assembly 5 are welded together at the fourth welding position 14. The high-voltage connector assembly 5 further includes a conical mounting surface 58 located on the atmospheric side of the ceramic insulator 51. Through a specific design of the conical surface angle and length, such as the cone angle α being α = 10.45 degrees and the ceramic insulator length L being L = 120.8 mm, the conical mounting surface 58 can be fully matched with the internationally common R28 high-voltage cable plug (R28 is the model of the internationally renowned high-voltage cable provider ESSEX, and a similar model of another well-known high-voltage cable provider Claymount is CA18). The first lead terminal 55, the second lead terminal 56, and the third lead terminal 57 of the high-voltage connector assembly 5 are electrically connected to the three high-voltage contacts of the R28, respectively. The end flange assembly 4 is also provided with a threaded hole 40. After the R28 high-voltage cable plug is connected to the high-voltage connector assembly 5, the connection between the bolt and the threaded hole 40 ensures that the conical surface of the R28 high-voltage cable head is tightly fitted with the conical mounting surface 58, achieving the optimal pressure resistance state without air gaps. The ceramic insulator 51 can be used for vacuum sealing or exposed to the atmospheric environment, and its insulation strength can easily reach over 10kV / mm. The R28 high-voltage cable plug can withstand a pressure of 225kV. The high-voltage connector assembly 5 based on the ceramic insulator of this invention has a ceramic insulator length of 120.8mm, which can achieve a pressure resistance of 225kV. Therefore, this embodiment greatly simplifies the high-voltage connection structure of the electron curtain accelerator, eliminating the need for an oil tank transition. While optimizing the structure and reducing the volume, it significantly reduces the difficulty of vacuum sealing and improves the vacuum sealing effect and stability.

[0043] Below, refer to Figure 5 The integrally sealed electron curtain accelerator according to different embodiments of the present invention is further described. Figure 5 This is a schematic diagram of the end sealing plate assembly of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0044] like Figure 5As shown, the integrally sealed electron curtain accelerator according to an embodiment of the present invention further includes an exhaust pipe 7. The exhaust pipe 7 includes a welded transition piece 71, an oxygen-free copper pipe 72, and a metal flange 73, with a through exhaust channel in the middle. The welded transition piece 71 and the metal flange 73 are made of stainless steel. The welded transition piece 71, the oxygen-free copper pipe 72, and the metal flange 73 are welded together by metal brazing, providing high vacuum sealing characteristics. The end sealing plate assembly 3 has a first vacuum extraction hole 31. The welded transition piece 71 of the exhaust pipe 7 is connected to the first vacuum extraction hole 31, and a vacuum-sealed connection between the exhaust pipe 7 and the end sealing plate assembly 3 is achieved by welding at the fifth welding position 15. The metal flange 73 of the exhaust pipe 7 is a standard CF flange or KF flange structure. After the vacuum chamber 100 of the electron curtain accelerator is welded and assembled to form an integral seal, the metal flange 73 is connected to an external vacuum device to exhaust air from the vacuum chamber 100, bringing the interior of the vacuum chamber 100 to a high vacuum state. Most of the gas inside the vacuum chamber 100 and the adsorbed gas on the material surface have been expelled, and the interior has reached a high vacuum state (e.g., vacuum degree better than 10). -7 After Pa, the oxygen-free copper tube 72 is cold-pressed and sealed using a special tool (cold press pliers) (commonly known as "tube cutting"), so that the vacuum chamber 100 forms an overall sealed state that is completely isolated from the outside, which is beneficial for the electron curtain accelerator to maintain a continuous high vacuum.

[0045] like Figure 5As shown, the integrally sealed electron curtain accelerator according to an embodiment of the present invention further includes an ion pump 8. According to an embodiment of the present invention, the ion pump 8 is located on the cylindrical cavity 1, or on the end sealing plate assembly 3, preferably on the end sealing plate assembly 3. The end sealing plate assembly 3 has a second vacuum extraction port 32, and the vacuum extraction port of the ion pump 8 is connected to the second vacuum extraction port 32. A vacuum-sealed connection between the ion pump 8 and the end sealing plate assembly 3 is achieved by welding at the sixth welding position 16. The ion pump operates under the control of the ion pump power supply to maintain a high vacuum state inside the electron curtain accelerator. Even after assembly and in the early stages, when the vacuum chamber of an electron curtain accelerator is evacuated by external vacuum equipment to achieve a high vacuum, during operation, the cathode assembly generates an electron beam. A portion of this beam bombards the grid assembly or the inner wall of the vacuum chamber, releasing gas molecules. These gas molecules need to be removed by vacuum equipment to prevent a deterioration in the vacuum chamber's vacuum level. A deteriorated vacuum increases the probability of electron beam impact, leading to greater electron beam loss, and also lowers the internal pressure resistance of the vacuum chamber, causing high-voltage arcing and unstable operation of the electron curtain accelerator. According to an embodiment of the present invention, the ion pump 8 is fixed to the end-sealing plate assembly 3 by welding, enabling real-time evacuation of the overall sealed electron curtain accelerator to maintain its internal high vacuum state, which is beneficial for the long-term stable operation of the electron curtain accelerator.

[0046] The above description illustrates an embodiment where the exhaust pipe 7 and ion pump 8 are located on the end cap assembly 3. However, the invention is not limited thereto. According to embodiments of the invention, the exhaust pipe 7 and / or ion pump 8 can be located in any other suitable location for welded sealing connection within the vacuum chamber 100, such as the cylindrical chamber 1, without affecting the working performance of the exhaust pipe 7 and ion pump 8; all such locations are feasible.

[0047] Below, refer to Figure 6 The integrally sealed electron curtain accelerator according to different embodiments of the present invention is further described. Figure 6 This is a cross-sectional view of the end flange assembly of an integrally sealed electron curtain accelerator according to an embodiment of the present invention, as well as a schematic diagram of the high-voltage connector and the cathode assembly.

[0048] like Figure 6As shown, in an exemplary embodiment, the end flange assembly 4 of the integrally sealed electron curtain accelerator consists of a first flange 41, a second flange 42, a sealing copper ring 43, and bolts 44. The first flange 41 has a mounting hole 411 in its center. A metal sealing blade 412 is provided on one side of the first flange 41, around the mounting hole 411. A ring of bolt holes 413, which are threaded blind holes, is provided around the metal sealing blade 412. On the other side of the first flange 41, a vacuum seal is achieved by welding to the other end of the cylindrical cavity 1 through a third welding position 13. The second flange 42 has a mounting hole 421 in its center. A metal sealing blade 422 of the same specification as the metal sealing blade 412 on the first flange 41 is provided on one side of the second flange 42 (the side opposite to the first flange 41), around the mounting hole 421. A ring of bolt holes 423, which are unthreaded through holes, is provided around the metal sealing blade 422. The sealing copper ring 43 is made of oxygen-free copper and its size matches the metal sealing blades 412 and 422. It is located between the first flange 41 and the second flange 42. The bolt 44 passes through the bolt hole 423 of the second flange 42 and connects to the bolt hole 413 of the first flange 41. It can be tightened by the bolt. The metal sealing blades 412 and 422 press the sealing copper ring, so that the second flange 42 and the first flange 41 form a vacuum seal structure through metal compression. On the other side of the second flange 42, there is a fourth welding position 14 around the mounting hole 421. The high-voltage connector assembly 5 is welded to the second flange 42 through the fourth welding position 14 to form a vacuum seal connection. The fourth welding position 14 has a ring of bolt holes 40, which are threaded blind holes. The R28 high-voltage cable can be installed and electrically connected to the high-voltage connector assembly 5 through the bolt holes 40.

[0049] According to an embodiment of the present invention, the cathode assembly 6 includes a filament cathode 61, a grid 62, and a support and electron reflection structure 63. The cathode assembly 6 is fixed to the high-voltage connector assembly 5 via the support and electron reflection structure 63, and can be kept at a high voltage negative relative to the vacuum chamber 100 under the control of an external high-voltage power supply connected to the high-voltage connector assembly 5. The two ends of the filament cathode 61 are electrically connected to the second lead terminal 56 and the third lead terminal 57 of the high-voltage connector assembly 5, respectively, generating free electrons under the filament power control of the external high-voltage power supply. The grid 62 is electrically connected to the first lead terminal 55 of the high-voltage connector assembly 5, and under the filament power control of the external high-voltage power supply, it draws the free electrons generated by the filament cathode 61 out of the cathode assembly. The free electrons drawn from the cathode assembly are accelerated by the high-voltage electric field between the cathode assembly 6 and the vacuum chamber 100, gaining energy and becoming a "curtain-like" electron beam. The cathode assembly 6 is an important part of the electron curtain accelerator and is prior art; therefore, it will not be described in detail here. The cathode assembly 6 operates under high voltage and high temperature conditions (the filament cathode typically requires a temperature close to 2000℃ to generate electron emission), and there is a certain risk of damage during operation, such as filament burnout.

[0050] According to an embodiment of the present invention, the integrally sealed electron curtain accelerator includes a metal press-fit sealing structure in its end flange assembly 4. Compared to the aforementioned fully welded sealing embodiment, this adds a detachable function: by loosening the bolts 44, the second flange 42 and the high-voltage connector assembly 5 welded to the second flange 42, along with the female grid assembly 6 already installed on the high-voltage connector assembly 5, can be removed from the vacuum chamber 100 through the mounting hole 411. This allows for the repair of any damaged female grid assembly 6 during operation. This metal press-fit sealing structure of the integrally sealed electron curtain accelerator can withstand high-temperature baking above 250°C, facilitating the vacuum chamber 100 to achieve a high vacuum state. Although it is not as reliable as a welded seal in terms of leakage rate and long-term reliability, it is the only non-welded sealing surface, posing a minimal risk, and the overall high vacuum state can still be guaranteed.

[0051] Below, refer to Figure 7 The integrally sealed electron curtain accelerator according to different embodiments of the present invention is further described. Figure 7 This is a schematic diagram of the overall structure of an integrally sealed electron curtain accelerator according to an embodiment of the present invention.

[0052] Figure 7The structure of an integrally sealed electron curtain accelerator is shown, including a vacuum chamber 100, a cathode grating assembly 6 located inside the vacuum chamber 100, and a cathode grating insulating support 9. The vacuum chamber 100 is composed of a cylindrical chamber 1, an electron beam window assembly 2, an end-capping plate assembly 3, an exhaust pipe 7, an ion pump 8, an end-flange assembly 4, and a high-voltage connector assembly 5, all welded together to form an integral sealed structure. Specifically: the electron beam window assembly 2, which forms a vacuum seal through welding, is welded to the cylindrical chamber 1 at a first welding position 11; the exhaust pipe 7, which forms a vacuum seal, and the ion pump 8, which also forms a vacuum seal, are welded to the end-capping plate assembly 3 at fifth welding positions 15 and sixth welding positions 16, respectively; the end-capping plate assembly 3 is then welded to the cylindrical chamber 1 at a second welding position 12; the high-voltage connector assembly 5, which forms a vacuum seal through welding, is welded to the end-flange assembly 4 at a fourth welding position 14; and the end-flange assembly 4 is then welded to the cylindrical chamber 1 at a third welding position 13. The cathode grid assembly 6 is mounted on the high-voltage connector assembly 5, with its grid facing the electron beam window assembly 2. The filament and grid of the cathode grid assembly 6 are connected to the lead terminals of the high-voltage connector assembly, respectively. In large electron curtain accelerators, the length of the cathode grid assembly 6 can be very large, for example, 2 meters. If a long cathode grid assembly is fixed only at one end, it is difficult to ensure installation accuracy. According to an embodiment of the present invention, the electron curtain accelerator also includes a cathode grid insulating support 9, which is made of ceramic insulating material. One end is fixed to the end sealing plate assembly 3, and the other end is connected to the cathode grid assembly 6, providing support for the cathode grid assembly 6. The cathode grid insulating support 9 improves the installation position accuracy of the long cathode grid assembly 6, while reducing the support strength of the high-voltage connector assembly 5 on the cathode grid assembly 6, which is beneficial to reducing the structural size of each component.

[0053] According to an embodiment of the present invention, an external high-voltage power supply provides a negative high voltage, such as -200kV, to the cathode assembly 6 via the high-voltage connector assembly 5, relative to the vacuum cavity 100, thereby generating a high-voltage electric field between the cathode assembly 6 and the vacuum cavity 100. Simultaneously, the filament cathode is controlled to generate free electrons, and the grid is further controlled to guide these free electrons to the outside of the cathode assembly. The free electrons E outside the cathode assembly are accelerated by the high-voltage electric field and move rapidly towards the electron beam window assembly 2, simultaneously gaining 200kV energy to become a high-energy electron beam. This high-energy electron beam passes through the titanium film of the electron beam window assembly, becoming an electron beam E capable of irradiating objects in an atmospheric environment. The stable establishment of the high-voltage electric field (maintaining high voltage stability and preventing arcing), the generation of the electron beam, and the uninterrupted movement of the electron beam all require a high-vacuum environment. Therefore, achieving and maintaining a high vacuum within the vacuum cavity 100 is crucial. Furthermore, the higher the vacuum level, the smaller the distance required for high-voltage withstand; that is, the higher the vacuum level, the smaller the diameter of the cylindrical cavity 1 can be.

[0054] According to an embodiment of the present invention, the integrally sealed electron curtain accelerator utilizes a welded sealing structure to the maximum extent. After assembly, the gas is exhausted by baking at 400°C, allowing the surface adsorbed gas in each part of the vacuum chamber 100 to be fully released. Simultaneously, the gas inside the electron curtain accelerator is extracted by an external vacuum device connected to the exhaust pipe 7, achieving a gas extraction efficiency better than 10. -7 A high vacuum of Pa is achieved. The exhaust pipe is then cold-pressed and welded to maintain a high vacuum inside the electron curtain accelerator. Simultaneously, due to the extremely low vacuum leakage rate caused by the welding sealing method, only a small ion pump with a pumping speed not exceeding 20 L / s is needed to maintain the high vacuum inside the electron curtain accelerator. Therefore, the electron curtain accelerator does not require complex external vacuum equipment in subsequent operations. Furthermore, the ion pump is relatively small, reducing the complexity and weight of the system. The overall sealed structure essentially eliminates the need for vacuum maintenance. Except for one metal press-fit sealing surface reserved for the maintenance of the cathode grating assembly, all other sealing surfaces are welded sealing structures, minimizing the use of large flanges, reducing volume and weight. At 10 -7 In a high vacuum environment of Pa, the cylindrical cavity of the integrally sealed electron curtain accelerator can achieve a withstand voltage of 200kV with an outer diameter not exceeding 200mm, further reducing the overall volume and weight. The titanium film outer surface of the electron beam window assembly has no complex structure; the electron beam E can be used for irradiation processing immediately after exiting the window. The electron beam E has a short path in air, resulting in minimal loss and high utilization efficiency. This lightweight, compact, and efficient integrally sealed electron curtain accelerator significantly improves ease of use, expanding its application scenarios and economic benefits.

[0055] The integrally sealed electron curtain accelerator of this invention employs numerous welded and sealed components, particularly miniaturized electron beam window components and high-voltage connector components, and forms an integrally sealed vacuum chamber through welding and sealing. It also utilizes a cold-pressable weldable and sealed exhaust pipe and incorporates a miniaturized ion pump. High-temperature baking of the exhaust gas achieves and maintains a temperature of 10... -7 A high vacuum of over Pa can be achieved and maintained at 10 Pa. -7 A high vacuum of over Pa is a prerequisite for further miniaturization of the entire electron curtain accelerator, enabling the electron beam high voltage of over 200kV to be achieved in a small size with an outer diameter of no more than 200mm. The above technical points are interconnected and cannot be viewed separately. Together, they significantly improve the high vacuum effect of the electron curtain accelerator.

[0056] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the constructions and methods of the above embodiments. Rather, the invention is intended to cover various modifications and equivalent configurations. Furthermore, while various elements and method steps of the disclosed invention have been shown in various exemplary combinations and constructions, other combinations including more or fewer elements or methods also fall within the scope of the invention.

Claims

1. A fully sealed electron curtain accelerator, characterized in that, include: The vacuum chamber is an integrally sealed vacuum cavity and a cathode grating assembly installed inside the vacuum cavity. The vacuum cavity includes a cylindrical cavity, an electron beam window assembly, an end cap assembly, an end flange assembly, and a high-voltage connector assembly. The cylindrical cavity, the electron beam window assembly, the end cap assembly, the end flange assembly, and the high-voltage connector assembly are connected by welding to form a vacuum structure. The interior of the vacuum structure is the integrally sealed vacuum cavity. It also includes an exhaust pipe, which is located on the vacuum chamber and is welded to the vacuum chamber via a fifth welding position; It also includes an ion pump, which is mounted on the vacuum chamber and is sealed to the vacuum chamber via a sixth welding position; The cylindrical cavity has a first opening on its side parallel to the axis, and the two ends of the cylindrical cavity have a second opening and a third opening, respectively. The electron beam window assembly is connected to the first opening of the cylindrical cavity by welding at the first welding position, and forms a vacuum-sealed connection with the cylindrical cavity; The end cap assembly is connected to the second opening of the cylindrical cavity by welding at the second welding position, and forms a vacuum-sealed connection with the cylindrical cavity; The outer edge of the end flange assembly is connected to the third opening of the cylindrical cavity by welding at the third welding position, and forms a vacuum-sealed connection with the cylindrical cavity; The end flange assembly has a mounting hole in the middle. One end of the high-voltage connector assembly is connected to the mounting hole of the end flange assembly by welding through a fourth welding position, and forms a vacuum-sealed connection with the end flange assembly.

2. The integrally sealed electron curtain accelerator according to claim 1, characterized in that, The electron beam window assembly includes an electron beam window frame and a titanium film. The electron beam window frame and the titanium film are connected by welding to form a vacuum-sealed assembly. The electron beam window frame is made of stainless steel, and the titanium film is made of titanium with a thickness of 10µm to 50µm.

3. The integrally sealed electron curtain accelerator according to claim 2, characterized in that, The high-voltage connector assembly includes: a ceramic insulator, a first metal welding ring welded to one end of the ceramic insulator, a second metal welding ring welded to the other end of the ceramic insulator, a first lead terminal, a second lead terminal, and a third lead terminal mounted on the second metal welding ring, and small ceramic insulators that electrically insulate the three lead terminals from the second metal welding ring respectively; the components of the high-voltage connector assembly are connected by welding to form a vacuum-sealed assembly.

4. The integrally sealed electron curtain accelerator according to claim 3, characterized in that, The end flange assembly is made of stainless steel. The end flange assembly has a mounting hole in the middle and a ring of bolt holes around the mounting hole. The bolt holes are threaded blind holes and are used for the installation and connection of external high-voltage cables.

5. The integrally sealed electron curtain accelerator according to claim 4, characterized in that, The end sealing plate assembly and / or the end flange assembly are both integrally formed with the cylindrical cavity.

6. The integrally sealed electron curtain accelerator according to claim 5, characterized in that, The high-voltage connector assembly also includes a conical mounting surface disposed on the ceramic insulator.

7. The integrally sealed electron curtain accelerator according to claim 5, characterized in that, The end flange assembly includes a first flange, a second flange, a sealing copper ring, and bolts. The first flange and the second flange are arranged opposite to each other. Both the first flange and the second flange have mounting holes in their middle sections for installing a high-voltage connector assembly. The first metal welding ring of the high-voltage connector assembly is vacuum-sealed by welding to a fourth welding position located at the edge of the mounting hole of the second flange. Both the first flange and the second flange have opposing metal sealing blades for pressing the sealing copper ring. Both the first flange and the second flange have non-metallic sealing blade sides. The non-metallic sealing blade side of the first flange is welded to the cylindrical cavity through a third welding position. The non-metallic sealing blade side of the second flange has threaded holes for installing and connecting high-voltage cables.

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