A pulse electron gun for a microwave emission system and a microwave emission device thereof

Abstract

The present application relates to the technical field of electron emission and microwave emission, and provides a pulsed electron gun for a microwave emission system and a microwave emission device thereof, which comprises a pulsed high-voltage power supply, a cathode rod, a first electric field, a field emission cathode, an electron multiplication medium, a second electric field and a third electric field.Under the action of the high-voltage pulsed power supply, an electric field is formed between the cathode rod and an anode cylinder, the initial emission cathode emits electrons under the drive of the electric field, the electrons are amplified by the electron multiplication module, and an electron beam is formed to meet the demand of the microwave emission system.By optimizing the cathode structure, a diode type pulsed electron gun is designed, the voltage application mode is simplified, and the influence of stray capacitance is effectively reduced.The electron multiplication channels are constructed by selecting specific materials and the number of the channels is increased, the total output current is significantly improved, the risk of sparking is reduced, the life and working stability of the cathode are significantly improved, stable pulsed high-current output can be realized, and the demand of the high-power microwave emission system can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electron emission and microwave emission, in particular to a pulsed electron gun for a microwave emission system and a microwave emission device thereof. BACKGROUND

[0002] The content of this section is only to provide background information related to the present application, which may not constitute prior art.

[0003] In high power microwave emission systems, one of the core challenges is how to achieve a high emission current density, long life and stable electron beam source. In the prior art, Song Falun [Song Falun, Jin Xiao, Zhang Yonghui, et al. Research progress of explosive emission cathode characteristics, Physics, 2007, 36(3): 241-246] and others use explosive emission cathode because it can produce extremely high current density (up to kA / cm2order of magnitude) and is considered as a potential technical option. This kind of cathode theoretically has almost unlimited emission capacity. However, in practical application, the performance of the explosive emission cathode decreases rapidly, and the working life is usually limited to tens of thousands of pulses, which is mainly due to the expansion of plasma and the ablation loss of emission sites. These limitations seriously affect the stability of electronic devices and even the entire system.

[0004] Another prior art is field emission cathode [Chen Zexiang, Cao Guichuan, Zhang Qiang, et al. Development of high current density carbon nanotube field emission array, High Power Laser and Particle Beams, 2006, 18(12): 2070-2073], which can also provide a relatively high emission current density but is limited by the effective area of the emitter, and its total emission current is not ideal. In contrast, secondary electron emission, as an emerging technology, releases internal electrons through the interaction of primary electrons and solid surfaces to achieve current amplification. For example, photomultiplier tubes use this principle, but they are limited to small current environments. Dong Ye [Dong Ye. Theoretical and numerical simulation of secondary electron multiplication inhibition and enhancement [D]. Sichuan: Southwest Jiaotong University, 2019.] combines field emission and secondary electron multiplication, although high current density is achieved, but the space charge field caused by the deposition of positive charges in the secondary electron multiplication process leads to multiplication saturation, and increases the field strength of field emission, which may induce explosive emission, thereby shortening the life of the cathode.

[0005] Meanwhile, the secondary electron emission is applied to the accelerator, and Liao [Liao W. Research and design of microwave micro-pulse electron gun[J]. Graduate School of the Chinese Academy of Sciences (Shanghai Institute of Applied Physics), 2015] adopts the double-sided secondary electron multiplication mechanism based on the radio frequency field to realize the high-quality electron beam with a duration of several microseconds, low energy dispersion and low emission degree, but still faces the limitations of beam quality degradation caused by space charge effect, strict resonance condition, high material requirement and short pulse duration. The micro channel plate (MCP) [Hirshfield J L. HIGH-CURRENT COLD CATHODE FIELD EMISSION ARRAY FOR ELECTRON LENS APPLICATION[R]. Omega-P, Inc., 2012.] can output a relatively high current density, but is also easy to saturate when working at a large current, and is difficult to continuously and stably output, which is difficult to meet the needs of high-power microwave sources. In order to overcome the saturation problem in the secondary electron multiplication process, Tang Yongliang [L. Wang, Y. Hao, W. Lv, D. Wang, Y. Zhang, Y. Lu, Q. Liu, J. Luo, and Y. Tang, “A comprehensive study of pulsed high-current secondary electron emission cathode,” Journal of Applied Physics, vol. 136, no. 4, 2024.] and others use SnO2 material with high secondary electron emission coefficient and high electrical conductivity, combine field emission with secondary electron multiplication, and realize a large-current secondary electron multiplication emission cathode with an output current density of up to 100 A / cm2. Although this breakthrough has improved the performance of secondary electron emission, the multi-pole pressing method not only easily introduces a large amount of stray capacitance in the experiment, but also needs a complex power supply system to support, so it is difficult to meet the actual needs of high-power microwave systems.

[0006] In view of the above problems, there is an urgent need for a pulsed electron gun for a microwave emission system to overcome the technical challenges of low emission current density, short service life and complex voltage application of cold cathode type electron beam diode. SUMMARY

[0007] In order to solve the above technical problems, the purpose of the present application is to provide a kind of for microwave emission system's pulse electron gun, by redesigning cathode structure, Simplify voltage application mode, and make it suitable for high power microwave system;Select the material (such as ZnO, SnO2, etc.) with higher conductivity, high breakdown threshold, higher secondary electron multiplication coefficient to construct electron multiplication channel, the positive charge deposited on the surface of the channel during high-current electron emission can be effectively neutralized by channel conduction current, inhibit the saturation effect of secondary electron multiplication;Further by increasing the number of electron multiplication channel, to improve the total channel area, so as to solve the problem of low emission current density of cold cathode type electron beam diode, and reduce the probability of striking, improve the life and stability of cathode, finally realize stable pulse high-current output.

[0008] The purpose of the present application is realized by the following technical solutions:

[0009] The present application provides a kind of for microwave emission system's pulse electron gun, comprising:

[0010] Electron gun, electron gun includes high-voltage pulse power supply, cathode rod, initial emission cathode, electron multiplication module and anode cylinder, the negative pole of high-voltage pulse power supply is electrically connected with cathode rod, the positive pole of high-voltage pulse power supply is electrically connected with anode cylinder;Cathode rod and anode cylinder form the electric field covering initial emission cathode and electron multiplication module;Cathode rod is equipped with placing cavity, placing cavity is equipped with opening, opening is towards the electron output channel in anode cylinder;Initial emission cathode is arranged on the end of placing cavity far from opening;Electron multiplication module includes multiplication medium and multiple electron multiplication channels through multiplication medium, the side wall of multiplication medium and the side wall of opening are in good electrical connection, each electron multiplication channel is vertically arranged with initial emission cathode, and secondary electron multiplication material plating layer is arranged on the inner wall of each electron multiplication channel;

[0011] Further, annular metal gasket is arranged between multiplication medium and initial emission cathode, and the metal gasket separates an isolation space between the multiplication medium and the initial emission cathode.

[0012] Further, the electric field includes a first electric field located in the isolation space, a second electric field located in the electron multiplication module, and a third electric field located between the side of the cathode rod provided with the opening and the anode cylinder, the first electric field, the second electric field and the third electric field are all axisymmetric electric fields.

[0013] Further, it further comprises focusing equipment, the focusing equipment is arranged around the anode cylinder at the position of the third electric field, and the focusing equipment focuses the electron beam in the third electric field through a focusing magnetic field.

[0014] Further, the thickness of the metal gasket is 0.1-1 millimeter.

[0015] Further, the initial emission cathode adopts at least one of a tungsten or molybdenum needle tip, a carbon nanotube, graphene, a carbon fiber array or a metal nanorod array.

[0016] Further, the anode cylinder is provided with an annular protrusion near the opening of the placement cavity.

[0017] Further, the inner diameter of the annular protrusion is greater than the outer diameter of the electron multiplication module, and the difference between the inner diameter and the outer diameter ranges from 0 to 10 mm.

[0018] Further, the outer circumference and the inner circumference of the protrusion are both provided with a fillet. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A structure schematic diagram of a pulse electron gun suitable for a microwave emission system provided by the present application;

[0020] Figure 2 A structure schematic diagram of a multiplication medium in the multiplication module;

[0021] Figure 3 A system structure schematic diagram of a microwave emission device driven by the pulse electron gun;

[0022] Figure: 1, microwave signal generator; 2, electron gun; 21, high-voltage pulse power supply; 22, cathode rod; 23, anode cylinder; 231, protrusion; 24, initial emission cathode; 25, metal gasket; 26, electron multiplication module; 261, electron multiplication channel; 262, multiplication medium; 3, electron motion tube; 31, drift tube; 32, input cavity; 321, input slit; 322, first coupling hole; 33, output cavity; 331, output slit; 332, second coupling hole; 34, collector; 4, antenna; 5, electron beam; 6, electron group; 7, first focusing device, 8, second focusing device. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0024] Embodiment 1

[0025] This application discloses a pulsed electron gun for a microwave transmitting system, comprising a high-voltage pulse power supply 21, a cathode rod 22, an initial emission cathode 24, an electron multiplication module 26, and an anode cylinder 23. The high-voltage pulse power supply 21 provides the necessary voltage difference for the electron gun 2. The negative terminal of the high-voltage pulse power supply 21 is connected to the cathode rod 22, and the positive terminal of the high-voltage pulse power supply 21 is connected to the anode cylinder 23. The cathode rod 22 has a placement cavity with an opening facing the channel inside the anode cylinder 23, thereby forming an electric field between the two.

[0026] The cathode rod 22 serves as the starting point for electron emission and features a special structure: a cavity for accommodating the initial emission cathode 24 and the electron multiplier module 26. This cavity has an opening facing the channel within the anode cylinder 23. This design ensures that the electric field covers the entire cavity (i.e., both the initial emission cathode 24 and the electron multiplier module 26) while simultaneously allowing the electron beam 5 to smoothly emit initial electrons from the initial emission cathode 24. After being multiplied by the electron multiplier module 26, the electrons enter the channel within the anode cylinder 23 and are then output. The electric field coincides with the axis of the electron multiplier module 26.

[0027] Additionally, the initial emission cathode 24, serving as the initial electron source, is positioned at the end of the placement cavity furthest from the opening, emitting initial electrons under the influence of an electric field. These electrons then enter the electron multiplication module 26 for amplification. The electron multiplication module 26 includes a multiplication medium 262 and multiple electron multiplication channels 261 penetrating the multiplication medium 262, such as... Figure 3 As shown, the sidewall of the multiplication medium 262 maintains a good electrical connection with the sidewall of the opening. Each electron multiplication channel 261 is arranged perpendicularly to the initial emission cathode 24, and a secondary electron multiplication material coating is provided on the inner wall of each electron multiplication channel 261. Figure 2 As shown, the multiplication medium 262 preferably uses at least one of GaAs, GaN, SiC, Al2O3, SiO2, and ZrO2. Each electron multiplication channel 261 in the multiplication medium 262 is perpendicular to the initial emitting cathode 24. The number of electron multiplication channels 261 is determined by the current that a single channel can withstand; for example, the surface-stable secondary electron current density within the multiplication medium 262 can reach several hundred mA / mm². While controlling the current density to several hundred mA / mm², the number of electron multiplication channels 261 can be increased to 10. 2 -10 6 pcs / cm 2 This increases the total channel area, thereby increasing the total transmit current.

[0028] The electron multiplication module 26 multiplies and amplifies the initial electrons entering the electron multiplication channel 261 under the action of an electric field to form a strong current electron beam 5, ensuring that there are sufficient electrons participating in subsequent microwave generation. Since the diameter of the electron multiplication channel 261 affects the degree of electron multiplication, if the spacing of the electron multiplication channel 261 is too large, the number of times that the electrons collide with the surface of the electron multiplication channel 261 becomes small; if the diameter of the channel is too small, the incident energy of the electrons colliding with the surface of the electron multiplication channel 261 is too small to pull out the electrons; therefore, in order to achieve efficient multiplication of electrons, the present application preferably adopts an electron multiplication channel 261 with a length-diameter ratio of 20-100, and the diameter of the electron multiplication channel 261 is preferably 5-300 μm. The length of the electron multiplication channel 261 also affects the strength of the final output current; under the selected conductivity, the secondary electrons are multiplied, and if the length of the electron multiplication channel 261 is appropriate, a large current output can be effectively achieved; if the length of the electron multiplication channel 261 is too long, the number of collisions of the electrons therein will increase, resulting in insufficient incident energy of the subsequent collision with the surface of the electron multiplication channel 261, making it difficult to effectively pull out the electrons. Therefore, the present application preferably adopts an electron multiplication channel 261 with a length of 200-20000 μm.

[0029] It should be noted that the inner wall of the electron multiplication channel 261 is provided with a secondary electron multiplication material plating layer. The resistivity of the secondary electron multiplication material plating layer is 10 -8 -10 12 Ω·m, and at least one of Cu, SiO2, Al2O3, ZnO, SnO, MgO, BeO2, and BaO is preferably used. The initial emission cathode 24 adopts a low work function nanomaterial, and at least one of a tungsten or molybdenum needle tip, a carbon nanotube, graphene, a carbon fiber array, and a metal nanorod (wire) array is preferably used as the initial emission cathode 24. By using a low work function nanomaterial as the initial emission cathode 24, the initial emission cathode 24 can emit electrons at a lower electric field.

[0030] Further, a circular ring-shaped metal gasket 25 is arranged between the multiplication medium 262 and the initial emission cathode 24, and the metal gasket 25 separates an isolation space between the multiplication medium 262 and the initial emission cathode 24.

[0031] Specifically, by adjusting the thickness of the metal gasket 25, the physical distance between the initial emission cathode 24 and the multiplication medium 262 can be accurately controlled. This distance has an important influence on the initial emission electron emission performance, because the process of electron emission from the cathode to the multiplication channel is highly dependent on the strength of the electric field formed between them. The greater the electric field strength, the stronger the driving force of the electron, so it can more effectively overcome the emission threshold to achieve efficient emission. But too high electric field strength will also cause the breakdown of the initial emission cathode 24, so in order to achieve efficient emission of electrons, the thickness of the metal gasket 25 is preferably 0.1-1mm, the outer diameter is 5-15mm, and the difference between the inner diameter and the outer diameter is 1-2mm.

[0032] In addition, according to the preferred design of the present application, the outer diameter of the cathode rod 22 is 15-50mm, the thickness of the placement cavity is 5-10mm, the radius is 5-15mm, the outer diameter of the part of the cathode rod 22 on which the anode cylinder 23 is sleeved is 40-100mm, the radius of the part of the anode cylinder 23 opposite to the cathode rod 22 is 20-50mm, the outer diameter of the initial emission cathode 24 is 5-15mm, the length of the electron multiplication module 26 is 5-10mm, the outer diameter is 5-15mm, the distance between the cathode rod 22 and the anode cylinder 23 is 20-40mm, and the thickness of the metal gasket 25 is preferably 0.1-1mm. Based on the above parameter settings, the electric field at each place can have a suitable field strength, which can be used to generate, form and accelerate a strong current electron beam.

[0033] After the above settings, the electric field is divided into multiple different regions, i.e. a first electric field in the isolation space, a second electric field in the electron multiplication module 26, and a third electric field between the opening of the cathode rod 22 and the anode cylinder 23, and the first electric field, the second electric field and the third electric field are all axisymmetric electric fields. The first electric field is used to provide emission conditions for the initial emission cathode 24 and drive the initial electrons to drift to the electron multiplication module 26, the electron multiplication module 26 is located in the second electric field, and the electron multiplication module 26 includes uniformly arranged electron multiplication channels 261, the electron multiplication channels 261 and the second electric field are used to multiply and amplify the initial emission electrons entering the electron multiplication channels 261 to obtain amplified electron beams 5, and finally enter the channel in the anode cylinder 23 under the acceleration of the third electric field and the constraint of the magnetic field and then output. Among them, the electric field strength of the first electric field is 1-10MV / m, the electric field strength of the second electric field is 0.1-10MV / m, and the electric field strength of the third electric field is 1-20MV / m. Among them, the axisymmetric electric field can ensure that the electron beam 5 is subjected to uniform and stable electric field force during transmission, and at the same time, under the constraint of the focusing magnetic field, the electron beam 5 will not diffuse during the advancement process, thereby ensuring the stability of the electron beam 5, and thereby improving the system energy conversion efficiency.

[0034] Further, the anode cylinder 23 is provided with an annular protrusion 231 near the opening of the placement cavity. The protrusion 231 can form the required electric field strength with the cathode rod 22 at a closer distance, and can preliminarily focus the electron beam 5. In addition, the inner diameter of the annular protrusion 231 is greater than the outer diameter of the electron multiplication module 26, and the difference between the inner diameter and the outer diameter is in the range of 0-10 mm. That is, by setting the inner diameter of the anode cylinder 23 to be slightly larger than the outer diameter of the electron multiplication module 26, the anode cylinder 23 can cover the electron beam 5 transmitted out of the electron multiplication module 26, and ensure the stability of the electron movement.

[0035] Further, the outer circumference and the inner circumference of the protrusion 231 are both provided with a fillet. The design of the fillet can disperse the high-intensity electric field region that may be formed due to sharp corners, reduce the electric field strength of the region, and thus reduce the risk of the electric field reaching the breakdown threshold at the region. The durability and reliability of the protrusion 231 are improved.

[0036] Further, the focusing device is also included, and a plurality of first focusing devices are arranged around the anode cylinder at the third electric field position. Each first focusing device focuses the electron beam in the third electric field through a focusing magnetic field.

[0037] Specifically, in order to improve the trajectory stability and transmission efficiency of the electron beam 5, the first focusing device is arranged around the anode cylinder at the third electric field position. The first focusing device generates a focusing magnetic field with adjustable intensity, and precisely controls the movement trajectory of the electron beam 5 through the focusing magnetic field, so as to focus the electron beam 5 to a smaller area, reduce scattering, and keep the energy and shape stable. That is, the first focusing device 7 focuses the electron beam 5 in the third electric field through the focusing magnetic field, so that the electron beam 5 is continuously constrained and adjusted during the transmission process, and finally reaches the target area with a stable trajectory and high electron density.

[0038] In the embodiment of the present application, the electron gun 2 forms an electric field between the cathode rod 22 and the anode cylinder 23 under the action of the high-voltage pulse power supply 21. The initial emission cathode 24 emits electrons under the action of the electric field. The electrons enter the electron multiplication module 26 made of GaAs or the like to be multiplied, and form a high-energy electron beam 5. The length-diameter ratio, diameter and length of the electron multiplication channel 261 are optimized and designed to improve the electron multiplication efficiency and output current intensity. At the same time, the metal gasket 25 optimizes the initial electron emission performance, the electron multiplication module 26 improves the total output electron of the electron beam 5, and the focusing device focuses the electron beam 5 through the focusing magnetic field to improve the precision of the electron beam 5 and the system efficiency.

[0039] Embodiment 2

[0040] Based on the same concept, the present application provides an electron beam microwave emission device based on electron multiplication.

[0041] Specifically, the common electrical signal is converted into a signal in the microwave frequency band by the microwave signal generator 1 to provide necessary support for wireless communication. Then, the electron gun 2 generates and accelerates the electron beam 5, in which the initial emission cathode 24 emits electrons under the action of an electric field, and the high-energy electron beam 5 is formed after the electrons are multiplied by the electron multiplication module 26. In this process, the optimization of the length-diameter ratio, diameter, and length of the electron multiplication channel 261 ensures efficient multiplication of electrons, thereby increasing the total emission current and providing an adequate electron source for subsequent microwave generation. The electron motion tube 3 is responsible for modulating the speed of the electron beam 5 generated by the electron gun 2 and converting the energy of the electron beam 5 into a microwave signal. In the input cavity 32, the microwave signal generated by the microwave signal generator 1 establishes a high-frequency electric field to modulate the speed of the electron beam 5. The speed-modulated electron beam 5 is decelerated in the output cavity 33 and efficiently converts energy into a microwave signal. This conversion process not only improves the generation efficiency of the microwave signal but also ensures the stability and quality of the microwave signal.

[0042] The antenna 4 receives and concentrates the output microwave energy, and then radiates the microwave signal into space in its specific radiation mode, realizing wireless communication between the microwave transmission system and mobile devices. In addition, the setting of the metal pad 25 optimizes the emission performance of the initial electrons, and the preferred electron multiplication material improves the multiplication characteristics of the multiplication medium 262, ensuring the output performance of the electron beam 5 and further improving the energy conversion efficiency.

[0043] The microwave signal transmission device also focuses the electron beam 5 through a plurality of first and second focusing devices. The plurality of second focusing devices 8 are arranged around the electron motion tube 3, and each second focusing device 8 focuses the electron beam in the electron motion tube through a focusing magnetic field, improving the precision of the electron beam 5 and the working efficiency of the system. The magnetic field generated by these focusing devices can finely control the motion trajectory of the electron beam 5 and tightly constrain it together, reducing the scattering of the electron beam 5. This not only ensures that the electron beam 5 can reach the target area with extremely high precision, but also improves the focusing effect of the electron beam 5, thereby enhancing the transmission capability and coverage range of the microwave signal in the system.

[0044] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art can make various changes and modifications to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A pulsed electron gun for a microwave emission system, characterized by, The pulse electron gun comprises a high-voltage pulse power supply, a cathode rod, an initial emission cathode, an electron multiplication module and an anode cylinder, a negative electrode of the high-voltage pulse power supply is electrically connected with the cathode rod, and a positive electrode of the high-voltage pulse power supply is electrically connected with the anode cylinder; an electric field formed by the cathode rod and the anode cylinder covers the initial emission cathode and the electron multiplication module; the cathode rod is provided with a placing cavity, the placing cavity is provided with an opening, and the opening faces an electron output channel in the anode cylinder; the initial emission cathode is arranged on one end of the placing cavity away from the opening; the electron multiplication module comprises a multiplication medium and a plurality of electron multiplication channels penetrating through the multiplication medium, a side wall of the multiplication medium is in good electrical connection with a side wall of the opening, each electron multiplication channel is arranged vertically to the initial emission cathode, and a secondary electron multiplication material coating is arranged on an inner wall of each electron multiplication channel.

2. The pulsed electron gun for a microwave emission system of claim 1, wherein: A circular metal gasket is arranged between the multiplication medium and the initial emission cathode, and the metal gasket separates an isolation space between the multiplication medium and the initial emission cathode.

3. The pulsed electron gun for a microwave emission system of claim 2, wherein: The electric field comprises a first electric field in the isolation space, a second electric field in the electron multiplication module and a third electric field between the cathode rod provided with the opening and the anode cylinder, and the first electric field, the second electric field and the third electric field are all axisymmetric electric fields.

4. The pulsed electron gun for a microwave emission system of claim 3, wherein: Further comprising a first focusing device, the first focusing device is arranged around the anode cylinder at the position of the third electric field, and the first focusing device focuses an electron beam in the third electric field through a focusing magnetic field.

5. The pulsed electron gun for a microwave emission system of claim 2, wherein: The thickness of the metal gasket is 0.1-1 mm.

6. The pulsed electron gun for a microwave emission system of claim 1, wherein: The initial emission cathode adopts at least one of a tungsten or molybdenum needle tip, a carbon nanotube, graphene, a carbon fiber array or a metal nanorod array.

7. The pulsed electron gun for a microwave emission system of claim 1, wherein: The anode cylinder is provided with an annular protruding portion close to the opening of the placing cavity.

8. The pulsed electron gun for a microwave emission system of claim 7, wherein: The inner diameter of the annular protruding portion is greater than the outer diameter of the electron multiplication module, and the difference between the inner diameter and the outer diameter is 0-10 mm.

9. The pulsed electron gun for a microwave emission system of claim 8, wherein: The protruding portion is provided with a fillet on the outer circumference and the inner circumference.

10. An electron multiplier based electron beam microwave emission device, characterized by, The pulse electron gun for a microwave emission system comprises the pulse electron gun according to any one of claims 1-9.

Images