Numerical study of chaotic oscillations in the electron beam with virtual cathode in the external non-uniform magnetic fields

In this Letter the results of theoretical investigations of the chaotic microwave oscillator based on the electron beam with a virtual cathode are presented. Nonlinear non-stationary processes in these electron systems are studied by means of numerical analysis of 2.5D model. It was discovered that the non-uniform external magnetic field value controls the dynamical regime of oscillations in the virtual cathode oscillator. The processes of the chaotization of output microwave radiation are described and interpreted from the point of view of the formation and interaction of electron structures (bunches) in the electron beams. The numerical results have shown that the investigated electron system with virtual cathode could be considered as a promising controlled source of wideband chaotic oscillations in the microwave range.     

Wideband chaotic oscillation in a self-oscillatory system with a nonlinear transmission line on magnetostatic waves

Wideband chaotic microwave oscillation in a ring self-oscillatory system is studied. The system includes a solid-state power amplifier and a wideband nonlinear transmission line with a ferromagnetic film in which magnetostatic waves of different types are excited. It is found that the eigenmodes of the self-oscillatory system excited in the passband of the transmission line on magnetostatic waves become noisy because of spin wave parametric excitation due to the magnetostatic wave and nonlinearity of the power amplifier. A continuous spectrum of modes observed in the wideband chaotic signal is associated with the presence of a descending portion in the dynamic characteristic of the nonlinear transmission line, which arises when a magnetostatic surface wave is excited.     

Experimental results from a tandem BWO-TWT system used to generatehigh-power microwaves

A relativistic backward wave oscillator (BWO) in tandem with a traveling wave tube (TWT) amplifier has been used to generate relatively long pulses of high-power X-band microwaves. In these experiments, a BWO is used to modulate the annular relativistic electron beam, which subsequently drives a TWT producing high-power microwave radiation. A special RF sever located between the two structures cuts off microwaves generated in the BWO from the TWT. Peak powers in excess of 100 MW are observed with overall beam-to-microwave efficiencies as high as 35%. By operating the BWO below saturation levels, pulse-shortening effects are minimized so that microwave pulses of duration comparable to that of the beam (100 ns) are possible. The operating frequency of the tandem system is tuned from 11 to 12 GHz by varying the effective energy of the beam     

An ultrabroadband microwave chaos generator with electron feedback: On the band of generation,statistical properties of signals,and field of application

An experimental investigation of the chaotic signals of a microwave generator with electron feedback (based on a virtual cathode) was carried out. It was found that microwave chaos generators with electron feedback are of ultraband generation. The statistical properties of the generated chaotic signals were shown. The perspective fields of application for the considered ultrabroadband chaos generators were given.     

Study of a compact external magnetic field radial split-cavity oscillator

With the experiment result analyses of a coaxial virtual cathode oscillator (CVCO), a new kind of compact radial split cavity oscillator (RSCO) is presented in this paper. On the oscillator, a low resistance tube is formed by using the diode structure of a CVCO, and a radial split-cavity structure is formed by several meshes that cause the electronic beam to transmit. Calculating all kinds of parameter, at the input parameter 350 kV, 27 kA, the numerical simulation results show that the average output microwave power is about 4.0 GW, the microwave frequency is 1.37 GHz, and the electronic efficiency is 42.3%.     

An investigation into density-wave propagation within high-temperature superconducting plasmas for use in creating traveling-wave devices

This paper theoretically investigates a novel application of high-temperature superconductors where the superconductor serves as the active component in a microwave or millimeter traveling-wave amplifier. A guided electromagnetic wave interacts with a dc superconducting electron current to set up charge-density gradients within the superconducting electron "plasma." The electromagnetic wave gradually extracts energy from the superconducting electrons by traveling in phase synchronism with these charge gradients. The interaction mechanism is similar to that of a conventional traveling-wave tube amplifier or oscillator. We have modeled the wave behavior of superconducting electrons using the London equations and a two-fluid approach. Our model includes dissipation within the superconductor, and it shows that traveling-wave devices may be possible using high-quality thin-film superconductors in which dissipation is kept low.     

新型高功率虚阴极径向反射速调管振荡器

 提出了一种新型的高功率虚阴极径向反射速调管振荡器,它结合了虚阴极振荡器容易起振和速调管微波产生效率较高的特点。利用虚阴极反射电子束对调制腔的正反馈,可以减小起振电流和起振时间,而且提高了微波产生效率。它是一种结构简单、紧凑的器件。用2.5维PIC程序对这种器件进行了数值模拟研究。得到的数值模拟结果表明,输入电压620 kV,电流25 kA,输出微波周期平均功率为2.5 GW。虚阴极振荡频率被锁定,频率为1.25 GHz。     

行波管放大器中场极限环和混沌行为的阈值分析

以场方程和电子运动方程为基础，分析了行波管放大器中辐射场演化过程中出现极限环振荡和混沌态的电流阈值.结果表明：在某些参数范围内，辐射场会出现这些非线性不稳定态.相互作用区域越长，失谐量对阈值的影响越明显.当器件工作在非线性区域时，输出功率与电流、失谐量和相互作用区长度三个参数的关系变得紊乱无序，控制这三个参数在输出功率曲线的峰值点上，可在非线性区域获得较高的输出功率. 关键词： 行波管 辐射场 阈值 混沌     

同轴波导虚阴极振荡器二极管参数优化的研究

采用粒子模拟研究了同轴波导虚阴极振荡器二极管参数对微波效率和频率的影响,得到了由二极管参数改变引起的二极管阻抗变化及其对微波效率的影响规律. 借鉴具有慢波结构的高功率微波器件中微波模式特性阻抗的计算方法,给出同轴波导虚阴极振荡器中微波主模式特性阻抗的理论计算公式. 将理论计算结果与由粒子模拟对器件进行优化后得到的二极管阻抗进行比较,发现当反映电子束特性的二极管阻抗与微波主模式特性阻抗匹配时,虚阴极振荡器具有较高的束波功率转换效率. 进一步用特性阻抗对其他几种典型结构的虚阴极振荡器进行分析,验证了该方法的合理性,为设计高效率虚阴极振荡器提供了理论指导. 关键词： 虚阴极振荡器 同轴波导 二极管参数 特性阻抗     

轴向提取矩形波导TE10模虚阴极振荡器

 轴向提取矩形波导TE₁₀模虚阴极振荡器可以不需要模式转换器或弯曲过渡波导而直接通过天线轴向辐射微波，从而使微波源及其辐射系统更加紧凑。粒子模拟结果表明，在400 keV，8.9 kA的束流条件下，轴向提取矩形波导TE₁₀模虚阴极振荡器在2.12 GHz处可以获得功率为500 MW的高功率微波输出，功率效率为14%，频率、模式纯净。这些结果为相同波段同类装置的小型化提供了一条可能的技术途径。     

Analysis of the instability in relativistic traveling wave tube

The relativistic traveling wave tube is an important high power microwave source. The corrugated cylindrical waveguide is usually used as slow wave structure of this device. Starting from wave equation and using boundary conditions, dispersion relation is derived for the corrugated waveguide, in which an intense relativistic electron beam propagates along the axis. Two cases which are shorter period and longer period are discussed in this paper respectively. The small signal gain of the relativistic traveling wave tube is analyzed and some conclusions are drawn. The analysis method presented in this paper can be extended to other types of slow wave structures of relativistic traveling wave tube.     

预调制型同轴虚阴极振荡器数值模拟

提出一种高效率预调制型同轴虚阴极振荡器,进行了数值模拟研究。研究表明:径向束流预调制型同轴虚阴极振荡器利用在束-波互作用区加载金属圆环形成谐振腔,改变束-波互作用区的电场,对电子束进行调制。圆筒形金属形成的调制腔产生的电场既对电子束进行了调制,同时对微波频率进行了锁定,其谐振频率主要是由加载的金属圆筒的长度和两个圆筒之间的径向距离决定。经过优化设计,在600 kV,73 kA无外加引导磁场的条件下,预调制型同轴虚阴极振荡器获得了平均功率6 GW,频率为2.575 GHz的微波输出,效率达到13.94%。     

吉瓦级强流相对论多注电子束二极管的优化设计与实验研究

多注相对论速调管放大器可在较高的工作频段实现GW级功率微波产生,在很多领域得到了发展和应用.多注相对论速调管中强流相对论多注电子束相互之间存在空间电磁场的作用,使得多注电子束从二极管引入多注漂移管,以及在多注漂移管中的传输运动受到影响,导致电子束会轰击到管壁上,早期实验中多注电子束的传输通过率较低.本文对功率数GW的强流相对论多注电子束在二极管与多注漂移管中的运动过程进行了理论分析与粒子仿真模拟,得到强流相对论多注电子束的传输运动规律.对多注二极管的结构进行了优化设计,仿真设计实现强流相对论多注电子束的传输通过率达到99%,并且开展了验证实验研究,实验在电子束电压为801 kV,电流为9.3 kA的情况下,电子束的传输通过率达到92%.     

新型虚阴极振荡器的研究

 采用小信号理论，在考虑到透射、反射束电子不同作用下，分析了虚阴极振荡器产生微波的机制，获得了计算微波主频的方法，讨论了增强束波作用效率的方法，并提出一种新型结构的虚阴极振荡器。该振荡器的阳极后放置了一个谐振腔，谐振腔长度很小，虚阴极不能在其中形成，谐振腔受到反射电子束激励并建立强场，场对入射电子进行调制，同时采用同轴结构引出微波。利用2.5D PIC 程序对新型的结构进行了数值模拟，验证了理论分析的正确性。在入射电子束电子能量为520keV和电子束流12.5kA的条件下，获得微波平均功率为1GW，频率为3.66GHz，平均束波转换效率为15.3%。     

Mutual Amplification of two Traveling Transverse Waveguide Modes Coupled by a Bragg Structure

We study the possibilities of using mutual amplification (at one frequency) of two traveling transverse waveguide-system modes, coupled by a Bragg structure, in electron microwave amplifiers. Based on the universal asymptotic equations, we show that the broadening of the bandwidth of resonant electron–wave interaction in such a device can lead to a significant increase in the efficiency and make the amplifier less sensitive to the electron velocity spread.     

Chaotic soliton switching generation using a nonlinear micro ring resonator for secure packet switching use

We propose a new design of the secure packet switching device using the nonlinear behaviors of soliton in a micro ring resonator, where the nonlinear penalty of light traveling in the device becomes beneficial. The chaotic signals are generated by a Kerr effects nonlinear type of the input soliton pulse in a micro ring resonator, where the control input power can be used to specify the output filtering signals. Some device parameters are chosen and simulated using the proposed model. The potential of using such a device for communication security is performed and discussed. For instance, the packet switching of the chaotic encoding data increases from the chaotic signal encoding of 100 bits⁻¹. Results obtained have shown the potential of using such a proposed device for the tunable bandpass and band-stop filters, in which packet switching data can be performed and secured.     

Feasibility Study of Axially- Extracted Virtual Cathode Oscillator

In this paper, we have analyzed the design parameters of the axially - extracted virtual cathode oscillator, which is high-power microwave source based on the concept of the virtual cathode associated with the intense relativistic electrons beam oscillations in the electrostatic potential well. The microwave emission by the virtual cathode oscillator results from both the space and time oscillations of virtual cathode and reflexing electrons trapped in the potential well between the virtual and real cathodes. In the X-band frequency spectrum 700 MW microwave peak power has been obtained analytically by the solid electron beam of 300 kV and 20 kA for feasible design parameters. The analysis has been performed by 2-dimensional, relativistic, electromagnetic particle-in-cell simulation code XOOPIC.     

同轴虚阴极谐振效应研究

中国工程物理研究院应用电子学研究所的一些实验表明由阳极反射板、阳极网和阴极发射的电子束形成的环状虚阴极围成的准谐振腔是决定同轴虚阴极输出微波功率和传输模式的关键所在. 在二极管电压350kV，电流23kA条件下，获得了500MW的微波输出功率，能量转换效率约6.2％，工作频率3.3GHz，输出微波主要由TM₀₁模式和TE₁₁模式组成. 对同轴虚阴极的谐振效应进行了分析. 关键词： 高功率微波 同轴虚阴极 谐振腔 模式竞争     

Relativistic carcinotron with a thermionic injector of electrons

An experimental study directed to the determination of a mechanism for microwave breakdown in a relativistic X-band carcinatron is presented. An electron beam was generated using a thermionic cathode, which provided a stable beam geometry. The use of this cathode decreased the probability of breakdown caused by electron bombardment of the slow-wave structure. An important part played in microwave breakdown are molecules absorbed on the slow-wave structure surface. It is shown that the presence of these molecules, an implementation of conditions for secondary-electron resonant discharge (SERD), can result in a very fast (during 10-20 ns) limitation of the radiation pulsewidth. To remove the adsorbed molecules, heat degassing of the slow-wave structure and a collector of electrons was applied, going on continuously, during a working day of the device. By degassing and choice of slow-wave structure material, output radiation power of the device was increased by a factor of ten (up to 5 MW at the pulsewidth of 10 μs)     

X波段长脉冲同轴多注相对论速调管放大器的分析与设计

为了提高相对论速调管放大器的工作频率、输出功率以及转换效率, 结合三重轴相对论速调管和多注速调管的特点, 采用三维电磁粒子模拟软件分析与设计了工作在X波段的长脉冲同轴多注相对论速调管放大器, 通过优化设计有效地抑制了X波段长脉冲相对论速调管放大器的自激振荡, 避免了脉冲缩短现象的产生, 使X波段相对论速调管放大器在长脉冲状态下能够稳定工作, 在注入微波功率为70 kW、束压为600 kV、束流为5 kA、轴向引导磁感应强度为0.8 T的条件下, 输出微波功率达到了1.23 GW, 效率为41%, 增益为42 dB.