Double-cycle magnetic focusing system and traveling wave tube

Abstract

The invention provides a double-cycle magnetic focusing system and a traveling wave tube. The double-cycle magnetic focusing system comprises an integrally-formed pole shoe structure and magnetic steel coaxial with the pole shoe structure. The pole shoe structure comprises a channel penetrating in the axial direction of the pole shoe structure and a plurality of periodic annular grooves formed in the side wall of the outer circumferential face of the pole shoe structure. The annular grooves are axially arranged along the pole shoe structure and are coaxial with the channel; the channel is used for accommodating a slow wave circuit; the magnetic steel is annular and is fixed in the annular groove; an annular boss is formed in the annular groove; an annular groove body used for containing the annular boss is formed in the side wall of the inner circumferential face of the magnetic steel. According to the double-cycle magnetic focusing system, the good focusing state of electron beams can be kept, meanwhile, use of a non-magnetic spacer ring is avoided, the process step of multi-welding-seam welding of the pole shoe spacer ring is eliminated fundamentally, the production efficiency is greatly improved, and the air leakage risk is reduced.

Description

Technical Field

[0001] The present invention relates to the field of microwave vacuum electronic technology, and more specifically, to a dual-period magnetic focusing system and a traveling wave tube. Background Art

[0002] The PPM periodic permanent magnet focusing system is the most commonly used focusing method for traveling wave tubes. The typical feature of this structure is that each pole shoe is connected by a non-magnetic spacer ring to achieve magnetic focusing performance, and airtightness is ensured by brazing. Figure 1 As shown. In the long-term pipe manufacturing process, this structure has the following problems: 1. Since the magnetic system is usually welded by a large number of pole shoes and spacer rings, a lot of manpower costs are required to carry out measurement, screening, assembly, welding and other work, and the production efficiency is low. 2. Since the adjacent pole shoes and spacer rings need to be connected by brazing, there are many welds, and welding defects are prone to leakage. 3. The pole shoes and spacer rings are brazed in sequence along the axial direction, resulting in a large accumulation of longitudinal tolerances. The total length of the magnetic focusing system is difficult to adapt to the length of the slow-wave line, resulting in frequent inconsistencies in the distance between the input and output ports of the slow-wave line, affecting the assembly and use of the system. 4. Due to the frequent accumulation and dispersion of solder on the surface of the pole shoes and spacer rings, it is difficult to achieve good coaxiality in the magnetic steel assembly, which affects the improvement of the circulation rate. What's more, it flows into the slow-wave line, seriously deteriorating the matching performance of the slow-wave circuit and increasing the risk of reflection oscillation of the traveling wave tube. Summary of the invention

[0003] In response to the above problems, the present invention provides a dual-period magnetic focusing system, which can not only maintain a good focusing state of the electron beam, but also avoid the use of non-magnetic spacer rings, fundamentally eliminating the problematic process steps of multiple welds of pole shoe spacer rings, greatly improving production efficiency and reducing the risk of air leakage.

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

[0005] The present invention provides a dual-period magnetic focusing system, comprising:

[0006] An integrally formed pole shoe structure and a magnetic steel coaxially arranged with the pole shoe structure; the pole shoe structure comprises a channel penetrating along its own axial direction and a plurality of periodic annular grooves formed on the side wall of the outer peripheral surface of the pole shoe structure; the annular grooves are arranged along the axial direction of the pole shoe structure and coaxially arranged with the channel; the channel is used to accommodate a slow wave circuit;

[0007] The magnetic steel is annular and fixed in the annular groove; an annular boss is formed in the annular groove; and an annular groove body for accommodating the annular boss is formed on the inner peripheral side wall of the magnetic steel.

[0008] A preferred solution is that the pole shoe structure includes a plurality of pole shoe units of a periodic structure, and the pole shoe units include a first pole shoe ring portion, a second pole shoe ring portion, a third pole shoe ring portion and a fourth pole shoe ring portion which are arranged in sequence; the outer radius of the first pole shoe ring portion is r1, the outer radius of the second pole shoe ring portion and the fourth pole shoe ring portion are both r2, and the outer radius of the third pole shoe ring portion is r3, and the relationship between r1, r2 and r3 is: 0.4*r1≤r3≤0.6*r1, 1.4*r2≤r3≤1.6*r2.

[0009] A preferred solution is that the annular groove is formed between the two first pole shoe ring parts of two adjacent pole shoe units, and the magnetic steel is fixed between the two first pole shoe ring parts of the two adjacent pole shoe units.

[0010] Preferably, the third pole shoe ring portion forms the annular boss.

[0011] A preferred solution is that the outer boundary of the magnetic steel is arranged to protrude from the outer boundary of the pole shoe structure.

[0012] The preferred solution is that the half-period length of the dual-period magnetic focusing system is p, the thickness of the first pole shoe ring portion is d3, and the thickness of the third pole shoe ring portion is d1; the relationship between p, d1, and d3 is: 0.3*p≤d1≤0.45*p, 0.1*p≤d3≤0.3*p.

[0013] A preferred solution is that the channel is a circular cross-section channel, and the inner diameters of the first pole shoe ring portion, the second pole shoe ring portion, the third pole shoe ring portion and the fourth pole shoe ring portion are all equal and equal to the inner diameter of the channel.

[0014] A preferred solution is that the magnetic steel includes a first magnetic ring, a second magnetic ring and a third magnetic ring which are arranged and fixed axially along the pole shoe structure; an annular groove body is formed between the second magnetic ring and the inner side wall of the first magnetic ring and the inner side wall of the third magnetic ring to accommodate and fix the annular boss.

[0015] The preferred solution is that the magnetizing directions of the magnetic rings of the same magnetic steel are the same, and the magnetizing directions of two adjacent magnetic steels are opposite.

[0016] The present invention also provides a traveling wave tube, comprising a slow wave circuit and the magnetic focusing system as described above; the slow wave circuit is arranged in the channel and extends axially along the channel.

[0017] The beneficial effects of the present invention are:

[0018] The present invention uses an integrally formed pole shoe structure and a magnetic steel coaxially arranged with the pole shoe structure to enable the dual-period magnetic focusing system provided by the present invention to still maintain a relatively high third harmonic component of the axial magnetic field, which is sufficient to ensure that the dual-period focusing magnetic field achieves good focusing of the electron beam. In addition, the integrated pole shoe structure is simple and can be manufactured in one step through mechanical processing. Since the present invention avoids the use of non-magnetic spacer rings, it fundamentally solves the problem of frequent welding of multiple welds of pole shoe spacer rings, which can greatly improve production efficiency and tube manufacturing yield, reduce the risk of air leakage, and provide a simplified process for the large-scale manufacturing of traveling wave tubes. Electronic optical system technology route. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0020] Figure 1 It is a schematic diagram of the structure of a conventional periodic permanent magnet focusing system.

[0021] Figure 2 It is a schematic diagram of the structure of the magnetic focusing system of the present invention.

[0022] Figure 3 It is a vertical cross-sectional schematic diagram of the magnetic focusing system of the present invention.

[0023] Figure 4 It is a structural schematic diagram of the pole shoe structure of the present invention.

[0024] Figure 5 It is a magnetic field distribution curve diagram of the magnetic focusing system of the present invention.

[0025] Figure 6 It is the electron injection envelope diagram of the magnetic focusing system of the present invention.

[0026] Figure 7 It is the Fourier transform diagram of the axial magnetic field of the magnetic focusing system of the present invention.

[0027] Figure numerals: 1. pole shoe structure, 2. magnetic steel, 11. channel, 12. first pole shoe ring part, 13. second pole shoe ring part, 14. third pole shoe ring part, 15. fourth pole shoe ring part, 16. annular groove, 21. first magnetic ring, 22. second magnetic ring, 23. third magnetic ring. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0029] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0030] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0031] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0032] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] In the periodic permanent magnet focusing system, the commonly used structural design is to connect the pole shoes through non-magnetic spacer rings to prevent magnetic short circuit and ensure that the magnetic lines of force will not be excessively concentrated inside the pole shoes, thereby maintaining the magnetic field distribution intensity in the electron injection channel. Figure 1 As shown. However, those skilled in the art generally believe that the design of directly connecting the pole shoes will cause the magnetic lines of force to be too concentrated in the pole shoes, making the magnetic field in the electron injection channel very weak or even disappearing. Therefore, those skilled in the art will not use the above design in the periodic permanent magnet focusing system. However, after research, it is found that this understanding is not completely accurate. This is because the magnetic permeability of the pole shoes is usually limited. Even if the design of directly connecting the pole shoes is adopted, a certain magnetic field strength can still be maintained in the electron injection channel. In addition, the specific structure, size and arrangement of the pole shoes will have an important influence on the magnetic field distribution. Through reasonable design, the method of directly connecting the pole shoes can still exert a magnetic field performance comparable to the traditional periodic permanent magnet focusing system design.

[0034] In contrast, the method of connecting pole shoes through non-magnetic spacer rings has some significant disadvantages. First, the magnetic focusing system is usually connected by welding a large number of pole shoes and spacer rings, which requires a lot of manpower for measurement, screening, assembly and welding, resulting in low production efficiency and increased manufacturing costs. Secondly, the brazing connection between the pole shoes and the spacer rings is prone to welding defects, such as air leakage, which may affect the overall performance and reliability of the system. Third, the brazing arrangement of the pole shoes and the spacer rings in the axial direction will lead to the accumulation of longitudinal tolerances, making it difficult to accurately match the total length of the magnetic focusing system with the length of the slow-wave line, resulting in the distance between the input and output ports of the slow-wave line often inconsistent, affecting the assembly and use of the system. Finally, solder accumulation or dispersion often occurs on the surface of the pole shoes and spacer rings, making it difficult to achieve good coaxiality in the magnetic steel assembly. This not only affects the improvement of the flow rate, but may also cause the solder to flow into the slow-wave line, thereby seriously deteriorating the matching performance of the slow-wave circuit and increasing the risk of reflection oscillation of the traveling wave tube.

[0035] In summary, although connecting pole shoes through non-magnetic spacer rings has certain advantages in preventing magnetic short circuits, its manufacturing complexity, welding defects, length mismatch and assembly accuracy problems need to be solved in the design and production process. A reasonably designed direct connection method of pole shoes can effectively avoid these problems while maintaining a strong magnetic field in the electron injection channel, thereby providing a more efficient and reliable magnetic focusing solution. Based on the above research and analysis, the present invention provides a dual-period magnetic focusing system, which can maintain a good focusing state of the electron beam while avoiding the use of non-magnetic spacer rings, fundamentally eliminating the problematic process steps of multiple welds of pole shoe spacer rings, greatly improving production efficiency, and reducing the risk of structural leakage, combined with Figures 1 to 7 As shown, the dual-period magnetic focusing system specifically comprises: an integrally formed pole shoe structure 1 and a magnetic steel 2 coaxially arranged with the pole shoe structure 1, the axis of the pole shoe structure 1 is Figure 3 and Figure 4 The dotted line L in the figure; the pole shoe structure 1 includes a channel 11 which penetrates along its own axial direction and a plurality of periodic annular grooves 16 formed on the side wall of the outer peripheral surface of the pole shoe structure 1; the annular grooves 16 are arranged along the axial direction of the pole shoe structure 1 and are coaxially arranged with the channel 11; the channel 11 is used to accommodate a slow-wave circuit; the magnetic steel 2 is annular in structure and is fixed in the annular groove 16; an annular boss is formed in the annular groove 16; an annular groove body for accommodating the annular boss is formed on the side wall of the inner peripheral surface of the magnetic steel 2, and the cooperation between the annular boss and the annular groove body can ensure that the magnetic focusing system generates a third harmonic component.

[0036] In the above embodiment, regarding the specific structure of the pole shoe structure 1, the pole shoe structure 1 includes a plurality of pole shoe units of a periodic structure, and the plurality of pole shoe units are integrally formed; the pole shoe unit includes a first pole shoe ring portion 12, a second pole shoe ring portion 13, a third pole shoe ring portion 14 and a fourth pole shoe ring portion 15 arranged in sequence; the outer radius of the first pole shoe ring portion 12 is r1, the outer radius of the second pole shoe ring portion 13 and the fourth pole shoe ring portion 15 are both r2, and the outer radius of the third pole shoe ring portion 14 is r3, and the above outer radii are all based on the axis of the pole shoe structure 1 as the circle point, and the relationship between r1, r2, and r3 is: 0.4*r1≤r3≤0.6*r1, 1.4*r2≤r3≤1.6*r2, within the above value range, the dual-period magnetic focusing system can obtain a higher axial magnetic field third harmonic component, and is close to the optimal third harmonic ratio, so that the focusing ability is enhanced. The present invention changes the protrusion height (r3-r2) of the annular boss by adjusting the outer radius r3 of the third pole shoe ring portion 14, thereby effectively adjusting the third harmonic component of the axial magnetic field. The higher the protrusion height of the boss, the larger the third harmonic component and the stronger the focusing ability. In order to ensure the focusing ability of the system, the third harmonic component should be close to and not exceed 50%. If the third harmonic component exceeds 50%, the focusing ability will gradually deteriorate. Furthermore, the annular groove 16 is formed between the two first pole shoe ring portions 12 of the two adjacent pole shoe units, the magnetic steel 2 is fixed between the two first pole shoe ring portions 12 of the two adjacent pole shoe units, and the third pole shoe ring portion 14 forms the annular boss.

[0037] In order to facilitate the assembly of the magnetic steel 2 and the pole shoe structure 1 and to facilitate the removal of the magnetic steel 2 from the pole shoe structure 1 , the outer boundary of the magnetic steel 2 is arranged to protrude from the outer boundary of the pole shoe structure 1 along the radial direction of the pole shoe structure 1 .

[0038] The half-period length of the magnetic focusing system is p, the thickness of the first pole shoe ring portion 12 is d3, the thickness of the second pole shoe ring portion 13 and the fourth pole shoe ring portion 15 are both d2, and the thickness of the third pole shoe ring portion 14 is d1, d1+2d2+d3=p, the relationship between p and d1 is: 0.3*p≤d1≤0.45*p; the relationship between p and d3 is: 0.1*p≤d3≤0.3*p. Within this range, the magnetic focusing system can obtain a higher axial magnetic field third harmonic component, close to the optimal third harmonic ratio, and has a strong focusing ability. In this embodiment, d1>0, d2>0, d3>0, and by adjusting d1 and d3, the third harmonic component of the magnetic field and the shape of the magnetic field distribution curve can be easily adjusted. Generally speaking, the larger d1 is, the larger the third harmonic component is, and the smaller d3 is, the larger the third harmonic ratio is.

[0039] In a specific embodiment, the channel 11 is a circular cross-section channel, and the inner diameters of the first pole shoe ring portion 12, the second pole shoe ring portion 13, the third pole shoe ring portion 14, and the fourth pole shoe ring portion 15 are all equal and equal to the inner diameter of the channel 11. As shown in the accompanying drawings, the inner radius of the first pole shoe ring portion, the second pole shoe ring portion, the third pole shoe ring portion, and the fourth pole shoe ring portion and the radius of the channel are all r4, that is, the inner peripheral wall surfaces of the first pole shoe ring portion 12, the second pole shoe ring portion 13, the third pole shoe ring portion 14, and the fourth pole shoe ring portion 15 enclose the above-mentioned channel 11.

[0040] Regarding the structure of the magnetic steel 2, the magnetic steel 2 includes a first magnetic ring 21, a second magnetic ring 22 and a third magnetic ring 23 arranged and fixed along the axial direction of the pole shoe structure 1; an annular groove body for accommodating and fixing the annular boss is formed between the second magnetic ring 22 and the inner side wall of the first magnetic ring 21 and the inner side wall of the third magnetic ring 23, and the magnetization direction of each magnetic ring of the same magnetic steel 2 is the same, and the magnetization directions of two adjacent magnetic steels 2 are opposite. The axial thickness of the first magnetic ring 21 and the third magnetic ring 23 is equal to the thickness d2 of the second pole shoe ring portion 13 and the fourth pole shoe ring portion 15. The axial thickness of the second magnetic ring 22 is equal to the thickness d1 of the third pole shoe ring portion 14.

[0041] The present invention further provides a traveling wave tube, which includes a slow wave circuit and the magnetic focusing system as described above; the slow wave circuit is arranged in the channel and extends axially along the channel 11.

[0042] The present application specifically relates to a dual-period magnetic focusing system, which aims to avoid the use of non-magnetic spacer rings while maintaining a good focusing state of the electron beam. In the electron optical system, the electron beam voltage is set to 14kV, the current is 50mA, and the electron beam channel radius is 0.20mm, which parameters can ensure good device performance.

[0043] Magnetic field design is the core of this system. This application increases the third harmonic component of the focused magnetic field to more than 41.5% by adjusting the pole shoe parameters d1, d3, r1, and r3, which is close to the optimal third harmonic ratio. Figure 7 shown. Figure 5 The spatial distribution of the focusing magnetic field is shown. The system effectively utilizes the third harmonic to enhance the magnetic field focusing capability and offsets the shunting effect of the integrated pole shoe structure on the magnetic field lines, thereby obtaining a magnetic field distribution curve of sufficient intensity to ensure that the magnetic field in the focusing area supports the stable transmission of the electron beam.

[0044] Figure 6The envelope of the electron beam in the dual-period magnetic field is shown, and it can be seen that the electron beam fluctuates very little, with a relative fluctuation of less than 9.1%. In the magnetic focusing system of the present application, the maximum envelope radius of the electron beam is less than 0.12 mm, indicating that the electron beam can maintain a smaller envelope radius under the action of the magnetic field, reducing the risk of electron scattering to the tube body. This design of the present application enhances the redundancy of the system against assembly errors, reduces the interception loss of the electron beam, and improves the flow rate. In addition, the dual-period magnetic focusing system also achieves non-interception transmission within a distance of 100 mm, fully verifying the effectiveness and accuracy of the magnetic field design of the system.

[0045] The innovation of the present invention lies in the use of an integrally formed pole shoe structure in combination with a coaxially arranged magnetic steel. This integrated design maintains a relatively high third harmonic component of the axial magnetic field, ensures a good focusing effect of the dual-period focusing magnetic field on the electron beam, and simplifies the manufacturing process. The pole shoe structure that can be completed in one go through mechanical processing avoids the use of non-magnetic spacer rings and multiple welding steps in the traditional process, thereby improving production efficiency and yield rate, while reducing the risk of air leakage. This simplified process provides a more efficient and reliable technical solution for the large-scale manufacture of traveling wave tubes, demonstrating the practicality of the present invention in the field of electronic optical systems.

[0046] The dual-period magnetic focusing system of the present application enhances the magnetic field focusing capability by controlling the third harmonic component of the magnetic field, offsets the shunting effect of the integrated pole shoe on the magnetic field lines, can maintain the small envelope transmission characteristics of the electron beam, and can achieve efficient and stable electron beam transmission over long distances. The present application not only provides a simpler and more efficient manufacturing process for related applications, but also ensures the focusing performance of the magnetic focusing system, demonstrating its practical application value in the field of electron beam focusing and transmission.

[0047] In summary, the present invention, through the cooperation of the integrally formed pole shoe structure and the magnetic steel coaxially arranged with the pole shoe structure, enables the dual-period magnetic focusing system provided by the present invention to still maintain a relatively high third harmonic component of the axial magnetic field, which is sufficient to ensure that the dual-period focusing magnetic field achieves good focusing of the electron beam. In addition, the integrated pole shoe structure is simple and can be manufactured in one step through mechanical processing. Since the use of non-magnetic spacer rings is avoided, the problem of multiple welds of the pole shoe spacer rings is fundamentally solved, which can greatly improve the production efficiency and the tube production yield, reduce the risk of air leakage, and provide a simplified process for the large-scale manufacturing of traveling wave tubes. Electronic optical system technology route.

[0048] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A dual-period magnetic focusing system, characterized in that: include: An integrally formed pole shoe structure and a magnetic steel coaxially arranged with the pole shoe structure; the pole shoe structure comprises a channel penetrating along its own axial direction and a plurality of periodic annular grooves formed on the side wall of the outer peripheral surface of the pole shoe structure; the annular grooves are arranged along the axial direction of the pole shoe structure and coaxially arranged with the channel; the channel is used to accommodate a slow wave circuit; The magnetic steel is annular and fixed in the annular groove; an annular boss is formed in the annular groove; and an annular groove body for accommodating the annular boss is formed on the inner peripheral side wall of the magnetic steel.

2. The dual-period magnetic focusing system according to claim 1, characterized in that: The pole shoe structure includes multiple pole shoe units with a periodic structure, and the pole shoe units include a first pole shoe ring portion, a second pole shoe ring portion, a third pole shoe ring portion and a fourth pole shoe ring portion which are arranged in sequence; the outer radius of the first pole shoe ring portion is r1, the outer radius of the second pole shoe ring portion and the fourth pole shoe ring portion are both r2, and the outer radius of the third pole shoe ring portion is r3, and the relationship between r1, r2, and r3 is: 0.4*r1≤r3≤0.6*r1, 1.4*r2≤r3≤1.6*r2.

3. The dual-period magnetic focusing system according to claim 2, characterized in that: The annular groove is formed between the two first pole shoe ring parts of the two adjacent pole shoe units, and the magnetic steel is fixed between the two first pole shoe ring parts of the two adjacent pole shoe units.

4. The dual-period magnetic focusing system according to claim 2, characterized in that: The third pole shoe ring portion forms the annular boss.

5. The dual-period magnetic focusing system according to claim 2, characterized in that: The outer boundary of the magnetic steel is arranged to protrude from the outer boundary of the pole shoe structure.

6. The dual-period magnetic focusing system according to claim 2, characterized in that: The half-period length of the dual-period magnetic focusing system is p, the thickness of the first pole shoe ring portion is d3, and the thickness of the third pole shoe ring portion is d1; the relationship among p, d1, and d3 is: 0.3*p≤d1≤0.45*p, 0.1*p≤d3≤0.3*p.

7. The dual-period magnetic focusing system according to claim 2, characterized in that: The channel is a circular cross-section channel, and the inner diameters of the first pole shoe ring portion, the second pole shoe ring portion, the third pole shoe ring portion and the fourth pole shoe ring portion are all equal and equal to the inner diameter of the channel.

8. The dual-period magnetic focusing system according to claim 1, characterized in that: The magnetic steel includes a first magnetic ring, a second magnetic ring and a third magnetic ring which are arranged and fixed along the axial direction of the pole shoe structure; an annular groove body for accommodating and fixing the annular boss is formed between the second magnetic ring and the inner side wall of the first magnetic ring and the inner side wall of the third magnetic ring.

9. The dual-period magnetic focusing system according to claim 8, characterized in that: The magnetizing directions of the magnetic rings of the same magnetic steel are the same, and the magnetizing directions of the two adjacent magnetic steels are opposite.

10. A traveling wave tube, characterized in that: It comprises a slow-wave circuit and a magnetic focusing system as described in any one of claims 1 to 9; the slow-wave circuit is arranged in the channel and extends axially along the channel.

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