Permanent magnet focusing system for traveling wave tube

Abstract

The invention discloses a permanent magnet focusing system for a traveling wave tube, and the system comprises a housing which comprises a connecting cavity, a first inner cavity, and a second inner cavity. The first magnet, the second magnet, the first inner magnet, the second inner magnet and the third inner magnet are located in the first inner cavity; the third magnet, the fourth magnet and the fourth inner magnet are located in the second inner cavity; a first through hole is formed in the center of the first magnet and the center of the second magnet, a second through hole is formed in the center of the third magnet, and the first through hole and the second through hole communicate 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 magnetized in the radial direction, and the third magnet, the first inner magnet and the third inner magnet are magnetized in the axial direction. Through the specific arrangement of the magnets and the combination of the magnetizing direction, a magnetic field uniform area is effectively prolonged, and the energy utilization rate can be improved.

Description

Technical Field

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

[0002] As a vacuum electronic device, the traveling wave tube has a wide range of applications in detection, imaging, communication and other fields. The high-frequency traveling wave tube has the characteristics of small size and light weight. Compared with the microwave frequency traveling wave tube, it is easier to install in the installation cavity 6 of the focusing system (such as Figure 1 The function of the focusing system is to use the magnetic field force generated to offset the space charge repulsion force generated by the electron beam itself, and to constrain the electron beam so that it can pass through the traveling wave tube smoothly without defocusing and interception.

[0003] In high-frequency traveling wave tubes, electron beams have the characteristics of small cross-sectional dimensions and high charge density, and conventional magnetic focusing systems are difficult to meet the focusing requirements. For example, the average magnetic field of periodic permanent magnets is low, and the peak magnetic field is difficult to reach 7000Gs; although the magnetic field strength of coil magnets is high, they are large in size and weight, and require a water cooling system, which is not conducive to use in airborne and vehicle-mounted environments. Summary of the invention

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

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

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

[0007] A shell, the shell comprising a connecting cavity, and a first inner cavity and a second inner cavity respectively located at two ends of the connecting cavity;

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

[0009] a third magnet, a fourth magnet and a fourth inner magnet located in the second inner cavity;

[0010] The first magnet, the second magnet, the third magnet and the fourth magnet are arranged in sequence along the axial direction of the 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] A first through hole is formed at the center of the first magnet and the second magnet, a second through hole is formed at the center of the third magnet, and both the first through hole and the second through hole are connected to the connection cavity;

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

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

[0014] In addition, an optional solution is that the first inner magnet, the second inner magnet, the third inner magnet and the fourth inner magnet are all annular magnets with a through hole in the center, and the through hole is connected to the connecting cavity.

[0015] In addition, an optional solution is that a third through hole extending along the axial direction of the shell is opened at the center of the fourth magnet, 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, the fourth inner magnet, the third through hole and the connecting cavity are connected to form an installation cavity for inserting the traveling wave tube.

[0017] In addition, an optional solution is that the first magnet, the second magnet and the second inner magnet have the same magnetization direction, the inner end thereof is an N pole and the outer end thereof is an S pole;

[0018] The fourth magnet and the fourth inner magnet have the same magnetization direction, the inner end thereof is an S pole and the outer end thereof is an N pole;

[0019] The magnetization directions of the third magnet and the third inner magnet are the same, the end close to the fourth magnet is the S pole, and the end close to the first magnet is the N pole;

[0020] An end of the first inner magnet close to the second inner magnet is an N pole, and an end of the first inner magnet away from the second inner magnet is an S pole.

[0021] In addition, an optional solution is that the first magnet, the second magnet, the third magnet and the fourth magnet are all formed by splicing a plurality of magnetic blocks;

[0022] The first magnet and the fourth magnet are of annular structures, the second magnet and the third magnet are of truncated cone structures, and the outer wall surfaces of the first magnet, the second magnet, the third magnet and the fourth magnet are bonded and fixed to the inner wall surface of the shell.

[0023] In addition, an optional solution is that the inner diameter of the connecting cavity is smaller than the inner diameters of the first cavity and the second cavity, the first cavity and the second cavity have a conical structure at one end close to the connecting cavity, and the first cavity and the second cavity gradually converge and transition to the connecting cavity at one end close to the connecting cavity.

[0024] In addition, an optional solution is that the permanent magnet focusing system also includes soft iron, and the soft iron is installed on the inner wall surface of the installation cavity.

[0025] In addition, an optional solution is that the permanent magnet focusing system further includes a first cover plate and a second cover plate, wherein the first cover plate covers an end of the first inner cavity away from the connecting cavity and abuts against an end of the first magnet away from the second magnet;

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

[0027] In addition, an optional solution is 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;

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

[0029] In addition, an optional solution is that an annular support is disposed in the connecting cavity, both ends of the annular support are respectively abutted against one end of the third inner magnet and the fourth inner magnet close to each other, and the annular support is arranged around the periphery of the installation cavity.

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

[0031] In view of the technical problems existing in the prior art, the present invention provides a permanent magnet focusing system for a traveling wave tube. Through the specific arrangement of each magnet and the magnetization direction of each magnet, the uniform magnetic field area is effectively extended, so that charged particles can more effectively use the magnetic field energy for focusing, improve energy utilization, and can also be applied to more application scenarios that require high-precision focusing or long-distance transmission of charged particles. In addition, the structure of the permanent magnet focusing system is optimized and designed, and the overall structure is shaped like a dumbbell, with the characteristics of large ends and small middle, which expands the installation space of the energy transmission circuit, is more conducive to the installation and precise adjustment of the energy transmission circuit, meets the requirements of miniaturized design, and shortens the length of the external energy transmission waveguide when the energy transmission circuit is installed, greatly reducing the energy transmission loss of the high-frequency traveling wave tube; in addition, it can effectively reduce the fluctuation of the transverse magnetic field and improve the efficiency of electron beam focusing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

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

[0034] Figure 2A schematic diagram of splicing annular magnet units in the prior art is shown.

[0035] Figure 3 A schematic diagram showing the installation of an energy transmission circuit in an existing focusing system.

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

[0037] Figure 5 A schematic structural diagram of a housing provided by an embodiment of the present invention is shown.

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

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

[0040] Figure 8 A schematic diagram showing the arrangement of magnets of the permanent magnet focusing system provided in an embodiment of the present invention is shown.

[0041] Fig. 9 A schematic diagram showing the main magnetic circuit.

[0042] Fig.10 A schematic diagram showing the auxiliary magnetic circuit.

[0043] Fig.11 A schematic diagram showing an energy transmission circuit installed in a focusing system provided by an embodiment of the present invention.

[0044] Fig.12 The central axis magnetic field distribution diagram of the permanent magnet focusing system provided in Example 1 is shown.

[0045] Fig.13 The figure shows the distribution of the transverse magnetic field of the permanent magnet focusing system when soft iron is installed and when soft iron is not installed.

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

[0047] Fig.15 The central axis magnetic field distribution diagram of the permanent magnet focusing system provided in Example 2 is shown. DETAILED DESCRIPTION

[0048] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0049] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] In the present invention, unless otherwise clearly stipulated and limited, a first feature being “on” or “under” a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them.

[0051] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0052] At present, there are few types of focusing systems that can be used for high-frequency traveling wave tube electron beam focusing. Among them, the hollow cylindrical rare earth permanent magnet structure is more common. This type of focusing system has the advantages of a small number of magnet units, simple magnetization direction arrangement, high permanent magnet utilization rate, and small volume and weight. It can solve the problem of difficulty in focusing high-frequency traveling wave tube electron beams to a certain extent. However, there are still the following three problems in the process of use:

[0053] 1. The magnetic circuit of this type of focusing system is usually composed of two large annular magnet units 7 (such as Figure 1 As shown in the middle left figure, due to the large size of the annular magnet unit 7, it is difficult to ensure the magnetization orientation during the pressing process, and a method of splicing small magnetic blocks is usually used as an alternative, such as Figure 1 Right picture and Figure 2 The splicing method in the embodiment uses 18 small-volume magnetic blocks 70. Since each small-volume magnetic block 70 is magnetized independently, it is difficult to ensure that the magnetic declination angle is completely consistent, and additional pairing tests and selection are required; in addition, 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 uneven splicing may seriously affect the transverse magnetic field (X and Y directions) in the area 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 30 mm, and there is a problem of insufficient length of the magnetic field uniformity zone when it is used.

[0055] 3. When this type of focusing system is used with a high-frequency traveling wave tube, there are problems such as the external energy transmission circuit being too long and the circuit assembly space being too small. Figure 3 The distance L between the two large annular magnetic units 7 is 20 mm. When installing a waveguide energy transmission circuit with a flange, the length a of the waveguide 8 should be at least 8 cm, which seriously increases the energy transmission loss of the high-frequency traveling wave tube circuit and requires the assembly operation of the waveguide energy transmission circuit to be carried out in a narrow space, which is not conducive to precise adjustment.

[0056] In view of the defects of the prior art, the present invention provides a permanent magnet focusing system for a traveling wave tube, Figure 4-15 As shown, the permanent magnet focusing system includes a shell 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 in the shell 1.

[0057] The housing 1 includes a connecting cavity 11 and a first inner cavity 12 and a second inner cavity 13 respectively located at two 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 in 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 shell 1, and are arranged coaxially with the 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 area 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 in the lifting area; the connecting cavity 11 and the second inner cavity 13 correspond to the uniform area of ​​the permanent magnet focusing system, and the third magnet 23, the fourth magnet 24 and the fourth inner magnet 34 are in the uniform area.

[0061] An installation cavity 6 for installing the traveling wave tube is formed in the shell, and the installation cavity 6 is extended along the axial direction of the shell and is coaxial with the shell. The first magnet 21, the second magnet 22, the third magnet 23 and the fourth magnet 24 are respectively arranged around the periphery of the installation cavity 6. The first inner magnet 31 is arranged between the first magnet 21 and the installation cavity 6, the second inner magnet 32 ​​and the third inner magnet 33 are arranged between the second magnet 22 and the installation cavity 6, and the fourth inner magnet 34 is arranged between the third magnet 23 and the installation cavity 6.

[0062] like Figure 6-7 As shown, a first through hole 201 is formed in the center of the first magnet 21 and the second magnet 22 , and a second through hole (not shown) is formed in the center of the third magnet 23 . 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 housing 1, and the fourth inner magnet 34 is arranged in the second through hole, and the end of the fourth inner magnet 34 away from the connecting cavity 11 abuts 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 arranged coaxially with the housing 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 magnetized radially, and the third magnet 23, the first inner magnet 31 and the third inner magnet 33 are magnetized axially.

[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 in the center, the through hole 301 is connected and coaxially arranged with the connecting cavity 11, and the traveling wave tube is installed in 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, the fourth inner magnet 34 occupies the outer edge of the second through hole, and the first through hole 201 and the second through hole and the central overlapping part of the through hole 301 together constitute the installation cavity 6.

[0065] In a specific embodiment, a third through hole 202 extending along the axial direction of the housing 1 is provided at the center of the fourth magnet 24, the third through hole 202 is connected to 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, and 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 and the part where the second through hole and the through hole 301 overlap, the connecting cavity 11, and the third through hole 202.

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

[0067] Among them, Fig. 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 exerts a Lorentz force on the charged particles, controls their motion trajectory, and realizes the focusing of the electron beam. Fig.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, balancing the unevenness at the end of the magnetic field, extending the length of the magnetic field uniform zone, and enabling charged particles to more effectively utilize the magnetic field energy for focusing, thereby improving energy utilization and being applicable to more application scenarios that require high-precision focusing or long-distance transmission of charged particles.

[0068] In a specific embodiment, the first magnet 21, the second magnet 22, the third magnet 23 and the fourth magnet 24 are all made of a plurality of magnetic blocks, and the first inner magnet 31, the second inner magnet 32, the third inner magnet 33 and the fourth inner magnet 34 can be made by splicing or by using a ring structure magnet made of a whole ring. Among them, the first magnet 21, the fourth magnet 24 and the first inner magnet 31 are all ring structures, and the second magnet 22 and the third magnet 23 are all truncated cone structures. Figure 6 A schematic diagram of the splicing structure of the first magnet 21 is shown, and 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 The schematic diagram of the splicing structure of the second magnet 22 is shown, and 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 annular magnets, and the overall firing process is complicated, so they are spliced ​​by 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 annular magnets, which can be processed in an integrated manner without the need for splicing of magnetic blocks, which can ensure the consistency of magnetic declination, increase accuracy, and reduce time costs.

[0069] When the permanent magnet focusing system is assembled, the first magnet 21, the second magnet 22, the third magnet 23 and the fourth magnet 24 and the housing 1 attract each other, and the outer wall surface of the first magnet 21, the second magnet 22, the third magnet 23 and the fourth magnet 24 and the inner wall surface of the housing 1 are bonded and fixed by adhesive, and the first magnet 21 and the second magnet 22, the third magnet 23 and the fourth magnet 24 are bonded and fixed by adhesive respectively. The first inner magnet 31, the second inner magnet 32 ​​and the third inner magnet 33 are bonded and fixed in the first through hole 201 by adhesive, and are bonded and connected to each other. The fourth inner magnet 34 is bonded and fixed in the second through hole by adhesive.

[0070] In one embodiment, Figure 5 As shown, the inner diameter of the connecting cavity 11 is smaller than the inner diameters of the first cavity 12 and the second cavity 13. The first cavity 12 and the second cavity 13 are tapered at one end close to the connecting cavity 11. The edges of the first cavity 12 and the third cavity 13 are gradually converged to the connecting cavity 11. The housing 1 is shaped like a dumbbell, with large ends and a small middle. Figure 3 and Fig.11 The conical transition between the first inner cavity 12 and the second inner cavity 13 and the connecting cavity 11 expands the installation space of the energy transmission circuit, is more conducive to the installation and precise adjustment of the energy transmission circuit, and shortens the length of the external energy transmission waveguide 8 when the energy transmission circuit is installed. The existing required length is at least 8 cm. When the permanent magnet focusing system provided in the present application is connected to the energy transmission circuit, it only requires the length a of the external energy transmission waveguide 8 of the energy transmission circuit to reach 3 cm to realize the installation of the energy transmission circuit in the permanent magnet focusing system, which greatly reduces the energy transmission loss of the high-frequency traveling wave tube.

[0071] In one embodiment, Figure 4 As shown, the permanent magnet focusing system further includes a soft iron 4, and the thickness of the soft iron 4 is 2 mm. The soft iron 4 is installed on the inner wall surface of the installation cavity and is adsorbed and connected with each magnet to suppress the fluctuation of the transverse magnetic field. Fig.13 The figure shows the magnetic induction intensity B of the transverse magnetic field when there is or is not soft iron 4 in the installation cavity. x The impact of Fig.13 It can be seen that when the soft iron 4 is not installed, the magnetic induction intensity B of the transverse magnetic field x About 100Gs; after installing the soft iron 4, the magnetic induction intensity of the transverse magnetic field is B 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 one end of the first inner cavity 12 away from the connecting cavity 11 and is assembled and fixed by screws. The first cover plate 14 and one end surface of the first magnet 21 away from the second magnet 22 abut against each other. The second cover plate 15 covers one end of the second inner cavity 13 away from the connecting cavity 11 and is assembled and fixed by screws. One end surface 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 1.43-1.48 T. 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 1.28-1.32 T.

[0074] Fig.12 The magnetic field distribution at the central axis of the permanent magnet focusing system is shown. Since the magnetization directions of the second magnet 22, the first inner magnet 31 and the third inner magnet 33 all point to the second inner magnet 32, the second inner magnet 32 ​​produces a strong magnetic field focusing effect, which greatly shortens the length of the lifting area to 14.25 mm. Since there is a gap between the third inner magnet 33 and the fourth inner magnet 34 (i.e., the part connecting the cavity 11), the axial magnetic field B z It drops slightly at z=0, but the magnetic field uniformity zone still maintains a magnetic induction intensity of more than 0.954 Tesla. Due to the different remanence of the fourth magnet 24 and the fourth inner magnet 34, the magnetic induction intensity at the end of the magnetic field uniformity zone will not drop rapidly, which in turn extends the length of the magnetic field uniformity zone to 45.6 mm. The length of the magnetic field uniformity zone of the existing focusing system is generally between 22-30 mm. Compared with the existing technology, the length of the magnetic field uniformity zone is effectively extended, so that charged particles can more effectively use the magnetic field energy for focusing, improve energy utilization, and can also be applied to more application scenarios that require high-precision focusing or long-distance transmission of charged particles. It can be seen from the figure that the peak value of the magnetic induction intensity in the magnetic field uniformity zone is 1.023 Tesla, the maximum waveguide is 690Gs, and the uniformity is ≤±3.49%, where the uniformity = ±(maximum magnetic induction intensity-minimum magnetic induction intensity) / average magnetic induction intensity / 2*100%.

[0075] In one embodiment, Figure 4As shown, an annular support member 5 is disposed in the connecting cavity 11, and both ends of the annular support member 5 are respectively in contact with one end of the third inner magnet 33 and the fourth inner magnet 34 close to each other, and the annular support member 5 is arranged around the periphery of the installation cavity 6, and the traveling wave tube passes through the annular support member 5 when being installed. The annular support member 5 plays a role in supporting the third inner magnet 33 and the fourth inner magnet 34, and can ensure the stability of the permanent magnet focusing system structure.

[0076] The advantages of the permanent magnet focusing system for a traveling wave tube provided by the embodiment of the present invention will be described below with reference to examples:

[0077] Example 1

[0078] The permanent magnet focusing system provided in the above embodiment has a magnetizing direction such as Figure 8 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 coercive force 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 coercive force H cb ≥955kA / m, intrinsic coercivity H cj =1353kA / m, maximum magnetic energy product (BH) max =318-342kJ / m 3 .

[0081] The central axial magnetic field distribution is as follows Fig.12 As shown, the magnetic induction intensity B in the uniform area z =0.954-1.023 Tesla, uniform zone length 45.6 mm, lifting zone distance 14.25 mm, uniformity of magnetic induction intensity in uniform zone ≤±3.49%. Overall length ≤15 cm, overall diameter ≤15 cm, total weight ≤12 kg, working temperature Temp=0-60℃.

[0082] Example 2

[0083] Compared with Example 1, the materials of the first cover plate 14 and the second cover plate 15 are 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: Fig.14 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 coercive force 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=1.2 Tesla and a coercive force H cb ≥899kA / m, intrinsic coercivity H cj =1353kA / m, maximum magnetic energy product (BH) max =287-310kJ / m 3 .

[0086] The central axial magnetic field distribution is as follows Fig.15 As shown, the magnetic induction intensity B in the uniform area z =0.843-0.915 Tesla, uniform zone length 48.4 mm, lifting zone distance 14.4 mm, uniformity of magnetic induction intensity in uniform zone ≤±4.09%. Overall length ≤14 cm, overall diameter ≤14 cm, total weight ≤14 kg, working temperature Temp=0-60℃.

[0087] According to the results of Example 1 and Example 2, it can be seen that the permanent magnet focusing system for a traveling wave tube provided by the embodiment of the present invention has a significant effect in extending the uniform zone, and has the characteristics of small size and light weight.

[0088] The permanent magnet focusing system for a traveling wave tube provided in the embodiment of the present invention effectively extends the uniform magnetic field area through the specific arrangement of each magnet combined with the magnetization direction of each magnet, so that charged particles can more effectively use the magnetic field energy for focusing, improve energy utilization, and can also be applied to more application scenarios that require high-precision focusing or long-distance transmission of charged particles. In addition, the structure of the permanent magnet focusing system has been optimized and designed, and the overall structure is shaped like a dumbbell, with large ends and a small middle, which expands the installation space of the energy transmission circuit, is more conducive to the installation and precise adjustment of the energy transmission circuit, and shortens the length of the external energy transmission waveguide when the energy transmission circuit is installed, greatly reducing the energy transmission loss of the high-frequency traveling wave tube; in addition, it can effectively reduce the fluctuation of the transverse magnetic field and improve the efficiency of electron beam focusing.

[0089] 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 permanent magnet focusing system for a traveling wave tube, characterized in that: include: A shell, the shell comprising a connecting cavity, and a first inner cavity and a second inner cavity respectively located at two ends of the connecting cavity; a first magnet, a second magnet, a first inner magnet, a second inner magnet, and a third inner magnet located within the first inner cavity; as well as a third magnet, a fourth magnet and a fourth inner magnet located in the second inner cavity; The first magnet, the second magnet, the third magnet and the fourth magnet are arranged in sequence along the axial direction of the 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; A first through hole is formed at the center of the first magnet and the second magnet, a second through hole is formed at the center of the third magnet, and both the first through hole and the second through hole are connected to the connection cavity; The first inner magnet, the second inner magnet and the third inner magnet are sequentially arranged in the first through hole along the axial direction of the shell, and the fourth inner magnet is arranged in the second through hole, and one end away from the connecting cavity abuts against the fourth magnet; The first magnet, the second magnet, the fourth magnet, the second inner magnet and the fourth inner magnet are magnetized radially, and the third magnet, the first inner magnet and the third inner magnet are magnetized axially.

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

3. The permanent magnet focusing system for a traveling wave tube according to claim 2, characterized in that: A third through hole extending along the axial direction of the shell is formed at the center of the fourth magnet, 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, the fourth inner magnet, the third through hole and the connecting cavity are connected to form an installation cavity for inserting the traveling wave tube.

4. The permanent magnet focusing system for a traveling wave tube according to claim 3, characterized in that: The first magnet, the second magnet and the second inner magnet have the same magnetization direction, with the inner end being an N pole and the outer end being an S pole; The fourth magnet and the fourth inner magnet have the same magnetization direction, the inner end thereof is an S pole and the outer end thereof is an N pole; The magnetization directions of the third magnet and the third inner magnet are the same, the end close to the fourth magnet is the S pole, and the end close to the first magnet is the N pole; An end of the first inner magnet close to the second inner magnet is an N pole, and an end of the first inner magnet away from the second inner magnet is an 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 formed by splicing a plurality of magnetic blocks; The first magnet and the fourth magnet are of annular structures, the second magnet and the third magnet are of truncated cone structures, and the outer wall surfaces of the first magnet, the second magnet, the third magnet and the fourth magnet are bonded and fixed to the inner wall surface of the 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 cavity and the second cavity. The ends of the first cavity and the second cavity close to the connecting cavity are conical structures. The ends of the first cavity and the second cavity close to the connecting cavity are gradually converged and transitioned 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 soft iron, which is installed on the inner wall surface of the installation cavity.

8. The permanent magnet focusing system for a traveling wave tube according to claim 1, characterized in that: The permanent magnet focusing system further comprises a first cover plate and a second cover plate, wherein the first cover plate covers an end of the first inner cavity away from the connecting cavity and abuts against an end of the first magnet away from the second magnet; The second cover plate covers one end of the second inner cavity away from the connecting cavity, and abuts against one 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 inner magnet, the third inner magnet and the fourth inner magnet 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 arranged in the connecting cavity, two ends of the annular support are respectively in contact with one end of the third inner magnet and the fourth inner magnet close to each other, and the annular support is arranged around the periphery of the installation cavity.

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