Dual-period magnetic focusing system and traveling wave tube

Abstract

The application provides a double-period magnetic focusing system and a traveling wave tube. The double-period magnetic focusing system comprises 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 the axial direction of the pole shoe structure and a plurality of periodic annular grooves formed on the side wall of the outer circumferential 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. An annular groove body used to accommodate the annular boss is formed on the side wall of the inner circumferential surface of the magnetic steel. The double-period magnetic focusing system can not only maintain a good focusing state of the electron beam, but also avoid the use of a non-magnetic ring, fundamentally eliminating the problem of the multiple-welding-seam welding process of the pole shoe ring, greatly improving the production efficiency, and reducing the risk of gas leakage.

Description

Technical Field

[0001] This invention relates to the field of microwave vacuum electronics technology. More specifically, it relates to a dual-cycle magnetic focusing system and a traveling wave tube. Background Technology

[0002] The PPM periodic permanent magnet focusing system is the most commonly used focusing method for traveling wave tubes. A typical feature of this structure is that each pole piece is connected by a non-magnetic spacer ring, thus achieving magnetic focusing performance. Brazing ensures airtightness. Figure 1 As shown. During long-term tube manufacturing, this structure presents the following problems: 1. Because the magnetic system is typically welded from numerous pole shoes and spacers, significant manpower is required for measurement, screening, assembly, and welding, resulting in low production efficiency. 2. The brazing connection between adjacent pole shoes and spacers leads to numerous weld seams, increasing the risk of welding defects and air leakage. 3. The sequential brazing of pole shoes and spacers along the axial direction results in large longitudinal tolerances, making it difficult to match the total length of the magnetic focusing system with the slow-wave circuit length. This often leads to inconsistencies in the distance between the input and output ports of the slow-wave circuit, affecting system assembly and use. 4. Solder accumulation and flow on the surfaces of the pole shoes and spacers make it difficult to achieve good coaxiality during magnet assembly, affecting flux conversion. Furthermore, solder flowing into the slow-wave circuit severely degrades the slow-wave circuit matching performance, increasing the risk of traveling wave tube reflection oscillation. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a dual-cycle magnetic focusing system that not only maintains a good focusing state of the electron beam but also avoids the use of non-magnetic spacers, fundamentally eliminating the frequent process steps involving multiple weld seams in the pole shoe spacers, greatly improving production efficiency, and reducing the risk of gas leakage.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention provides a dual-cycle magnetic focusing system, comprising:

[0006] An integrally formed pole shoe structure and a magnet coaxially arranged with the pole shoe structure; the pole shoe structure includes a channel extending along its own axial direction and a plurality of periodic annular grooves formed on the outer peripheral sidewall of the pole shoe structure; the annular grooves are arranged along the axial direction of the pole shoe structure and are coaxially arranged with the channel; the channel is used to accommodate a slow wave circuit.

[0007] The magnet is ring-shaped and fixed in the annular groove; an annular boss is formed in the annular groove; an annular groove is formed on the inner circumferential sidewall of the magnet to accommodate the annular boss.

[0008] A preferred embodiment is that the pole shoe structure includes multiple pole shoe units with a periodic structure. Each pole shoe unit includes a first pole shoe ring, a second pole shoe ring, a third pole shoe ring, and a fourth pole shoe ring arranged sequentially. The outer radius of the first pole shoe ring is r1, the outer radii of the second and fourth pole shoe rings are both r2, and the outer radius of the third pole shoe ring is r3. The relationship between r1, r2, and r3 is: 0.4*r1≤r3≤0.6*r1, 1.4*r2≤r3≤1.6*r2.

[0009] In a preferred embodiment, the annular groove is formed between the two first pole shoe rings of adjacent pole shoe units, and the magnet is fixed between the two first pole shoe rings of adjacent pole shoe units.

[0010] In a preferred embodiment, the third pole shoe ring portion forms the annular boss.

[0011] A preferred embodiment is that the outer boundary of the magnet protrudes beyond the outer boundary of the pole shoe structure.

[0012] The preferred embodiment is that the half-cycle length of the dual-cycle magnetic focusing system is p, the thickness of the first pole shoe ring is d3, and the thickness of the third pole shoe ring 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 embodiment is that the channel is a circular cross-section channel, and the inner diameters of the first pole shoe ring, the second pole shoe ring, the third pole shoe ring, and the fourth pole shoe ring are all equal to the inner diameter of the channel.

[0014] In a preferred embodiment, the magnet includes a first magnetic ring, a second magnetic ring, and a third magnetic ring arranged and fixed along the axial direction of the pole shoe structure; an annular groove is formed between the second magnetic ring and the inner wall of the first magnetic ring and the inner wall of the third magnetic ring to accommodate and fix the annular boss.

[0015] The preferred approach is that the magnetization direction of each magnetic ring of the same magnet is the same, and the magnetization direction of two adjacent magnets is opposite.

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

[0017] The beneficial effects of this invention are as follows:

[0018] This invention, through the integration of an integrally molded pole piece structure and a magnet coaxially positioned with it, enables the dual-cycle magnetic focusing system to maintain a high third harmonic component of the axial magnetic field, sufficient to ensure good electron beam focusing in the dual-cycle focusing magnetic field. Furthermore, the integral pole piece structure is simple and can be manufactured in a single machining operation. By avoiding the use of non-magnetic spacers, this invention fundamentally solves the frequent problem of multiple weld seams in the pole piece spacer process, significantly improving production efficiency and tube yield, reducing the risk of leakage, and providing a simplified electron optical system technology route for the mass production of traveling wave tubes. Attached Figure Description

[0019] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

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

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

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

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

[0024] Figure 5 This is a graph showing the magnetic field distribution of the magnetic focusing system of the present invention.

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

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

[0027] Reference numerals: 1. Pole shoe structure; 2. Magnet; 11. Channel; 12. First pole shoe ring; 13. Second pole shoe ring; 14. Third pole shoe ring; 15. Fourth pole shoe ring; 16. Annular groove; 21. First magnetic ring; 22. Second magnetic ring; 23. Third magnetic ring. Detailed Implementation

[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, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

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

[0030] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

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

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

[0033] In periodic permanent magnet focusing systems, a common structural design involves connecting the pole shoes with non-magnetic spacers to prevent magnetic short circuits and ensure that magnetic field lines do not become excessively concentrated inside the pole shoes, thereby maintaining the magnetic field distribution intensity within the electron beam channel. The structure is as follows: Figure 1 As shown. Those skilled in the art generally believe that the design of directly connected pole shoes leads to excessive concentration of magnetic field lines within the pole shoes, resulting in a weak or even absent magnetic field within the electron beam channel. Therefore, this design is not used in periodic permanent magnet focusing systems. However, research has shown that this understanding is not entirely accurate. This is because the permeability of pole shoes is typically limited, and even with a directly connected pole shoe design, a certain magnetic field strength can still be maintained within the electron beam channel. Furthermore, the specific structure, size, and arrangement of the pole shoes have a significant impact on the magnetic field distribution. With proper design, the directly connected pole shoe method can still achieve magnetic field performance comparable to traditional periodic permanent magnet focusing systems.

[0034] In contrast, connecting pole pieces via non-magnetic spacers has several significant drawbacks. First, magnetic focusing systems typically consist of numerous pole pieces and spacers welded together, requiring substantial manpower for measurement, selection, assembly, and welding, leading to low production efficiency and increased manufacturing costs. Second, the brazing connections between pole pieces and spacers are prone to defects such as air leakage, which can affect the overall performance and reliability of the system. Third, the axial brazing arrangement of pole pieces and spacers results in accumulated longitudinal tolerances, making it difficult to precisely match the total length of the magnetic focusing system with the length of the slow-wave circuit. This often leads to inconsistencies in the distance between the input and output ports of the slow-wave circuit, affecting system assembly and use. Finally, solder accumulation or flow often occurs on the surfaces of the pole pieces and spacers, making it difficult to achieve good coaxiality in the magnet assembly. This not only affects the flow rate but may also cause solder to flow into the slow-wave circuit, severely deteriorating the matching performance of the slow-wave circuit and increasing the risk of traveling wave tube reflection oscillations.

[0035] In summary, while connecting pole shoes via non-magnetic spacers offers advantages in preventing magnetic short circuits, its manufacturing complexity, welding defects, length mismatches, and assembly precision issues need to be addressed during design and production. A rationally designed direct pole shoe connection method can effectively avoid these problems while maintaining a strong magnetic field within the electron beam channel, thus providing a more efficient and reliable magnetic focusing solution. Based on the above research and analysis, this invention provides a dual-cycle magnetic focusing system that maintains good electron beam focusing while avoiding the use of non-magnetic spacers. This fundamentally eliminates the frequent problem of multi-weld welding of pole shoe spacers, significantly improving production efficiency and reducing the risk of structural leakage. Figures 1 to 7 As shown, the dual-cycle magnetic focusing system specifically includes: an integrally formed pole shoe structure 1 and a magnet 2 coaxially arranged with the pole shoe structure 1, wherein 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 extending along its own axis and a plurality of periodic annular grooves 16 formed on the outer peripheral sidewall 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 the slow wave circuit; the magnet 2 has an annular structure and is fixed in the annular groove 16; an annular boss is formed in the annular groove 16; an annular groove is formed on the inner peripheral sidewall of the magnet 2 to accommodate the annular boss, and the cooperation of the annular boss and the annular groove can ensure that the magnetic focusing system generates the third harmonic component.

[0036] In the above embodiments, regarding the specific structure of the pole shoe structure 1, the pole shoe structure 1 includes multiple pole shoe units with a periodic structure, and the multiple pole shoe units are integrally formed; the pole shoe unit includes a first pole shoe ring 12, a second pole shoe ring 13, a third pole shoe ring 14, and a fourth pole shoe ring 15 arranged sequentially; the outer radius of the first pole shoe ring 12 is r1, the outer radius of the second pole shoe ring 13 and the fourth pole shoe ring 15 is r2, and the outer radius of the third pole shoe ring 14 is r3. The outer radii are all centered on the axis of the pole shoe structure 1. 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 approach the optimal third harmonic ratio, thus strengthening the focusing ability. This invention effectively adjusts the third harmonic component of the axial magnetic field by adjusting the outer radius r3 of the third pole shoe ring 14 to change the protrusion height (r3-r2) of the annular boss. The higher the protrusion height, the larger the third harmonic component and the stronger the focusing ability. 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 rings 12 of adjacent pole shoe units, the magnet 2 is fixed between the two first pole shoe rings 12 of adjacent pole shoe units, and the annular boss is formed by the third pole shoe ring 14.

[0037] To facilitate the assembly of the magnet 2 with the pole shoe structure 1 and to make it easier to take the magnet 2 off and on the pole shoe structure 1, the outer boundary of the magnet 2 is set 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-cycle length of the magnetic focusing system is p. The thickness of the first pole shoe ring 12 is d3, the thicknesses of the second pole shoe ring 13 and the fourth pole shoe ring 15 are both d2, and the thickness of the third pole shoe ring 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 high axial magnetic field third harmonic component, approaching the optimal third harmonic ratio, and exhibiting strong focusing ability. In this embodiment, d1 > 0, d2 > 0, and d3 > 0. By adjusting d1 and d3, the third harmonic component and the shape of the magnetic field distribution curve can be easily adjusted. Generally, the larger d1 is, the larger the third harmonic component; the smaller d3 is, the larger the third harmonic ratio.

[0039] In one specific embodiment, the channel 11 is a circular cross-section channel, and the inner diameters of the first pole shoe ring 12, the second pole shoe ring 13, the third pole shoe ring 14, and the fourth pole shoe ring 15 are all equal to the inner diameter of the channel 11. Referring to the accompanying drawings, the inner radii of the first pole shoe ring, the second pole shoe ring, the third pole shoe ring, and the fourth pole shoe ring, as well as the radius of the channel, are all r4. That is, the inner peripheral walls of the first pole shoe ring 12, the second pole shoe ring 13, the third pole shoe ring 14, and the fourth pole shoe ring 15 enclose and form the aforementioned channel 11.

[0040] Regarding the structure of the magnet 2, the magnet 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 is formed between the second magnetic ring 22 and the inner wall of the first magnetic ring 21 and the inner wall of the third magnetic ring 23 to accommodate and fix the annular boss. The magnetization directions of the magnetic rings of the same magnet 2 are the same, while the magnetization directions of adjacent magnets 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 also provides a traveling wave tube, which includes a slow wave circuit and a magnetic focusing system as described above; the slow wave circuit is disposed in the channel and extends axially along the channel 11.

[0042] This application specifically relates to a dual-cycle magnetic focusing system designed to avoid the use of non-magnetic spacers while maintaining good focusing of the electron beam. In this electron-optical system, the electron beam voltage is set to 14kV, the current to 50mA, and the electron beam channel radius to 0.20mm; these parameters ensure good device performance.

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

[0044] Figure 6The electron beam envelope in a dual-period magnetic field is shown, revealing minimal fluctuation, with a relative fluctuation of less than 9.1%. In the magnetic focusing system of this application, the maximum envelope radius of the electron beam is less than 0.12 mm, indicating that the electron beam can maintain a small envelope radius under the influence of this magnetic field, reducing the risk of electron scattering into the tube. This design enhances the system's redundancy against assembly errors, reduces electron beam interception losses, and improves throughput. Furthermore, this dual-period magnetic focusing system achieves intercept-free transmission over a distance of 100 mm, fully validating the effectiveness and accuracy of the system's magnetic field design.

[0045] The innovation of this invention lies in the use of a one-piece molded pole piece structure in conjunction with a coaxially positioned magnet. This integrated design maintains a high third harmonic component of the axial magnetic field, ensuring excellent focusing effect of the dual-cycle focusing magnetic field on the electron beam, and simplifies the manufacturing process. The pole piece structure, which can be machined in one step, avoids the use of non-magnetic spacers and multiple welding steps in traditional processes, thereby improving production efficiency and yield while reducing the risk of leakage. This simplified process provides a more efficient and reliable technical solution for the large-scale manufacturing of traveling wave tubes, demonstrating the practicality of this invention in the field of electron optical systems.

[0046] This application's dual-cycle magnetic focusing system enhances the magnetic field focusing capability by controlling the third harmonic component of the magnetic field, counteracting the shunting effect of the integrated pole shoe on the magnetic field lines. This maintains the small envelope transmission characteristics of the electron beam, enabling efficient and stable electron beam transmission over long distances. This 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, this invention, through the integrated pole shoe structure and the coaxially arranged magnet, enables the dual-cycle magnetic focusing system to maintain a high axial magnetic field third harmonic component, sufficient to ensure good electron beam focusing in the dual-cycle focusing magnetic field. Furthermore, the integrated pole shoe structure is simple and can be manufactured in a single machining operation. By avoiding the use of non-magnetic spacers, the frequent problem of multiple weld seams in pole shoe spacers is fundamentally solved, significantly improving production efficiency and tube yield, reducing the risk of leakage, and providing a simplified electro-optical system technology route for the mass production of traveling wave tubes.

[0048] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A two-period magnetic focusing system, characterized in that, include: An integrally formed pole shoe structure and a magnet coaxially arranged with the pole shoe structure; the pole shoe structure includes a channel extending along its own axial direction and a plurality of periodic annular grooves formed on the outer peripheral sidewall of the pole shoe structure; the annular grooves are arranged along the axial direction of the pole shoe structure and are coaxially arranged with the channel; the channel is used to accommodate a slow wave circuit. The magnet is ring-shaped and fixed in the annular groove; an annular boss is formed in the annular groove; an annular groove is formed on the inner circumferential sidewall of the magnet to accommodate the annular boss; The pole shoe structure includes multiple pole shoe units with a periodic structure. Each pole shoe unit includes a first pole shoe ring, a second pole shoe ring, a third pole shoe ring, and a fourth pole shoe ring arranged sequentially. The outer radius of the first pole shoe ring is r1, the outer radii of the second and fourth pole shoe rings are both r2, and the outer radius of the third pole shoe ring is r3. The relationship between r1, r2, and r3 is: 0.4*r1≤r3≤0.6*r1, 1.4*r2≤r3≤1.6*r2.

2. The dual-period magnetic focusing system of claim 1, wherein, The annular groove is formed between the two first pole shoe rings of adjacent pole shoe units, and the magnet is fixed between the two first pole shoe rings of adjacent pole shoe units.

3. The dual-period magnetic focusing system of claim 1, wherein, The third pole shoe ring portion forms the annular boss.

4. The dual-period magnetic focusing system of claim 1, wherein, The outer boundary of the magnet protrudes beyond the outer boundary of the pole shoe structure.

5. The dual-period magnetic focusing system of claim 1, wherein, The half-cycle length of the dual-cycle magnetic focusing system is p, the thickness of the first pole shoe ring is d3, and the thickness of the third pole shoe ring is d1. The relationship between p, d1, and d3 is: 0.3*p≤d1≤0.45*p, 0.1*p≤d3≤0.3*p.

6. The dual-period magnetic focusing system of claim 1, wherein, The channel is a circular cross-section channel, and the inner diameters of the first pole shoe ring, the second pole shoe ring, the third pole shoe ring, and the fourth pole shoe ring are all equal to the inner diameter of the channel.

7. The dual-cycle magnetic focusing system according to claim 1, characterized in that, The magnet includes a first magnetic ring, a second magnetic ring, and a third magnetic ring arranged and fixed along the axial direction of the pole shoe structure; an annular groove is formed between the second magnetic ring and the inner wall of the first magnetic ring and the inner wall of the third magnetic ring to accommodate and fix the annular boss.

8. The dual-period magnetic focusing system of claim 7, wherein, All magnetic rings of the same magnet are magnetized in the same direction, while adjacent magnets are magnetized in opposite directions.

9. A traveling wave tube, characterized by, It includes a slow-wave circuit and a magnetic focusing system as described in any one of claims 1-8; the slow-wave circuit is disposed within the channel and extends along the channel axis.

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