Cavity chain structure for standing wave accelerating tube, standing wave accelerating tube and accelerator

Abstract

The invention provides a cavity chain structure for a standing wave accelerating tube, the standing wave accelerating tube and an accelerator. The cavity chain structure comprises a plurality of bunching cavity units which are sequentially arranged in the direction of an electron beam current; the coupling cavities are arranged between the adjacent bunching cavity units; the bunching cavity unit comprises a bunching cavity and a beam hole used for forming an electron beam channel. Beam bunching cavities of the beam bunching cavity units on the side, close to the electron gun, of the cavity chain structure are designed to be in an asymmetric cavity type in the electron beam current direction. The small focus design of the standing wave accelerating tube can be realized through the cavity chain structure.

Description

Technical Field

[0001] The present invention relates to the field of microwave vacuum electron technology. More specifically, it relates to a cavity chain structure for a standing wave accelerating tube, a standing wave accelerating tube, and an accelerator. Background Art

[0002] High-energy X-ray sources have been widely used in the fields of medical and health (such as radiotherapy and diagnosis), industrial non-destructive testing, food irradiation sterilization, and security inspection due to their excellent penetration and imaging capabilities. As the core component of high-energy X-ray sources, electron linear accelerators have shown unique performance advantages through long-term technical optimization and engineering practice. However, the focal spot size of current mainstream electron linear accelerators is usually 1 mm - 2 mm, resulting in limited spatial resolution and difficulty in meeting the increasing imaging requirements of modern high-precision detection equipment. Summary of the Invention

[0003] In view of the above problems, the present invention provides a cavity chain structure for a standing wave accelerating tube, which can control the focal spot size of the accelerating tube within 0.5 mm, achieving a small focal spot design for the accelerating tube and thus improving the spatial resolution.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a cavity chain structure for a standing wave accelerating tube, including a plurality of bunching cavity units arranged in sequence along the electron beam direction; and

[0006] coupling cavities between adjacent bunching cavity units;

[0007] The bunching cavity unit includes a bunching cavity and a beam hole for forming an electron beam channel;

[0008] The bunching cavity of the bunching cavity unit near the electron gun side of the cavity chain structure is designed with an asymmetric cavity type along the electron beam direction.

[0009] Preferably, the aperture of the beam hole of the first bunching cavity unit near the electron gun is larger than the aperture of the beam hole away from the electron gun.

[0010] Preferably, the number of bunching cavity units is n, 3 ≤ n ≤ 5; the aperture of the beam hole of the first bunching cavity unit near the electron gun is D1, 4 mm ≤ D1 ≤ 5 mm; the aperture of the beam hole of the first bunching cavity unit away from the electron gun is D2, 3 mm ≤ D2 ≤ 3.5 mm; through this cavity chain structure, the focal spot size of the accelerating tube can be controlled within 0.5 mm.

[0011] Preferably, starting from the second bunching cavity unit, the aperture of the beam hole is equal to the aperture of the beam hole of the first bunching cavity unit away from the electron gun.

[0012] Preferably, the length dimension of the bunching cavity of the first bunching cavity unit along the electron beam direction is smaller than that of the bunching cavity of the adjacent bunching cavity unit along the electron beam direction; starting from the second bunching cavity unit, the length dimensions of the bunching cavities along the electron beam direction are the same.

[0013] Preferably, the bunching cavity unit further includes two convex structures formed on two opposite cavity side walls of the bunching cavity and extending into the bunching cavity along the electron beam direction; the beam holes penetrate through the convex structures; the radial dimension of the convex structure of the first bunching cavity unit close to the electron gun is larger than that of the convex structure far from the electron gun; the two convex structures in the bunching cavity units starting from the second bunching cavity unit are symmetrically arranged.

[0014] The present invention also provides a standing wave accelerating tube, including the cavity chain structure as described above; an electron gun and a target component respectively sealed and fixed at both ends of the cavity chain structure along the electron beam direction; a feeding waveguide fixedly connected to the cavity chain structure; and a microwave input window and a titanium pump fixedly arranged on the feeding waveguide.

[0015] Preferably, the electron gun is a diode electron gun or a grid-controlled electron gun; the waist diameter of the electron beam emitted by the electron gun is less than 1.5 mm.

[0016] Preferably, the central frequency range of the standing wave accelerating tube is 5707 MHz - 5717 MHz.

[0017] The present invention also provides an accelerator, including a power source for generating microwaves; the standing wave accelerating tube as described above; a microwave system connected between the power source and the standing wave accelerating tube; and a solid-state modulator system for providing high-voltage pulses to the power source and the electron gun.

[0018] The beneficial effects of the present invention are as follows:

[0019] Through the cooperation of a plurality of bunching cavity units arranged in sequence along the electron beam direction, and by designing the bunching cavity of the bunching cavity unit on the side close to the electron gun as an asymmetric cavity type along the electron beam direction, the present invention can achieve a small focus design of the accelerating tube while ensuring the acceleration performance, thereby improving the spatial resolution. Moreover, it can achieve an ultra-fine focus size of less than 0.5 mm, and the focus size is reduced by more than 50% compared with that of a conventional accelerating tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following further describes in detail the specific embodiments of the present invention with reference to the drawings.

[0021] Figure 1 It is a schematic structural diagram of the cavity chain structure of the present invention.

[0022] Figure 2It is one of the schematic structural diagrams of the standing wave accelerating tube of the present invention.

[0023] Figure 3 It is the second of the schematic structural diagrams of the standing wave accelerating tube of the present invention.

[0024] Figure 4 It is the schematic structural diagram of the accelerator of the present invention.

[0025] Figure 5 It is the transverse density curve diagram of the X-direction target-hitting electrons of an example of the present invention.

[0026] Figure 6 It is the transverse density curve diagram of the Y-direction target-hitting electrons of an example of the present invention.

[0027] Figure 7 It is the transverse density curve diagram of the X-direction target-hitting electrons of another example of the present invention.

[0028] Figure 8 It is the transverse density curve diagram of the Y-direction target-hitting electrons of another example of the present invention.

[0029] Reference numerals: 1. Power source, 2. Standing wave accelerating tube, 3. Inflated straight waveguide, 4. Inflated bent waveguide, 5. Four-port circulator, 7. Solid-state modulator control unit, 8. Power source pulse unit, 9. Electron gun pulse unit, 10. Collimator unit, 11. Frame structure, 21. Cavity chain structure, 22. Electron gun, 23. Target component, 24. Feeding waveguide, 25. Input window, 26. Titanium pump, 211. First bunching cavity unit, 212. Second bunching cavity unit, 213. Third bunching cavity unit, 214. Coupling cavity, 215. Inter-cavity coupling hole, 2111. First beam hole, 2112. Second beam hole, 2122. Third beam hole, 2133. Fourth beam hole, 2113. First nose cone, 2114. Second nose cone, 2121. Third nose cone, 2131. Fourth nose cone, 2132. Coupling hole, 121. First bunching cavity, 122. Second bunching cavity, 123. Third bunching cavity. Detailed implementation manners

[0030] Now, various exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that: Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0031] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present invention or its application or use.

[0032] Techniques and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques and devices shall be regarded as part of the specification.

[0033] In all of the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0034] It should be noted that like reference numerals and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

[0035] To solve the problem that the focus size of existing electron linear accelerators is relatively large, resulting in limited spatial resolution. The present invention provides a cavity chain structure for a standing wave accelerating tube, combined with Figures 1 to 8 As shown, specifically, the cavity chain structure includes a plurality of bunching cavity units arranged in sequence along the electron beam direction and coupling cavities 214 between adjacent bunching cavity units. The bunching cavity unit includes a bunching cavity and beam holes for forming an electron beam channel; the beam holes are formed on both sides of the bunching cavity along the electron beam direction; both ends of the beam holes along their own axial directions are respectively communicated with the bunching cavity and the coupling cavity 214; all the beam holes are coaxially arranged along the electron beam direction to form an electron beam channel, that is, the electron beam direction is the axial direction of the electron beam channel. The bunching cavity of the bunching cavity unit on the side of the cavity chain structure close to the electron gun has an asymmetric cavity type design along the electron beam direction. The bunching cavity unit of the cavity chain structure for cooperating with the electron gun is the first bunching cavity unit 211; the aperture of the first beam hole 2111 of the first bunching cavity unit 211 close to the electron gun is larger than the aperture of the second beam hole 2112 far from the electron gun. The first beam hole 2111 of the first bunching cavity unit 211 close to the electron gun is used to cooperate with the electron gun so that the electrons emitted by the electron gun can enter the bunching cavity, so this first beam hole 2111 can also be called an injection hole. The cavity chain structure of the present invention only adopts a plurality of bunching cavity units and does not include accelerating cavities. Through multi-stage bunching and the asymmetric cavity type design of the first bunching cavity unit, the focus size can finally be controlled within 0.5 mm, realizing a small focus design.

[0036] In the above embodiments, the aperture of the beam hole of the first bunching cavity unit 211 near the electron gun is larger than the aperture of the beam hole far from the electron gun. More specifically, the value range of the aperture D1 of the first beam hole 2111 is 4 mm ≤ D1 ≤ 5 mm; the value range of the aperture D2 of the second beam hole 2112 is 3 mm ≤ D2 ≤ 3.5 mm. Through this cavity chain structure, the focus size of the accelerating tube can be controlled within 0.5 mm. The apertures of the beam holes of the bunching cavity units other than the first bunching cavity unit 211 are all equal to the aperture of the second beam hole 2112 of the first bunching cavity unit 211 far from the electron gun, that is, the apertures of the third beam hole 2122 and the fourth beam hole 2133 are both equal to the aperture of the second beam hole 2112. The number of the bunching cavity units is n, and 3 ≤ n ≤ 5. Through the above settings, the injection aperture of the first bunching cavity unit 211 is larger than the second beam aperture, which can avoid the rapid reduction of the transverse size of the bunch due to excessive focusing in the first bunching cavity unit 211, resulting in a sharp increase in the space charge force, thus facilitating the suppression of the space charge effect. And by designing the aperture D1 of the first beam hole 2111 of the first bunching cavity unit 211 to be 4 mm ≤ D1 ≤ 5 mm and the aperture D2 of the second beam hole of the first bunching cavity unit 211 to be 3 mm ≤ D2 ≤ 3.5 mm, an ultra-fine focus size of less than 0.5 mm of the accelerating tube can be achieved, and the focus size is reduced by more than 50% compared with that of a conventional accelerating tube.

[0037] In a specific embodiment, in order to ensure that the phase velocity of the first bunching cavity unit 211 is less than the phase velocity of the subsequent connected bunching cavity units, the length dimension of the first bunching cavity 121 of the first bunching cavity unit 211 along the electron beam direction is less than the length dimension of the bunching cavity of the adjacent bunching cavity unit along the electron beam direction; the length dimensions of the bunching cavities of the bunching cavity units other than the first bunching cavity unit 211 are all the same. More specifically, taking Figure 1 the three bunching cavity units as an example, from left to right are the first bunching cavity unit 211, the second bunching cavity unit 212, and the third bunching cavity unit 213. The length dimension of the first bunching cavity 121 of the first bunching cavity unit 211 along the electron beam direction is less than the length dimension of the second bunching cavity 122 of the second bunching cavity unit 212 along the electron beam direction, and the length dimension of the second bunching cavity 122 of the second bunching cavity unit 212 along the electron beam direction is equal to the length dimension of the third bunching cavity 123 of the third bunching cavity unit 213 along the electron beam direction. For the convenience of assembly, the outer dimension of the third bunching cavity unit 213 is larger than that of the first bunching cavity unit 211 and the second bunching cavity unit 212.

[0038] In a specific embodiment, the bunching cavity unit further includes two convex structures formed on two opposite cavity side walls of the bunching cavity and extending into the bunching cavity along the electron beam flow direction; the beam holes on both sides of the same bunching cavity unit respectively penetrate through the two convex structures; the size of the convex structure of the first bunching cavity unit 211 close to the electron gun is larger than the size of the convex structure far from the electron gun to match and form an injection hole with a larger aperture. Specifically, the radial size of the convex structure of the first bunching cavity unit 211 close to the electron gun is larger than the radial size of the convex structure far from the electron gun. The above-mentioned radial size is the size of the convex structure in the direction perpendicular to the electron beam flow direction. The two convex structures in the bunching cavity units starting from the second bunching cavity unit 212 are symmetrically arranged. That is to say, the two convex structures in the second bunching cavity unit 212 and the third bunching cavity unit 213 except the first bunching cavity unit 211 are symmetrically arranged, and their size and shape are exactly the same. Through the above settings, the growth of the beam emittance caused by the non-linear component of the radial electric field and the amplitude of the high-order harmonic wave can be reduced. The size of the convex structure of the first bunching cavity unit 211 close to the electron gun is larger than the size of the convex structure far from the electron gun, which can make an asymmetric cavity design formed in the first bunching cavity unit 211. By cooperating with the multi-stage bunching method, the focus size can finally be controlled within 0.5 mm to achieve a small focus design. It can be understood that the bunching cavity units are all in a cylindrical structure. The two opposite cavity side walls of the above-mentioned bunching cavity refer to the two end side walls of the bunching cavity unit along the electron beam flow direction, and the two end side walls are connected by the circumferential side wall. The beam holes and the convex structures are coaxial with the end face of the bunching cavity. Further combined with Figure 1 As shown, the convex structure on the left side in the first bunching cavity unit 211 is the first nose cone 2113, and the convex structure on the right side is the second nose cone 2114. The size of the first nose cone 2113 is larger than that of the second nose cone 2114. The convex structure in the second bunching cavity 122 is the third nose cone 2121, and the convex structure in the third bunching cavity 123 is the fourth nose cone 2131. The shapes and sizes of the third nose cone 2121 and the fourth nose cone 2131 are the same. The size of the second nose cone 2114 is smaller than that of the third nose cone 2121, and the size of the third nose cone 2121 is smaller than that of the first nose cone 2113. It should be noted that for the convenience of processing, an arc-shaped transition is formed at the corner connection between the convex structure and the inner side wall of the bunching cavity and at the corner connection between the convex structure and the bunching hole.

[0039] In a specific embodiment, a coupling hole 2132 communicating with its own bunching cavity is formed on the circumferential side wall of the last bunching cavity unit far from the first bunching cavity unit 211. The coupling hole 2132 is used to cooperate with an external energy transmission structure to realize the connection between the energy transmission structure and the bunching cavity. That is, a coupling hole 2132 is provided on the third bunching cavity unit 213 at the rightmost end. The coupling hole 2132 communicates with the third bunching cavity 123 and is precisely docked with the external energy transmission structure, thereby establishing an efficient energy transmission channel. Further, the bunching cavity unit further includes an inter-cavity coupling hole 215. The bunching cavity communicates with the coupling cavity 214 through the inter-cavity coupling hole 215. It can be understood that the inter-cavity coupling holes 215 on adjacent bunching cavity units are arranged in a cross-orthogonal manner. Therefore, in Figure 1 the view, only the inter-cavity coupling hole 215 on the second bunching cavity unit 212 can be shown.

[0040] The present invention also provides a standing wave accelerating tube, including the cavity chain structure 21 as described above; an electron gun 22 and a target component 23 respectively sealed and fixed at both ends of the cavity chain structure 21 along the electron beam direction; a feeding waveguide 24 fixedly connected to the circumferential side wall of the cavity chain structure 21; and a microwave input window 25 and a titanium pump 26 fixedly arranged on the feeding waveguide 24.

[0041] Further, the electron gun 22 is used to emit an electron beam into the cavity chain structure 21. The electron gun 22 is a diode electron gun or a grid-controlled electron gun. The waist diameter of the electron beam emitted by the electron gun 22 is less than 1.5 mm. The central frequency range of the standing wave accelerating tube is 5707 MHz - 5717 MHz. The above-mentioned target component 23 is a heavy metal target. Electrons bombard the heavy metal target at the end of the accelerating tube, generating bremsstrahlung and producing X-rays. A cooling water path is arranged inside the target component 23, and the circulating cooling water in the water path can cool the working target component. A cooling water jacket or a water pipe structure is arranged outside the above-mentioned cavity chain structure 21, and the cavity chain structure 21 is fully cooled through the cooling water jacket or the water pipe structure. The above-mentioned feeding waveguide 24 is a rectangular waveguide, and its output end is welded and fixed to the circumferential side wall of the cavity chain structure 21 and communicates with the coupling hole 2132. The cavity chain structure 21 is coupled with the feeding waveguide 24 through the coupling hole 2132. During the cavity chain tuning process, the size of the coupling hole 2132 between the feeding waveguide 24 and the cavity chain structure 21 can be adjusted to make the standing wave accelerating tube in the best coupling state. The above-mentioned titanium pump 26 makes titanium atoms chemically react with space gas molecules through heating and ionization, deposits the gas, thereby reducing the concentration of space gas molecules and achieving the purpose of obtaining a vacuum.

[0042] Specifically, in the small-focus standing-wave accelerating tube provided by the present invention, the cavity chain structure 21 is a double-period axial-coupled accelerating cavity chain structure composed of three bunching cavity unit structures with an injection hole aperture of 4 mm - 5 mm and a beam hole aperture of 3 mm - 3.5 mm. After adopting the cavity chain structure with the injection aperture and beam aperture within the above-mentioned size ranges, the focus size can be made less than 0.5 mm, which is reduced by more than 50% compared with the conventional accelerating tube, thus realizing the small-focus design of the accelerating tube.

[0043] The following gives the specific structural dimensions of an example of the present invention. The number of bunching cavity units n = 3, and the length dimension ratio of the first bunching cavity, the second bunching cavity, and the third bunching cavity along the beam direction is 0.84:1:1, D1 = 4.5 mm, D2 = 3.5 mm. When the waist diameter of the electron gun injection is 1 mm, the transverse density fitting curves of the target electrons in the X direction and the Y direction are as Figure 5 shown in Figure 6 . By reading the fitting curves, it is obtained that the FWHM in the X direction is 0.39 mm, the FWHM in the Y direction is 0.40 mm, and the beam spot diameter is 0.40 mm. The focus size is less than 0.5 mm.

[0044] The following gives the specific structural dimensions of another example of the present invention. The number of bunching cavity units n = 3, and the length dimension ratio of the first bunching cavity, the second bunching cavity, and the third bunching cavity along the beam direction is 0.84:1:1, D1 = 4 mm, D2 = 3 mm. When the waist diameter of the electron gun injection is 0.6 mm, the transverse density fitting curves of the target electrons in the X direction and the Y direction are as Figure 7 shown in Figure 8 . By reading the fitting curves, it is obtained that the FWHM in the X direction is 0.17 mm, the FWHM in the Y direction is 0.15 mm, and the beam spot diameter is 0.17 mm. The focus size is less than 0.5 mm.

[0045] The present invention also provides an accelerator, which includes a power source 1 for generating microwaves; a standing-wave accelerating tube 2 as described above for accelerating electrons; a microwave system connected between the power source 1 and the standing-wave accelerating tube 2, the microwave system being used to feed the microwaves generated by the power source 1 into the standing-wave accelerating tube 2; and a solid-state modulator system for providing high-voltage pulses to the power source 1 and the electron gun. The above solid-state modulator system can convert the obtained DC high voltage into high-voltage pulses to supply power to the power source and the electron gun. The above standing-wave accelerating tube 2 is a small-focus accelerating tube, and its focus size is less than 0.5 mm. The above microwave system includes a waveguide and a four-port circulator 5. The waveguide is used to transmit microwave power, and the four-port circulator 5 is used to isolate the microwave power fed back to the power source 1. The above waveguide includes an air-filled straight waveguide 3 and an air-filled bent waveguide 4. The air-filled straight waveguide 3 is connected between the power source 1 and the four-port circulator 5, and the air-filled bent waveguide 4 is connected between the four-port circulator 5 and the standing-wave accelerating tube 2. The solid-state modulator system includes a solid-state modulator control unit 7, a power source pulse unit 8, and an electron gun pulse unit 9. The solid-state modulator system is used to convert the input DC high voltage into pulsed high voltage. The solid-state modulator system is connected to the power source 1 and the electron gun of the standing-wave accelerating tube 2. The power source 1 is used to receive the pulsed high voltage to generate microwaves, and the electron gun of the standing-wave accelerating tube 2 is used to receive the pulsed high voltage to generate electrons. The accelerator further includes a collimator unit 10. In the installed state of the accelerator, the collimator unit 10 is located at the rear end of the standing-wave accelerating tube 2. The accelerator further includes a frame structure 11. The power source 1, the microwave system, the standing-wave accelerating tube 2, and the collimator unit 10 are all arranged inside the frame structure 11 and distributed along the length direction of the frame structure 11. The power source pulse unit 8 and the electron gun pulse unit 9 are both arranged inside the frame structure 11 and distributed along the width direction of the frame structure 11, and the solid-state modulator control unit 7 is arranged outside the frame structure 11. In this small-focus accelerator, the accelerating tube is a small-focus accelerating tube with a focus size less than 0.5 mm, which is reduced by more than 50% compared with a conventional accelerating tube.

[0046] In summary, through the cooperation of multiple bunching cavity units sequentially arranged along the electron beam direction, the present invention designs the bunching cavity of the bunching cavity unit close to the electron gun side as an asymmetric cavity type along the electron beam direction, so that on the premise of ensuring the acceleration performance, a small-focus design of the accelerating tube can be realized, and the spatial resolution can be improved. And by designing the aperture D1 of the beam hole of the first bunching cavity unit close to the electron gun to be 4 mm ≤ D1 ≤ 5 mm, and the aperture D2 of the beam hole of the first bunching cavity unit far from the electron gun to be 3 mm ≤ D2 ≤ 3.5 mm, an ultra-fine focus size less than 0.5 mm can be achieved, which is reduced by more than 50% compared with the focus size of a conventional accelerating tube.

[0047] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is impossible to enumerate all the implementation manners here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A cavity chain structure for a standing wave accelerating tube, characterized in that: include A plurality of focusing cavity units are sequentially arranged along the direction of the electron beam flow; and A coupling cavity between adjacent bunching cavity units; The bunching cavity unit comprises a bunching cavity and a beam hole for forming an electron beam channel; The focusing cavity of the focusing cavity unit of the cavity chain structure close to the electron gun is designed as an asymmetric cavity along the electron beam flow direction.

2. The cavity chain structure according to claim 1, characterized in that: The aperture of the beam hole of the first focusing cavity unit close to the electron gun is larger than the aperture of the beam hole far from the electron gun.

3. The cavity chain structure according to claim 1, characterized in that: The number of the bunching cavity units is n, 3≤n≤5; the aperture of the beam hole of the first bunching cavity unit close to the electron gun is D1, 4mm≤D1≤5mm; the aperture of the beam hole of the first bunching cavity unit far from the electron gun is D2, 3mm≤D2≤3.5mm; through the cavity chain structure, the focus size of the accelerating tube can be controlled within 0.5mm.

4. The cavity chain structure according to claim 1, characterized in that: The apertures of the beam holes starting from the second focusing cavity unit are all equal to the aperture of the beam hole of the first focusing cavity unit far away from the electron gun.

5. The cavity chain structure according to claim 1, characterized in that: The length of the focusing cavity of the first focusing cavity unit along the electron beam flow direction is smaller than the length of the focusing cavity of the adjacent focusing cavity unit along the electron beam flow direction; the lengths of the focusing cavities along the electron beam flow direction are the same starting from the second focusing cavity unit.

6. The cavity chain structure according to claim 1, characterized in that: The focusing cavity unit also includes two protruding structures formed on two opposite cavity side walls of the focusing cavity and extending into the focusing cavity along the direction of the electron beam flow; the beam hole passes through the protruding structures; the radial size of the protruding structure close to the electron gun of the first focusing cavity unit is greater than the radial size of the protruding structure far from the electron gun; the two protruding structures in the focusing cavity units starting from the second focusing cavity unit are symmetrically arranged.

7. A standing wave accelerating tube, characterized in that: It comprises a cavity chain structure as described in any one of claims 1 to 6; an electron gun and a target component respectively sealed and fixed to the two ends of the cavity chain structure along the electron beam direction; a feeding waveguide fixedly connected to the cavity chain structure; and a microwave input window and a titanium pump fixedly arranged on the feeding waveguide.

8. The standing wave accelerating tube according to claim 7, characterized in that: The electron gun is a diode electron gun or a grid-controlled electron gun; the injection waist diameter of the electron beam emitted by the electron gun is less than 1.5 mm.

9. The standing wave accelerating tube according to claim 7, characterized in that: The central frequency range of the standing wave accelerating tube is 5707 MHz-5717 MHz.

10. An accelerator, characterized in that: It comprises a power source for generating microwaves; a standing wave accelerating tube as described in claim 7; a microwave system connected between the power source and the standing wave accelerating tube; and a solid-state modulator system for providing high voltage pulses to the power source and the electron gun.

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