Low back-bomb standing wave accelerator

Abstract

The utility model relates to the field of accelerating tube provides a low anti -bomb standing wave accelerating tube, including bunching section and light speed section, the bunching section includes first accelerating chamber and second accelerating chamber, first accelerating chamber sets up in the starting point of bunching section, second accelerating chamber sets up in the terminal point of bunching section, still be provided with a plurality of intermediate accelerating chambers of length growth gradually before first accelerating chamber and second accelerating chamber, first accelerating chamber and first intermediate accelerating chamber are communicated through beam hole, the light speed section includes a plurality of coupling cavities and a plurality of light speed accelerating chambers, a plurality of light speed accelerating chambers are same in length, and two adjacent light speed accelerating chambers are communicated through a coupling cavity. To solve the defect that standing wave accelerating tube in the relevant art has hidden danger or use stability is not high, the scheme of the application can realize the efficient use of microwave power, improve the stability of accelerating tube operation.

Description

Technical Field

[0001] This utility model relates to the field of accelerator tube technology, and in particular to a low-reverse-wave accelerator tube. Background Technology

[0002] Accelerator tubes are the core components of particle accelerators. They are divided into two types: traveling wave accelerator tubes and standing wave accelerator tubes. They use microwave electric fields to accelerate electrons to a high-energy state to bombard the target material and generate X-rays.

[0003] Accelerator tubes in related technologies are mainly divided into two types. The first type involves loading a high-dielectric-constant material into a suppression cavity located between the electron gun and the first cavity. The generated second electromagnetic field cancels out and overcomes the force exerted on electrons by the leakage field of the first cavity, thereby suppressing electrons from moving towards the electron gun and reducing the back-bombardment phenomenon of electrons moving in the opposite direction. However, with long-term operation of the accelerator tube, electrons are prone to charge accumulation on the material surface, posing safety hazards such as discharge, and in severe cases, potentially damaging the accelerator tube. In this case, although charge accumulation can be avoided by spraying a very thin conductive film on the material surface, it increases the manufacturing cost of the accelerator tube. The second type involves setting a nose cone and a beam aperture transition section upstream of the first cavity of the accelerator tube to reduce the back-bombardment of electrons to the electron gun to a large extent. However, with long-term operation of the accelerator tube, the back-bombardment electron beam will hit the nose cone of the first cavity for a long time, which will cause deformation of the nose cone or even change its surface shape, thereby affecting the electromagnetic field distribution in the first cavity, affecting the acceleration of the electron beam, and ultimately shortening the service life of the accelerator tube.

[0004] In summary, all standing wave accelerator tubes in the relevant technologies have their own drawbacks and cannot meet the needs of users. Utility Model Content

[0005] This utility model provides a low-back-thunder standing wave accelerator tube to solve the defects of standing wave accelerator tubes in related technologies, such as safety hazards or low stability. The solution of this application can realize the efficient utilization of microwave power and improve the stability of accelerator tube operation.

[0006] This utility model provides a low-reverse-thunder standing-wave accelerator tube, including a focusing section and a light speed section;

[0007] The beam-gathering segment includes a first acceleration cavity and a second acceleration cavity, wherein the first acceleration cavity is located at the starting point of the beam-gathering segment and the second acceleration cavity is located at the ending point of the beam-gathering segment;

[0008] Several intermediate acceleration cavities with progressively increasing lengths are provided before the first acceleration cavity and the second acceleration cavity;

[0009] The first acceleration chamber and the first intermediate acceleration chamber are connected by a beam aperture;

[0010] The light speed segment includes several coupling cavities and several light speed acceleration cavities. The light speed acceleration cavities have the same length, and two adjacent light speed acceleration cavities are connected through a coupling cavity.

[0011] According to the low-reflection standing wave accelerating tube provided by this utility model, the length of the light speed accelerating cavity is greater than the length of the second accelerating cavity.

[0012] According to the low-reflection standing wave accelerating tube provided by this utility model, the second accelerating cavity is connected to the light speed accelerating cavity of the light speed segment through each coupling cavity.

[0013] According to the low-reverse-thunder standing-wave accelerating tube provided by this utility model, the focusing section further includes a coupling cavity;

[0014] The two adjacent intermediate acceleration cavities are connected by the coupling cavity;

[0015] The intermediate acceleration cavity and the second acceleration cavity are connected through the coupling cavity.

[0016] According to the low-reverse-thunder standing-wave accelerating tube provided by this utility model, no coupling cavity is provided between the first accelerating cavity and the intermediate accelerating cavity.

[0017] According to the low back-thunder standing wave accelerator tube provided by this utility model, the light speed section also includes a power feed waveguide.

[0018] According to the low-reverse-thunder standing-wave accelerating tube provided by this utility model, the cross-section of the power feed waveguide is rectangular.

[0019] According to the low-reflection standing wave accelerating tube provided by this utility model, the first accelerating cavity is connected to the electron gun, and the electron beam emitted by the electron gun is injected into the accelerating tube through the first accelerating cavity.

[0020] The low-back-bombardment standing-wave accelerator tube provided by this invention features a beam-focusing section where the length of each accelerating cavity gradually increases with increasing electron energy, while maintaining a consistent length across the light-speed section. This significantly improves the electron transport efficiency of the entire accelerator tube and enhances the beam structure at the tube exit, fundamentally reducing the number of electrons that travel backward and bombard the electron gun. By increasing the coupling coefficient between the cavities of the entire accelerator tube to approximately 10%, high group velocity and low fill time are achieved, resulting in efficient utilization of microwave power and improved operational stability of the accelerator tube. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is one of the structural schematic diagrams of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model;

[0023] Figure 2 This is the second schematic diagram of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model;

[0024] Figure 3 This is one of the performance test schematic diagrams of the low-reverse-thunder standing wave accelerator tube provided in this embodiment of the utility model;

[0025] Figure 4 This is the second schematic diagram of the performance test of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model;

[0026] Figure 5 This is the third schematic diagram of the performance test of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model;

[0027] Figure 6 This is the fourth schematic diagram of the performance test of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model.

[0028] in:

[0029] 1-Beam-focusing section; 2-Light speed section; 3-Power feed waveguide; 11-First accelerating cavity;

[0030] 12-First intermediate acceleration cavity; 13-First coupling cavity; 14-Second intermediate acceleration cavity;

[0031] 15-Second coupling cavity; 16-Second acceleration cavity; 17-Third coupling cavity;

[0032] 21-Light speed acceleration cavity; 22-Fourth coupling cavity; 211-Magnetic coupling window. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0034] Figure 1 This is one of the structural schematic diagrams of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model;

[0035] Figure 2 This is the second schematic diagram of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model.

[0036] in, Figure 2 for Figure 1 The cross-sectional view along the AA direction, as shown below. Figure 1 and Figure 2 As shown, this embodiment provides a low-reflection standing wave accelerator tube, including a focusing section 1 and a light speed section 2;

[0037] The focusing segment 1 includes a first acceleration cavity 11 and a second acceleration cavity 16. The first acceleration cavity 11 is located at the starting point of the focusing segment 1, and the second acceleration cavity 16 is located at the ending point of the focusing segment 1.

[0038] A plurality of intermediate acceleration cavities with progressively increasing lengths are provided before the first acceleration cavity 11 and the second acceleration cavity 16;

[0039] The first acceleration chamber and the first intermediate acceleration chamber are connected by a beam aperture;

[0040] The light speed segment 2 includes several coupling cavities and several light speed acceleration cavities 21. The several light speed acceleration cavities 21 have the same length, and two adjacent light speed acceleration cavities 21 are connected through a coupling cavity.

[0041] In practical applications, the entire accelerator tube can be divided into two segments: a focusing segment 1 and a light-speed segment 2. Each segment contains one or more accelerating cavities and / or coupling cavities. The length of each accelerating cavity in the focusing segment 1 gradually increases with increasing electron energy, while the length of each accelerating cavity in the light-speed segment 2 remains constant. Throughout the entire accelerator tube, the dimensions of all coupling cavities are essentially the same. The coupling cavities can be arranged coaxially with the accelerating cavities (axial coupling) or alternately on either side of the accelerating cavity array (side coupling).

[0042] The first accelerating cavity 11 and the second accelerating cavity 16 are respectively located at the beginning and end of the focusing section 1. An intermediate accelerating cavity with progressively increasing length is located between the first accelerating cavity 11 and the second accelerating cavity 16. No coupling cavity is provided between the first accelerating cavity 11 and the intermediate accelerating cavity; instead, a large-aperture beam aperture directly connects them to achieve strong axial electrical coupling. This allows the first accelerating cavity 11 to obtain an electromagnetic field with an intensity at least one order of magnitude lower than that of the intermediate accelerating cavity. The specific ratio of the electromagnetic field intensity needs to match the velocity of the electrons injected into the first accelerating cavity 11 by the electron gun. The first accelerating cavity 11 operates in π-mode, and its main function is to modulate the sinusoidal velocity of electrons from the electron gun to achieve longitudinal focusing. This not only increases the electron transmission efficiency of the entire accelerating tube from approximately 40% in the prior art to at least 60%, but also improves the electron cluster structure at the accelerating tube exit, especially the phase spectrum and energy spectrum, thereby fundamentally reducing the number of electrons that move in the opposite direction and bombard the electron gun. Compared to the prior art, the electromagnetic field amplitude of the first accelerating cavity 11 of the accelerating tube is at least one order of magnitude lower. Beam dynamics calculations show that the lower electromagnetic field amplitude within the first accelerating cavity 11 helps improve the electron transport efficiency of the entire accelerating tube, thereby reducing the number of electrons reflected back to the electron gun. Apart from the first accelerating cavity 11, all other accelerating cavities and / or coupling cavities in the entire accelerating tube operate in π / 2 mode.

[0043] A large-size wide magnetic coupling window 211 is used between the accelerating cavity and the coupling cavity, which increases the inter-cavity coupling coefficient by about 10%, resulting in high group velocity and low fill time, reducing beam load effect and achieving high efficiency utilization of microwave power. At the same time, the frequency spacing between resonant modes is also greatly increased, achieving high stability of the accelerating tube operation.

[0044] The working principle of the low-back-thunder standing wave accelerating tube provided in this embodiment includes:

[0045] After microwave power is fed into the accelerating tube through a rectangular power feed waveguide 3, it undergoes multiple transmissions and reflections between the accelerating cavities and the coupling cavities, establishing an electromagnetic field throughout the accelerating tube capable of lateral focusing, longitudinal beam convergence, and longitudinal acceleration of the beam. For this purpose, each cavity must be coupled with its adjacent cavity using electric and / or magnetic fields. Except for the axial electric coupling between the first accelerating cavity 11 and the intermediate accelerating cavity, the electromagnetic field coupling between the other cavities and their adjacent cavities is achieved through a large, wide magnetic coupling window 211, which is axial magnetic coupling. Beam dynamics calculations show that a lower electromagnetic field amplitude within the first accelerating cavity 11 helps improve the overall electron transport efficiency of the accelerating tube, thereby reducing the number of electrons reflected back to the electron gun. Therefore, to achieve an electron transport efficiency of at least 60% for the accelerating tube, the axial accelerating electric field amplitude within the first accelerating cavity 11 must be at least one order of magnitude lower than that of the intermediate accelerating cavity. This requires significantly increasing the electromagnetic field coupling between the first accelerating cavity 11 and the intermediate accelerating cavity, which cannot be achieved using the wide magnetic coupling window 211 due to lateral size limitations. Therefore, no coupling cavity is provided between the first accelerating cavity 11 and the intermediate accelerating cavity. The electromagnetic field coupling between the two is achieved through the downstream beam aperture of the first accelerating cavity 11 and the upstream beam aperture of the intermediate accelerating cavity, and the coupling method is axial electric coupling. In the standing wave accelerating tube, the magnitude of the coupling coefficient between adjacent cavities is related to the size of the beam aperture connecting the two cavities and / or the magnetic coupling window 211.

[0046] In one specific embodiment, the entire accelerating tube can be broadly divided into two segments: a focusing segment 1 and a light-speed segment 2. The focusing segment 1 consists of a first accelerating cavity 11, a second accelerating cavity 16, and a first intermediate accelerating cavity 12 and a second intermediate accelerating cavity 14 disposed between the first accelerating cavity 11 and the second accelerating cavity 16. It also includes a first coupling cavity 13, a second coupling cavity 15, and a third coupling cavity 17. The lengths of the first accelerating cavity 11, the first intermediate accelerating cavity 12, the second intermediate accelerating cavity 14, and the second accelerating cavity 16 gradually increase with the increase of the accelerated electron energy, which can further improve the electron transport efficiency of the entire accelerating tube. The light-speed segment 2 consists of multiple accelerating cavities and coupling cavities with the same length as the light-speed accelerating cavity 21 and the fourth coupling cavity 22.

[0047] Throughout the accelerator tube, all coupling cavities have the same length and radial radius to reduce the difficulty of developing the accelerator tube. The electron beam extracted from the electron gun is injected into the accelerator tube through the upstream beam aperture of the first accelerator cavity 11, and its energy is continuously increased through the stepwise focusing and acceleration in the focusing section 1 and the light speed section 2.

[0048] Besides the first accelerating cavity 11 used for longitudinal beam focusing, other accelerating cavities and coupling cavities are arranged coaxially and alternately. Taking a 2998MHz S-band accelerating tube as an example, it can be scaled up to other bands to obtain a more compact accelerating tube with high inter-cavity coupling coefficient and low back-bombardment standing wave. Beam dynamics calculations show that when the electron beam energy extracted from the electron gun and injected into the first accelerating cavity 11 is 30keV, the number of electrons reaching the exit of the accelerating tube is 62.29% of the number of electrons injected from the electron gun, which is about 1.5 times that of the prior art. Among them, most of the electrons are located near the 0 degrees of the reference particle, and the energy of these electrons is relatively concentrated, that is, the energy dispersion of the extracted electron beam is relatively small. The inter-cavity coupling coefficient of the accelerating tube is about 9%. With 13 accelerating cavities and 11 coupling cavities, at an operating frequency of 2998MHz, the downward and upward mode frequency intervals of the accelerating tube are 26MHz and 17.2MHz, respectively, demonstrating the advantage of high inter-cavity coupling coefficient.

[0049] Figure 3 This is one of the performance test schematic diagrams of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model.

[0050] Figure 4 This is the second schematic diagram of the performance test of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model.

[0051] Figure 5 This is the third schematic diagram of the performance test of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model.

[0052] Figure 6 This is the fourth schematic diagram of the performance test of the low-reverse-thunder standing wave accelerating tube provided in this embodiment of the utility model.

[0053] like Figures 3 to 6 As shown, this application also provides simulation diagrams of performance tests for low-back-bombardment standing-wave accelerating tubes.

[0054] like Figure 3 and Figure 4 It can be seen that the first accelerating cavity mainly modulates the velocity of the electron beam extracted from the electron gun and injected into the standing-wave accelerating tube. After the electron gun extracts a 30keV electron beam and injects 10,000 electrons into the standing-wave accelerating tube, after focusing and acceleration, 6,229 electrons can be obtained at the exit of the accelerating tube, that is, the electron beam transmission efficiency reaches 62.29%. Moreover, most of the electrons are located near the 0-degree position of the reference particle, and the energy of these electrons is relatively concentrated, that is, the relative energy dispersion of the extracted electron beam is small.

[0055] like Figure 5 and Figure 6As shown, the ratio of the axial electric field amplitude from the first acceleration cavity to the second acceleration cavity is 0.055:0.861:0.942:0.973:1. The electric field amplitude in the first acceleration cavity is only 6.388% of that in the middle acceleration cavity, about 1.5 orders of magnitude lower. At the operating frequency of 2998MHz, the frequency intervals of the downward and upward modes of the acceleration tube are 26MHz and 17.2MHz, respectively, which demonstrates the advantage of the high inter-cavity coupling coefficient.

[0056] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0057] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of various embodiments or some parts of embodiments.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A low-back-thunder standing-wave accelerating tube, characterized in that, Includes the beam-focusing segment and the light-speed segment; The beam-gathering segment includes a first acceleration cavity and a second acceleration cavity, wherein the first acceleration cavity is located at the starting point of the beam-gathering segment and the second acceleration cavity is located at the ending point of the beam-gathering segment; Several intermediate acceleration cavities with progressively increasing lengths are provided before the first acceleration cavity and the second acceleration cavity; The first acceleration chamber and the first intermediate acceleration chamber are connected by a beam aperture; The light speed segment includes several coupling cavities and several light speed acceleration cavities. The light speed acceleration cavities have the same length, and two adjacent light speed acceleration cavities are connected through one of the coupling cavities. The coupling cavity and the light speed acceleration cavity are coupled in either axial coupling or side coupling.

2. The low-back-thunder standing-wave accelerating tube according to claim 1, characterized in that, The length of the light speed acceleration cavity is greater than the length of the second acceleration cavity.

3. The low-back-thunder standing-wave accelerating tube according to claim 1, characterized in that, The second acceleration cavity is connected to the light speed acceleration cavity of the light speed segment through each coupling cavity.

4. The low-back-thunder standing-wave accelerating tube according to claim 1, characterized in that, The beam-gathering segment also includes a coupling cavity; The two adjacent intermediate acceleration cavities are connected by the coupling cavity; The intermediate acceleration cavity and the second acceleration cavity are connected through the coupling cavity.

5. The low-reverse-wave standing-wave accelerating tube according to claim 1 or 4, characterized in that, The coupling cavity is not provided between the first acceleration cavity and the intermediate acceleration cavity.

6. The low-back-thunder standing-wave accelerating tube according to claim 1, characterized in that, The light speed band also includes a power-feed waveguide.

7. The low-reverse-wave accelerator tube according to claim 6, characterized in that, The cross-section of the power feed waveguide is rectangular.

8. The low-reverse-wave accelerator tube according to claim 1, characterized in that, The first acceleration chamber is connected to the electron gun, and the electron beam emitted by the electron gun is injected into the acceleration tube through the first acceleration chamber.

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