Electron beam extraction device and electron accelerator thereof

Abstract

The present application relates to an electron beam extraction device and an electron accelerator, the electron beam extraction device comprising a frame, a titanium film and a solder, the frame being a flat plate structure with a window in the middle, the titanium film having an area larger than that of the window of the frame, the titanium film completely covering the window, the titanium film and the frame forming a lap area outside the edges of the window of the frame; wherein the solder is located in the lap area and between the frame and the titanium film, and the solder forms a ring around the window, the solder tightly connecting the frame and the titanium film together by welding at a first welding position to form a sealed structure. The electron beam extraction device of the present application has the advantages of providing high vacuum sealing, long-term reliability, being suitable for high-temperature baking, simplified structure and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of electron accelerators, and more specifically to an electron beam extraction device for an electron accelerator and an electron accelerator thereof. Background Technology

[0002] Electron accelerators have extremely wide applications 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 involve direct irradiation processing using electron beams. Electron accelerators require a vacuum environment to generate and accelerate electron beams to achieve high energy. However, irradiation processing can only be carried out in an atmospheric environment. Therefore, it is necessary to extract the electron beam from the vacuum environment into the atmosphere. The electron beam extraction device must, on the one hand, isolate the accelerator vacuum chamber from the atmosphere, requiring good vacuum sealing characteristics and a structure capable of withstanding atmospheric pressure; on the other hand, it must allow the electron beam to penetrate while minimizing energy loss during penetration. This necessitates that the isolation structure be as thin as possible. Typically, titanium films, which possess high structural strength and can be processed into very thin films, are used as the isolation material for electron beam extraction.

[0003] Electron beam extraction devices typically consist of a frame and a titanium membrane. The frame, usually made of stainless steel, provides structural support and mounting for the titanium membrane, and may even include cooling for it. The titanium membrane, made of pure titanium, possesses excellent density properties, isolating it from the atmosphere and vacuum. It must withstand atmospheric pressure over a certain area without breaking, while allowing the electron beam to penetrate with minimal loss; its thickness is typically tens of micrometers. The frame that mounts the titanium membrane is connected to the accelerator's vacuum chamber. Because it must withstand atmospheric pressure, it is typically several millimeters or even more than ten millimeters thick. The significant difference in thickness and material composition between these two materials makes it difficult to join using traditional welding techniques such as argon arc welding, laser welding, and resistance welding.

[0004] Argon arc welding (argon arc welding) joins two materials by simultaneously melting them together using an electric arc. However, for titanium films and stainless steel plates with thicknesses differing by hundreds of times (tens of micrometers vs. millimeters), the thicker steel plate often fails to reach its full temperature before the extremely thin titanium film, with its minimal heat capacity, melts instantly (similar to burning). Therefore, argon arc welding is unsuitable. Similarly, laser welding is also unsuitable; the titanium film, with its extremely low heat capacity, melts instantly, while the stainless steel plate, with its high heat capacity, is far from molten. Resistance welding also struggles to achieve proper heat distribution among the welding head, titanium film, and stainless steel plate. The extremely thin titanium film is easily torn and adhered to by the welding head, and the tiny sharp points on the welding head cannot prevent puncturing the titanium film during welding, making vacuum sealing impossible. More importantly, stainless steel and titanium have poor weldability due to their poor metallurgical compatibility (Fe-Ti contains numerous intermetallic compounds), making it difficult to obtain a satisfactory weld joint using fusion welding methods.

[0005] In existing technologies, electron beam extraction devices typically employ a titanium membrane with a thickness of 30-50 micrometers and a square stainless steel flange frame. For example, Chinese patents with publication numbers CN215299173U and CN214279901U describe a square stainless steel flange consisting of two pieces, upper and lower, with one or more sealing grooves. Elastic sealing materials, such as rubber rings, are placed within these grooves. The titanium membrane is positioned between the two flange pieces, which are then connected by bolts. Mechanical extrusion is used to tightly compress the "flange + titanium membrane + elastic sealing material + flange" combination to achieve a vacuum seal. A similar technical solution is proposed in Chinese patent application number 201910561459.1, which describes a titanium window assembly. This mechanical sealing technology has several drawbacks: firstly, the sealing effect is poor, making it difficult for accelerators to achieve ultra-high vacuum; secondly, due to the rubber ring sealing method, the leakage rate is typically high, and the vacuum level is usually difficult to reach above 10⁻⁶. -5 A lower vacuum level, even with optimal vacuum conditions, can negatively impact accelerator electron beam generation. Furthermore, the electron beam is more susceptible to loss due to collisions with gas molecules during acceleration, and the probability of arcing in the high-voltage electric field is also higher, affecting the accelerator's high-voltage stability. Secondly, the long-term reliability of the seal is poor. Elastic materials like rubber weaken or even lose elasticity over prolonged use, leading to a deterioration in the vacuum seal and affecting the accelerator's normal operation. Thirdly, it is unsuitable for high-temperature baking. After vacuum sealing, accelerators and other vacuum chambers typically require high-temperature baking to release adsorbed gases from the surfaces of components like the chamber walls, achieving the required ultra-high vacuum. Elastic sealing materials, such as rubber, cannot withstand baking temperatures above 200 degrees Celsius, while metal sealing materials like copper rings, although permissible at higher temperatures,... The following factors contribute to the problem: First, temperature fluctuations during the baking process and reduced elasticity due to high temperatures can all affect the vacuum sealing effect, leading to a poorer seal and impacting the normal operation of the accelerator. Second, the large size and weight of the flange, due to its mechanical sealing method, require high mechanical rigidity to achieve reliable compression sealing. Furthermore, the design of the sealing groove and screw holes necessitates a large flange size, resulting in a large and heavy electron beam extraction device that is inconvenient to use and economically unfeasible. Third, the large thickness of the flange and the height of the bolts on it increase the distance between the titanium window surface and the outermost edge of the electron beam extraction device. This makes it difficult for objects irradiated by the electron beam to get close to the titanium window, causing the electron beam to travel a considerable distance in the air before reaching the surface of the irradiated object, resulting in significant energy loss and reduced electron beam utilization efficiency.

[0006] Therefore, an electron beam extraction device that is ultra-high vacuum sealed, reliable over long periods, suitable for high-temperature baking, has a simplified structure, and is highly efficient is needed. Summary of the Invention

[0007] One object of the present invention is to provide an electron beam extraction device that is ultra-high vacuum sealed, reliable over long periods, suitable for high-temperature baking, structurally simplified, and highly efficient. Another object of the present invention is to provide an electron accelerator incorporating an electron beam extraction device that is ultra-high vacuum sealed, reliable over long periods, suitable for high-temperature baking, structurally simplified, and highly efficient.

[0008] One aspect of the present invention provides an electron beam extraction device and an electron accelerator thereof that are ultra-high vacuum sealed, reliable over long periods of time, suitable for high-temperature baking, have a simplified structure, and are highly efficient.

[0009] An electron beam extraction device includes a frame, a titanium film, and solder. The solder is located between the frame and the titanium film. The frame has a flat plate structure with a window in the middle. The area of ​​the titanium film is larger than the area of ​​the window of the frame, and the titanium film completely covers the window. The titanium film and the frame form an overlap area on the outer edge of the window of the frame. The solder is located in the overlap area and between the frame and the titanium film, and the solder forms a ring around the window. The solder causes the frame and the titanium film to be tightly connected together by welding at a first welding position to form a sealed structure.

[0010] In one embodiment, the frame is made of stainless steel or copper, and the frame thickness is 0.5 mm to 5 mm; the distance from the upper surface of the titanium film to the highest point of the upper surface or the top surface of the frame is less than or equal to 5 mm.

[0011] In one embodiment, the thickness of the titanium film is from 5 μm to 100 μm.

[0012] In one embodiment, the solder has a melting temperature of 450°C to 800°C and a thickness of less than or equal to 100 μm.

[0013] In one embodiment, a welding transition piece is further included, which is located between the frame and the solder. The shape of the welding transition piece matches the frame, and a window is opened in the middle of the welding transition piece. The welding transition piece and the frame form a structure of stacking in parallel. The material of the welding transition piece is one of Kovar alloy, copper, and gold.

[0014] In one embodiment, the thickness of the welded transition piece is 0.5 mm to 10 mm.

[0015] In one embodiment, the frame and the welding transition piece form a second welding position at the edge of the window position of the frame, and the frame and the welding transition piece are connected by welding to achieve a high vacuum seal. The surface of the second welding position is arc-shaped or sloped. Alternatively, the size of the welding transition piece is smaller than that of the frame, and a third welding position is formed between the outer edge of the welding transition piece and the frame. The outer edge of the welding transition piece is welded to the frame by argon arc welding or laser welding, and the surface of the third welding position is arc-shaped or sloped.

[0016] In one embodiment, a support member is further included, which is disposed on the vacuum side of the titanium film, and the support member is provided with a plurality of grids and a plurality of grid holes spaced apart from each other.

[0017] In one embodiment, the support member is U-shaped, with the top of the boss of the U-shaped support member contacting the surface of the titanium film, and the two shoulders of the U-shaped support member contacting the surface of the frame.

[0018] According to another aspect of the present invention, an electron accelerator is also disclosed, the electron accelerator including the aforementioned electron beam extraction device, an accelerator vacuum chamber, and an electron beam generator, wherein the electron beam generator is located in the middle of the accelerator vacuum chamber for generating an electron beam, the electron beam extraction device and the accelerator vacuum chamber have a fourth welding position, the electron beam extraction device and the accelerator vacuum chamber are connected by welding to form an integrally sealed structure, and the electron beam extraction device is used to extract the electron beam generated by the electron beam generator and accelerated by the electron accelerator into the atmosphere. Attached Figure Description

[0019] Figure 1 This is a cross-sectional schematic diagram of an electron beam extraction device according to an embodiment of the present invention.

[0020] Figures 2a to 2c This is a schematic diagram of an electron beam extraction device according to three embodiments of the present invention.

[0021] Figure 3 This is a schematic diagram of the structure of an electron beam extraction device according to an embodiment of the present invention.

[0022] Figure 4a , Figure 4b These are schematic diagrams of electron beam extraction devices according to two embodiments of the present invention.

[0023] Figure 5 This is a schematic diagram of an electron beam accelerator according to an embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1: Frame; 2: Titanium film; 3: Solder, first welding position; 4: Welding transition piece;

[0026] 10: Window; 11: Overlapping area; 12: Second welding position; 13: Third welding position; 14: Fourth welding position;

[0027] 5: Support component; 51: Grid; 52: Grid hole; 53: Cooling channel;

[0028] 6: Accelerator vacuum chamber; 7: Electron beam generator;

[0029] d1: Frame thickness; d2: Titanium film thickness; d3: Solder thickness; d4: Welding transition thickness; d5: Distance from the surface of the titanium film to the outermost edge of the electron beam extraction device;

[0030] R: Diameter of the circular window; a: Side length of the square window;

[0031] L: Length of the rectangular window; W: Width of the rectangular window;

[0032] T: Solder melting temperature; E: Electron beam current; A: Atmospheric side; B: Vacuum side; Detailed Implementation

[0033] 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.

[0034] Below, refer to Figure 1 and Figures 2a to 2c An electron beam extraction device according to an embodiment of the present invention is described. Figure 1 This is a cross-sectional schematic diagram of an electron beam extraction device according to an embodiment of the present invention. Figures 2a to 2c This is a front view of an electron beam extraction device according to three embodiments of the present invention.

[0035] like Figure 1As shown, the electron beam extraction device according to an embodiment of the present invention includes a frame 1, a titanium film 2, and a solder 3, with the solder 3 located between the frame 1 and the titanium film 2. In an exemplary embodiment, the frame 1 is a flat plate structure with a window 10 in the middle. The titanium film 2 has a larger area than the window 10 in the middle of the frame 1 and completely covers the window 10, forming an overlap area 11 with the frame 1 on the outer edge of the window. The solder 3 is located between the frame 1 and the titanium film 2 corresponding to the overlap area 11, forming a complete annular circumference around the window 10. Through welding, the titanium film 2 and the frame 1 are tightly connected to form an ultra-high vacuum sealing structure. The position of the solder 3 is the first welding position where the titanium film 2 and the frame 1 are welded. The thickness of the titanium film 2 is d2, the thickness of the solder 3 is d3, and the distance from the upper surface of the titanium film 2 to the highest point or top surface of the upper surface of the frame 1 is d5.

[0036] In an exemplary embodiment, the frame 1 is made of either stainless steel or copper, preferably stainless steel. The thickness d1 of the frame 1 is 0.5 mm to 5 mm, preferably 1 mm. The distance d5 from the upper surface of the titanium film 2 to the highest point of the upper surface of the frame 1 is less than 5 mm. In some embodiments, the frame 1 is made of stainless steel, the thickness d1 is 1 mm, and the distance d5 from the upper surface of the titanium film 2 to the highest point of the upper surface of the frame 1 is 1.1 mm.

[0037] In the exemplary embodiment, the overlapping area 11 between the frame 1 and the titanium membrane 2 does not require a sealing groove, simplifying the structure. The outer side of the overlapping area 11 does not require threaded holes or bolt connections, resulting in a simple structure, small size, and light weight. The welding connection between the frame 1 and the titanium membrane 2 via solder 3 is an all-metal connection, which is dense, strong, and has an extremely low gas leakage rate, providing ultra-high vacuum sealing. The small distance from the upper surface of the titanium membrane to the outermost edge of the entire electron beam extraction device allows items subjected to electron beam irradiation to be close to the titanium membrane, reducing electron beam loss in the air and improving electron beam utilization efficiency.

[0038] like Figure 2a , Figure 2b and Figure 2c As shown, the electron beam extraction device according to an embodiment of the present invention can have various shapes, such as circular and square. Figure 2a A circular electron beam extraction device is shown, with a circular window 10 having a diameter of R and a circular frame 1. Figure 2b A square electron beam extraction device is shown, with a side length of a for the square window 10 and a square frame 1. Figure 2c A rectangular electron beam extraction device is shown, with a rectangular window 10 having a length of L and a width of W, and a rectangular frame 1.

[0039] According to embodiments of the present invention, the thickness d2 of the titanium film 2 is 5 μm to 100 μm, preferably 10 μm to 30 μm. The thickness of the titanium film 2 is minimized while meeting the structural strength required to withstand atmospheric pressure; therefore, its thickness selection is related to the size of the window 10. In an exemplary embodiment, when the diameter R of a circular window, the side length a of a square window, or the width W of a rectangular window is greater than or equal to 50 mm, the thickness of the titanium film is 30 μm. In an exemplary embodiment, when the diameter R of a circular window, the side length a of a square window, or the width W of a rectangular window is less than 5 mm, the thickness of the titanium film is 10 μm. The smaller the thickness of the titanium film, the less energy loss occurs when the electron beam penetrates the titanium film, and the higher the penetration ratio of the electron beam. In an exemplary embodiment, the window 10 can also be easily made large in size, for example... Figure 2c The rectangular window 10 can easily achieve a window size of L=2000mm and W=60mm.

[0040] The melting temperature T of solder 3 is 450℃~800℃, preferably 650℃~750℃. The electron beam extraction device features good vacuum sealing performance, high structural strength, and suitability for high-temperature baking and degassing. In an exemplary embodiment, the frame 1, titanium film 2, and solder 3 are heated together to a temperature slightly higher than the melting temperature of solder 3 and then cooled. Through a metallurgical welding process, a fully metallic and tight connection is achieved between the frame 1 and the titanium film 2, providing ultra-high vacuum sealing. The upper limit of the melting temperature T is lower than the phase transition temperature of the titanium film, eliminating the risk of reduced structural strength of the titanium film due to high-temperature phase transition. The lower limit of the melting temperature T allows the electron beam extraction device to withstand temperatures not exceeding 400 degrees Celsius without undergoing a change in state, meeting the requirements for high-temperature baking and degassing of the electron accelerator, improving the internal vacuum state, and enhancing the stability of the electron accelerator operation.

[0041] The thickness d3 of solder 3 is less than or equal to 100 μm, preferably less than 50 μm. The thickness d3 of solder 3 is positively correlated with the thickness d2 of titanium film 2; that is, the smaller the thickness d2 of titanium film 2, the smaller the thickness d3 of solder 3. In an exemplary embodiment, solder 3 has a certain thickness, which can completely fill the microscopic gaps between frame 1 and titanium film 2, making the first welding position a dense fill and achieving vacuum sealing. Frame 1 has good flatness and high surface finish, such as flatness 0.1 and surface finish Ra 0.8, which minimizes the microscopic gaps at the first welding position between frame 1 and titanium film 2, thus minimizing the thickness d3 of solder 3. This minimizes the potential erosive damage to titanium film 2 caused by solder 3 in its liquid state, preventing the titanium film 2 from losing its airtightness due to erosive damage. Reducing the thickness d3 of solder 3 is an important technical measure when the titanium film is thinner.

[0042] The above describes three typical window shapes for electron beam extraction devices. However, the present invention is not limited to these. According to embodiments of the present invention, the window shape can be any other shape, such as a parallelogram, a rhombus, or two parallel rectangles, without affecting the connection relationship and sealing effect between the frame, solder, and titanium film, and all such designs are feasible.

[0043] Below, refer to Figure 3 An electron beam extraction device according to another embodiment of the present invention is described. Figure 3 This is a schematic diagram of an electron beam extraction device according to an embodiment of the present invention.

[0044] like Figure 3 As shown, the electron beam extraction device according to an embodiment of the present invention includes a frame 1, a titanium film 2, a solder 3, and a welding transition piece 4. The welding transition piece 4 is located between the frame 1 and the solder 3, has a structural shape similar to that of the frame 1, and has a window 10 in the middle. The welding transition piece 4 and the frame 1 are arranged in a parallel stacked relationship. The frame 1 has a thickness d1, and the welding transition piece 4 has a thickness d4.

[0045] The description of the titanium film 2 and solder 3 according to embodiments of the present invention is as above and will not be repeated here. The frame 1 is typically made of stainless steel for easy vacuum sealing connection with the accelerator cavity. As mentioned in the background art, stainless steel and titanium have poor weldability, making it difficult to obtain a qualified weld joint using fusion welding methods. The present invention solves this problem by using solder 3 for metallurgical fusion; however, selecting a solder that has fusion properties with both titanium and stainless steel places high demands on solder 3. Figure 3 The embodiment of the present invention shown has a welding transition piece 4 that exhibits good weldability with stainless steel, allowing for ultra-high vacuum sealing by common methods such as argon arc welding and laser welding. Furthermore, it possesses good metallurgical fusion with titanium, enabling ultra-high vacuum sealing by welding with solder 3. The welding transition piece 4 solves the problem of direct welding between the titanium membrane 2 and the frame 1. Its material composition and structure significantly influence the welding process, particularly the vacuum sealing effect after welding. Through extensive experimental testing and meticulous design, the present invention has successfully achieved the embodiments with specific material and structural characteristics described below.

[0046] In some embodiments, the welding transition piece 4 is a metal material such as Kovar alloy, copper, or gold, preferably copper, which has good economic advantages. The solder 3 is a nickel-based, silver-based, or copper-based solder. Kovar alloy, copper, gold, etc. are all materials suitable for ultra-high vacuum and can be directly welded to stainless steel, while also having good metallurgical fusion properties with various nickel-based, silver-based, and copper-based solders.

[0047] The thickness d4 of the welding transition piece 4 is 0.5mm to 10mm, preferably 1mm. A thickness of 1mm provides good mechanical strength and ease of machining, while also resulting in a thin, lightweight, and low-cost overall electron beam extraction device. The thickness d1 of the frame 1 is 0.5mm to 5mm, preferably 1-2mm. A thickness of 1-2mm provides good mechanical strength and ease of machining, while also resulting in a thin, lightweight, and low-cost overall electron beam extraction device. The low cost stems from both the low welding cost of achieving an ultra-high vacuum seal between the two materials and the low machining cost. Furthermore, the specific design of the structural thicknesses d1 and d4 allows the sealed body formed by welding the welding transition piece 4 and the frame 1 to easily accommodate thermal expansion and contraction through slight deformation during high-temperature baking, without affecting the overall vacuum seal performance.

[0048] like Figure 3 As shown, in an exemplary embodiment, the frame 1 and the welding transition piece 4 form a second welding position 12 at the edge of the window 10. They are welded using methods such as argon arc welding or laser welding to form an ultra-high vacuum sealed connection. The surface of the second welding position 12 forms a smooth arc shape or a slope shape, either directly or through post-weld processing. In some embodiments, the welding transition piece 4 is smaller than the frame 1. The outer edge of the welding transition piece 4 forms a third welding position 13 with the frame 1. This position is welded using methods such as argon arc welding or laser welding to form an ultra-high vacuum sealed connection. The surface of the third welding position 13 forms a smooth arc shape or a slope shape, either directly or through post-weld processing. In some embodiments, the external dimensions of the welding transition piece 4 are smaller than those of the frame 1. The frame 1 and the welding transition piece 4 form a second welding position 12 at the edge of the window 10. They are welded using methods such as argon arc welding or laser welding to form an ultra-high vacuum sealed connection. The surface of the second welding position 12 forms a smooth arc or slope shape, either through post-weld processing or by other means. Simultaneously, the outer edge of the welding transition piece 4 forms a third welding position 13 with the frame 1. This position is welded using argon arc welding or laser welding, and the surface of the third welding position 13 forms a smooth arc or slope shape, either through post-weld processing or by other means. The second welding position 12 and the third welding position 13 form a double-protected ultra-high vacuum seal. The surface of the welding transition piece 4 in contact with the solder 3 undergoes good flatness and high surface finish processing, minimizing the microscopic gaps between the welding transition piece 4 and the titanium film 2. This achieves the goal of minimizing the thickness d3 of the solder 3 while ensuring complete filling of the first welding position.

[0049] It should be noted that other connection methods, such as brazing or explosive welding, which have higher welding costs, can also achieve the ultra-high vacuum sealing purpose of this invention and have the characteristic of being able to be baked at high temperatures, and are all within the scope of this invention.

[0050] It should be noted that if welded transition piece 4 is used to replace frame 1, (that is, ...) Figure 1 It is also feasible to replace the frame 1 in Figure 2 with a welded transition piece 4, which is directly connected to the vacuum chamber of the accelerator. This can achieve the ultra-high vacuum sealing purpose of the present invention and has the characteristic of being able to be baked at high temperatures, all of which are within the scope of the present invention.

[0051] The following reference Figure 4a and Figure 4b An electron beam extraction device according to two embodiments of the present invention is described. Figure 4a This is a schematic diagram of an electron beam extraction device according to an embodiment of the present invention. Figure 4b This is a schematic diagram of another electron beam extraction device according to an embodiment of the present invention.

[0052] like Figure 4a As shown, in an exemplary embodiment, the electron beam extraction device includes a frame 1, a titanium film 2, solder 3, a welding transition piece 4, and a support 5. The support 5 is provided with a grid 51, grid holes 52, and cooling channels 53. The support 5 is located on the vacuum side of the titanium film 2. Figure 4a Below the titanium film (in the middle), the grid 51 and the grid hole 52 are positioned corresponding to the window 10. The grid 51 provides support for the titanium film 2 against atmospheric pressure, and the grid hole 52 facilitates the passage of the electron beam through the support member 5. In some embodiments, the area of ​​the window 10 is relatively large, with a diameter R, or side length a, or width W of 100 mm, and a length L that can reach 2000 mm. The thickness d2 of the titanium film remains 15 mm, the width of the grid 51 is 0.6 mm, the width of the grid hole 52 is 4 mm, and the diameter of the cooling channel 53 is 8 mm, achieving better electron beam penetration. Especially for lower energy electron beams, the penetration improvement is particularly significant. For example, for electron beams with energy below 200 keV, reducing the titanium film thickness from 30 μm to 15 μm can reduce the amount of electron beam lost due to obstruction by the titanium film 2 by more than half. The smaller grid / (grid + grid hole) width ratio, 0.6 / 4.6 = 0.13, helps to reduce the proportion of electron beam obstruction by the grid 51.

[0053] The support component 5 is made of a metal material suitable for ultra-high vacuum environments and with excellent thermal conductivity. In some embodiments, the support component 5 is made of copper. The electron beam blocked by the grid 51 and the titanium film 2 will cause the support component 5 to heat up (the heat from the titanium film is conducted to the support component 5 through contact). The cooling channel 53 can cool the support component 5. The copper material facilitates the rapid conduction of heat from the titanium film 2 and the grid 51 to the cooling medium in the cooling channel 53, ensuring the stable operation of the electron beam extraction device. The surface of the support component 5 in contact with the titanium film 2 has good flatness and high smoothness, such as flatness 0.1 and smoothness Ra 0.4, achieving good contact with the titanium film 2, improving the efficiency of heat conduction, and without damaging the titanium film (if the surface is uneven or has small burrs, it is very easy to puncture the titanium film, leading to vacuum sealing failure).

[0054] like Figure 4b As shown, in an exemplary embodiment, the electron beam extraction device includes a frame 1, a titanium film 2, solder 3, a welding transition piece 4, and a support 5. The support 5 is provided with a grid 51, grid holes 52, and cooling channels 53. The support 5 is located on the vacuum side of the titanium film 2. Figure 4b Below the titanium film (in the middle), the grid 51 and grid holes 52 are positioned corresponding to the window 10. The grid 51 provides support for the titanium film 2 against atmospheric pressure, and the grid holes 52 facilitate the passage of the electron beam through the support member 5. The support member 5 is convex, with the top of the convex protrusion contacting the titanium film and the two shoulders of the convex protrusion contacting the surface of the frame 1. That is, the height of the top of the convex protrusion is equal to the sum of the thicknesses of the frame 1, the welding transition member 4, and the solder 3. Viewed from the atmospheric side A to the vacuum side B, the window portion consists of the titanium film 2, the support member 5 (the protrusion portion, including the grid 51 and grid holes 52), and the support member 5 provides support for the titanium film 2 against atmospheric pressure. The outer edge of the window consists of the titanium film 2, the solder 3, the welding transition member 4, the frame 1, and the support member 5 (the two shoulders). The support member 5 is relatively thick, such as 10mm to 30mm, which can provide support for the thinner frame 1 against atmospheric pressure.

[0055] Figure 4b The illustrated embodiment, relative to Figure 4a In the embodiment shown, the titanium film 2, solder 3, and frame 1 are arranged such that the titanium film 2 is on the outermost side (atmospheric side A). Atmospheric pressure causes the titanium film 2 to be squeezed toward the frame 1, which helps to enhance the connection strength between the titanium film 2 and the frame.

[0056] Figure 4b In the embodiment shown, the titanium film 2 is located on the outermost side of the entire electron beam extraction device, i.e., d5 = 0, which allows the article being processed by electron beam irradiation to be closer to the electron beam extraction window, reducing the loss of electron beam in the air and improving the utilization efficiency of electron beam.

[0057] like Figure 4a , Figure 4b As shown, in some exemplary embodiments, the frame 1 has a thickness of 1 mm, the titanium film 2 has a thickness of 15 μm, the brazing filler metal 3 has a thickness of 50 μm, the welding transition piece 4 has a thickness of 1 mm, the support piece 5 has a thickness of 20 mm, and the window 10 has a size of 60 mm × 2000 mm.

[0058] The foregoing described various schemes for the electron beam extraction device. However, the present invention is not limited thereto. According to embodiments of the present invention, the support member can also have other structures, including different shapes or width ratios of grids or grid holes, whether or not it has cooling channels, or the position and size of the cooling channels, and changes in the overall shape of the support member, etc., all of which can achieve the supporting effect of the support member on the titanium film, and can reduce the thickness of the titanium film relative to when there is no support member, thereby reducing the loss of the electron beam when passing through the titanium film 2 and improving the energy and quantity transmittance of the electron beam.

[0059] The following reference Figure 5 An electron accelerator according to the present invention is described. Figure 5 This is a cross-sectional structural schematic diagram of an electron accelerator according to an embodiment of the present invention.

[0060] Figure 5 The diagram illustrates the structure of an electron accelerator, comprising an electron beam extraction device (composed of a frame 1, a titanium film 2, solder 3, a welding transition piece 4, and a support piece 5), an accelerator vacuum chamber 6, and an electron beam generator 7. The electron beam extraction device and the accelerator vacuum chamber 6 have a fourth welding position, welded using methods such as argon arc welding or laser welding to form an integrally sealed vacuum structure. The electron beam generator 7 is located in the center of the accelerator vacuum chamber 6. The electron accelerator operates as follows: the accelerator cavity is at ground potential (i.e., zero voltage). An electron beam generator 7 is subjected to a negative high voltage relative to ground, such as -200 keV. An accelerating electric field is formed between the electron beam generator, the accelerator vacuum cavity 6, and the electron beam extraction device. Simultaneously, under electrical control, the electron beam generator 7 generates a free electron beam E directed towards the electron beam extraction device. After being accelerated by the high-voltage electric field, the electron beam E rapidly moves towards the electron beam extraction device, passing through the grid holes 52 of the support member 5 (a very small percentage, such as 13%, is blocked by the grid 51), and then through a 15 μm thick titanium film 2, resulting in some energy loss (the thinner the titanium film, the lower the energy loss). The high-energy electron beam reaching the atmosphere can then perform the electron beam irradiation and other services required by the accelerator. The distance from the surface of the titanium film 2 to the highest point of the electron beam extraction device is only 2 mm (the frame 1 and the welded transition member 4 are each 1 mm thick). The electron beam only needs to pass through 2 mm of air, resulting in very little loss and extremely high electron beam utilization. The all-metal connection structure of the electron beam extraction device and its metal welding to the accelerator vacuum chamber enable the electron accelerator to achieve ultra-high vacuum sealing characteristics, while also being able to withstand high-temperature baking of no more than 400 degrees Celsius, achieving 10-7 With an ultra-high vacuum of Pa, the electron accelerator can operate more stably at high power.

[0061] The above describes an electron accelerator structure that uses a high-voltage electric field for direct acceleration. However, the present invention is not limited thereto. According to embodiments of the present invention, the electron acceleration section of the electron accelerator can also be implemented in other ways, such as microwave linear accelerators, cyclotron accelerators, induction accelerators, etc., as long as its vacuum cavity can be welded to the frame 1 of the electron beam extraction device of the present invention to achieve ultra-high vacuum sealing, the electron beam extraction device of the present invention can extract the generated electron beam into the atmosphere, minimizing energy loss and quantity loss during the electron beam extraction process.

[0062] Existing electron beam extraction devices rely on mechanical compression sealing, employing two thick rectangular stainless steel flanges connected by a ring of bolts. One or more sealing grooves are formed on the opposing surfaces of the flanges, containing elastic sealing materials such as rubber rings. A titanium diaphragm is also placed between the flanges, and mechanical compression is used to tightly press this "flange + titanium diaphragm + elastic sealing material + flange" combination to achieve a vacuum seal. To maintain the elasticity of the material, a noticeable gap exists between the two flanges. The existing structure suffers from several drawbacks: the sealing grooves and bolt fixings occupy a significant width, requiring the flanges to possess high structural strength, resulting in substantial thickness and area, thus increasing the overall size and weight of the electron beam extraction device. Sealing through elastic material compression leads to a high leakage rate and poor vacuum sealing performance. The flanges must uniformly compress the elastic material around the entire circumference, demanding high machining precision on both opposing flange surfaces, increasing costs. Long-term reliability of elastic material compression sealing is poor. Furthermore, elastic materials typically cannot withstand high temperatures, or will lose elasticity at high temperatures, compromising the vacuum seal; therefore, high vacuum cannot be achieved through baking and venting. During electron beam irradiation processing, the irradiated item usually passes through the area outside the titanium window at a certain speed and cannot collide with the electron beam extraction device. Therefore, in the existing electron beam extraction device, the distance between the titanium film surface and the bolt surface is large. After the electron beam passes through the titanium window, it still needs to travel a long distance in the air, resulting in a considerable proportion of loss. Therefore, the electron beam utilization efficiency is low.

[0063] In the electron beam extraction device of this invention, the frame 1 is welded to the accelerator vacuum cavity 6 through the fourth welding position 14, and the surfaces are on the same plane. The thickness of the frame 1 is only 1 mm. Therefore, the distance d5 from the surface of the titanium film 2 to the high point of the electron beam extraction device (i.e., the upper surface of the frame 1) is only 1 mm. The irradiated object can be very close to the titanium film. After the electron beam passes through the titanium film 2, it only needs to travel a few millimeters in the air to reach the surface of the irradiated object. Therefore, in this embodiment, the electron beam loss is minimal and the utilization rate is high due to the few millimeters of transmission distance. Experimental data shows that the loss of the electron beam in the air is exponentially related to the distance. For an electron beam with an energy of 200 keV, there is almost no loss when the transmission distance in the air is 5 mm, but if the transmission distance is 90 mm, the loss will exceed 50%. The titanium film 2 has a very small thickness, and the grid of the support member 5 below the titanium film 2 provides support for the titanium film 2. In this embodiment, the titanium film thickness is even smaller. The smaller titanium film thickness results in higher electron beam penetration. The titanium membrane 2, frame 1, and accelerator vacuum chamber 6 are all formed into an integral structure by welding and sealing. This structure has good vacuum sealing performance, low leakage rate, good long-term stability, small size, and light weight. Furthermore, it can be baked at a high temperature of 400 degrees to obtain a higher vacuum degree, which improves the working stability of the system.

[0064] 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. An electron beam extraction device, characterized in that, The device includes a frame, a titanium film, and solder, as well as a welding transition piece. The solder is located between the frame and the titanium film. The frame has a flat plate structure with a window in the middle. The area of ​​the titanium film is larger than the area of ​​the window of the frame. The titanium film completely covers the window. The titanium film and the frame form an overlapping area on the outer edge of the window of the frame. The solder is located in the overlapping area and between the frame and the titanium film, and the solder forms a ring around the window. The solder causes the frame and the titanium film to be tightly connected together by welding at the first welding position to form a sealed structure. The melting temperature of the solder is 450℃ to 800℃, the thickness of the solder is less than or equal to 100μm, the thickness of the solder is positively correlated with the thickness of the titanium film, the flatness of the frame is 0.1, and the surface finish Ra is 0.

8. The welding transition piece is located between the frame and the solder. The shape of the welding transition piece matches the frame. A window is opened in the middle of the welding transition piece. The welding transition piece and the frame form a structure of stacking in parallel. The material of the welding transition piece is one of Kovar alloy, copper, and gold. The thickness of the welding transition piece is 0.5mm to 10mm. The frame is made of stainless steel or copper, and its thickness is 0.5mm to 5mm.

2. The electron beam extraction device according to claim 1, characterized in that, The distance from the upper surface of the titanium film to the highest point of the upper surface or the top surface of the frame is less than or equal to 5 mm.

3. The electron beam extraction device according to claim 2, characterized in that, The thickness of the titanium film is from 5 μm to 100 μm.

4. The electron beam extraction device according to claim 1, characterized in that, The frame and the welding transition piece form a second welding position at the edge of the window position of the frame. The frame and the welding transition piece are connected by welding to achieve a high vacuum seal. The surface of the second welding position is arc-shaped or sloped. Alternatively, the size of the welding transition piece is smaller than that of the frame. The outer edge of the welding transition piece forms a third welding position with the frame. The outer edge of the welding transition piece is welded to the frame by argon arc welding or laser welding. The surface of the third welding position is arc-shaped or sloped.

5. The electron beam extraction device according to claim 1, characterized in that, It also includes a support member disposed on the vacuum side of the titanium film, the support member having a plurality of grids and a plurality of grid holes spaced apart from each other.

6. The electron beam extraction device according to claim 5, characterized in that, The support member is convex in shape, with the top of the protrusion of the convex support member contacting the surface of the titanium film, and the two shoulders of the convex support member contacting the surface of the frame.

7. An electron accelerator, characterized in that, The electron accelerator includes an electron beam extraction device as described in any one of claims 1-6, an accelerator vacuum chamber, and an electron beam generator, wherein the electron beam generator is located in the middle of the accelerator vacuum chamber for generating an electron beam, the electron beam extraction device and the accelerator vacuum chamber have a fourth welding position, the electron beam extraction device and the accelerator vacuum chamber are connected by welding to form an integrally sealed structure, and the electron beam extraction device is used to extract the electron beam generated by the electron beam generator and accelerated by the electron accelerator into the atmosphere.

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