Two-dimensional planar array multichannel periodic permanent magnet focusing system and design method thereof

Abstract

The invention provides a two-dimensional planar array multichannel periodic permanent magnet focusing system and a design method thereof. The periodic permanent magnet focusing system comprises pole shoes and magnetic groups which are arranged at intervals along a first direction, the pole shoes and the magnetic groups are periodically and alternately arranged along a first direction to form a plurality of periodic permanent magnet structures; the magnetic group comprises a plurality of magnetic steels which are arranged at intervals along a second direction; the magnetic steel extends along a third direction; a plurality of through holes arranged in an array are formed in the pole shoe, and the through holes are used for assembling a slow wave structure; the through holes form through hole units, and the through hole units comprise transverse through hole units arranged in the second direction and longitudinal through hole units arranged in the third direction; and the transverse through hole units are located between two adjacent magnetic steels arranged along the second direction. The integration of a plurality of amplification channels is realized in one set of magnetic focusing system, the distance between the amplification channels is reduced, the unit density is improved, and the focusing performance of the magnetic focusing system on electron beams is not influenced.

Description

Technical Field

[0001] The present invention relates to the field of microwave vacuum electronic technology, and more specifically, to a two-dimensional planar array multi-channel periodic permanent magnet focusing system and a design method thereof. Background Art

[0002] The traveling wave tube is a vacuum amplifier device. As the final power amplifier of the radar, it has now put forward clear application requirements in communication radar information confrontation. The focusing system is one of the core components of the traveling wave tube. Its function is to constrain the radial divergence of the electron beam so that the electron beam can be transmitted stably along the axial direction.

[0003] The periodic permanent magnet focusing system is one of the commonly used focusing systems in traveling wave tubes. The principle is to constrain the electron beam through the Lorentz force exerted on the electron beam in the periodically changing magnetic field. Usually, a set of periodic permanent magnet focusing systems can only focus the electron beam in one amplification channel. When a traveling wave tube with such a single-channel periodic permanent magnet focusing system is used for array formation, due to the existence of the magnetic steel fixing structure and the magnetic shielding structure, and in order to prevent mutual interference between units, the spacing between array units usually needs to be larger than the cross-sectional size of the periodic permanent magnet focusing system, resulting in the unit density of the traveling wave tube being limited when the array is formed, which restricts the application of traveling wave tubes in array systems represented by active phased array radars. Summary of the invention

[0004] In response to the above problems, the present invention provides a two-dimensional planar array multi-channel periodic permanent magnet focusing system and a design method thereof, so as to integrate multiple amplification channels in a set of magnetic focusing system, reduce the distance between the amplification channels, and improve the unit density without affecting the focusing performance of the magnetic focusing system on the electron beam.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a two-dimensional planar array multi-channel periodic permanent magnet focusing system, comprising:

[0007] Pole shoes and magnetic groups are arranged at intervals along a first direction; the pole shoes and magnetic groups are periodically and alternately arranged along the first direction to form a plurality of periodic permanent magnetic structures;

[0008] The magnetic group includes a plurality of magnetic steels arranged at intervals along the second direction; the magnetic steels are extended along the third direction;

[0009] The pole shoe is provided with a plurality of through holes arranged in an array, and the through holes are used to assemble a slow-wave structure; the plurality of through holes constitute a through hole unit, and the through hole unit includes a transverse through hole unit arranged along the second direction, and a longitudinal through hole unit arranged along the third direction; the transverse through hole unit is located between two adjacent magnetic steels arranged along the second direction.

[0010] A preferred solution is that the pole shoe includes m×n through holes arranged in a rectangular array, wherein m is the number of columns of through holes in the third direction, n is the number of rows of through holes in the second direction, m>1, n>1.

[0011] The preferred solution is that the width of the pole shoe in the third direction is w p , the height of the pole shoe in the second direction is h p , the through hole diameter is D0;

[0012] A preferred solution is that the distance between two adjacent through holes of the transverse through hole unit in the third direction is d x ,

[0013] The distance between two adjacent through holes in the longitudinal through hole unit in the second direction is d y ,

[0014] A preferred solution is that the magnetic group includes at least three magnetic steels, the two magnetic steels located at the two ends of the magnetic group along the second direction are outer magnetic steels, and the magnetic steel located between the two outer magnetic steels is inner magnetic steel; the outer magnetic steel is located on the outside of the through-hole unit, and the inner magnetic steel is located between two adjacent transverse through-hole units; the widths of the outer magnetic steel and the inner magnetic steel in the third direction and the thicknesses in the first direction are equal; the heights of the outer magnetic steel and the inner magnetic steel in the second direction are equal or unequal.

[0015] The preferred solution is that the width of the magnetic steel in the third direction is w m ;w m ≥d x ×(n-1)+D0;

[0016] The height of the inner magnetic steel in the second direction is h1; 0 y -D0.

[0017] A preferred solution is that the magnets in the same magnetic group have the same magnetization direction, and the magnets in two adjacent magnetic groups have opposite magnetization directions.

[0018] The present invention also provides a design method for a two-dimensional planar array multi-channel periodic permanent magnet focusing system, the design method comprising:

[0019] A plurality of pole shoes and magnetic groups are designed to be periodically arranged along a first direction to form a periodic permanent magnetic structure, wherein the magnetic group includes a plurality of magnetic steels arranged at intervals along a second direction, and the magnetic steels are extended along a third direction;

[0020] ​A plurality of through holes arranged in an array for assembling a slow-wave structure are designed on the pole shoe, and the plurality of through holes constitute a through hole unit, wherein the through hole unit includes a transverse through hole unit arranged along the second direction and a longitudinal through hole unit arranged along the third direction, and the transverse through hole unit is located between two adjacent magnetic steels arranged along the second direction.

[0021] A preferred solution is that the magnetic group includes at least three magnetic steels, the two magnetic steels located at the two ends of the magnetic group along the second direction are outer magnetic steels, and the magnetic steel located between the two outer magnetic steels is inner magnetic steel; the outer magnetic steel is located on the outside of the through-hole unit, and the inner magnetic steel is located between two adjacent transverse through-hole units; the widths of the outer magnetic steel and the inner magnetic steel in the third direction and the thicknesses in the first direction are equal; the heights of the outer magnetic steel and the inner magnetic steel in the second direction are equal or unequal.

[0022] The preferred solution is to adjust the axial magnetic field strength and angular magnetic field emphasis of the periodic permanent magnet focusing system by changing the width of the magnetic steel in the third direction and the height of the external magnetic steel in the second direction, so as to optimize the focusing performance of the periodic permanent magnet focusing system.

[0023] The beneficial effects of the present invention are:

[0024] The present invention can realize the integration of traveling wave tube amplification channel array by integrating multiple channels equipped with slow wave structures into the same focusing system, thereby effectively reducing the unit spacing of the channel, improving the unit density, and adapting to the application requirements of array systems represented by active phased arrays. In addition, the present invention can ensure that the ratio of the angular magnetic field peak to the axial magnetic field peak in the channel of the periodic permanent magnet focusing system is less than 0.5%, so as not to affect the focusing performance of the electron beam. The present invention adjusts the axial magnetic field intensity and angular magnetic field emphasis of the periodic permanent magnet focusing system by changing the width of the magnetic steel in the third direction and the height of the external magnetic steel in the second direction, thereby optimizing the focusing performance of the periodic permanent magnet focusing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0026] Figure 1 It is one of the structural schematic diagrams of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0027] Figure 2 This is the second structural schematic diagram of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0028] Figure 3 This is the third structural schematic diagram of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0029] Figure 4It is a BH characteristic curve diagram of the pole shoe material during the simulation process of the present invention.

[0030] Figure 5 It is a magnetic field intensity distribution diagram of the pole shoe center section of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0031] Figure 6 It is a magnetic field intensity distribution diagram of the central section of the magnetic steel of the two-dimensional planar array multi-channel periodic permanent magnetic focusing system of the present invention.

[0032] Figure 7 It is a distribution diagram of the axial magnetic field intensity along the axial position on the axis of each channel of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0033] Figure 8 It is a distribution diagram of the angular position of the angular magnetic field of each channel at a distance rc from the channel axis on the central section of the pole shoe of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0034] Fig. 9 It is a distribution diagram of the axial magnetic field intensity along the axial position on the axis of channel 3-3 under different magnetic steel widths of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0035] Fig.10 It is a distribution diagram of the angular position of the angular magnetic field at rc from the channel axis of channel 3-3 under different magnetic steel widths on the central section of the pole shoe of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0036] Fig.11 It is a distribution diagram of the axial magnetic field intensity along the axial position on the axis of channel 3-3 at different external magnetic steel heights of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0037] Fig.12 It is a distribution diagram of the angular position of the angular magnetic field at rc from the channel axis of channel 3-3 at different external magnetic steel heights on the central section of the pole shoe of the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention.

[0038] Figure numerals: 1, pole shoe, 21, outer magnetic steel, 22, inner magnetic steel, 3, through hole. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0040] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0041] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0042] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0043] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0044] The periodic permanent magnet focusing system is one of the most commonly used electron beam focusing systems for traveling wave tubes. Compared with electron beam focusing systems such as single permanent magnet focusing and solenoid magnetic field focusing, the periodic permanent magnet focusing system has a smaller size. Normally, a set of periodic permanent magnet focusing systems can only focus one electron beam, which means that a single traveling wave tube can only have one amplification channel. Therefore, when the traveling wave tube is applied to an array system represented by an active phased array radar, the spacing of the amplification channels is usually not less than the cross-sectional size of the traveling wave tube, which limits the unit density when the traveling wave tube is arrayed, and restricts the application of the traveling wave tube in array systems represented by active phased array radars. In addition, in the existing process operation process, due to the inhomogeneity of the magnetic material, if the spacing of the amplification channels is less than the cross-sectional size of the traveling wave tube, different amplification channels will interfere with each other, resulting in poor focusing performance of the magnetic focusing system.

[0045] In order to solve the above problems, the present invention provides a two-dimensional planar array multi-channel periodic permanent magnet focusing system, combined with Figures 1 to 12As shown, specifically, the two-dimensional planar array multi-channel periodic permanent magnet focusing system includes: a pole shoe 1 and a magnetic group arranged at intervals along a first direction z, and the pole shoe 1 and the magnetic group are periodically and alternately arranged along the first direction z to form a plurality of periodic permanent magnet structures. The magnetic group includes a plurality of magnetic steels arranged at intervals along a second direction y, and the magnetic steels are extended along a third direction x. A plurality of through holes 3 arranged in an array are formed on the pole shoe, and the through holes 3 are used to assemble a slow wave structure. A plurality of through holes 3 constitute a through hole unit, and the through hole unit includes a transverse through hole unit arranged along the second direction y and a longitudinal through hole unit arranged along the third direction x. The transverse through hole unit is located between two adjacent magnetic steels arranged along the second direction y. For example, when the number of transverse through hole units is five, the number of magnetic steels is six, and a transverse through hole unit is included between each two adjacent magnetic steels. Furthermore, the through holes 3 are used to form a channel for assembling the slow-wave structure, and the axis of the channel is arranged along the first direction, that is, the through holes 3 coaxially arranged along the first direction on each pole shoe 1 are connected in the first direction to form a channel, and the slow-wave structure is assembled in the channel. Figure 1 and Figure 2 As shown, the z direction is the first direction, the y direction is the second direction, the x direction is the third direction, the x direction is perpendicular to the y direction, and the z direction is perpendicular to both the x direction and the y direction. The present invention can realize the integration of multiple channels in the same magnetic focusing system, reduce the distance between channels, and improve the unit density. The traveling wave tube based on the two-dimensional planar array multi-channel periodic permanent magnetic focusing system of the present invention can be widely used in array systems represented by active phased arrays.

[0046] In one embodiment, the pole shoe 1 includes m×n through holes 3 arranged in a rectangular array, wherein m is the number of columns of the through holes 3 in the third direction, n is the number of rows of the through holes 3 in the second direction, m>1, n>1. That is, the periodic permanent magnet focusing system includes m×n channels equipped with slow-wave structures. The number of magnetic steels in the same magnetic group is n+1.

[0047] More specifically, the pole shoe 1 is a flat plate structure, and the width of the pole shoe 1 in the third direction is w p , the height of the pole shoe 1 in the second direction is h p , the thickness of the pole shoe 1 in the first direction is L p . Value range: w p >0;h p >0;L p > 0. The diameter of through hole 3 is D0; The distance between two adjacent through holes 3 of the transverse through hole unit in the third direction is d x , The distance between two adjacent through holes 3 of the longitudinal through hole unit in the second direction is d y ,

[0048] In a specific embodiment, the magnetic group includes at least three magnetic steels, the two magnetic steels located at the two ends of the magnetic group along the second direction are outer magnetic steels 21, and the magnetic steel located between the two outer magnetic steels 21 is inner magnetic steel 22; the outer magnetic steel 21 is located on the outside of the through-hole unit, and the inner magnetic steel 22 is located between two adjacent transverse through-hole units; the width of the outer magnetic steel 21 and the inner magnetic steel 22 in the third direction and the thickness in the first direction are equal; the height of the outer magnetic steel 21 and the inner magnetic steel 22 in the second direction is equal or unequal. In the two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention, the inner magnetic steel 22 mainly plays the role of controlling the magnetic field strength of the system, and the outer magnetic steel 21 mainly plays the role of adjusting the magnetic field shape distribution and the size of the transverse field in the channel. Furthermore, the width of the magnetic steel in the third direction is w m ;w m ≥d x ×(n-1)+D0; the height of the inner magnetic steel 22 in the second direction is h1, and the value range is: 0 y -D0. Specifically, the width of the outer magnetic steel 21 is w m , value range: w m ≥d x ×(n-1)+D0; height is h2, value range: h2>0; thickness is L m , value range: L m > 0. The n-1 magnetic steels on the inner side are the inner magnetic steels 22, and their width is w m , height is h1, value range: 0 y -D0; thickness is L m In addition, the distance between two adjacent magnetic steels is d m , d m =d y -h1.

[0049] In a specific embodiment, the magnets in the same magnetic group are magnetized in the same direction, and the magnets in two adjacent magnetic groups are magnetized in opposite directions. The half-period length of the periodic permanent magnet focusing system is L, and the value range is: L = L p +L m ; The magnetic field direction of the magnet is the same in the same half cycle, and the magnetic field direction of the magnet is opposite in adjacent half cycles.

[0050] Reference Figure 1 and Figure 2 As shown, the present invention lists a 5×5 channel two-dimensional planar array multi-channel periodic permanent magnet focusing system, and its specific structural dimensions are as follows (unit: mm): w p =41,h p =29,L p =1, D0=3, d y =6,d​​x =6,w m =45, h1=3, h2=2, L m =2,d m =3, L=3.

[0051] Reference Figure 3 As shown in FIG. 1 , a schematic diagram of the main hole numbering of the above-mentioned 5×5 channel two-dimensional planar array multi-channel periodic permanent magnet focusing system is shown. Due to the symmetry of the rectangular array, only Figure 3 The nine through holes are marked as 1-1, 1-2, 1-3, 2-1, 2-2, 2-3, 3-1, 3-2 and 3-3. The electron beam channel radius of the preset slow wave structure is rc, which is rc=0.12 mm, and the electron beam will be confined in the electron beam channel with a radius of rc.

[0052] A 5×5-channel two-dimensional planar array multi-channel periodic permanent magnet focusing system of the present invention is simulated using three-dimensional electromagnetic software, and the relevant magnetic field intensity and field distribution characteristics are calculated.

[0053] Reference Figure 4 As shown, it is the BH characteristic curve of the pole shoe material during the simulation process. In addition, the remanent magnetism Br of the magnetic steel is set to 10000Gs.

[0054] Reference Figure 5 As shown, the magnetic field intensity distribution of the central section of the pole shoe of a two-dimensional planar array multi-channel periodic permanent magnet focusing system with 5×5 channels is shown. The magnetic field distribution in the channel is concentric circles, which meets the requirements of the magnetic field morphology for cylindrical electron beam focusing.

[0055] Reference Figure 6 As shown, the magnetic field intensity distribution of the polar magnetic steel core section of a two-dimensional planar array multi-channel periodic permanent magnet focusing system with 5×5 channels. The magnetic field distribution in the channel is concentric circles, which meets the requirements of cylindrical electron beam focusing on the magnetic field shape.

[0056] Reference Figure 7 The figure shows the distribution of the axial magnetic field intensity along the axial position of each hole channel axis of the 2D planar array multi-channel periodic permanent magnet focusing system with 5×5 channels. The axial magnetic field on the axis of channel 3-1 is the strongest, with a maximum value of 3083.2Gs, and the axial magnetic field on the axis of channel 1-3 is the weakest, with a maximum value of 3080.6Gs. The difference in the maximum value of the axial magnetic field on the axis of each channel does not exceed 0.084%, which has no effect on the focusing performance.

[0057] Reference Figure 8As shown, the angular position distribution diagram of the angular magnetic field of each channel at rc from the channel axis on the center section of the pole shoe of the 5×5 channel two-dimensional planar array multi-channel periodic permanent magnet focusing system. Among them, the angular magnetic field in channel 3-3 at rc from the channel axis is the strongest, with a maximum value of 1.67Gs, accounting for 0.054% of the axial magnetic field peak on the channel axis, and has no effect on the electron beam focusing performance.

[0058] The present invention also provides a design method for a two-dimensional planar array multi-channel periodic permanent magnet focusing system, which includes: designing a pole shoe 1 and a magnetic group that are periodically arranged along a first direction to form a plurality of periodic permanent magnet structures, wherein the magnetic group includes a plurality of magnetic steels that are arranged at intervals along a second direction, and the magnetic steels are extended along a third direction; designing a plurality of through holes 3 that are arranged in an array on the pole shoe 1 and are used to assemble a slow-wave structure, wherein the plurality of through holes 3 constitute a through hole unit, wherein the through hole unit includes a transverse through hole unit that is arranged along the second direction and a longitudinal through hole unit that is arranged along the third direction, and wherein the transverse through hole unit is located between two adjacent magnetic steels that are arranged along the second direction.

[0059] Further, the magnetic group includes at least three magnetic steels, the two magnetic steels located at the two ends of the magnetic group along the second direction are outer magnetic steels 21, and the magnetic steel located between the two outer magnetic steels 21 is inner magnetic steel 22. The outer magnetic steel 21 is located outside the through-hole unit, and the inner magnetic steel 22 is located between two adjacent transverse through-hole units. The width of the outer magnetic steel 21 and the inner magnetic steel 22 in the third direction and the thickness in the first direction are equal, and the height of the outer magnetic steel 21 and the inner magnetic steel 22 in the second direction are equal or unequal.

[0060] Reference Fig. 9 It can be seen that the width of the magnetic steel in the third direction has little effect on the axial magnetic field intensity on the channel axis. Fig.10 It can be seen that the width of the magnet in the third direction has a greater impact on the diagonal magnetic field. Fig.11 It can be seen that the height of the outer magnetic steel 21 in the second direction has a significant effect on the axial magnetic field strength on the channel axis. Fig.12 It can be seen that the height of the external magnetic steel 21 in the second direction has a greater influence on the diagonal magnetic field.

[0061] Combination Figure 9-12 As shown, more specifically, by changing the width of the magnetic steel in the third direction and the height of the outer magnetic steel 21 in the second direction, the axial magnetic field strength and the angular magnetic field emphasis of the periodic permanent magnetic focusing system are adjusted to optimize the focusing performance of the periodic permanent magnetic focusing system. This prevents the angular magnetic field from accounting for too much of the axial magnetic field, which affects the effect of electron beam focusing. The smaller the value of the angular magnetic field accounting for the axial magnetic field, the smaller the impact on electron beam focusing. When the angular magnetic field peak value accounts for less than 0.5% of the axial magnetic field peak value, there is basically no impact on the electron beam focusing performance.

[0062] In summary, the present invention can realize the integration of the traveling wave tube amplification channel array by integrating multiple channels equipped with slow-wave structures into the same focusing system, thereby effectively reducing the unit spacing of the channel, improving the unit density, and adapting to the application requirements of array systems represented by active phased arrays. In addition, the present invention can ensure that the ratio of the angular magnetic field peak to the axial magnetic field peak in the channel of the periodic permanent magnet focusing system is less than 0.5%, so as not to affect the focusing performance of the electron beam. The present invention adjusts the axial magnetic field intensity and angular magnetic field emphasis of the periodic permanent magnet focusing system by changing the width of the magnetic steel in the third direction and the height of the external magnetic steel in the second direction, thereby optimizing the focusing performance of the periodic permanent magnet focusing system.

[0063] 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 two-dimensional planar array multi-channel periodic permanent magnet focusing system, characterized in that: include: Pole shoes and magnetic groups are arranged at intervals along a first direction; the pole shoes and magnetic groups are periodically and alternately arranged along the first direction to form a plurality of periodic permanent magnetic structures; The magnetic group includes a plurality of magnetic steels arranged at intervals along the second direction; the magnetic steels are extended along the third direction; The pole shoe is provided with a plurality of through holes arranged in an array, and the through holes are used to assemble a slow-wave structure; the plurality of through holes constitute a through hole unit, and the through hole unit includes a transverse through hole unit arranged along the second direction, and a longitudinal through hole unit arranged along the third direction; the transverse through hole unit is located between two adjacent magnetic steels arranged along the second direction.

2. The two-dimensional planar array multi-channel periodic permanent magnet focusing system according to claim 1, characterized in that: The pole shoe includes m×n through holes arranged in a rectangular array, wherein m is the number of columns of through holes in the third direction, n is the number of rows of through holes in the second direction, m>1, n>1.

3. The two-dimensional planar array multi-channel periodic permanent magnet focusing system according to claim 2, characterized in that: The width of the pole shoe in the third direction is w p , the height of the pole shoe in the second direction is h p , the through hole diameter is D0; 4. The two-dimensional planar array multi-channel periodic permanent magnet focusing system according to claim 3, characterized in that: The distance between two adjacent through holes of the transverse through hole unit in the third direction is d x , The distance between two adjacent through holes in the longitudinal through hole unit in the second direction is d y , 5. The two-dimensional planar array multi-channel periodic permanent magnet focusing system according to claim 3, characterized in that: The magnetic group includes at least three magnetic steels, the two magnetic steels located at the two ends of the magnetic group along the second direction are outer magnetic steels, and the magnetic steel located between the two outer magnetic steels is inner magnetic steel; the outer magnetic steel is located on the outside of the through-hole unit, and the inner magnetic steel is located between two adjacent transverse through-hole units; the widths of the outer magnetic steel and the inner magnetic steel in the third direction and the thicknesses in the first direction are equal; the heights of the outer magnetic steel and the inner magnetic steel in the second direction are equal or unequal.

6. The two-dimensional planar array multi-channel periodic permanent magnet focusing system according to claim 5, characterized in that: The width of the magnet in the third direction is w m ;w m ≥d x ×(n-1)+D0; The height of the inner magnetic steel in the second direction is h1; 0 y -D0.​ 7. The two-dimensional planar array multi-channel periodic permanent magnet focusing system according to claim 1, characterized in that: The magnetization directions of the magnets in the same magnetic group are the same, and the magnetization directions of the magnets in two adjacent magnetic groups are opposite.

8. A design method for a two-dimensional planar array multi-channel periodic permanent magnet focusing system, characterized in that: The design approach includes: A plurality of pole shoes and magnetic groups are designed to be periodically arranged along a first direction to form a periodic permanent magnetic structure, wherein the magnetic group includes a plurality of magnetic steels arranged at intervals along a second direction, and the magnetic steels are extended along a third direction; A plurality of through holes arranged in an array for assembling a slow-wave structure are designed on the pole shoe, and the plurality of through holes constitute a through hole unit, wherein the through hole unit includes a transverse through hole unit arranged along the second direction and a longitudinal through hole unit arranged along the third direction, and the transverse through hole unit is located between two adjacent magnetic steels arranged along the second direction.

9. The design method according to claim 8, characterized in that: The magnetic group includes at least three magnetic steels, the two magnetic steels located at the two ends of the magnetic group along the second direction are outer magnetic steels, and the magnetic steel located between the two outer magnetic steels is inner magnetic steel; the outer magnetic steel is located on the outside of the through-hole unit, and the inner magnetic steel is located between two adjacent transverse through-hole units; the widths of the outer magnetic steel and the inner magnetic steel in the third direction and the thicknesses in the first direction are equal; the heights of the outer magnetic steel and the inner magnetic steel in the second direction are equal or unequal.

10. The design method according to claim 9, characterized in that: By changing the width of the magnetic steel in the third direction and the height of the external magnetic steel in the second direction, the axial magnetic field strength and angular magnetic field emphasis of the periodic permanent magnet focusing system are adjusted to optimize the focusing performance of the periodic permanent magnet focusing system.

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