Single-anode magnetic control injection electron gun adopting magnetic field secondary compression structure

Abstract

The invention discloses a single-anode magnetic control injection electron gun adopting a magnetic field secondary compression structure, and belongs to the field of microwave electric vacuum devices. An external magnetic field of the magnetic control injection electron gun is a secondary compression magnetic field; the electron gun anode is divided into a starting section, a smooth section and a transition section, the starting section is located on the outer side of the cathode, the smooth section is used for being matched with the secondary compression magnetic field, and the transition section is used for continuously restraining the electron beam track after the smooth section. According to the invention, an external magnetic field is changed into a magnetic field distribution mode of a secondary compression structure, and the smooth section is correspondingly added at the anode part, so that the area of a cathode emission band can be effectively increased, the electron gun is enabled to adapt to higher power, the emission pressure of the electron gun is reduced, and the service life of the electron gun is prolonged.

Description

Technical Field

[0001] The invention belongs to the field of microwave electric vacuum devices, and in particular relates to a single-anode magnetron injection electron gun adopting a magnetic field secondary compression structure. Background Art

[0002] A traveling-wave gyrotron tube (TWT) is a vacuum electronic device based on the electron cyclotron maser mechanism. Through the injection-wave interaction between charged particles and electromagnetic waves, it transfers electron energy to electromagnetic signals, thereby amplifying the signal. TWTs offer high power, high efficiency, wide bandwidth, and high gain, and are widely used in satellite communications, radar, electronic countermeasures, and other fields.

[0003] As the core component of a traveling-wave gyrotron tube (TWT), the magnetron injection electron gun (MIG) generates a hollow, gyrotron electron beam. The electron gun consists of a cathode and an anode. During operation, the cathode is typically subjected to a negative high voltage of tens of kilovolts. Electrons overflow from the cathode's emission band under the influence of the filament's heating. These electrons, influenced by the magnetic field and high-voltage electric field, perform a gyroscopic motion forward. These electrons then transfer energy to the high-frequency signal through beam-wave interaction within the high-frequency system.

[0004] Since current must be applied to the cathode emission strip during electron gun operation, applying too high a current, given a given emission strip area, can cause excessive emission pressure on the strip, potentially damaging the cathode. Increasing the emission strip area allows it to withstand higher currents, thus accommodating higher-power electron guns. Furthermore, under the same current conditions, a larger emission strip area allows for lower operating temperatures, reducing emission pressure and extending the gun's service life. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention proposes a magnetron injection electron gun with a secondary compression structure. By modifying the applied magnetic field to adopt the magnetic field distribution of a secondary compression structure and adding a corresponding smoothing section to the anode, the present invention effectively increases the area of ​​the cathode emission zone, enabling the electron gun to adapt to higher power, reducing the emission pressure, and extending the gun's service life.

[0006] The technical solution adopted in the present invention is as follows:

[0007] A magnetron injection electron gun with a secondary compression structure, characterized in that the external magnetic field of the magnetron injection electron gun is a secondary compression magnetic field;

[0008] The electron gun includes: an anode and a cathode;

[0009] The anode is a metal shell structure, including a starting section, a smooth section and a transition section arranged in sequence along the axial direction; wherein the starting section is located outside the cathode and matches the cathode structure; the internal cavity of the smooth section is a cylindrical cavity for cooperating with the secondary compression magnetic field; the internal cavity of the transition section is a truncated cone-shaped cavity that is wide in front and narrow in the back, for continuing to constrain the electron beam trajectory after the smooth section.

[0010] Preferably, the magnetic field distribution of the secondary compression magnetic field is in the order of: a first compression section, a gentle section, and a second compression section along the axial direction; the starting section is located in the first compression section, the smooth section is located in the gentle section, and the transition section is located in the second compression section;

[0011] Assume that the magnetic field strength at the end of the second compression section is B0, and the average magnetic field strength of the flat section is B ′ 0, magnetic field distribution meets: B0 ≥ (3.25 ~ 3.35) B ′ 0; at the same time, the difference between the maximum magnetic field intensity and the minimum magnetic field intensity in the flat section is in the range of 0.05T to 0.07T.

[0012] Preferably, the axial length of the smooth section ranges from 57 mm to 63 mm.

[0013] Preferably, a cylindrical shell with a constant diameter is extended axially from the end of the transition section for connection with a subsequent high-frequency system.

[0014] Preferably, the cathode includes a front-formed pole, an emission belt, a rear-formed pole, and a base connected in sequence; the front-formed pole and the rear-formed pole are used to adjust the electric field between the cathode and the anode; the emission belt is used to emit electrons under the heating of the filament, and the electrons form an electron beam under the action of the electromagnetic field; the base supports and fixes the cathode to ensure the accurate position of the cathode in the electron gun.

[0015] Preferably, the front forming pole, the emission band, and the rear forming pole are all in the shape of a truncated cone, and the base is in the shape of a cylinder.

[0016] Preferably, the front end of the base and the front end of the front forming pole are chamfered to prevent the edges from being too sharp and causing an excessively strong electric field to cause breakdown.

[0017] The working principle of the present invention is as follows:

[0018] Based on the design indicators, some initial parameters of the electron gun can be calculated using the following formula:

[0019]

[0020] Where B0 is the magnetic field at the exit of the electron gun, m0 and e are the mass and charge of the electron respectively, γ0 is the relativistic factor of the interaction region, which is determined by the electron injection energy, f0 is the frequency of the input microwave signal, and k z is the longitudinal wave number of the electromagnetic wave, v z is the longitudinal velocity of the electron beam; r w is the electron gun exit radius, X mn is the root of the Bessel function, which is related to the transmission mode of the wave in the electron gun, f c is the cut-off frequency, ε and μ represent the dielectric constant and magnetic permeability respectively; r g0 represents the guiding center radius of the electron beam, λ is a value related to the transmission mode; r c is the radius of the cathode emission zone, f m is the magnetic compression ratio, r L0 is the Larmor radius of the electron beam, which is determined by the transverse velocity of the electron motion and the magnetic field.

[0021] At the same time, according to the above formula, it can be deduced that the cathode emission zone radius r c It is inversely proportional to the magnetic field B0 at the electron gun outlet. Therefore, in the present invention, the magnetic field is adjusted to a secondary compression structure, and the electrons are concentrated twice under the action of the magnetic fields of the first compression section and the second compression section; after the first compression, the average magnetic field strength of the flat section is B ′ 0, the magnetic field B ′ 0 is about two-thirds lower than the magnetic field B0 at the electron gun outlet, thus effectively increasing the emission zone area. The electron gun of the present invention can significantly increase the emission zone area compared to electron guns using traditional magnetic field structures by adopting a magnetic field secondary compression structure while maintaining the same operating voltage, operating current, and maximum magnetic field strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a three-dimensional structural diagram of a single-anode magnetron injection electron gun with a secondary compression structure according to the present invention;

[0023] Figure 2 Dimensional diagram of the single-anode magnetron injection electron gun with secondary compression structure of the present invention;

[0024] Figure 3 Schematic diagram of the magnetic field of the secondary compression structure used in the present invention and the magnetic field of the traditional structure;

[0025] Figure 4 This is the electric field diagram between the cathode and anode of the single anode magnetron injection electron gun with secondary compression structure of the present invention;

[0026] Figure 5 The electron beam and the electron distribution diagram of the muzzle section of the single-anode magnetron injection electron gun with a secondary compression structure of the present invention are shown;

[0027] Figure 6 The present invention provides a speed ratio and speed dispersion of a single-anode magnetron injection electron gun with a secondary compression structure.

[0028] Figure labeling: 1. Anode, 11. Starting section, 12. Smooth section, 13. Transition section, 2. Cathode, 21. Front

[0029] Forming pole, 22. Emission belt, 23. Post-forming pole, 24. Base. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0031] This embodiment provides a single-anode magnetron injection electron gun with a secondary compression structure, including an anode and a cathode.

[0032] The anode, such as Figure 1 (a) shows a metal shell structure, comprising a starting section, a smooth section and a transition section arranged in sequence along the axial direction; wherein the starting section is located outside the cathode and matches the cathode structure; the internal cavity of the smooth section is a cylindrical cavity for cooperating with the secondary compression magnetic field; the internal cavity of the transition section is a truncated cone-shaped cavity that is wide in the front and narrow in the back, for continuing to constrain the electron beam trajectory after the smooth section.

[0033] The cathode, such as Figure 1 As shown in (b), it includes a front-shaped electrode, an emission belt, a back-shaped electrode, and a base connected in sequence; wherein the front-shaped electrode, the emission belt, and the back-shaped electrode are all truncated cone-shaped, and the base is cylindrical. The front end of the base and the front end of the front-shaped electrode are chamfered to prevent the electric field from being too strong due to sharp edges and causing breakdown. The front-shaped electrode and the back-shaped electrode are used to adjust the electric field between the cathode and the cathode; the emission belt is used to emit electrons under the influence of the electromagnetic field when the filament is heated, and the electrons form an electron beam under the influence of the electromagnetic field; the base supports and fixes the cathode to ensure the accurate position of the cathode in the electron gun.

[0034] Specifically, such as Figure 2 As shown in the figure, the dimensions of the various parts of the electron gun are: Ra1 = 39.6mm, Ra2 = 25.8mm, Ra3 = 17.4mm, the smooth section radius Ra4 = Ra5 = 14.1mm, Ra6 = 6.9mm. The smooth section length l1 = 60mm, the transition section length l2 = 231.5mm. The radius of the front end of the cathode front forming pole is Rc1 = 4.1mm, the radius of the rear end of the front forming pole is Rc2 = 6.98mm, and the center radius of the emission band is r c=10.4mm, the inclination angle of the launch band θ = 62.6°, the radius of the front end of the post-forming pole Rc3 = 13.82mm, the radius of the rear end of the post-forming pole Rc4 = 15.3mm, the radius of the base Rc5 = 24.1mm; the length of the whole gun is 373mm.

[0035] The external magnetic field of the magnetron injection electron gun is a secondary compression magnetic field. The magnetic field distribution along the axial direction is: first compression section, gentle section, second compression section; the starting section is located in the first compression section, the smooth section is located in the gentle section, and the transition section is located in the second compression section. The magnetic field distribution satisfies: B0≥(3.25~3.35)B ′ 0; at the same time, the difference between the maximum magnetic field intensity and the minimum magnetic field intensity in the flat section is in the range of 0.05T to 0.07T.

[0036] Figure 3 The figure shows a schematic diagram of a conventional magnetic field structure and a secondary compression magnetic field structure used in this embodiment. The magnetic field strength of both structures at the electron gun outlet is 1.09T. The difference is that the magnetic field strength of the conventional magnetic field structure increases steadily, while the secondary compression magnetic field structure of the present invention has a plateau in the middle, which corresponds to the smooth section of the electron gun. According to formulas (1) to (4), this plateau will provide a lower B0, thereby obtaining a higher emission band center radius r c Since the front and rear end radius of the launch belt is determined by the center radius of the launch belt and the launch belt inclination, the higher r c This means a larger emission band surface area.

[0037] The voltages applied to the cathode and anode of the electron gun in this embodiment are -100Kv and 0Kv respectively. Figure 4 The figure shows the electric field between the cathode and cathode. When the electron gun is operating, electrons overflow from the cathode's emission band due to the heating of the internal filament. These electrons then undergo a cyclotron motion forward under the influence of the high-voltage electric field and the static magnetic field. This cyclotron electron beam undergoes adiabatic compression in the electron gun, gradually converting its longitudinal energy into transverse energy. Ultimately, a high-performance, stable electron beam is generated with a specific transverse-to-longitudinal velocity ratio and low velocity dispersion. This electron beam then undergoes a beam-wave interaction with the high-frequency signal in the subsequent high-frequency system, transferring energy to the high-frequency signal and achieving signal amplification.

[0038] Figure 5 as well as Figure 6 After continuous optimization to improve electron beam performance after adopting a secondary compression structure, under operating conditions of 100kV and 48A, the electron beam achieved a velocity ratio of 1.049, a velocity dispersion of 1.97%, and a guide center radius of 3.48mm. Comparisons show that the emission band surface area of ​​the new structure has been significantly increased compared to the previous one.

[0039] In summary, the single-anode magnetron injection electron gun with a magnetic field secondary compression structure of the present invention can significantly increase the emission band surface area while ensuring high electron injection performance, thereby increasing the power that the electron gun can adapt to and extending the service life of the electron gun.

Claims

1. A single-anode magnetron injection electron gun using a magnetic field secondary compression structure, characterized in that: The external magnetic field of the magnetron injection electron gun is a secondary compression magnetic field; The electron gun includes: an anode and a cathode; The anode is a metal shell structure, including a starting section, a smooth section and a transition section arranged in sequence along the axial direction; wherein the starting section is located outside the cathode and matches the cathode structure; the internal cavity of the smooth section is a cylindrical cavity for cooperating with the secondary compression magnetic field; the internal cavity of the transition section is a truncated cone-shaped cavity that is wide in front and narrow in the back, for continuing to constrain the electron beam trajectory after the smooth section.

2. The single-anode magnetron injection electron gun using a magnetic field secondary compression structure according to claim 1, characterized in that: The magnetic field distribution of the secondary compression magnetic field is as follows along the axial direction: a first compression section, a gentle section, and a second compression section; the starting section is located in the first compression section, the smooth section is located in the gentle section, and the transition section is located in the second compression section; Assume that the magnetic field strength at the end of the second compression section is B0, and the average magnetic field strength of the flat section is B ′ 0, magnetic field distribution meets: B0 ≥ (3.25 ~ 3.35) B ′ 0; at the same time, the difference between the maximum magnetic field intensity and the minimum magnetic field intensity in the flat section is in the range of 0.05T to 0.07T.

3. The single-anode magnetron injection electron gun using a magnetic field secondary compression structure according to claim 2, characterized in that: The axial length of the smooth section ranges from 57 mm to 63 mm.

4. A single anode magnetron injection electron gun using a magnetic field secondary compression structure according to claim 2 or 3, characterized in that: The end of the transition section is axially extended with a cylindrical shell having a constant diameter, which is used for connecting with a subsequent high-frequency system.

5. The single-anode magnetron injection electron gun using a magnetic field secondary compression structure according to claim 4, characterized in that: The cathode comprises a front-shaped electrode, an emission strip, a rear-shaped electrode, and a base connected in sequence; the front-shaped electrode and the rear-shaped electrode are used to adjust the electric field between the cathode and the anode; the emission strip is used to emit electrons under the heating of the filament, and the electrons form an electron beam under the action of the electromagnetic field; The base supports and fixes the cathode, ensuring the cathode is positioned accurately in the electron gun.

6. The single-anode magnetron injection electron gun using a magnetic field secondary compression structure according to claim 5, characterized in that: The front forming pole, emission band and rear forming pole are all in the shape of a truncated cone, and the base is in the shape of a cylinder.

7. The single-anode magnetron injection electron gun using a magnetic field secondary compression structure according to claim 6, characterized in that: The front end of the base and the front end of the front forming pole are chamfered to prevent the edges from being too sharp and causing an excessively strong electric field to cause breakdown.

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