Low-back-bombardment standing wave accelerating tube

Abstract

The invention relates to the field of accelerating tubes, and provides a low-detonation-back standing wave accelerating tube which comprises a bunching section and a light velocity section. The bunching section comprises a first acceleration cavity and a second acceleration cavity, the first acceleration cavity is arranged at the starting point of the bunching section, and the second acceleration cavity is arranged at the end point of the bunching section; a plurality of middle acceleration cavities with sequentially increased lengths are arranged in front of the first acceleration cavity and the second acceleration cavity, and the first acceleration cavity is communicated with the first middle acceleration cavity through a beam hole; the light velocity section comprises a plurality of coupling cavities and a plurality of light velocity acceleration cavities, the lengths of the light velocity acceleration cavities are the same, and every two adjacent light velocity acceleration cavities are communicated through one coupling cavity. The standing wave accelerating tube is used for overcoming the defect that a standing wave accelerating tube in the prior art has potential safety hazards or is not high in use stability, efficient utilization of microwave power can be achieved, and the operation stability of the accelerating tube is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of accelerating tubes, in particular to a low-rebound standing wave accelerating tube. BACKGROUND

[0002] An accelerating tube is a core component of a particle accelerator, which is divided into two types of traveling wave accelerating tube and standing wave accelerating tube, and the electrons are accelerated to a high-energy state by a microwave electric field to bombard a target material to generate X-rays.

[0003] The accelerating tube in the related art is mainly divided into two types, the first type is to load a high dielectric constant material into a suppression cavity located between an electron gun and a first cavity, and a second electromagnetic field is generated to offset and overcome the force of the first cavity leakage field on the electrons, thereby suppressing the movement of the electrons towards the electron gun and reducing the rebound phenomenon of the electrons to the electron gun, but in this way, the electrons are prone to charge accumulation on the surface of the material during long-term operation of the accelerating tube, and there are potential safety hazards such as discharge, and in serious cases, the accelerating tube may be damaged. In this case, although a very thin conductor film can be sprayed on the surface of the material to avoid the charge accumulation phenomenon, the processing and manufacturing cost of the accelerating tube is increased. The other type is to set a nose cone and a beam hole gradual change section on the upstream side of the first cavity of the accelerating tube to reduce the electrons rebounding to the electron gun to a greater extent, but the rebounding electron beam will hit the nose cone of the first cavity for a long time during long-term operation of the accelerating tube, which will cause the nose cone to deform or even change the surface shape, thereby affecting the electromagnetic field distribution in the first cavity and affecting the acceleration of the electron beam, and finally shortening the service life of the accelerating tube.

[0004] To sum up, the standing wave accelerating tube in the related art has its own drawbacks and cannot meet the needs of users. SUMMARY

[0005] The application provides a low-rebound standing wave accelerating tube to solve the defects of the standing wave accelerating tube in the related art, such as potential safety hazards or low use stability, and the scheme of the application can realize efficient utilization of microwave power and improve the stability of the operation of the accelerating tube.

[0006] The application provides a low-rebound standing wave accelerating tube, which comprises a bunching section and a light speed section.

[0007] The bunching section comprises a first accelerating cavity and a second accelerating cavity, the first accelerating cavity is arranged at the starting point of the bunching section, and the second accelerating cavity is arranged at the terminal point of the bunching section.

[0008] A plurality of intermediate accelerating cavities with increasing lengths are further arranged between the first accelerating cavity and the second accelerating cavity.

[0009] The first accelerating cavity and the first intermediate accelerating cavity are connected through a beam hole.

[0010] The light speed section comprises a plurality of coupling cavities and a plurality of light speed accelerating cavities, the lengths of the plurality of light speed accelerating cavities are the same, and two adjacent light speed accelerating cavities are communicated through a coupling cavity.

[0011] According to the low-recoil-resistance standing wave accelerating tube provided by the application, the length of the light speed accelerating cavity is greater than the length of the second accelerating cavity.

[0012] According to the low-recoil-resistance standing wave accelerating tube provided by the application, the second accelerating cavity is communicated with the light speed accelerating cavities of the light speed section through the coupling cavities.

[0013] According to the low-recoil-resistance standing wave accelerating tube provided by the application, the bunching section further comprises coupling cavities.

[0014] Two adjacent intermediate accelerating cavities are communicated through the coupling cavities.

[0015] The intermediate accelerating cavities are communicated with the second accelerating cavity through the coupling cavities.

[0016] According to the low-recoil-resistance standing wave accelerating tube provided by the application, the coupling cavities are not arranged between the first accelerating cavities and the intermediate accelerating cavities.

[0017] According to the low-recoil-resistance standing wave accelerating tube provided by the application, the light speed section further comprises a power feeding waveguide.

[0018] According to the low-recoil-resistance standing wave accelerating tube provided by the application, the cross section of the power feeding waveguide is rectangular.

[0019] According to the low-recoil-resistance standing wave accelerating tube provided by the application, the first accelerating cavities are connected with an electron gun, and the electron beam emitted by the electron gun is injected into the accelerating tube through the first accelerating cavities.

[0020] The length of each accelerating cavity in the bunching section of the low-recoil-resistance standing wave accelerating tube provided by the application gradually increases with the increase of the electron energy, the lengths of the accelerating cavities in the light speed section remain the same, the electron transmission efficiency of the whole accelerating tube is greatly improved, the beam group structure at the outlet of the accelerating tube is improved, and the number of electrons moving in the reverse direction and bombarding the electron gun is fundamentally reduced. By increasing the coupling coefficient between the cavities of the whole accelerating tube to about 10%, high group speed and low filling time are obtained, the microwave power is used efficiently, and the stability of the operation of the accelerating tube is improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] To more clearly illustrate the technical solutions in this invention 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 invention. 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 the embodiments of the present invention;

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

[0024] Figure 3 This is one of the performance test schematic diagrams of the low-reverse-bombardment standing wave accelerator tube provided in the embodiments of the present invention;

[0025] Figure 4 This is the second schematic diagram of the performance test of the low-reverse-bombardment standing-wave accelerating tube provided in the embodiment of the present invention;

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

[0027] Figure 6 This is the fourth schematic diagram of the performance test of the low-reverse-bombardment standing wave accelerating tube provided in the embodiment of the present invention.

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

[0034] Figure 1 is one of the structural schematic diagram of the low-reflection-bombardment standing wave acceleration tube provided by the embodiment of the present application;

[0035] Figure 2 is the second structural schematic diagram of the low-reflection-bombardment standing wave acceleration tube provided by the embodiment of the present application.

[0036] wherein, Figure 2 Figure 1 According to the sectional view in AA direction, as shown in Figure 1 and Figure 2 The embodiment provides a low-reflection-bombardment standing wave acceleration tube, which comprises a bunching section 1 and a light speed section 2.

[0037] The bunching section 1 comprises a first acceleration cavity 11 and a second acceleration cavity 16, wherein the first acceleration cavity 11 is arranged at the starting point of the bunching section 1, and the second acceleration cavity 16 is arranged at the ending point of the bunching section 1.

[0038] A plurality of intermediate acceleration cavities with gradually increasing lengths are arranged between the first acceleration cavity 11 and the second acceleration cavity 16.

[0039] The first acceleration cavity and the first intermediate acceleration cavity are connected through a beam hole.

[0040] The light speed section 2 comprises a plurality of coupling cavities and a plurality of light speed acceleration cavities 21, wherein the lengths of the plurality of light speed acceleration cavities 21 are the same, and two adjacent light speed acceleration cavities 21 are connected through a coupling cavity.

[0041] In actual application, the entire acceleration tube can be divided into two sections: the bunching section 1 and the light speed section 2, and each section comprises one or more acceleration cavities and / or coupling cavities. The lengths of the acceleration cavities in the bunching section 1 gradually increase with the increase of the electron energy, and the lengths of the acceleration cavities in the light speed section 2 remain the same. In the entire acceleration tube, the sizes of all the coupling cavities are basically the same. The coupling cavities can be coaxially arranged alternately with the acceleration cavities, that is, the coupling mode is axial coupling; or the coupling cavities can be alternately arranged on both sides of the acceleration cavity column, that is, the coupling mode is side coupling.

[0042] ​The first accelerating cavity 11 and the second accelerating cavity 16 are respectively arranged at the head and tail of the bunching section 1, and intermediate accelerating cavities with increasing lengths are arranged between the first accelerating cavity 11 and the second accelerating cavity 16. No coupling cavity is arranged between the first accelerating cavity 11 and the intermediate accelerating cavities, and a large-aperture beam hole is directly used between the two to obtain strong axial electric coupling, so that an electromagnetic field with an intensity at least one order of magnitude lower than that of the intermediate accelerating cavities can be obtained in the first accelerating cavity 11. The specific proportion of the electromagnetic field intensity needs to be matched with the motion speed of the electrons injected into the first accelerating cavity 11 by the electron gun. The working mode of the first accelerating cavity 11 is π mode, and the main function is to perform sinusoidal speed modulation on the electrons from the electron gun to realize longitudinal bunching. This not only can improve the electron transmission efficiency of the entire accelerating tube from about 40% in the prior art to at least 60% or more, but also can improve the bunch structure of the electrons at the outlet of the accelerating tube, especially the phase spectrum and the energy spectrum, so as to fundamentally reduce the number of electrons moving in the opposite direction and bombarding the electron gun. Compared with 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 calculation shows that the lower electromagnetic field amplitude in the first accelerating cavity 11 helps to improve the electron transmission efficiency of the entire accelerating tube, thereby reducing the number of electrons bombarding the electron gun. Except for the first accelerating cavity 11, the working mode of the other accelerating cavities and / or coupling cavities in the entire accelerating tube is π / 2 mode.

[0043] A wide magnetic coupling window 211 with a large size is used between the accelerating cavities and the coupling cavities, the inter-cavity coupling coefficient is increased to about 10%, high group velocity and low filling time are obtained, the beam loading effect is reduced, and high efficiency of microwave power utilization is realized. At the same time, the frequency interval between the resonance modes is also greatly increased, and high stability of the accelerating tube operation is realized.

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

[0045] The microwave power is fed into the accelerating tube through the power feeding waveguide 3 with a rectangular cross section, and the electromagnetic field for transversely focusing, longitudinally bunching and longitudinally accelerating the beam is established in the entire accelerating tube after multiple transmissions and reflections between the accelerating cavities and the coupling cavities. For this purpose, the cavities and the corresponding adjacent cavities need to have coupling of electric field and / or magnetic field. Except that the electromagnetic field coupling between the first accelerating cavity 11 and the intermediate accelerating cavity is axial electric coupling, the electromagnetic field coupling between the rest of the cavities and the adjacent cavities is realized through the wide magnetic coupling window 211 with a large size, which is axial magnetic coupling. Beam dynamics calculation shows that the lower electromagnetic field amplitude in the first accelerating cavity 11 helps to improve the electron transmission efficiency of the entire accelerating tube, thereby reducing the number of electrons bombarding the electron gun. Therefore, in order to make the electron transmission efficiency of the accelerating tube reach at least 60% or more, the axial accelerating electric field amplitude in the first accelerating cavity 11 needs to be lower than that in the intermediate accelerating cavity by more than one order of magnitude, which requires a large degree of improvement of the electromagnetic field coupling between the first accelerating cavity 11 and the intermediate accelerating cavity. Due to the limitation of the transverse size, this cannot be realized by the wide magnetic coupling window 211. Therefore, no coupling cavity is arranged between the first accelerating cavity 11 and the intermediate accelerating cavity, and the electromagnetic field coupling between them is realized through the beam holes downstream of the first accelerating cavity 11 and upstream of the intermediate accelerating cavity, and the coupling mode is axial electric coupling. In the standing wave accelerating tube, the size of the coupling coefficient between adjacent cavities is related to the size of the beam hole connecting the two cavities and / or the size of the magnetic coupling window 211.

[0046] In a specific embodiment, the entire accelerating tube can be generally divided into two sections: a bunching section 1 and a light speed section 2. The bunching section 1 is composed of the first accelerating cavity 11, the second accelerating cavity 16, and the first intermediate accelerating cavity 12 and the second intermediate accelerating cavity 14 arranged between the first accelerating cavity 11 and the second accelerating cavity 16, and further includes the first coupling cavity 13, the second coupling cavity 15 and the 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 energy of the accelerated electrons, which can further improve the electron transmission efficiency of the entire accelerating tube. The light speed section 2 is composed of a plurality of accelerating cavities and coupling cavities with the same length as the light speed accelerating cavity 21 and the fourth coupling cavity 22.

[0047] In the entire accelerating tube, the lengths and radial radius sizes of all the coupling cavities are uniform to reduce the development difficulty of the accelerating tube. The electron beam extracted from the electron gun is injected into the accelerating tube through the beam hole upstream of the first accelerating cavity 11, and the energy is continuously increased through the step-by-step bunching and acceleration in the bunching section 1 and the light speed section 2.

[0048] In addition to the first accelerating cavity 11 for longitudinal bunching, other accelerating cavities are arranged coaxially with the coupling cavities alternately, and taking the 2998MHz accelerating tube of S-band as an example, the accelerating tube can be scaled to other bands to obtain a more compact high inter-cavity coupling coefficient, low anti-bomb standing wave accelerating tube. Beam dynamics calculation shows that when the energy of the electron beam emitted by the electron gun and injected into the first accelerating cavity 11 is 30keV, the number of electrons reaching the outlet of the accelerating tube is 62.29% of the number of electrons injected by the electron gun, which is about 1.5 times that of the prior art. Most of the electrons are located near 0 degrees where the reference particles are located, and the energy of these electrons is also relatively concentrated, that is, the energy dispersion of the emitted electron beam is relatively small. The inter-cavity coupling coefficient of the accelerating tube is about 9%, and when the number of accelerating cavities and coupling cavities is 13 and 11 respectively, the frequency interval between the downward and upward modes of the accelerating tube is 26MHz and 17.2MHz respectively near the operating frequency of 2998MHz, which embodies the advantages of high inter-cavity coupling coefficient.

[0049] Figure 3 is one of the performance test schematic diagrams of the low anti-bomb standing wave accelerating tube provided by the embodiment of the application.

[0050] Figure 4 is another performance test schematic diagram of the low anti-bomb standing wave accelerating tube provided by the embodiment of the application.

[0051] Figure 5 is a third performance test schematic diagram of the low anti-bomb standing wave accelerating tube provided by the embodiment of the application.

[0052] Figure 6 is a fourth performance test schematic diagram of the low anti-bomb standing wave accelerating tube provided by the embodiment of the application.

[0053] As Figures 3 to 6 shown, the application also provides a simulation diagram of the performance test of the low anti-bomb standing wave accelerating tube.

[0054] As Figure 3 and Figure 4 can be seen, the first accelerating cavity mainly modulates the speed of the electron beam emitted by the electron gun and injected into the standing wave accelerating tube. After 10000 electrons are injected into the standing wave accelerating tube, the electron beam transmission efficiency reaches 62.29% after being bunched and accelerated, that is, 6229 electrons can be obtained at the outlet of the accelerating tube. Moreover, most of the electrons are located near 0 degrees where the reference particles are located, and the energy of these electrons is also relatively concentrated, that is, the relative energy dispersion of the emitted electron beam is small.

[0055] As Figure 5 and Figure 6As shown, the axial electric field amplitude ratio of the first accelerating cavity to the second accelerating cavity is 0.055:0.861:0.942:0.973:1, wherein the electric field amplitude in the first accelerating cavity is only 6.388% of the middle accelerating cavity, about 1.5 orders of magnitude lower, and at the working frequency of 2998 MHz, the downward and upward mode frequency intervals of the accelerating tube are 26 MHz and 17.2 MHz, respectively, which embodies the advantages of high inter-cavity coupling coefficient.

[0056] The device embodiments described above are only illustrative, wherein the units illustrated as separate components can or can not be physically separated, and the components illustrated as units can or can not be physical units, i.e., can be located in one place or distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0057] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be realized by means of software and the necessary general hardware platform, and of course, it can also be realized by hardware. Based on such understanding, the above technical solutions can be embodied in the form of software products, and the computer software products can be stored in a computer readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the method of each embodiment or some parts of the embodiment.

[0058] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A low-bombardment standing wave accelerator tube, characterized by, The bunching section and the light speed section are included; The bunching section includes a first accelerating cavity and a second accelerating cavity, the first accelerating cavity is arranged at the starting point of the bunching section, and the second accelerating cavity is arranged at the ending point of the bunching section; A plurality of intermediate accelerating cavities with increasing lengths are further arranged before the first accelerating cavity and the second accelerating cavity; The first accelerating cavity and the first intermediate accelerating cavity are communicated through a beam hole; The light speed section includes a plurality of coupling cavities and a plurality of light speed accelerating cavities, the lengths of the light speed accelerating cavities are the same, and two adjacent light speed accelerating cavities are communicated through a coupling cavity; The coupling mode of the coupling cavities and the light speed accelerating cavities is axial coupling or edge coupling.

2. The low-bombardment standing wave accelerator tube of claim 1, wherein, The length of the light speed accelerating cavity is greater than the length of the second accelerating cavity.

3. The low-bombardment standing wave accelerator tube of claim 1, wherein, The second accelerating cavity is communicated with the light speed accelerating cavities of the light speed section through the coupling cavities.

4. The low-bombardment standing wave accelerator tube of claim 1, wherein, The bunching section further includes a coupling cavity; Two adjacent intermediate accelerating cavities are communicated through the coupling cavity; The intermediate accelerating cavities and the second accelerating cavity are communicated through the coupling cavity.

5. The low-bunched wave accelerator of claim 1 or 4, wherein The coupling cavity is not arranged between the first accelerating cavity and the intermediate accelerating cavities.

6. The low-bombardment standing wave accelerator tube of claim 1, wherein, The light speed section further includes a power feeding waveguide.

7. The low-bunched wave accelerator of claim 6, wherein, The cross section of the power feeding waveguide is rectangular.

8. The low-bombardment standing wave accelerator tube of claim 1, wherein, The first accelerating cavity is connected with an electron gun, and the electron beam emitted by the electron gun is injected into the accelerating tube through the first accelerating cavity.

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