阅读说明：本技术 一种间隙宽度渐变的分布式输出谐振腔 (Distributed output resonant cavity with gradually-changed gap width ) 是由 李仁杰 陶理 郑生全 赵逸夫 钟小瑛 于 2020-07-23 设计创作，主要内容包括：本发明涉及一种间隙宽度渐变的分布式输出谐振腔,包括上耦合腔、下耦合腔、电子注通道以及多个不同宽度的间隙,间隙采用长槽间隙和短槽间隙交替分布排列的方式；同步周期根据电子注速度与工作模式相速度的同步关系确定；间隙数量的选择兼顾有效特性阻抗和模式间隔,在满足模式间隔大于设计带宽2倍的前提下,间隙数量取最大值；渐变式间隙宽度通过仿真优化确定,通过分析不同渐变间隙宽度方案的电场分布、模式间隔和有效特性阻抗,确定最佳的渐变间隙宽度。本发明间隙宽度渐变的分布式输出谐振腔,建立了能够避免模式竞争和增加有效特性阻抗的物理模型,实现了对间隙电场的优化以增大注波互作用效率的目的,提高了分布作用速调管的输出功率。(The invention relates to a distributed output resonant cavity with gradually changed gap width, which comprises an upper coupling cavity, a lower coupling cavity, an electron beam channel and a plurality of gaps with different widths, wherein the gaps adopt a mode of alternately arranging long slot gaps and short slot gaps; the synchronous period is determined according to the synchronous relation between the electron beam speed and the phase speed of the working mode; the selection of the number of the gaps gives consideration to effective characteristic impedance and mode intervals, and the number of the gaps is the maximum value on the premise that the mode intervals are larger than 2 times of the designed bandwidth; the gradual change gap width is determined through simulation optimization, and the optimal gradual change gap width is determined through analyzing the electric field distribution, the mode interval and the effective characteristic impedance of different gradual change gap width schemes. The distributed output resonant cavity with gradually changed gap width establishes a physical model which can avoid mode competition and increase effective characteristic impedance, realizes the optimization of a gap electric field to increase the wave injection interaction efficiency, and improves the output power of the distributed action klystron.)

1. A distributed output resonant cavity with gradually changed gap width is characterized by comprising an upper coupling cavity, a lower coupling cavity, an electron beam channel and a plurality of gaps with different widths, wherein the gaps adopt a mode that long groove gaps and short groove gaps are alternately distributed and arranged;

the synchronous period is determined according to the synchronous relation between the electron beam speed and the phase speed of the working mode;

the selection of the number of the gaps gives consideration to effective characteristic impedance and mode intervals, and the number of the gaps is the maximum value on the premise that the mode intervals are larger than 2 times of the designed bandwidth;

the gradual change gap width is determined through simulation optimization, and the optimal gradual change gap width is determined through analyzing the electric field distribution, the mode interval and the effective characteristic impedance of different gradual change gap width schemes.

2. A distributed output resonator according to claim 1, wherein the synchronization period represents a center distance between each adjacent gap, as determined by equation (1):

wherein p represents a synchronization period, v_pIndicating phase velocity of the operating mode, f₀For the operating frequency, m represents a phase shift parameter, the value of which is related to the selected operating mode.

3. A distributed output resonator according to claim 2, wherein for efficient beam interaction, the phase velocity of the working mode is approximately equal to the electron beam velocity, i.e. v_p≈v_eThe electron beam velocity is determined by equation (2):

in the formula, v_eRepresenting the electron beam velocity, c being the speed of light, U₀Is the operating voltage (unit: kV).

4. The cavity according to claim 1, wherein the mode spacing is defined as the minimum frequency difference between the operating mode and the adjacent mode, denoted as Δ f, the frequencies of the different modes can be obtained through simulation, and the difference between the frequency of the operating mode obtained through simulation and the frequency of the adjacent mode is calculated as the mode spacing.

5. The distributed output resonator according to claim 1, wherein the effective characteristic impedance reflects the intensity of the beam interaction capability, and the larger the number of gaps, the larger the effective characteristic impedance, the stronger the beam interaction capability; as defined in formula (3):

wherein (R/Q). M²Representing the effective characteristic impedance, E_zRepresenting the gap electric field, ω representing the resonance angular frequency, W_sIndicating the total stored energy of the resonator, β_eRepresenting the spatial phase wavenumber, j representing the imaginary unit, and z representing the lateral length.

6. The distributed output resonator according to claim 1, wherein the gap width is gradually changed by a specific method of determining the gradually changing gap width through simulation optimization: firstly, determining an initial value of the gap width, and scanning the gap width on the basis of the initial value of the gap width to obtain larger effective characteristic impedance and larger mode interval so as to obtain the optimized gradual change type gap width.

7. The graded gap width distributed output resonator according to claim 6, wherein the initial value of the gap width is determined by equation (4):

wherein d represents a gap width, θ_dRepresenting the gap transit angle, v_eRepresenting the electron beam velocity and ω the resonance angular frequency.

8. The graded gap width distributed output resonator cavity of claim 7, wherein the graded gap width distributed output resonator cavity comprises a plurality of tapered slotsVelocity v of electron beam_eDetermined by equation (2):

in the formula, v_eRepresenting the electron beam velocity, c being the speed of light, U₀Is the operating voltage (unit: kV).

Technical Field

The invention relates to the technical field of vacuum electronics, in particular to an output resonant cavity with multi-gap coupling and gap electric field optimization.

Background

The terahertz wave has the excellent characteristics of wide frequency band, good coherence, easy anti-stealth, strong anti-interference performance, strong penetration capacity and the like, and has very good application characteristics and technical advantages in the aspects of high-speed data transmission, broadband high-capacity communication, high-resolution imaging, medical detection and diagnosis and the like. However, the development of terahertz scientific technology is limited by the lack of being able to generate high-power and broadband terahertz radiation sources. The research work of the distributed action klystron based on the vacuum electronics is an important technical approach for generating a high-power, wide-band, high-efficiency and high-reliability radiation source in a terahertz frequency band, and has important application potential in the aspects of space-borne imaging radar, meteorological radar, fire control, monitoring and tracking radar, space-based and space-based high-power damage and destructive weapons.

Due to the limitation of the working frequency and geometric size similarity effect, the characteristic size of the terahertz frequency band distribution acting klystron is sharply reduced, and the power capacity of the device is rapidly reduced. The output resonant cavity is a core component of the distributed action klystron, and clustered electron beams and a gap electric field in the output cavity have strong interaction, so that the output power is obviously influenced. The traditional structure of the output resonant cavity with the equal gap width has the defect of insufficient output power.

Disclosure of Invention

The invention aims to solve the technical problem that the output power of the traditional output resonant cavity structure with equal gap width is not high enough, and provides a distributed output resonant cavity with gradually changed gap width, which can improve the distribution characteristic of a gap electric field, so that the interaction between clustered electron beams and the gap electric field is more sufficient, and the output resonant cavity can be used as the output cavity structure of a distributed action klystron to improve the output power of the distributed action klystron.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a distributed output resonant cavity with gradually changed gap width comprises an upper coupling cavity, a lower coupling cavity, an electron beam channel and a plurality of gaps with different widths, wherein the gaps adopt a mode that long groove gaps and short groove gaps are alternately distributed and arranged;

the synchronous period is determined according to the synchronous relation between the electron beam speed and the phase speed of the working mode;

the selection of the number of the gaps gives consideration to effective characteristic impedance and mode intervals, and the number of the gaps is the maximum value on the premise that the mode intervals are larger than 2 times of the designed bandwidth;

the gradual change gap width is determined through simulation optimization, and the optimal gradual change gap width is determined through analyzing the electric field distribution, the mode interval and the effective characteristic impedance of different gradual change gap width schemes.

In the above solution, the synchronization period represents a center distance between each adjacent gap, and is determined by equation (1):

wherein p represents a synchronization period, v_pIndicating phase velocity of the operating mode, f₀For the operating frequency, m represents a phase shift parameter, the value of which is related to the selected operating mode.

In the above scheme, for effective beam interaction, the phase velocity of the working mode is approximately equal to the electron beam velocity, i.e., v_p≈v_eThe electron beam velocity is determined by equation (2):

in the formula, v_eRepresenting the electron beam velocity, c being the speed of light, U₀Is the operating voltage (unit: kV).

In the above scheme, the mode interval is defined as the minimum frequency difference between the working mode and the adjacent mode, and is represented by Δ f, frequencies of different modes can be obtained through simulation, and the difference between the frequency of the working mode obtained through simulation and the frequency of the adjacent mode is calculated, that is, the mode interval.

In the above scheme, the effective characteristic impedance reflects the strength of the wave-filling interaction capability, and the larger the number of gaps is, the larger the effective characteristic impedance is, the stronger the wave-filling interaction capability is; as defined in formula (3):

wherein (R/Q). M²Representing the effective characteristic impedance, E_zRepresenting the gap electric field, ω representing the resonance angular frequency, W_sIndicating the total stored energy of the resonator, β_eRepresenting the spatial phase wavenumber, j representing the imaginary unit, and z representing the lateral length.

In the above scheme, the specific method for determining the gradual change gap width by simulation optimization is as follows: firstly, determining an initial value of the gap width, and scanning the gap width on the basis of the initial value of the gap width to obtain larger effective characteristic impedance and larger mode interval so as to obtain the optimized gradual change type gap width.

In the above scheme, the initial value of the gap width is determined by equation (4):

wherein d represents a gap width, θ_dRepresenting the gap transit angle, v_eRepresenting the electron beam velocity and ω the resonance angular frequency.

In the above scheme, the electron beam velocity v_eDetermined by equation (2):

in the formula, v_eRepresenting the electron beam velocity, c being the speed of light, U₀Is the operating voltage (unit: kV).

The invention has the beneficial effects that:

the invention provides a distributed output resonant cavity with gradually changed gap width, establishes a physical model capable of avoiding mode competition and increasing effective characteristic impedance, realizes the optimization of a gap electric field to increase the interaction efficiency of wave injection, and improves the output power of a distributed action klystron to a certain extent.

The invention has concise and clear principle and strong engineering practicability.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic diagram of a distributed output cavity with gradually changing gap widths according to an embodiment of the present invention;

FIG. 2 is a graphical illustration of the effect of gap count on effective characteristic impedance and mode spacing for an embodiment of the present invention;

FIG. 3 is a schematic diagram of the electric field distribution of the output cavity of an embodiment of the present invention;

FIG. 4 is a transverse electric field distribution plot at the center of the electron beam channel of the output resonator of an embodiment of the present invention;

FIG. 5 is a graph comparing the output power versus operating frequency for the gradual gap width of the present invention and a conventional equal gap width.

In the figure: 10. an upper coupling cavity; 20. a lower coupling cavity; 30. an electron beam channel; 40. a gap.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

The invention provides a distributed output resonant cavity with gradually changed gap width, which comprises an upper coupling cavity 10, a lower coupling cavity 20, an electron beam channel 30 and a plurality of gaps 40 with different widths, wherein the gaps adopt a mode of alternately distributing and arranging long-groove gaps and short-groove gaps, and can play a role in expanding the working bandwidth, as shown in figure 1. The gap 40 is the location where the electron beam interacts with the electric field, and thus the gap size has a significant effect on the interaction of the electron beam with the electromagnetic wave, and the determination of the gap size includes several:

(1) a synchronization period is determined.

The synchronous period represents the center distance between each adjacent gap, is determined according to the synchronous relation between the electron beam speed and the phase speed of the working mode, and can be determined by the formula (1):

wherein p represents a synchronization period, v_pIndicating phase velocity of the operating mode, f₀For the operating frequency, m represents a phase shift parameter, the value of which is related to the selected operating mode.

For efficient beam interaction, the phase velocity of the operating mode is approximately equal to the electron beam velocity (i.e., remains synchronous), i.e., v_p≈v_e. The electron beam velocity is determined by equation (2):

in the formula, v_eRepresenting the electron beam velocity, c being the speed of light, U₀Is the operating voltage (unit: kV).

(2) The number of gaps is determined.

The multi-gap resonant cavity adopts a plurality of distributed gap structures, so that the effective characteristic impedance is improved, and the interaction between the electron beam and the working mode is more sufficient. However, only one mode of the multiple resonant modes of the multi-gap resonant cavity can be used as a working mode, and the complexity of mode distribution is increased by the multi-gap structure, so that the mode competition risk between the working mode and the non-working mode is increased. Generally, the larger the number of gaps, the larger the effective characteristic impedance, and the stronger the wave-injection interaction capability; however, the larger the number of gaps, the smaller the pattern spacing, and the greater the risk of pattern competition. Therefore, the number of gaps in the multi-gap resonator is selected to achieve both effective characteristic impedance and mode spacing, i.e., to avoid mode competition and to increase effective characteristic impedance.

The mode spacing is defined as the minimum frequency difference between the operating mode and the adjacent mode, denoted as Δ f. Through simulation, the frequencies of different modes can be obtained, and the difference value between the frequency of the working mode obtained through simulation and the frequency of the adjacent mode is calculated, namely the mode interval. Typically the mode spacing is greater than 2 times the design operating bandwidth.

The effective characteristic impedance reflects the strength of the wave-filling interaction capacity and is defined as formula (3):

wherein (R/Q). M²Representing the effective characteristic impedance, E_zRepresenting the gap electric field, ω representing the resonance angular frequency, W_sIndicating the total stored energy of the resonator, β_eRepresenting the spatial phase wavenumber, j representing the imaginary unit, and z representing the lateral length.

(3) A progressive gap width is determined.

The scheme of the gradual change gap width needs to be determined through simulation optimization, and the optimal gradual change gap width is determined by analyzing the electric field distribution, the mode interval and the effective characteristic impedance of different gradual change gap width schemes. The specific method comprises the following steps: firstly, determining an initial value of gap width, scanning the gap width on the basis of the initial value of the gap width to obtain larger effective characteristic impedance and larger mode interval so as to obtain optimized gradual change type gap width, wherein the initial value of the gap width is determined by an equation (4):

wherein d represents a gap width, θ_dRepresenting the gap transit angle, v_eRepresenting the electron beam velocity and ω the resonance angular frequency.

In this embodiment, the operating voltage U₀16.5kV, operating frequency f₀At 220GHz, a phase shift parameter m of π, a synchronization period p of 0.168mm as obtained from equations (1) and (2), consideringThe processing precision and the phase velocity of 10 mu m are slightly less than the requirement of the electron beam velocity, and the period value is 0.16 mm. In equation (4), the gap transition angle θ is determined according to engineering experience_dThe value is 1.5, and the resonance angular frequency omega is 1.38 × 10¹²rad/s, the initial value of the gap width d obtained from equation (4) is 0.08 mm. The radius of the channel is 0.15mm, and the radius of the electron beam is 0.10 mm.

As shown in fig. 2, is the effect of the number of gaps on the effective characteristic impedance and the mode spacing, where the effective characteristic impedance curve is obtained according to equation (3). As the number of gaps increases, the effective characteristic impedance gradually increases and the mode spacing gradually decreases. When the number of the gaps is 9, 11 and 13, the mode spacing is respectively 2.62GHz, 1.96GHz and 1.70GHz, and the designed resonant cavity adopts 11 gaps based on the consideration that the design bandwidth of about 1GHz, the larger effective characteristic impedance and the mode spacing are 2 times larger than the design bandwidth.

In FIG. 1, parameter d₁～d₁₁The gap widths of the respective gaps are indicated respectively. A simulation model is constructed in electromagnetic simulation software CST, in order to observe electric field distribution conveniently, a background material is set as PEC, a resonant cavity model adopts a vacuum model with an inverted structure (namely, the position of an electric field is vacuum) to facilitate modeling, and boundary conditions are set as electric boundaries. On the basis that the initial value of the gap width is 0.08mm, scanning the gap width to obtain larger effective characteristic impedance and larger mode interval, wherein the optimized gradual change gap width is d₁＝d₂＝d₃＝0.12mm，d₄＝d₅＝d₆＝d₇＝0.10mm，d₈＝d₉＝d₁₀＝d₁₁＝0.08mm。

Performing eigenmode simulation under the parameter to determine the working mode as TM₁₁₀The electric field distribution of the-pi film is shown in fig. 3, the electric field is concentrated in the gaps, the electric field directions of the adjacent gaps are opposite, and the positive and negative alternate distribution rule is presented. The distribution of the transverse electric field in the center of the channel is shown in fig. 4, each electric field peak corresponds to a corresponding gap, and the electric field intensity of the long slot gap is stronger than that of the short slot gap.

To verify the gap width gradient proposed by the present inventionThe performance of the variable distributed output resonant cavity is changed, a distributed action klystron simulation model consisting of an input cavity with equal gap width, two middle cavities with equal gap width and a designed output cavity with gradually changed gap width is constructed to carry out particle simulation, and the conductivity of oxygen-free copper of a cavity material is set to be 2.36 × 10 in the simulation process in consideration of the metal loss of a terahertz frequency band⁷And (5) S/m. By scanning the operating frequency, the variation curve of the output power with the operating frequency is obtained as shown in fig. 5, and the maximum peak output power reaches 650W. When an output cavity with equal gap width is used, the maximum peak power is only 360W. Compared with an output resonant cavity with equal gap width, the distributed output resonant cavity with gradually changed gap width provided by the invention has the advantages that the output power is improved by 80%, and the output power is obviously improved.

The multi-gap distributed output resonant cavity with gradually changed gap widths increases the interaction capacity of electron beams and electromagnetic waves by optimizing the distribution of the transverse electric field of the output resonant cavity, and provides a feasible solution for improving the output power of the distributed action klystron.

While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.