Concave permanent magnet structure

Abstract

The invention discloses a concave permanent magnet structure, which belongs to the technical field of vacuum electronics, solves the technical problems of surface damage and plasma generation of a permanent magnet anode in a zero field region, is in a circular ring shape, and comprises an axial leftward magnetized magnetic block, an axial rightward magnetized magnetic block and a radial circle center magnetized magnetic block. The radial magnetizing magnetic block towards the circle center is a circular ring with a step which is located on the right side of the inner ring. And the axially leftward magnetized magnetic block and the axially rightward magnetized magnetic block are positioned in the step. An interval groove is formed between the axially leftward magnetized magnetic block and the axially rightward magnetized magnetic block, and the ratio of the axial width to the radial depth of the inner ring of the interval groove is 35%-55%. The magnetization direction of the axial leftward magnetization magnetic block is leftward in the axial direction, the magnetization direction of the axial rightward magnetization magnetic block is rightward in the axial direction, and the magnetization direction of the radial circle center magnetization magnetic block is towards the circle center in the radial direction. The device is used for inhibiting plasma generation in a null field region in a permanent magnet structure and charged particle backflow caused by the plasma generation.

Description

A concave permanent magnet structure Technical Field

[0001] This invention belongs to the field of vacuum electronics technology, specifically relating to a concave permanent magnet structure. Background Technology

[0002] Electron backflow in diodes has become a key factor restricting the long-term stable operation of permanent magnet packaged high-power microwave devices. During actual operation, there are electrons moving in the reverse direction from various sources within the diode, including electrons emitted laterally from the cathode and field-induced emission electrons from the cathode leads due to the strong electric field. Although most of the current emitted from the cathode propagates in the forward direction of the device, some electrons still move in the reverse direction, including secondary electrons or backscattered electrons generated during device operation; these are collectively referred to as backflow electrons.

[0003] As shown in Figure 1, these returning electrons are accelerated along path A and bombard the anode surface, causing the anode material to desorb and melt, generating plasma. In a permanent magnet structure, magnetic field lines converge at the ends of the magnet's N and S poles, forming a region where the axial magnetic field strength approaches zero—the zero-field region. This region lacks effective magnetic insulation, causing the returning electrons to be unconstrained by the Lorentz force and easily accelerated by the electric field, impacting the surface of the zero-field region along the magnetic field line trajectory (the path approximates path A), resulting in localized overheating, material damage, and further excitation of plasma or generation of charged particles (such as charged dust). (See Figure 2.)

[0004] The positive ions in the generated plasma are accelerated under the influence of a strong electric field, bombarding the cathode lead along the electric field lines and triggering additional field-induced electron emission, forming a positive feedback loop. This process not only exacerbates the backflow of electrons but also causes significant fluctuations in diode impedance and a decrease in output power, severely weakening the device's conversion efficiency and operational stability.

[0005] Therefore, studying and effectively suppressing plasma generation in the zero-field region of permanent magnet structures and the resulting backflow of charged particles is crucial for improving the long-term stable operation of high-power microwave devices. Current technology urgently needs to develop methods to delay or block the movement of ions and charged dust generated in the zero-field region towards the cathode guide rod, thereby breaking the aforementioned positive feedback mechanism, significantly reducing the impact of backflowing electrons, mitigating damage to the anode under electron bombardment, and improving the overall reliability and lifespan of the system. Summary of the Invention

[0006] To overcome the shortcomings of permanent magnet anode surface damage and plasma generation in the zero-field region, this invention proposes a concave permanent magnet structure.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A concave permanent magnet structure is located in the zero-field region of the permanent magnet and is circular in shape, including a magnetized block axially to the left, a magnetized block axially to the right, and a magnetized block radially towards the center.

[0009] Both the axially left-hand magnetized block and the axially right-hand magnetized block are circular rings. The inner diameters of the axially left-hand magnetized block and the axially right-hand magnetized block are equal, and the outer diameters of the axially left-hand magnetized block and the axially right-hand magnetized block are equal.

[0010] The radially oriented magnetizing block is an integral structure, a stepped ring with the step located on the right side of the inner ring. The diameter of the inner ring of the step is equal to the inner diameter of the axially left-oriented magnetizing block, and the diameter of the outer ring of the step is equal to the outer diameter of the axially left-oriented magnetizing block.

[0011] The left end face of the axially left-facing magnetized block is a plane, which is in contact with the bottom surface of the step. The outer ring surface of the axially left-facing magnetized block and the outer ring surface of the axially right-facing magnetized block are in contact with the outer ring surface of the step.

[0012] The right end face of the axially right-facing magnetized block is a plane, flush with the right end face of the radially center-facing magnetized block.

[0013] A gap groove is formed between the axially left-handed magnetized block and the axially right-handed magnetized block, and the ratio of the axial width to the radial depth of the inner ring of the gap groove is 35%-55%.

[0014] The axially right-facing magnetized block is an integral structure, consisting of an inner ring, a middle ring, and an outer ring. The inner and outer rings are circular, with the inner ring having a smaller axial thickness than the outer ring. The middle ring is also circular, with its right end face forming an angle of 10° to 30° with the radial direction.

[0015] The axially left-facing magnetized block is an integral structure, consisting of a connected inner ring and an outer ring. The outer ring is circular; the inner ring is annular, with the left end face of the inner ring making an angle of 10° to 30° with the radial direction; the axial thickness of the outer ring is less than that of the inner ring.

[0016] The magnetization direction of the axially left-hand magnetized block is along the axial direction to the left, the magnetization direction of the axially right-hand magnetized block is along the axial direction to the right, and the magnetization direction of the radially center-magnetized block is along the radially center-magnetized block.

[0017] In the above-mentioned concave permanent magnet structure, the axial width of the spacer groove is 15mm~20mm.

[0018] In the aforementioned concave permanent magnet structure, the axial width of the inner ring of the spacer groove is 18mm.

[0019] The right end face of the axially right-facing magnetized block has an angle of 14° with the radial direction, and the radial height of the outer ring of the axially right-facing magnetized block is 10mm.

[0020] The angle between the left end face of the inner ring of the axially left magnetized magnetic block and the radial direction is 14°, and the radial height of the outer ring of the axially left magnetized magnetic block is 20mm.

[0021] In the aforementioned concave permanent magnet structure, the axial width of the inner ring of the spacer groove is equal to the axial width of the outer ring.

[0022] In the aforementioned concave permanent magnet structure, the radial height of the inner ring of the axially right-facing magnetized block is equal to the radial height of the outer ring.

[0023] The beneficial effects of this invention are:

[0024] A concave permanent magnet structure, when the return current emitted from the cathode side bombards the anode along the magnetic field lines, compared with the commonly used structure, by adjusting the angle between the inclined plane and the magnetic field lines, the bombarded area of ​​the anode is maximized, the heat deposition density caused by bombardment is reduced, and the surface damage and plasma generation of the anode are reduced.

[0025] A concave permanent magnet structure is used where the return current emitted from the cathode side has axial diffusion, i.e., it has width in the axial direction. According to the magnetic field line structure, part of it may bombard the left slope and part of it may bombard the right slope, thereby increasing the bombarded area of ​​the anode. The heat deposition density caused by bombardment is reduced, thus reducing anode surface damage and plasma generation.

[0026] A concave permanent magnet structure is proposed. The concave structure achieves electrostatic shielding, and the electrostatic field strength at the electron beam bombardment location inside the groove is significantly reduced. Compared with the commonly used structure (a non-polar electrostatic shielded concave structure), the polarized concave structure significantly slows down the plasma diffusion rate due to the substantial decrease in electric field strength at the plasma generation location.

[0027] A concave permanent magnet structure, compared with the commonly used structure, increases the distance of the anode plasma to the cathode, delays the time of the anode plasma to reach the cathode, reduces the bombardment of the cathode by the anode plasma, reduces the negative impact of the anode plasma, and improves the stability of the diode.

[0028] A concave permanent magnet structure is set in the reflow bombardment region of the zero field region of the permanent magnet to increase the bombardment area of ​​the anode, reduce the density of bombardment heat deposition, thereby reducing anode surface damage and plasma generation, and realizing stable operation of the diode. Attached Figure Description

[0029] Figure 1 is a schematic diagram of the existing diode structure and reflow process;

[0030] Figure 2 is a schematic diagram of the structure and magnetic lines of force of a permanent magnet in the prior art;

[0031] Figure 3 is a schematic diagram of the concave permanent magnet structure in the zero field region of the permanent magnet according to Embodiment 1 of the present invention.

[0032] Figure 4 is a schematic diagram of the magnetic field lines of the concave permanent magnet structure in Embodiment 2 of the present invention.

[0033] Figure 5 is a schematic diagram of the concave permanent magnet structure of Embodiment 3 of the present invention;

[0034] Figure 6 is a schematic diagram of the magnetization direction of the concave permanent magnet structure in Embodiment 3 of the present invention.

[0035] The attached figures are labeled as follows:

[0036] 1. Axially magnetized block towards the center, 2. Axially magnetized block to the left, 3. Radially magnetized block to the right. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] A concave inclined surface type zero-field permanent magnet for suppressing backflow includes a concave permanent magnet structure.

[0040] The concave permanent magnet structure is located in the zero-field region of the permanent magnet, where the backflow bombardment is reduced, thus ensuring stable operation of the diode. (See Figure 3.)

[0041] The concave permanent magnet structure includes a magnetic block portion magnetized to the left axially, a magnetic block portion magnetized to the right axially, and a magnetic block portion magnetized radially toward the center. The magnetic block portion magnetized to the left axially and the magnetic block portion magnetized to the right axially are spaced apart by 35%-55% of the groove depth. The magnetic block portion magnetized radially toward the center is positioned above and to the left of the magnetic block portions magnetized to the left and right axially.

[0042] In the aforementioned concave permanent magnet structure, the magnetic block portion magnetized to the left and the magnetic block portion magnetized to the right are spaced 35%-55% of the groove depth. Within this distance range, the magnetic field lines are in a balanced state. If the distance is less than this, the magnetic field lines may only strike one side slope, instead of both slopes simultaneously; if the distance is greater than this, the magnetic field lines may strike the upper radially centered magnetic block portion.

[0043] In the aforementioned concave permanent magnet structure, the right end face of the axially right-magnetized magnetic block portion includes a slope and two flat surfaces. The slope and flat surfaces form an angle of 10° to 30° on the right end face. Similarly, the left end face of the axially left-magnetized magnetic block portion includes a slope and a flat surface, with the slope and flat surfaces forming an angle of 10° to 30°. The specific angle is determined based on the incident angle of the magnetic field lines, and is generally chosen to be approximately parallel to the incident angle of the magnetic field lines to increase the recirculation bombardment area.

[0044] In the aforementioned concave permanent magnet structure, the left end face of the axially left-magnetized magnetic block portion includes a slope and a plane.

[0045] In the aforementioned concave permanent magnet structure, the radially magnetized magnetic block portion is positioned above and to the left of the axially magnetized left magnetic block portion and the axially magnetized right magnetic block portion.

[0046] Example 2

[0047] A concept for a concave permanent magnet structure to suppress backflow is as follows: a concave permanent magnet structure is set in the backflow bombardment region of the zero-field region of the permanent magnet, as shown in Figure 3. By adjusting the relevant dimensions of the concave permanent magnet structure, the magnetic lines of force are concentrated on the side of the concave permanent magnet structure, and the backflow moves along the direction of the magnetic lines of force, as shown in Figure 4. This can increase the area of ​​backflow bombardment on the anode, reduce the heat deposition density caused by bombardment, and thus reduce anode surface damage and plasma generation.

[0048] Specifically as follows:

[0049] (1) The concave permanent magnet structure for suppressing backflow includes a magnetic block part magnetized to the left axially, a magnetic block part magnetized to the right axially, and a magnetic block part magnetized radially toward the center.

[0050] (2) The magnetic block portion magnetized to the left and the magnetic block portion magnetized to the right are spaced 15~20mm apart, with the concave structure openings spaced 18mm apart.

[0051] (3) The right end face of the magnetic block part magnetized to the right in the axial direction includes a section of inclined plane and two sections of plane. The inclined plane is located between the two sections of plane, and the angle between the inclined plane and the plane is 14°.

[0052] (4) The distance between the inclined surface of the right end face of the magnetic block part magnetized to the right in the axial direction and the magnetic block part magnetized radially to the center above is 10mm.

[0053] (5) The left end face of the magnetic block part magnetized to the left by the axis includes a section of inclined plane and a section of plane. The inclined plane is located at the opening of the concave structure, and the angle between the inclined plane and the plane is 14°.

[0054] (6) The distance between the inclined surface of the left end face of the magnetic block part magnetized to the left in the axial direction and the magnetic block part magnetized radially to the center above is 20mm.

[0055] (7) The magnetic block portion that is radially magnetized toward the center is positioned above and to the left of the magnetic block portion that is axially magnetized to the left and the magnetic block portion that is axially magnetized to the right.

[0056] (8) Each parameter can be adaptively adjusted according to the actual simulation and experimental results, and the adjusted parameters still fall within the protection scope of this invention.

[0057] Example 3

[0058] A concave permanent magnet structure is located in the zero-field region of the permanent magnet and is circular in shape. It includes a magnetizing block 2 axially to the left, a magnetizing block 3 axially to the right, and a magnetizing block 1 radially towards the center, as shown in Figure 5.

[0059] Both the left-axis magnetized block 2 and the right-axis magnetized block 3 are circular rings. The inner diameter of the left-axis magnetized block 2 and the inner diameter of the right-axis magnetized block 3 are equal, and the outer diameter of the left-axis magnetized block 2 and the outer diameter of the right-axis magnetized block 3 are equal.

[0060] The radially oriented magnetizing block 1 is an integral structure, which is a stepped ring with the step located on the right side of the inner ring. The diameter of the inner ring of the step is equal to the inner diameter of the axially left-oriented magnetizing block 2, and the diameter of the outer ring of the step is equal to the outer diameter of the axially left-oriented magnetizing block 2.

[0061] The left end face of the axially left-facing magnetized block 2 is a plane, which is in contact with the bottom surface of the step. The outer ring surface of the axially left-facing magnetized block 2 and the outer ring surface of the axially right-facing magnetized block 3 are in contact with the outer ring surface of the step.

[0062] The right end face of the axially right-magnetized magnetic block 3 is a plane, which is flush with the right end face of the radially center-magnetized magnetic block 1.

[0063] An intervening groove is formed between the axially left-facing magnetized block 2 and the axially right-facing magnetized block 3. The axial width of the inner ring of the intervening groove is equal to the axial width of the outer ring. The ratio of the axial width to the radial depth of the inner ring of the intervening groove is 35%-55%.

[0064] Preferably, the axial width of the inner ring of the interval groove is equal to the axial width of the outer ring.

[0065] The axially right-magnetized magnetic block 3 is an integral structure, consisting of an inner ring, a middle ring, and an outer ring. The inner and outer rings are circular, with the axial thickness of the inner ring being less than that of the outer ring. The middle ring is also circular, with its right end face forming an angle of 10° to 30° with the radial direction.

[0066] Preferably, the radial height of the inner ring is equal to the radial height of the outer ring.

[0067] The axially left-facing magnetized block 2 is an integral structure, consisting of an inner ring and an outer ring connected together. The outer ring is circular; the inner ring is annular, with the left end face of the inner ring making an angle of 10° to 30° with the radial direction; the axial thickness of the outer ring is less than that of the inner ring.

[0068] The axial width of the interval groove is 15mm~20mm.

[0069] Preferably, the axial width of the inner ring of the spacer groove is 18mm. The right end face of the axially right-facing magnetized block 3 has a radial angle of 14° with the radial direction, and the radial height of the outer ring of the axially right-facing magnetized block 3 is 10mm. The left end face of the axially left-facing magnetized block 2 has a radial angle of 14° with the radial direction, and the radial height of the outer ring of the axially left-facing magnetized block 2 is 20mm.

[0070] Magnetizing block 2 axially to the left, magnetizing block 3 axially to the right, and magnetizing block 1 radially towards the center of the circle, as shown in Figure 6.

Claims

1. A concave permanent magnet structure, characterized in that, Located in the zero-field region of the permanent magnet, the recirculation bombardment area is annular, comprising an axially left-facing magnetized block (2), an axially right-facing magnetized block (3), and a radially center-facing magnetized block (1). The axially left-facing magnetized block (2) and the axially right-facing magnetized block (3) are both annular. The inner diameter of the axially left-facing magnetized block (2) is equal to the inner diameter of the axially right-facing magnetized block (3), and the outer diameter of the axially left-facing magnetized block (2) is equal to the outer diameter of the axially right-facing magnetized block (3). The radially center-facing magnetized block (1)... The magnetized block (1) is an integral structure, a stepped ring, with the step located on the right side of the inner ring; the inner ring diameter of the step is equal to the inner diameter of the axially left-facing magnetized block (2), and the outer ring diameter of the step is equal to the outer diameter of the axially left-facing magnetized block (2); the left end face of the axially left-facing magnetized block (2) is a plane, connected to the bottom surface of the step; the outer ring surface of the axially left-facing magnetized block (2) and the outer ring surface of the axially right-facing magnetized block (3) are connected to the outer ring surface of the step; the axially right-facing magnetized block (3) The right end face is a plane, flush with the right end face of the radially oriented magnetized block (1); an intervening groove is formed between the axially leftward magnetized block (2) and the axially rightward magnetized block (3), and the ratio of the axial width to the radial depth of the inner ring of the intervening groove is 35%~55%; the axially rightward magnetized block (3) is an integral structure, divided into an inner ring, a middle ring, and an outer ring; the inner ring and the outer ring are circular rings, and the axial thickness of the inner ring is less than the axial thickness of the outer ring; the middle ring is a circular ring, and the right end face of the middle ring is flush with the right end face of the inner ring. The radial angle is 10°~30°; the axial left-facing magnetized block (2) is an integral structure, divided into an inner ring and an outer ring; the outer ring is a circular ring; the inner ring is a circular ring, and the left end face of the inner ring has an angle of 10°~30° with the radial direction; the axial thickness of the outer ring is less than the axial thickness of the inner ring; the magnetization direction of the axial left-facing magnetized block (2) is along the axial left, the magnetization direction of the axial right-facing magnetized block (3) is along the axial right, and the magnetization direction of the radial center magnetized block (1) is along the radial center.

2. The concave permanent magnet structure according to claim 1, characterized in that, The axial width of the spacer groove is 15mm~20mm.

3. The concave permanent magnet structure according to claim 1, characterized in that, The axial width of the inner ring of the interval groove is 18mm; the right end face of the axially right magnetized block (3) has an angle of 14° with the radial direction, and the radial height of the outer ring of the axially right magnetized block (3) is 10mm; the left end face of the inner ring of the axially left magnetized block (2) has an angle of 14° with the radial direction, and the radial height of the outer ring of the axially left magnetized block (2) is 20mm.

4. The concave permanent magnet structure according to claim 1, characterized in that, The axial width of the inner ring of the interval groove is equal to the axial width of the outer ring.

5. The concave permanent magnet structure according to claim 1, characterized in that, The radial height of the inner ring of the axially right-facing magnetized block (3) is equal to the radial height of the outer ring.

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