MC55低阻抗强流脉冲电子加速器研制

介绍了MC55低阻抗强流脉冲电子加速器的结构及主要技术参数,给出了加速器的初步调试结果。该加速器由Marx发生器、10Ω水介质单筒形成线、高压自击穿气体开关、水介质传输线和真空二极管组成。经过初步调试,该加速器可以产生电压500 kV,电流50 kA,脉冲宽度50 ns的强流电子束。目前MC55加速器已应用于同轴虚阴极振荡器高功率微波源的实验研究。     

Study of transients in the formation of heavy-current nanosecond electron beams

Results are presented from experimental and numerical studies of the spatial and temporal microstructure of a relativistic heavy-current electron beam of nanosecond duration. The beam is formed in a magnetically insulated coaxial diode with an edge-emitting cathode. Microcurrent oscillations and azimuthal nonuniformity of the beam are seen, the scale of the latter depending on the maximum cyclotron radius of the electrons. Two- and three-dimensional numerical calculations performed by the macroparticle method show that space-charge oscillations near the cathode produce these phenomena even in the case of a uniform emission surface. It is shown that the increase in the full current of the beam that occurs during the pulse in a weak magnetic field is connected with the gradual propagation of emission to the cylindrical outside surface of the cathode. A study is made of the effect of the discreteness of the emission surface on the impedance and current of the vacuum diode. The linear increase seen in current during the pulse with a small number of emission centers is attributed to an increase in their size as a result of expansion of the cathode plasma. Institute of Heavy-Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, No. 12, pp. 31–48, December, 1996.     

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。     

325MHz微波栅控高压型热阴极电子枪的设计研究

高重复频率、高平均流强的电子枪具有十分广泛的应用。设计了一台束团重复频率为325 MHz在CW模式工作的微波栅控高压型热阴极电子枪,并详细论述了该类型微波栅控电子枪的实验原理。在该类型电子枪的设计中,首先需要利用仿真模拟软件EGUN、POISSON（PoissonSuperfish）、GPT（General Particle Tracer）完成300 kV直流高压电子枪的结构设计,并进行束流动力学验证计算。为将微波馈入该直流电子枪的阴栅极之间,进行了该微波栅控电子枪的供电系统设计,完成了从射频功率源到同轴热阴极的阻抗匹配方案,设计了一种325 MHz双模式同轴供电器件,并进行了验证与分析。     

同轴慢波结构相对论高功率微波产生器理论分析

 推导了同轴波导的空间电荷限制流,其值大于圆波导的空间电荷限制流。因此在阴极电势和束流相等的情况下,同轴波导中的束流具有更高的动能,同轴器件有可能获得更高的微波转换效率。理论推导出同轴慢波结构中考虑束流空间电荷影响的色散方程,利用Matlab进行了编程求解。不考虑束流空间电荷影响时,编程计算结果与Superfish模拟结果一致。由考虑束流空间电荷影响的色散方程数值计算结果,可知文献中提出的同轴慢波结构相对论高功率微波产生器工作在准TEM模的π模,频率为7.67 GHz,峰值时间增长率较高,电子束损失的能量与其初始能量之比为34%。这些结果均与文献中的数值模拟结果一致。同时理论分析说明该种器件无论在能量转换效率,还是在产生微波脉冲的上升时间上均具有优势。     

同轴虚阴极微波输出模式分析

 对不同透过率的阳极网进行实验研究，得到了主频为3.4 GHz和3.7 GHz的辐射微波，对同轴虚阴极内的电子束分布进行了分析。对同轴虚阴极内的本征模式进行了计算，并与实验结果进行比较。实验结果表明：网内电子束的分布对微波输出模式有重要影响；同轴虚阴极微波频率是阴阳极间距及谐振腔共同作用的结果；阳极网透过率对频率有显著影响，透过率越高，则微波频率相应提高。     

Space charge limiting current of an electron beam transported in a coaxial drift chamber

An expression for the space charge limiting current of an electron beam in a vacuum coaxial drift chamber is obtained in the strong field approximation. The expression is an analogue of the Bogdankevich-Rukhadze interpolation formula for a cylindrical drift chamber. The space charge limiting currents in the coaxial and cylindrical chambers are compared. The space charge limiting current in the vacuum coaxial chamber is numerically calculated and compared to analytical predictions.     

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     

Formation and dynamics of a virtual cathode in a tubular electron beam placed in a magnetic field

Mechanisms underlying the formation and dynamics of a virtual cathode (VC) in a tubular electron beam subjected to a magnetic field are studied using a numerical 2D model. Two qualitatively different competing types of space charge dynamics near the VC are discovered. Which of them predominates depends on the magnetic field strength. The beam current critical density at which a nonstationary VC forms in the system is also strongly dependent on the magnetic field. It is shown that the optimal strength of the magnetic field that minimizes the beam current critical density depends on the Brillouin magnetic field.     

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%。     

Calculation of the electron beam current in a vacuum diode with a magnetically insulated edge cathode

The current of a steady-state electron beam emitted from the magnetically insulated, finite-emissivity edge cathode of a two-electrode coaxial gun is calculated. The dependence of the emission current on the applied voltage is analyzed by solving a self-consistent problem. The field structure near the cathode edge is investigated, and its dependence on the current of the generated electron beam is determined.     

Dynamics and instability of electron phase-space tubes

Two-dimensional simulations of beam-driven turbulence in the auroral ionosphere have shown the formation and instability of phase-space tubes. These tubes are a generalization of electron phase-space holes in a one-dimensional plasma. In a strongly magnetized plasma, such tubes vibrate at frequencies below the bounce frequency of the trapping potential. A theory for these vibrations yields quantitative agreement with kinetic simulations. Furthermore, the theory predicts that the vibrations can become unstable when resonantly coupled to electrostatic whistlers-also in agreement with simulations.     

向内发射同轴虚阴极振荡器理论分析与数值模拟

 针对向内发射同轴虚阴极振荡器进行了1维理论分析,给出了电流电压关系的数值解,估算了同轴漂移区空间电荷限制流及虚阴极位置;同时使用MAFIA程序进行了全3维PIC数值模拟研究,通过调节阴极电子发射区与阳极反射板之间距离进行了一系列计算,得到了圆波导中各传输模式频谱及功率。结果表明,尽管使用圆周对称的同轴结构,输出模式中TE₁₁和TM₀₁仍占主导地位,两种模式共同存在,相互竞争。在最佳情况下,当二极管电压为250 kV,电流为20 kA时,得到了微波输出总功率最高为740 MW,功率效率超过10%,主频为3.18 GHz,同时含有较强TE₁₁和TM₀₁模式成分的微波输出。     

Effect of external magnetic field on critical current for the onset of virtual cathode oscillations in relativistic electron beams

In this Letter we research the space charge limiting current value at which the oscillating virtual cathode is formed in the relativistic electron beam as a function of the external magnetic field guiding the beam electrons. It is shown that the space charge limiting (critical) current decreases with growth of the external magnetic field, and that there is an optimal induction value of the magnetic field at which the critical current for the onset of virtual cathode oscillations in the electron beam is minimum. For the strong external magnetic field the space charge limiting current corresponds to the analytical relation derived under the assumption that the motion of the electron beam is one-dimensional [D.J. Sullivan, J.E. Walsh, E. Coutsias, in: V.L. Granatstein, I. Alexeff (Eds.), Virtual Cathode Oscillator (Vircator) Theory, in: High Power Microwave Sources, vol. 13, Artech House Microwave Library, 1987, Chapter 13]. Such behavior is explained by the characteristic features of the dynamics of electron space charge in the longitudinal and radial directions in the drift space at the different external magnetic fields.     

Nonlinear dynamics of an electron beam with a virtual cathode in a finite drift space

Nonlinear oscillations of an electron beam with a virtual cathode in a finite-length drift tube region are examined by numerical simulation (the PIC method). The change in dynamics of the beam complex with decreasing radius of the drift tube is investigated. The dynamical nature of the stochastic oscillations produced by the virtual cathode is demonstrated by an attractor dimension analysis. Physical processes in the electron beam are studied. It is found that one mechanism responsible for the chaotic behavior of the electron beam is due to the nonlinear interaction between the autostructures organized in it.State University, Saratov. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 3–4, pp. 268–274, March–April, 1995.     

用于真空电子太赫兹器件的微型热阴极电子束源研究

太赫兹波辐射源是太赫兹(THz)波技术的关键.真空电子太赫兹器件在高频、大功率太赫兹源发展中较其他技术有明显的优势,微米尺度高电流密度微型电子束源则是研制真空电子太赫兹器件的核心之一.本文在研制低温、大电流纳米粒子氧化钪掺杂含钪扩散阴极(nanosized-scandia doped dispenser cathode)的基础上,采用发射抑制膜沉积与聚焦离子束(FIB)刻蚀技术,研制无需压缩直接提供高电流密度的微型电子束的电子源.所研究的电子束源直径400μm,在工作温度950fiC,提供空间电荷限制电流密度50 A/cm2时,已稳定工作1000 h以上,并且层流性良好.本文阐述了阴极制备工艺、电子发射特性、微米尺度电子束源的获得和特性,介绍了发射抑制膜的结构和抑制特性的评估.并探讨了镀膜和刻蚀对发射的影响机理.这一电子束源在常规毫米尺度电子源的基础上产生微米尺度的微区高电流密度的电子束,为真空电子太赫兹辐射源的研制提供了新的途径.     

Simulation of the Formation of the Squeezed State of an Electron Beam with a Sublimiting Beam Current in a Closed Drift Tube

Technical Physics - The dynamics of formation of a virtual cathode and the squeezed beam state (SBS) in a setup with a sublimiting relativistic electron beam under repeated input of the electron...     

一种新型径向三腔同轴虚阴极振荡器全三维粒子模拟研究

提出了一种新型径向三腔同轴虚阴极振荡器,并进行了数值模拟研究. 研究表明: 这种径向三腔结构在束波转换面进行电场调制,能够大幅提高束波转换效率;同时,由阳极栅网和径向三腔结构构成的谐振装置能有效地抑制模式竞争;另外,由于采用了同轴引出结构,在提高能量引出的同时还能有效吸收漂移管中被利用过的电子,因此这种新型虚阴极振荡器能够获得较高的输出功率. 模拟的电子束电压为400 kV,电流为50 kA,主频为4.5 GHz,峰值功率达到6 GW,平均输出功率为3.1 GW,束波转换效率达到15%. 关键词： 高功率微波 同轴虚阴极振荡器 粒子模拟 束波转换效率     

Excess electron energy in vacuum diodes

The mechanism for generation of electrons with the anomalous energy in the spectrum of powerful nanosecond electron beams is investigated. One-dimensional propagation of the beam between spherical electrodes in vacuum diodes with a large potential difference is considered. It is shown that the excess electron energy increases as the curvature radius of the cathode decreases and the beam current is conserved. Theoretical results are compared with the experimental data.     

强流四脉冲电子束源实验研究

 为了进行强流多电子束源研究，对现有2MeV LIA 注入器进行了四脉冲改造，二极管脉冲电压约500kV。实验研究了天鹅绒阴极在四脉冲条件下的发射能力、传导电流负载效应以及阴极等离子体运动对阴极电子发射和束能量的影响。利用空间电荷限制流模型推算出阴极等离子体膨胀速率在1 ~4cm/μs之间。