CN110797243B - An Electron Optical System with Nested Coaxial Launch Asynchronous Electron Beam - Google Patents

Abstract

The invention discloses a nested coaxial electron optical system for emitting asynchronous electron beams, which is applied to the technical field of vacuum electrons and aims at solving the problem that the existing multi-beam terahertz electron gun cannot generate asynchronous electron beams, and the electron gun sequentially comprises: circular electron beam cathode emission face, transition structure and positive pole, the transition structure includes at least: an annular electron beam cathode emission surface; the circular electron beam emitted by the circular electron beam cathode emission surface is firstly accelerated by the voltage difference between the cathode emitting the circular electron beam and the transition structure for the first time, and then accelerated by the voltage difference between the transition structure and the anode for the second time; the annular electron beam emitted from the surface of the cathode of the annular electron beam is accelerated by the voltage difference between the transition structure and the anode, enters the high-frequency system with the circular electron beam accelerated twice, interacts with electromagnetic waves by the injection waves, and is collected by the collector.

Description

An Electron Optical System with Nested Coaxial Launch Asynchronous Electron Beam

technical field

The invention belongs to the technical field of vacuum electronics, in particular to a nested coaxial emission asynchronous electron injection electron optical system.

Background technique

With the application of terahertz technology in civil and military fields such as ultra-high-speed communication, ultra-high-resolution radar, and security inspection, the demand for terahertz sources with W-level power is increasing. The current generation methods of terahertz sources are mainly based on solid-state devices, optical devices and vacuum electronic devices. Among them, the terahertz source of vacuum electronic devices is currently the most potential terahertz source due to its advantages of high power, high efficiency, and strong stability. However, in the terahertz band, the interaction circuit also faces the problem of reducing the size, and it also poses a great challenge to the current processing technology, especially as the frequency band increases, the interaction circuit with small geometric size causes electronic The difficulty of injection transport poses certain challenges to the generation and focusing of large current densities.

In order to reduce the processing difficulty and generate high-power terahertz sources, cathodes capable of generating large currents and transporting large current densities in small-sized terahertz devices, novel terahertz slow-wave structures, and theory based on Pierce's Note-Wave Interaction Innovation is the current research focus of vacuum terahertz sources. Among them, the patent "a dual-electron injection terahertz folded line-return amplifier" is a theoretical innovation of injection-wave interaction, providing a new type of injection-wave interaction theory. In the wave amplification theory, two asynchronous electron beams interact with the forward wave and the backward wave, respectively. A feedback injection-wave interaction loop is constructed, which improves the output power, gain, and electronic efficiency compared with the traditional injection-wave interaction, thereby obtaining a high-power terahertz source. At the same time, through the establishment of a feedback loop, the interaction length can be shortened, the problem of the consistency of the electron injection channel caused by the interaction length can be greatly reduced, and the challenge to the current processing technology is reduced. Therefore, an electron optical system for generating asynchronous electron beams is imminent. The traditional multi-beam terahertz electron gun cannot generate asynchronous electron beams, and the distance between electron beams is too large due to the limitations of technology and materials, which poses certain challenges to the miniaturization of terahertz sources and the processing and assembly of multiple electron beam channels. , and therefore no longer meet the needs of development.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention proposes a nested electron optical system for coaxially emitting asynchronous electron beams, which can realize coaxial emission of electron beams while generating asynchronous electron beams, and shorten the distance between the electron beams. The distance is conducive to the miniaturization and integration of the device.

The technical scheme adopted in the present invention is as follows: a nested electron optical system for coaxially emitting asynchronous electron injection, comprising: an electron gun, a magnetic focusing system and a collector structure, the electron gun sequentially comprises: a circular electron injection cathode emitting surface, A transition structure and an anode, the transition structure at least includes: an annular electron injection cathode emitting surface.

Further, the anode potential is 0, the transition structure potential is -V1, the circular electron injection cathode emission surface potential is -V2, and V2>V1.

Further, it also includes: a first focusing electrode, the first focusing electrode is arranged at the emission surface of the circular electron injection cathode, and the potential of the first focusing electrode is -V2.

Further, it also includes a second focusing electrode, the second focusing electrode is a nested focusing electrode arranged at the position of the emission surface of the annular electron injection cathode.

Further, the circular electron injector and the annular electron injector are nested and coaxially distributed on the cross section of the electron injector channel.

Further, a protection electrode is further included between the transition structure and the circular electron injection cathode emitting surface.

Beneficial effects of the present invention: The electronic optical system of the present invention for nested coaxial emission of asynchronous electron beams realizes the nested coaxial emission of high-quality circular electron beams and annular electron beams, and has the following advantages:

1. Compared with the parallel arrangement or other non-nested arrangement of multiple cathode emitting surfaces in the multi-electron electron injection gun, the present invention adopts the method of nesting the cathode emitting surfaces to shorten the distance between the electron injection axes and reduce the cathode emission. The lateral size of the surface is conducive to the miniaturization and integration of the electron gun;

2. The present invention realizes the launch of two asynchronous electronic injections;

3. The present invention adopts the arrangement of nested cathode emission surfaces, which can reduce the difficulty of installation of the hot wire and the difficulty of processing and assembly of the electron gun;

4. The electronic optical system of the present invention for the nested coaxial emission of asynchronous electron beams can be nested to emit two coaxial electron beams, and the two electron beams can be transmitted in one electron beam channel, thereby reducing the electron beam injection in the slow wave structure The processing difficulty of the channel;

5. The present invention can generate two electron beams with different working voltages (ie asynchronous electron beams);

6. The present invention enables the secondary acceleration of the circular electron injection through the transition structure.

Description of drawings

Fig. 1 is the electron optical system schematic diagram of the nested coaxial emission asynchronous electron injection of the present invention;

Fig. 2 is the distribution schematic diagram of the cross section of electron injection channel in circular and annular electron injection channel according to the embodiment of the present invention;

3 is a schematic structural diagram of an electron gun and a magnetic focusing system according to an embodiment of the present invention;

Fig. 4 is the enlarged schematic diagram of the transition structure in Fig. 3;

Fig. 5 is the distribution of the magnetic field along the electron injection transport direction in the embodiment of the present invention;

6 is an electron injection trajectory diagram and a potential distribution diagram in an embodiment of the present invention;

Fig. 7 is the lateral distribution diagram of electron injection in the slow-wave structure in the embodiment of the present invention;

Fig. 8 is the electron injection current in the embodiment of the present invention;

Reference sign: 1 is an electron gun, 2 is a magnetic focusing system, 3 is a collector, 11 is a circular electron injection cathode emitting surface, 12 is a transition structure, 13 is an anode, 14 is a first focusing pole, and 15 is a circular electron Note, 16 is a ring electron injection, 17 is an electron injection channel, 18 is a protection electrode, 121 is a ring-shaped electron injection cathode emitting surface, 122 is a second focusing electrode (also called a nested focusing electrode in the embodiment of the present invention), 170 is a Electron injection channel wall.

Detailed ways

In order to facilitate those skilled in the art to understand the technical content of the present invention, the content of the present invention will be further explained below with reference to the accompanying drawings 1-6.

As shown in FIG. 1, the electron optical system for the nested emission of asynchronous electron beams includes: an electron gun 1, a magnetic focusing system 2 and a collector structure 3; the electron gun 1 sequentially includes: a circular electron beam cathode emitting surface 11, a transition structure 12 and an anode 13. The transition structure 12 at least includes: a ring-shaped electron injection cathode emitting surface 121; the circular electron injection 15 emitted by the circular electron injection cathode emitting surface 11 is subjected to a first pass through the voltage difference between the cathode 11 and the transition structure 2. The second acceleration is carried out through the voltage difference between the transition structure 2 and the anode 13; the annular electron injection 16 emitted by the annular electron injection cathode emitting surface 121 is accelerated through the voltage difference between the transition structure 2 and the anode 13 After that, the circular electron beam 15 after being accelerated twice enters the high-frequency system to interact with the electromagnetic wave and is collected by the collector 3 .

As shown in FIG. 1 , it also includes two focusing electrode structures, wherein the first focusing electrode 14 only focuses the circular electron beams 15 ; the transition structure 2 includes a nested focusing electrode in addition to the annular electron beam cathode emitting surface 121 . The pole 122 and the nested focusing pole 122 focus the circular electron bead 15 and the ring electron bead 16, and achieve high-quality electron beam emission.

As shown in FIG. 2 , the circular and annular electron injection channels are nested and coaxially distributed in the cross section of the electron injection channel, and the electron injection channel wall of the electron injection channel 17 is marked as 170 .

The circular electron note 15 and the ring electron note 16 enter the high frequency system through the same electron note channel.

In this embodiment, the cathode potential of emitting circular electrons is -V2, the transition structure potential is -V1, and the anode potential is 0;

The transition structure, as one of the components of the different velocity electron injection gun of the present invention, is an important part of the nested coaxial electron injection gun, and has the high potential function of the anode. -V1), to accelerate the circular electron injection for the first time; at the same time, it has the function of emitting electron injection of the cathode to realize the emission of annular electron injection, and also has the function of focusing pole. Through the design of the nested focusing pole, Realize the transmission of circular and annular electron beams. The nested coaxial emission of high-quality circular electron beams and annular electron beams is realized under the optimization of structural design and geometric dimensions.

The magnetic focusing system in the present invention plays an important role in the nested coaxial stable transmission of electron injection. In order to prevent the magnetic field from being too large or too small to affect the electron beam, attention should be paid to the adjustment of the electron beam voltage, current and radius in the selection of the beam interaction electron beam so that the Brillouin magnetic fields of the ring electron beam and the circular electron beam are approximated. equal. Therefore, a suitable magnetic field is selected to carry out the bunching of the electron beam, realize the stable transmission of the electron beam, and carry out the beam interaction with the electromagnetic wave to achieve the purpose of energy transfer.

Those skilled in the art should note that in practical applications, the cathode, the transition structure, the distance between anodes, the potential, the size and shape of the emitting surface, the shape of the focusing electrode, etc., can be adjusted according to the shape and size of the specific electron beam. ; As shown in Figure 3, the present embodiment provides an example of an electron optical system with a nested coaxial emission asynchronous electron injection of structural dimensions, and the specific parameters are as follows:

In this embodiment, the voltage of the circular electron bead is 16380V, the current is 0.013A, and the radius of the electron bead is 0.05mm; the voltage of the ring electron bezel is 5500V, the current is 0.013A, the inner radius of the electron bead is 0.09mm, and the outer radius is 0.12 mm.

As shown in Figure 3, the electron gun structure provided in this embodiment:

In order to avoid excessive voltage difference between the circular electron injection cathode and the transition structure, resulting in bombardment of the transition structure by electron injection, the present invention also adds a protective electrode 18 between the transition structure and the circular electron injection cathode with a potential of -12680V. As shown in FIG. 4 is an enlarged schematic view of the transition structure 12 in FIG. 3 . As shown in FIG. 4 , when the software simulation is used, the second focusing electrode and the cathode emitting annular electrons are integrated as a whole, which is no longer like the schematic focusing electrode in FIG. 1 . There is a gap with the cathode. The circular electron injection cathode potential V2=16380, the transition structure potential V1=5500V, and the anode structure potential is zero.

The magnetic field in the magnetic focusing system adopts a uniform magnetic field, and is wound from the position of the transition structure through coil winding. After size optimization, a uniform magnetic field of 0.2T is achieved within the range of 70mm, as shown in Figure 5;

Finally, a high-quality coaxial asynchronous electron beam with a stable transmission of 70mm is emitted. Its potential distribution and electron trajectory are shown in Figure 6. The distribution of the electron beam on the electron beam channel is shown in Figure 7. The electron at z=72.43mm is shown in Figure 7. Note shape, and the electron injection current is 0.013A as shown in Figure 8, so the electron optical system can realize two coaxial asynchronous electron beams (circular voltage is 16380V, current is 0.013A, electron beam radius is 0.05mm; annular The voltage is 5500V, the current is 0.013A, the inner radius of the electronic injection is 0.09mm, and the outer radius is 0.12mm) to meet the design requirements. z represents the electron injection channel position.

Those of ordinary skill in the art will appreciate that the embodiments described herein are intended to assist readers in understanding the principles of the present invention, and it should be understood that the scope of the present invention is not limited to such specific statements and embodiments. Various modifications and variations of the present invention are possible for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims (3)

1. A nested, co-axial electron optical system for emitting asynchronous electron beams, comprising: electron gun, magnetic focusing system and collector structure, electron gun includes in proper order: circular electron beam cathode emission face, transition structure and positive pole, the transition structure includes at least: an annular electron beam cathode emission surface; the circular electron beam emitted by the circular electron beam cathode emission surface is firstly accelerated through the voltage difference between the cathode and the transition structure for the first time, and then accelerated through the voltage difference between the transition structure and the anode for the second time; the circular electron beam emitted by the cathode emission surface of the annular electron beam is accelerated through the voltage difference between the transition structure and the anode, enters a high-frequency system through the circular electron beam after being accelerated twice, is subjected to wave injection interaction with electromagnetic waves, and is collected by a collector; the circular electron beams and the annular electron beams are nested and coaxially distributed on the cross section of the electron beam channel, so that the two electron beams are transmitted in one electron beam channel;

the anode potential is 0, the transition structure potential is-V1, the circular electron-beam cathode emission surface potential is-V2, and V2> V1.

2. The nested, coaxial electron optical system for emitting asynchronous electron beams according to claim 1, further comprising: the focusing electrode is arranged at the emitting surface of the circular electron beam cathode, and the potential of the first focusing electrode is-V2; the second focusing electrode is a nested focusing electrode arranged at the position of the emission surface of the annular electron beam cathode.

3. A nested, co-axial, asynchronous electron beam emitting electron optical system according to claim 1 or 2, further comprising a guard electrode between the transition structure and the circular electron beam cathode emission surface.

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