A radio frequency electron accelerator structure

Abstract

The present invention discloses a novel radio frequency electron accelerator structure, which includes an accelerating cavity, a coupling cavity, a sealing plate and a feeding waveguide, wherein the accelerating cavity and the coupling cavity are alternately assembled together, a sealing plate is arranged on the axial end face of the most tail-end accelerating cavity, beam holes are designed on the axial end faces of the accelerating cavity, the coupling cavity and the sealing plate, and the beam holes on the sealing plate are smaller than the other beam holes, and a feeding waveguide communicating with the accelerating cavity is arranged on the radial side wall of the most tail-end accelerating cavity. The novel accelerator structure created by the present invention cancels the external focusing system, and cancels the coupling hole structure on the cavity end face through optimized design, which greatly reduces the processing difficulty.

Description

Technical Field

[0001] The invention belongs to the technical field of accelerators, and in particular relates to a radio frequency electron accelerator structure with simple structure and low processing difficulty. Background Art

[0002] Small high-energy X-ray sources are the basis of the entire high-energy industrial CT system. To generate high-energy X-rays with an energy of more than 1MeV, electrons must be accelerated by an electron linear accelerator, and the high-energy electron beam hits the target material to generate high-energy X-rays. In order to ensure the spatial resolution of CT imaging, there are strict requirements on the focal spot size of the electron beam.

[0003] In the conventional design of the accelerator, a focusing system is added to the outside of the accelerating tube, and a magnetic field is generated by energizing the solenoid coil. For example, the patent number of an accelerating tube equipped with a focusing coil is CN201220722911.1. The technology includes an accelerating tube body, a drift tube is connected to the lower end of the accelerating tube body, and a solenoid coil is connected to the outer shell of the drift tube. The technology generates a magnetic field by energizing the solenoid coil. When the electron beam enters the magnetic field area in parallel, the magnetic field generates a tangential force to make the electrons obtain the tangential force linear velocity and rotate. The tangential linear velocity forms a force pointing to the axis center, causing the electrons to deviate toward the axis center. The electrons passing through the drift tube are always affected by the axial force during the entire movement. The farther the electrons in the electron beam are from the axis, the greater the axial force they are subjected to, thereby playing a converging role on the entire electron beam.

[0004] However, the inventors have found that this type of technology has at least the following technical problems during long-term use:

[0005] 1. The existing focusing system is installed outside the accelerating tube and includes a water cooling system, which has a complex structure and is inconvenient to use.

[0006] 2. In the existing design scheme, an arc-shaped coupling hole structure is designed on the cavity end face, which is difficult to process and assemble. Summary of the invention

[0007] In order to overcome the above-mentioned deficiencies, the inventors of the present invention have continuously reformed and innovated through long-term exploration and attempts, multiple experiments and efforts, and have provided a new type of radio frequency electron accelerator structure. Through this new accelerator structure, the lateral size of the electron beam at the accelerator outlet can be significantly reduced without adding an external focusing system, while ensuring that the electron beam reaches a certain energy and intensity, which can meet the requirements of high-energy industrial CT imaging for X-ray sources.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a novel radio frequency electron accelerator structure, which includes an accelerating cavity, a coupling cavity, a sealing plate and a feeding waveguide, wherein the accelerating cavity and the coupling cavity are assembled alternately with each other, a sealing plate is arranged on the axial end face of the accelerating cavity at the rear end, beam holes are designed on the axial end faces of the accelerating cavity, the coupling cavity and the sealing plate, and the beam holes on the sealing plate are smaller than the other beam holes, and a feeding waveguide communicating with the accelerating cavity is arranged on the radial side wall of the accelerating cavity at the rear end.

[0009] According to the novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is: a coupling cavity nose cone is provided in the coupling cavity, and an accelerating cavity nose cone is provided in one of the accelerating cavities.

[0010] According to the novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is that all coupling cavity nose cone structures are completely symmetrical and identical.

[0011] According to the novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is: the acceleration cavity nose cone is arranged in the acceleration cavity at the head end.

[0012] According to the novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is that the cross-sectional profiles of all acceleration cavity nose cones and coupling cavity nose cone structures are constructed in the form of circular arc tangents.

[0013] According to a novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is: the radius of the second arc is twice that of the first arc, the radius of the first arc is twice that of the third arc, and the third arc is a step-shaped arc formed by two sections of tangent arcs in positive and negative directions.

[0014] According to the novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is that the cross-sectional profile of the acceleration cavity nose cone and the coupling cavity nose cone structure is composed of three tangent circular arcs.

[0015] According to the novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is: the number of the accelerating cavities is 5 and the number of the coupling cavities is 4.

[0016] According to the novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is that the centers of the beam holes on the axial end faces of the accelerating cavity, the coupling cavity and the sealing plate are coaxial.

[0017] According to the novel radio frequency electron accelerator structure described in the present invention, a further preferred technical solution is that the length of the acceleration cavity increases sequentially from the head end to the tail end.

[0018] The beneficial effects of the present invention are as follows: the novel accelerator structure created by the present invention eliminates the external focusing system, and through optimized design, eliminates the coupling hole structure of the cavity end face, thereby greatly reducing the difficulty of processing.

[0019] This new accelerator structure can significantly reduce the lateral size of the electron beam at the accelerator exit without adding an external focusing system, while ensuring that the electron beam reaches a certain energy and intensity, which can meet the requirements of high-energy industrial CT imaging for X-ray sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

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

[0022] Figure 2 yes Figure 1 Schematic diagram of the local structure at point A in the middle.

[0023] Figure 3 yes Figure 2 Schematic diagram of the local enlarged structure at point B in the middle.

[0024] In the figure: 1 accelerating cavity A1, 2 coupling cavity C1, 3 accelerating cavity A2, 4 coupling cavity C2, 5 accelerating cavity A3, 6 coupling cavity C3, 7 accelerating cavity A4, 8 coupling cavity C4, 9 accelerating cavity A5, 10 closing plate, 11 feeding waveguide, 12 beam hole, 13 accelerating cavity nose cone, 14 coupling cavity nose cone, 15 first circular arc, 16 second circular arc, 17 third circular arc. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention.

[0026] Example

[0027] like Figure 1-3As shown: This embodiment is described by taking 5 accelerating cavities and 4 coupling cavities as an example, and the actual number can be adjusted by technicians in this field as needed. In this embodiment, the 5 accelerating cavities are named as accelerating cavity A1, accelerating cavity A2, accelerating cavity A3, accelerating cavity A4 and accelerating cavity A5, which are numbered 1, 3, 5, 7 and 9 in the figure respectively; the 4 coupling cavities are named as coupling cavity C1, coupling cavity C2, coupling cavity C3 and coupling cavity C4, which are numbered 2, 4, 6 and 8 in the figure respectively.

[0028] First, the accelerating cavities A1-A5 and the coupling cavities C1-C4 are assembled alternately, and then a sealing plate 10 is designed on the axial end face of the accelerating cavity A5. Beam holes 12 are designed on the axial end faces of the accelerating cavity, the coupling cavity and the sealing plate. The centers of these beam holes are coaxial, and the size of the beam holes on the sealing plate 10 is smaller than the remaining holes (the beam holes on the accelerating cavity and the coupling cavity). In this way, the scattered electrons on the outer edge of the electron beam can be shielded, the cross-sectional size of the electron beam can be limited, and the focal spot size of the electron beam can be ensured to meet the design requirements. A groove is set on the end face of the sealing plate, which can be used to place the brazing material. The brazing material melts during the brazing process, and the target assembly on the left and the sealing plate are welded together. The size of the groove is determined according to the brazing process.

[0029] Then, a feeding waveguide 11 is designed on the radial side wall of the accelerating cavity A5, and microwaves enter the accelerating cavity through the feeding waveguide to form a standing wave electric field to accelerate the electrons.

[0030] like Figure 3 As shown: In this embodiment, an accelerating cavity nose cone 13 is designed in the accelerating cavity A1. A coupling cavity nose cone 14 is designed in all other coupling cavities, and the structures of all coupling cavity nose cones are completely symmetrical and identical. When designing specifically, technicians in this field can make corresponding adjustments according to actual conditions, and only need to ensure that the accelerating cavity nose cone 13 is set in the accelerating cavity at the head end.

[0031] In this embodiment, the cross-sectional profiles of the nose cone structures of all the acceleration cavity nose cones and coupling cavity nose cones are formed in the form of three tangent arcs, namely, the first arc 15, the second arc 16 and the third arc 17, which reduces the total width of the nose cone structure and reduces the difficulty of processing. At the same time, the radius of the second arc 16 is set to twice the radius of the first arc 15, and the radius of the first arc 15 is set to twice the radius of the third arc 17. At the same time, the third arc 17 is formed into a step shape using two sections of positive and negative tangent arcs. In this way, the overall structural feature of the three arcs is that they are all connected by arcs in the axial direction, which changes the electric field distribution and enhances the electron focusing effect.

[0032] This embodiment eliminates the external focusing system and eliminates the coupling hole structure on the cavity end face through optimized design. This new accelerator structure can significantly reduce the lateral size of the electron beam at the accelerator exit without adding an external focusing system, while ensuring that the electron beam reaches a certain energy and intensity, which can meet the requirements of high-energy industrial CT imaging for X-ray sources.

[0033] In this embodiment, the outer diameter of the most tail-end accelerating cavity A5 is set larger than the outer diameters of other accelerating cavities, so that a mounting step surface can be processed in the diameter direction of the accelerating cavity A5 for mounting the feeding waveguide 11.

[0034] In this embodiment, the internal lengths of the accelerating chambers A1 to A5 are set to increase in sequence. On the right side of the accelerating chamber A1 is the electron gun assembly. The electron gun emits electrons into the accelerating chamber A1. At this time, the initial velocity of the electrons is small, and the distance they move in one acceleration cycle is short. After the electrons pass through the coupling chamber C1, they enter the accelerating chamber A2. At this time, the electron velocity has increased, and the distance they move in the same acceleration cycle has increased, so the A2 chamber is longer than the A1 chamber. The same applies thereafter. When the electrons are accelerated to the speed of light, the distance they move in each acceleration cycle is the same, and the length of the accelerating chamber is the same.

[0035] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0037] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A radio frequency electron accelerator structure, characterized in that The invention comprises an accelerating cavity, a coupling cavity, a sealing plate and a feeding waveguide, wherein the accelerating cavity and the coupling cavity are assembled alternately with each other, a sealing plate is arranged on the axial end face of the accelerating cavity at the rear end, beam holes are designed on the axial end faces of the accelerating cavity, the coupling cavity and the sealing plate, and the size of the beam hole on the sealing plate is smaller than the size of the other beam holes, a feeding waveguide communicating with the accelerating cavity is arranged on the radial side wall of the accelerating cavity at the rear end, a coupling cavity nose cone is arranged in the coupling cavity, an accelerating cavity nose cone is arranged in one of the accelerating cavities, and the cross-sectional profile of the accelerating cavity nose cone and the coupling cavity nose cone structure is formed in the form of three tangent arcs, the three arcs are respectively a first arc, a second arc and a third arc, wherein the radius of the second arc is twice that of the first arc, the radius of the first arc is twice that of the third arc, and the third arc is a step-shaped structure formed by two sections of tangent arcs in positive and negative directions.

2. A radio frequency electron accelerator structure according to claim 1, characterized in that: All coupling cavity nose cone structures are completely symmetrical and identical.

3. The radio frequency electron accelerator structure according to claim 1, characterized in that: The length of the acceleration cavity increases from the head end to the tail end.

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