Permanent magnet focusing system for traveling wave tubes

Abstract

The application discloses a permanent magnet focusing system for a traveling wave tube, which comprises a shell, the shell comprises a connecting cavity, a first inner cavity and a second inner cavity, a first magnet, a second magnet, a first inner magnet, a second inner magnet and a third inner magnet located in the first inner cavity, a third magnet, a fourth magnet and a fourth inner magnet located in the second inner cavity, a first through hole is formed in the center of the first magnet and the second magnet, a second through hole is formed in the center of the third magnet, the first through hole and the second through hole are communicated with the connecting cavity, the first inner magnet, the second inner magnet and the third inner magnet are sequentially arranged in the first through hole, and the fourth inner magnet is arranged in the second through hole, the first magnet, the second magnet, the fourth magnet, the second inner magnet and the fourth inner magnet are radially magnetized, and the third magnet, the first inner magnet and the third inner magnet are axially magnetized. Through the specific arrangement of the magnets and the magnetizing direction, the uniform magnetic field region is effectively extended, and the energy utilization rate can be improved.

Description

Technical Field

[0001] This invention relates to the field of microwave vacuum electronics technology. More specifically, it relates to a permanent magnet focusing system for a traveling wave tube. Background Technology

[0002] Traveling wave tubes (TWTs), as vacuum electronic devices, have wide applications in fields such as detection, imaging, and communication. High-frequency TWTs are characterized by their small size and light weight, making them easier to install into the mounting cavity of focusing systems (e.g., microwave TWTs) compared to microwave TWTs. Figure 1 (As shown). The function of the focusing system is to use the generated magnetic field force to counteract the space charge repulsion force generated by the electron beam itself, and to constrain the electron beam to pass smoothly through the traveling wave tube without defocusing or being intercepted.

[0003] In high-frequency traveling wave tubes, electron beams are characterized by small cross-sectional dimensions and high charge density, making it difficult for conventional magnetic focusing systems to meet focusing requirements. For example, periodic permanent magnets have low average magnetic fields, and the peak magnetic field is difficult to reach 7000 Gs; although coil magnets have high magnetic field strength, they are bulky and heavy, and require water cooling systems, making them unsuitable for use in airborne, vehicle-mounted, or other similar environments. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to provide a permanent magnet focusing system for traveling wave tubes that can improve the efficiency of electron beam focusing and meet the requirements of miniaturization design.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A permanent magnet focusing system for a traveling wave tube, comprising:

[0007] The outer casing includes a connecting cavity, and a first inner cavity and a second inner cavity located at both ends of the connecting cavity;

[0008] The first magnet, the second magnet, the first inner magnet, the second inner magnet, and the third inner magnet are located within the first inner cavity; and

[0009] The third magnet, the fourth magnet, and the fourth inner magnet are located within the second inner cavity;

[0010] The first magnet, the second magnet, the third magnet and the fourth magnet are arranged sequentially along the axial direction of the outer shell. The first magnet is located on the side of the second magnet away from the connecting cavity, and the fourth magnet is located on the side of the third magnet away from the connecting cavity.

[0011] The first magnet and the second magnet have a through hole at their center, and the third magnet has a through hole at its center. Both the first hole and the second hole are connected to the connecting cavity.

[0012] The first inner magnet, the second inner magnet, and the third inner magnet are sequentially disposed in the first through hole along the axial direction of the outer shell, and the fourth inner magnet is disposed in the second through hole, with one end away from the connecting cavity abutting against the fourth magnet;

[0013] The first magnet, the second magnet, the fourth magnet, the second inner magnet, and the fourth inner magnet are radially magnetized, and the third magnet, the first inner magnet, and the third inner magnet are axially magnetized.

[0014] Alternatively, the first, second, third, and fourth inner magnets are all annular magnets with a through hole in the center, and the through hole is connected to the connecting cavity.

[0015] Alternatively, the fourth magnet may have a third through hole extending along the axial direction of the outer shell at its center. The third through hole is connected to the through hole of the fourth inner magnet, and the inner diameter of the third through hole is equal to the inner diameter of the through hole.

[0016] The through holes of the first inner magnet, the second inner magnet, the third inner magnet, and the fourth inner magnet, the third through hole, and the connecting cavity are connected to form a mounting cavity for the insertion of the traveling wave tube.

[0017] Alternatively, the first magnet, the second magnet, and the second inner magnet are magnetized in the same direction, with their inner ends being N poles and their outer ends being S poles.

[0018] The fourth magnet and the fourth inner magnet are magnetized in the same direction, with their inner ends being S poles and their outer ends being N poles;

[0019] The third magnet and the third inner magnet are magnetized in the same direction, with the end closer to the fourth magnet being the S pole and the end closer to the first magnet being the N pole.

[0020] The end of the first inner magnet closer to the second inner magnet is the N pole, and the end farther away from the second inner magnet is the S pole.

[0021] Alternatively, the first magnet, the second magnet, the third magnet, and the fourth magnet may all be composed of multiple magnetic blocks joined together.

[0022] The first and fourth magnets are circular ring structures, and the second and third magnets are frustum structures. The outer wall surfaces of the first, second, third, and fourth magnets are bonded and fixed to the inner wall surface of the outer shell.

[0023] Alternatively, the inner diameter of the connecting cavity is smaller than the inner diameters of the first and second inner cavities, and the ends of the first and second inner cavities near the connecting cavity have a conical structure, with the ends of the first and second inner cavities gradually converging towards the connecting cavity.

[0024] Alternatively, the permanent magnet focusing system may also include a soft iron, which is mounted on the inner wall of the mounting cavity.

[0025] Alternatively, the permanent magnet focusing system may further include a first cover plate and a second cover plate, wherein the first cover plate covers the end of the first inner cavity away from the connecting cavity and abuts against the end of the first magnet away from the second magnet.

[0026] The second cover plate covers the end of the second inner cavity away from the connecting cavity and abuts against the end of the fourth magnet away from the third magnet.

[0027] Alternatively, the first magnet, second magnet, third magnet, fourth magnet and first inner magnet may be N52H neodymium iron boron with a remanence Br range of 1.43-1.48T.

[0028] The second, third, and fourth inner magnets are made of N42H neodymium iron boron with a remanence Br range of 1.28-1.32T.

[0029] Alternatively, an annular support member may be provided inside the connecting cavity, with both ends of the annular support member abutting against the ends of the third inner magnet and the fourth inner magnet respectively, and the annular support member being arranged around the periphery of the mounting cavity.

[0030] The beneficial effects of this invention are as follows:

[0031] To address the technical problems existing in the prior art, this invention provides a permanent magnet focusing system for traveling wave tubes. By specifically arranging the various magnets and combining their magnetization directions, the uniform magnetic field region is effectively extended, allowing charged particles to be focused more effectively using magnetic field energy, thus improving energy utilization. This system is also applicable to more applications requiring high-precision focusing or long-distance transmission of charged particles. Furthermore, the structure of the permanent magnet focusing system is optimized, adopting a dumbbell-like shape with larger ends and a smaller middle, expanding the installation space for the power transmission circuit. This facilitates the installation and precise adjustment of the power transmission circuit, meeting miniaturization requirements and shortening the length of the external power transmission waveguide during power transmission circuit installation, significantly reducing power transmission losses in high-frequency traveling wave tubes. Additionally, it effectively reduces transverse magnetic field fluctuations, improving electron beam focusing efficiency. Attached Figure Description

[0032] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0033] Figure 1 A schematic diagram of the structure of a focusing system in the prior art is shown.

[0034] Figure 2This diagram illustrates the assembly of a ring-shaped magnet unit in the prior art.

[0035] Figure 3 A schematic diagram of the power supply circuit installed in an existing focusing system is shown.

[0036] Figure 4 A half-sectional schematic diagram of the permanent magnet focusing system provided in an embodiment of the present invention is shown.

[0037] Figure 5 A schematic diagram of the structure of the outer casing provided in an embodiment of the present invention is shown.

[0038] Figure 6 A schematic diagram of the splicing structure of the first magnet provided in an embodiment of the present invention is shown.

[0039] Figure 7 A schematic diagram of the splicing structure of the second magnet provided in an embodiment of the present invention is shown.

[0040] Figure 8 This diagram illustrates the arrangement of magnets in the permanent magnet focusing system provided in an embodiment of the present invention.

[0041] Figure 9 A schematic diagram of the main magnetic circuit is shown.

[0042] Figure 10 A schematic diagram of the secondary magnetic circuit is shown.

[0043] Figure 11 A schematic diagram showing the power transmission circuit installed in the focusing system provided in an embodiment of the present invention is shown.

[0044] Figure 12 The diagram shows the magnetic field distribution along the central axis of the permanent magnet focusing system provided in Example 1.

[0045] Figure 13 The diagram shows the distribution of the transverse magnetic field of the permanent magnet focusing system with and without soft iron installed.

[0046] Figure 14 A schematic diagram showing the arrangement of magnets in the permanent magnet focusing system of Embodiment 2 is shown.

[0047] Figure 15 The diagram shows the magnetic field distribution along the central axis of the permanent magnet focusing system provided in Example 2. Detailed Implementation

[0048] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0049] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] In this invention, unless otherwise expressly specified and limited, the first feature "above" or "below" the second feature may include direct contact between the first and second features, or contact between the first and second features not in direct contact but through another feature between them.

[0051] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0052] Currently, there are relatively few focusing systems available for high-frequency traveling wave tube electron beam focusing. Among them, hollow cylindrical rare-earth permanent magnet structures are the most common. These focusing systems have the advantages of fewer magnet units, simple magnetization direction arrangement, high utilization of permanent magnets, and small size and weight. They can solve the problem of focusing high-frequency traveling wave tube electron beams to a certain extent. However, the following three problems still exist in their use:

[0053] I. The magnetic circuit of this type of focusing system typically consists of two large annular magnet units 7 (e.g., Figure 1 As shown in the left-middle figure, due to the large size of the annular magnet unit 7, it is difficult to ensure the magnetization orientation during pressing. Therefore, a method of splicing small-volume magnetic blocks is usually used as an alternative, for example... Figure 1 The right image and Figure 2 The splicing method uses 18 small-volume magnetic blocks 70. Since each small-volume magnetic block 70 is independently magnetized, it is difficult to guarantee that the magnetic declination angles are completely consistent, requiring additional pairing tests and selection; furthermore, the ideal structure of the splicing surface is as follows... Figure 2 As shown, since this surface is closest to the traveling wave tube, the non-uniformity of the splicing may seriously affect the transverse magnetic field (X and Y directions) in the region where the electron beam is located, resulting in a significant increase in transverse magnetic field fluctuations, which is not conducive to the focusing of the electron beam.

[0054] Second, the magnetic field uniformity zone of this type of focusing system is 30mm, which results in insufficient length of the magnetic field uniformity zone during use.

[0055] Third, when used in conjunction with high-frequency traveling wave tubes, this type of focusing system suffers from problems such as excessively long external power supply circuits and insufficient circuit assembly space. Figure 3 The distance between the two large ring magnet units 7 is L = 20mm. When installing the waveguide power transmission circuit with flange, the length a of the waveguide 8 should be at least 8cm, which seriously increases the power transmission loss of the high-frequency traveling wave tube circuit. In addition, the waveguide power transmission circuit needs to be assembled in a narrow space, which is not conducive to precise adjustment.

[0056] To address the shortcomings of existing technologies, this invention provides a permanent magnet focusing system for traveling wave tubes, combining... Figure 4-15 As shown, the permanent magnet focusing system includes a housing 1, and a first magnet 21, a second magnet 22, a third magnet 23, a fourth magnet 24, a first inner magnet 31, a second inner magnet 32, a third inner magnet 33, and a fourth inner magnet 34 installed inside the housing 1.

[0057] The housing 1 includes a connecting cavity 11 and a first inner cavity 12 and a second inner cavity 13 located at both ends of the connecting cavity 11.

[0058] The first magnet 21, the second magnet 22, the first inner magnet 31, the second inner magnet 32 ​​and the third inner magnet 33 are installed in the first inner cavity 12.

[0059] The third magnet 23, the fourth magnet 24 and the fourth inner magnet 34 are installed inside the second inner cavity 13.

[0060] The first magnet 21, the second magnet 22, the third magnet 23, and the fourth magnet 24 are sequentially arranged in the first inner cavity 12 and the second inner cavity 13 along the axial direction of the outer shell 1, and are coaxial with the outer shell 1. The first magnet 21 is located on the side of the second magnet 22 away from the connecting cavity 11, and the fourth magnet 24 is located on the side of the third magnet 23 away from the connecting cavity 11. The first inner cavity 12 corresponds to the lifting region of the permanent magnet focusing system, and the first magnet 21, the second magnet 22, the first inner magnet 31, the second inner magnet 32, and the third inner magnet 33 are located in the lifting region. The connecting cavity 11 and the second inner cavity 13 correspond to the uniform region of the permanent magnet focusing system, and the third magnet 23, the fourth magnet 24, and the fourth inner magnet 34 are located in the uniform region.

[0061] An installation cavity 6 for mounting a traveling wave tube is formed within the outer casing. The installation cavity 6 extends along the axial direction of the outer casing and is coaxially arranged with the outer casing. A first magnet 21, a second magnet 22, a third magnet 23, and a fourth magnet 24 are respectively arranged around the periphery of the installation cavity 6. A first inner magnet 31 is disposed between the first magnet 21 and the installation cavity 6, a second inner magnet 32 ​​and a third inner magnet 33 are disposed between the second magnet 22 and the installation cavity 6, and a fourth inner magnet 34 is disposed between the third magnet 23 and the installation cavity 6.

[0062] like Figure 6-7 As shown, the first magnet 21 and the second magnet 22 have a through hole 201 at their centers, and the third magnet 23 has a through hole 201 at its center (not shown). Both the first through hole 201 and the second through hole are connected to the connecting cavity 11.

[0063] The first inner magnet 31, the second inner magnet 32, and the third inner magnet 33 are sequentially arranged in the first through hole 201 along the axial direction of the outer shell 1. The fourth inner magnet 34 is arranged in the second through hole, with the end of the fourth inner magnet 34 away from the connecting cavity 11 abutting against the fourth magnet 24. The first inner magnet 31, the second inner magnet 32, the third inner magnet 33, and the fourth inner magnet 34 are all coaxially arranged with the outer shell 1. The first magnet 21, the second magnet 22, the fourth magnet 24, the second inner magnet 32, and the fourth inner magnet 34 are radially magnetized, while the third magnet 23, the first inner magnet 31, and the third inner magnet 33 are axially magnetized.

[0064] In one embodiment, the first inner magnet 31, the second inner magnet 32, the third inner magnet 33, and the fourth inner magnet 34 are all annular magnets with a through hole 301 at their center. The through hole 301 is connected to and coaxially arranged with the connecting cavity 11, and a traveling wave tube is installed through the through hole 301. The through hole 301 is coaxial with the first through hole 201 and the second through hole. The first inner magnet 31, the second inner magnet 32, and the third inner magnet 33 occupy the outer edge of the first through hole 201, and the fourth inner magnet 34 occupies the outer edge of the second through hole. The overlapping portion of the centers of the first through hole 201, the second through hole, and the through hole 301 together constitutes the mounting cavity 6.

[0065] In one specific embodiment, the fourth magnet 24 has a third through hole 202 extending along the axial direction of the outer shell 1 at its center. The third through hole 202 communicates with the through hole 301 of the fourth inner magnet 34, and the inner diameter of the third through hole 202 is equal to the inner diameter of the through hole 301. The third through hole 202 and the through hole 301 are coaxially arranged. The third through hole 202 and the connecting cavity 11 are both part of the mounting cavity 6. Specifically, the mounting cavity 6 is composed of the first through hole 201, the portion of the second through hole that overlaps with the through hole 301, the connecting cavity 11, and the third through hole 202.

[0066] In one embodiment, such as Figure 8As shown, the first magnet 21, the second magnet 22, and the second inner magnet 32 ​​are magnetized in the same direction, radially inward, with the inner end being the N pole and the outer end being the S pole. The fourth magnet 24 and the fourth inner magnet 34 are magnetized in the same direction, radially outward, with the inner end being the S pole and the outer end being the N pole. The third magnet 23 and the third inner magnet 33 are magnetized in the same direction, axially to the left, with the end closer to the fourth magnet 24 being the S pole and the end closer to the first magnet 21 being the N pole. The first inner magnet 31 is magnetized axially to the right, with the end closer to the second inner magnet 32 ​​being the N pole and the end farther from the second inner magnet 32 ​​being the S pole.

[0067] Among them, such as Figure 9 As shown, the first magnet 21, the second magnet 22, the third magnet 23, the first inner magnet 31, the second inner magnet 32, the third inner magnet 33, and the fourth inner magnet 34 constitute a main magnetic circuit. The magnetic field generated by the main magnetic circuit applies a Lorentz force to the charged particles, controlling their trajectory and achieving the focusing of the electron beam. Figure 10 As shown, the presence of the fourth magnet 24 enables the permanent magnet focusing system to form a secondary magnetic circuit on the basis of the main magnetic circuit, which balances the non-uniformity at the end of the magnetic field, extends the length of the uniform magnetic field region, and enables charged particles to be focused more effectively using magnetic field energy, thereby improving energy utilization. It can also be applied to more application scenarios that require high-precision focusing or long-distance transmission of charged particles.

[0068] In one specific embodiment, the first magnet 21, the second magnet 22, the third magnet 23, and the fourth magnet 24 are all composed of multiple magnetic blocks assembled together. The first inner magnet 31, the second inner magnet 32, the third inner magnet 33, and the fourth inner magnet 34 can be assembled together or manufactured as a single ring structure magnet. Specifically, the first magnet 21, the fourth magnet 24, and the first inner magnet 31 are all ring structures, while the second magnet 22 and the third magnet 23 are both frustum structures. Figure 6 The diagram shows the splicing structure of the first magnet 21. The splicing structure of the fourth magnet 24 and the first inner magnet 31 is similar to that of the first magnet 21. Figure 7 A schematic diagram of the splicing structure of the second magnet 22 is shown. The splicing structure of the third magnet 23 is similar to that of the second magnet 22. In this embodiment, the first magnet 21, the second magnet 22, the third magnet 23, and the fourth magnet 24 are large ring magnets, and the overall firing process is complex, so they are assembled from multiple magnetic blocks. The first inner magnet 31, the second inner magnet 32, the third inner magnet 33, and the fourth inner magnet 34 are small ring magnets, which can be processed as a single unit without the need for splicing magnetic blocks. This ensures consistent magnetic declination, increases accuracy, and reduces time costs.

[0069] During the assembly of the permanent magnet focusing system, the first magnet 21, the second magnet 22, the third magnet 23, and the fourth magnet 24 attract each other to the outer shell 1. The outer walls of the first magnet 21, the second magnet 22, the third magnet 23, and the fourth magnet 24 are bonded and fixed to the inner wall of the outer shell 1 using adhesive. Furthermore, the first magnet 21 and the second magnet 22, the third magnet 23, and the fourth magnet 24 are bonded and fixed to each other using adhesive. The first inner magnet 31, the second inner magnet 32, and the third inner magnet 33 are bonded and fixed within the first through hole 201 using adhesive, and are bonded and connected to each other. The fourth inner magnet 34 is bonded and fixed within the second through hole using adhesive.

[0070] In one embodiment, such as Figure 5 As shown, the inner diameter of the connecting cavity 11 is smaller than the inner diameters of the first inner cavity 12 and the second inner cavity 13. The ends of the first inner cavity 12 and the second inner cavity 13 near the connecting cavity 11 have a conical structure. The edges of the first inner cavity 12 and the third inner cavity 13 near the connecting cavity 11 gradually taper and transition to the connecting cavity 11. The outer shell 1 as a whole has a dumbbell-like structure, characterized by being large at both ends and small in the middle. (Comparison) Figure 3 and Figure 11 The conical transition between the first inner cavity 12, the second inner cavity 13, and the connecting cavity 11 expands the installation space of the power transmission circuit, which is more conducive to the installation and precise adjustment of the power transmission circuit. It also shortens the length of the external power transmission waveguide 8 when installing the power transmission circuit. The existing required length is at least 8cm, while the permanent magnet focusing system provided in this application only requires the length a of the external power transmission waveguide 8 of the power transmission circuit to reach 3cm when connected to the power transmission circuit, which greatly reduces the power transmission loss of the high-frequency traveling wave tube.

[0071] In one embodiment, such as Figure 4 As shown, the permanent magnet focusing system also includes a soft iron 4, which is 2mm thick. The soft iron 4 is installed on the inner wall of the mounting cavity and is attracted and connected to each magnet to suppress fluctuations in the transverse magnetic field. Figure 13 The magnetic induction intensity B of the transverse magnetic field is shown when there is soft iron 4 in the mounting cavity. x The impact, from Figure 13 As can be seen from this, without the soft iron 4 installed, the magnetic induction intensity B of the transverse magnetic field is... x Approximately 100 Gs; when soft iron 4 is installed, the magnetic induction intensity B of the transverse magnetic field x It drops rapidly, with an average value of about 50Gs.

[0072] In one embodiment, the permanent magnet focusing system further includes a first cover plate 14 and a second cover plate 15. The first cover plate 14 covers the end of the first inner cavity 12 away from the connecting cavity 11 and is fixed by screws. The first cover plate 14 and the end face of the first magnet 21 away from the second magnet 22 abut against each other. The second cover plate 15 covers the end of the second inner cavity 13 away from the connecting cavity 11 and is fixed by screws. The end face of the fourth magnet 24 away from the third magnet 23 abuts against each other. In this embodiment, the first cover plate 14 and the second cover plate 15 are made of aluminum alloy.

[0073] In one embodiment, the first magnet 21, the second magnet 22, the third magnet 23, the fourth magnet 24, and the first inner magnet 31 are made of N52H neodymium iron boron with a remanence Br range of 1.43-1.48T. The second inner magnet 32, the third inner magnet 33, and the fourth inner magnet 34 are made of N42H neodymium iron boron with a remanence Br range of 1.28-1.32T.

[0074] Figure 12 The magnetic field distribution at the central axis of the permanent magnet focusing system is shown. Because the magnetization directions of the second magnet 22, the first inner magnet 31, and the third inner magnet 33 all point towards the second inner magnet 32, the second inner magnet 32 ​​generates a strong magnetic focusing effect, significantly shortening the length of the lifting zone to 14.25 mm. Due to the gap between the third inner magnet 33 and the fourth inner magnet 34 (i.e., the connecting cavity 11 portion), the axial magnetic field B... z The magnetic field intensity decreases slightly at z=0, but the uniform magnetic field region still maintains a magnetic flux density above 0.954 Tesla. Due to the different remanence of the fourth magnet 24 and the fourth inner magnet 34, the magnetic flux density at the end of the uniform magnetic field region does not decrease rapidly, effectively extending the length of the uniform magnetic field region to 45.6 mm. The longest length of the uniform magnetic field region in existing focusing systems is generally between 22-30 mm. Compared to existing technologies, this effectively extends the length of the uniform magnetic field region, allowing charged particles to utilize magnetic field energy more effectively for focusing, improving energy utilization, and making it suitable for more applications requiring high-precision focusing or long-distance transmission of charged particles. The figure shows that the peak magnetic flux density of the uniform magnetic field region is 1.023 Tesla, the maximum waveguide is 690 Gs, and the uniformity is ≤±3.49%, where uniformity = ±(maximum magnetic flux density - minimum magnetic flux density) / average magnetic flux density / 2 * 100%.

[0075] In one embodiment, such as Figure 4As shown, an annular support 5 is disposed within the connecting cavity 11. Both ends of the annular support 5 abut against the ends of the third inner magnet 33 and the fourth inner magnet 34 closest to each other, respectively. The annular support 5 is arranged around the periphery of the mounting cavity 6, and the traveling wave tube passes through the annular support 5 during installation. The annular support 5 serves to support the third inner magnet 33 and the fourth inner magnet 34, ensuring the stability of the permanent magnet focusing system structure.

[0076] The advantages of the permanent magnet focusing system for traveling wave tubes provided in the embodiments of the present invention will be explained below with reference to examples:

[0077] Example 1

[0078] The permanent magnet focusing system provided in the above embodiments has the following magnetization direction: Figure 8 As shown.

[0079] The first magnet 21, the second magnet 22, the third magnet 23, the fourth magnet 24, and the first inner magnet 31 are made of N52H neodymium iron boron with a remanence Br = 1.45 Tesla and a coercivity H. cb ≥1059kA / m, intrinsic coercivity H cj =1353kA / m, maximum magnetic energy product (BH) max =398-422kJ / m 3 .

[0080] The second inner magnet 32, the third inner magnet 33, and the fourth inner magnet 34 are made of N42H neodymium iron boron with a remanence Br = 1.3 Tesla and a coercivity H. cb ≥955kA / m, intrinsic coercivity H cj =1353kA / m, maximum magnetic energy product (BH) max =318-342kJ / m 3 .

[0081] The magnetic field distribution along its central axis is as follows Figure 12 As shown, the magnetic induction intensity B in the uniform region z =0.954-1.023Tesla, uniform zone length 45.6mm, lifting zone distance 14.25mm, uniformity of magnetic induction intensity in the uniform zone ≤±3.49%. Outer length ≤15cm, outer diameter ≤15cm, total weight ≤12kg, operating temperature Temp=0-60℃.

[0082] Example 2

[0083] Compared to Embodiment 1, the first cover plate 14 and the second cover plate 15 are made of pure iron, the axial length of the second inner magnet 32 ​​is increased, the axial length of the third inner magnet 33 is shortened, and the magnetization direction is as follows: Figure 14 As shown.

[0084] The first magnet 21, the second magnet 22, the third magnet 23, the fourth magnet 24, and the first inner magnet 31 are made of N52H neodymium iron boron with a remanence Br = 1.45 Tesla and a coercivity H. cb ≥1059kA / m, intrinsic coercivity H cj =1353kA / m, maximum magnetic energy product (BH) max =398-422kJ / m 3 .

[0085] The second inner magnet 32, the third inner magnet 33, and the fourth inner magnet 34 are made of N38H neodymium iron boron with a remanence Br = 1.2Tesla and a coercivity H. cb ≥899kA / m, intrinsic coercivity H cj =1353kA / m, maximum magnetic energy product (BH) max =287-310kJ / m 3 .

[0086] The magnetic field distribution along its central axis is as follows Figure 15 As shown, the magnetic induction intensity B in the uniform region z =0.843-0.915Tesla, uniform zone length 48.4mm, lifting zone distance 14.4mm, uniformity of magnetic induction intensity in the uniform zone ≤±4.09%. Outer length ≤14cm, outer diameter ≤14cm, total weight ≤14kg, operating temperature Temp=0-60℃.

[0087] As can be seen from the results of Examples 1 and 2, the permanent magnet focusing system for traveling wave tubes provided by the embodiments of the present invention has a significant effect on the extension of the uniform region, and has the characteristics of small size and light weight.

[0088] The permanent magnet focusing system for traveling wave tubes provided in this invention effectively extends the uniform magnetic field region through a specific arrangement of the magnets and their magnetization direction. This allows charged particles to be focused more effectively using magnetic field energy, improving energy utilization and making it suitable for more applications requiring high-precision focusing or long-distance transmission of charged particles. Furthermore, the structure of the permanent magnet focusing system is optimized, adopting a dumbbell-like shape with larger ends and a smaller middle, expanding the installation space for the power transmission circuit. This facilitates the installation and precise adjustment of the power transmission circuit and shortens the length of the external power transmission waveguide during installation, significantly reducing power loss in the high-frequency traveling wave tube. Additionally, it effectively reduces transverse magnetic field fluctuations, improving electron beam focusing efficiency.

[0089] 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 permanent magnet focusing system for a traveling wave tube, characterized in that, include: The outer casing includes a connecting cavity, and a first inner cavity and a second inner cavity located at both ends of the connecting cavity; A first magnet, a second magnet, a first inner magnet, a second inner magnet, and a third inner magnet are located within the first inner cavity; as well as The third magnet, the fourth magnet, and the fourth inner magnet are located within the second inner cavity; The first magnet, the second magnet, the third magnet and the fourth magnet are arranged sequentially along the axial direction of the outer shell. The first magnet is located on the side of the second magnet away from the connecting cavity, and the fourth magnet is located on the side of the third magnet away from the connecting cavity. The first magnet and the second magnet have a through hole at their center, and the third magnet has a through hole at its center. Both the first hole and the second hole are connected to the connecting cavity. The first inner magnet, the second inner magnet, and the third inner magnet are sequentially disposed in the first through hole along the axial direction of the outer shell, and the fourth inner magnet is disposed in the second through hole, with one end away from the connecting cavity abutting against the fourth magnet; The first magnet, the second magnet, the fourth magnet, the second inner magnet, and the fourth inner magnet are radially magnetized, and the third magnet, the first inner magnet, and the third inner magnet are axially magnetized.

2. The permanent magnet focusing system for traveling wave tubes according to claim 1, characterized in that, The first, second, third, and fourth inner magnets are all annular magnets with a through hole in the center, and the through hole is connected to the connecting cavity.

3. The permanent magnet focusing system for traveling wave tubes according to claim 2, characterized in that, The fourth magnet has a third through hole extending along the axial direction of the outer shell at its center. The third through hole is connected to the through hole of the fourth inner magnet, and the inner diameter of the third through hole is equal to the inner diameter of the through hole. The through holes of the first inner magnet, the second inner magnet, the third inner magnet, and the fourth inner magnet, the third through hole, and the connecting cavity are connected to form a mounting cavity for the insertion of the traveling wave tube.

4. The permanent magnet focusing system for traveling wave tubes according to claim 3, characterized in that, The first magnet, the second magnet, and the second inner magnet are magnetized in the same direction, with their inner ends being N poles and their outer ends being S poles; The fourth magnet and the fourth inner magnet are magnetized in the same direction, with their inner ends being S poles and their outer ends being N poles; The third magnet and the third inner magnet are magnetized in the same direction, with the end closer to the fourth magnet being the S pole and the end closer to the first magnet being the N pole. The end of the first inner magnet closer to the second inner magnet is the N pole, and the end farther away from the second inner magnet is the S pole.

5. The permanent magnet focusing system for a traveling wave tube according to claim 1, characterized in that, The first magnet, the second magnet, the third magnet, and the fourth magnet are all composed of multiple magnetic blocks. The first and fourth magnets are circular ring structures, and the second and third magnets are frustum structures. The outer wall surfaces of the first, second, third, and fourth magnets are bonded and fixed to the inner wall surface of the outer shell.

6. The permanent magnet focusing system for a traveling wave tube according to claim 1, characterized in that, The inner diameter of the connecting cavity is smaller than the inner diameters of the first inner cavity and the second inner cavity. The ends of the first inner cavity and the second inner cavity near the connecting cavity have a conical structure. The ends of the first inner cavity and the second inner cavity near the connecting cavity gradually converge and transition to the connecting cavity.

7. The permanent magnet focusing system for a traveling wave tube according to claim 3, characterized in that, The permanent magnet focusing system also includes a soft iron, which is installed on the inner wall of the mounting cavity.

8. The permanent magnet focusing system for traveling wave tubes according to claim 1, characterized in that, The permanent magnet focusing system further includes a first cover plate and a second cover plate. The first cover plate covers the end of the first inner cavity away from the connecting cavity and abuts against the end of the first magnet away from the second magnet. The second cover plate covers the end of the second inner cavity away from the connecting cavity and abuts against the end of the fourth magnet away from the third magnet.

9. The permanent magnet focusing system for a traveling wave tube according to claim 1, characterized in that, The first magnet, the second magnet, the third magnet, the fourth magnet and the first inner magnet are made of N52H neodymium iron boron with a remanence Br range of 1.43-1.48T; The second, third, and fourth inner magnets are made of N42H neodymium iron boron with a remanence Br range of 1.28-1.32T.

10. The permanent magnet focusing system for a traveling wave tube according to claim 3, characterized in that, An annular support is provided inside the connecting cavity. The two ends of the annular support abut against the ends of the third inner magnet and the fourth inner magnet that are close to each other, respectively, and the annular support is arranged around the periphery of the mounting cavity.

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