Comparison of Electron-Beam-Misalignment Effect on Starting Current and Output Power in Coaxial-Cavity and Cylindrical-Cavity Gyrotron Oscillators

Comparative study is presented to the effect of the electron-beam misalignment on the starting current and output power of the coaxial-cavity and cylindrical-cavity gyrotron oscillators operating in the millimeter wave ranges. The numerical analysis is based on the gyrokinetic formulas for a TE_28,16,1 mode at a frequency of 140 GHz. Results show that the coaxial-cavity gyrotron oscillator has lower starting current and less power loss than the cylindrical-cavity gyrotron oscillator when the electron-beam axis has a misalignment to the cavity axis.     

Effective use of the electron beam in pulse-periodic electron-beam-controlled CO2 lasers and comprehensive optimization of their excitation parameters

Results are presented of experimental and theoretical investigations aimed at obtaining a maximum average generation power of pulse-periodic electron-beamcontrolled lasers at a limited average electron-beam current density. The conditions for the evolution of the post-pulse breakdown of the discharge gap are investigated and the parameters of the discharge circuit are optimized. Excitation regimes that ensure the most effective use of the electron beam are calculated with allowance for the beam divergence. Promising methods of improving the effective use of the laser beam and of increasing the output power of pulse-periodic electron-beam-controlled C0₂ lasers are considered.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 142, pp. 3–45, 1983.     

Kinetic theory of electron-cyclotron resonance masers withasymmetry of the electron beam in a cavity

On the basis of kinetic theory, general relations for the starting current and frequency shift in electron-cyclotron resonance masers are derived in the case of eccentricity of the electron beam in a cavity. The influence of a misalignment of the beam and cavity on the gyrotron operation is discussed as an example     

Analyses of two-cavity gyroklystron with feedback

Making use of the linear kinetic theory and the perturbation approach, a gyroklystron with feedback, in which a low order (TE₀₁₁) mode is presented in the bunching cavity by the feedback of the output cavity, and the low order mode in the bunching cavity is coupled by the electron beam to a high order (TE₀₂₁) mode in the output cavity, has been investigated in detail. And electron beam to wave interaction in each cavity and electron bunching mechanism in the bunching cavity have been analysed. The formulas of electron beam to wave interaction power and starting current etc. have been derived. Then some calculations are carried out.     

Decimeter-Wave Resonant Relativistic BWO

In this paper, we present the results of numerical and experimental studies of a resonant relativistic backward-wave oscillator. Using reflections of the operating TM₀₁ mode from the ends of an electrodynamic system, optimal conditions for the interaction of an electron beam with both the backward (-1)st-order spatial harmonic and the forward fundamental harmonic are reached. Single-mode oscillations at 3.6 GHz with a peak pulse power of 5 GW and an efficiency of 30% were obtained in the experiment. We show the possibility of a 15% oscillation-frequency change corresponding to the FWHM power level by varying the period of a slow-wave structure at constant electron-beam parameters.     

THE ELECTRON-BEAM IRRADIATION ON THE HIGH TEMPERATURE SUPERCONDUCTING THIN FILMS: A NUMERICAL SIMULATION OF THE LOW TEMPERATURE SCANNING ELECTRON MICROSCOPY

Low-temperature scanning electron microscopy (LTSEM) is a promising measuring technique for probing the spatial distribution of the superconducting properties of the high-temperature superconducting (HTS) thin films. A theoretical analysis of the electron-beam irradiation on the HTS thin films in the LTSEM has been carried out. An inhomogeneously distributed grain array model has been applied in the analysis, and some numerical sim-ulations have been carried out on the electron-beam induced voltage (EIV) signals in the LTSEM experiments. The comparisons of our numerical results with the LTSEM experi-mental data indicate that it is quite reasonable to use a two-dimensional Josephson junction array for stimulating the inhomogeneous HTS thin film sample. Our numerical results also show that the EIV signals are influenced by the electron-beam power used in the LTSEM, and a reduction of the electron-beam power is suggested in order to eliminate the errors in estimating the local values of critical temperature T_c and critical current I_c by the sample temperature and the bias current at which the first EIV signal occurs.     

On the possibility to realize the efficient relativistic Čerenkov microwave generator without an external guiding magnetic field

We consider the preconditions for efficient operation of the relativistic Čerenkov microwave generator in the absence of an external guiding magnetic field. The analytical expression for the length of propagation of a solid cylindrical electron beam along the drift tube is obtained in the framework of the paraxial approximation. The influence of preliminary modulation of the electron beam on the starting current of the generator and its linear efficiency is analyzed. We calculated the geometry of a relativistic Čerenkov microwave generator with an efficiency of about 30%, in which the solid cylindrical electron beam propagates over a short resonance decelerating system (with the length L ≈ 3λ, where λ is the radiation wavelength) in the absence of an external magnetic field. In experiments, the efficiency of power conversion from the high-current electron beam into the electromagnetic radiation of the E₀₁ mode reached 8%, approximately (relative to the total current of the vacuum diode), for a power of 1.2 ± 0.3 GW and a generation frequency of 4.06 GHz. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 829–836, October 2006.     

Polysilicon dry etching by a large-area electron beam

Dry etching using a novel large-area electron beam has been obtained on polysilicon over SiO₂/Si samples in the pressure range 0.1–0.4 Torr. The dependence of etching rate upon electron-beam power density, total pressure of the CF₄/He mixture, and the ratio of CF₄/He pressure has been determined. An etching rate of 150 nm/min without any addition of O₂ has been achieved with a low-energy density electron beam for poly-Si dry etching.     

重复脉冲强流电子束传输技术研究

分析并推导出了环形强流电子束的稳定传输条件，通过静电磁场模拟计算对CHP01强流电子加速器二极管引导磁场的位形分布、幅值大小及磁场电源进行了优化设计.经实验调试及束斑测量，表明设计的1秒磁场满足束流稳定传输条件，能使电压800kV、电流8kA、脉冲宽度40ns、脉冲重复频率100Hz的环形强流电子束稳定传输，并已成功运用于CHP01强流电子加速器束流传输系统. 关键词： 束流传输 引导磁场 二极管 重复脉冲 电子束     

Dependence of relativistic backward wave oscillator properties oneffective beam gamma

The operation of a backward wave oscillator (BWO) is shown to be critically dependent on the energy of the slow space-charge wave of the electron beam. Experimental work parameterizing the dependence of microwave frequency on effective beam energy, γ_beam, reveals that through an understanding of electron-beam dynamics, a BWO could be systematically tuned through a desired frequency range while maintaining a high power of a few hundred megawatts and narrow frequency bandwidth, which was 400 MHz. Through variation of γ_beam, 1.2 to 1.5 for the experiment, the lack of scaling of peak microwave power with the kinetic energy of the electron beam for γ_beam >1.32 was observed. This effect was previously found in numerical simulation. In order to explain this effect, the relationship of the beam current to the space-charge-limiting current for increasing γ_beam is examined. Dramatic evidence of pulse shortening, a phenomenon known to relativistic oscillators, was also seen     

Sustained kilowatt lasing in a free-electron laser with same-cell energy recovery

Jefferson Laboratory's kW-level infrared free-electron laser utilizes a superconducting accelerator that recovers about 75% of the electron-beam power. In achieving first lasing, the accelerator operated "straight ahead" to deliver 38-MeV, 1.1-mA cw current for lasing near 5 &mgr;m. The waste beam was sent directly to a dump while producing stable operation at up to 311 W. Utilizing the recirculation loop to send the electron beam back to the linac for energy recovery, the machine has now recovered cw average currents up to 5 mA, and has lased cw with up to 1720 W output at 3.1 &mgr;m.     

Mode excitation in a generator of diffraction radiation with a multistage interaction space

We present the results of studying theoretically and experimentally the peculiarities of mode excitation in a generator of diffraction radiation with the two- and three-cascade interaction space in one open resonator. To describe the multistage interaction mechanism, the theoretical model used considers the excitation of the TEM_0nq modes, which have n in-phase field “spots,” i.e., cascades, along the direction of the electron beam motion. It is shown that even the use of the two-cascade interaction space with the TEM_01q modes allows one to reduce the starting current of the generator by 1.91 times. The results of studying experimentally the two-cascade generator in the 5 and 1.5-mm wavelength ranges are presented. The in-phase property of the electron beam with the resonance field was achieved by disrupting the periodicity of the lattice slots at the center of the interaction space. The output power of the two-stage generator of 5-mm diffraction radiation in the TEM013 mode ranged from 3 to 5 W. We also observed a 4–5-fold increase in the starting current for the regime of surface waves.     

波瓣波导谐振腔太赫兹回旋管的研究

以电子回旋脉塞非线性理论为基础, 结合三维电磁仿真软件, 通过导入高频场数值解替代理论解析的方法, 对波瓣波导谐振腔高次谐波太赫兹回旋管进行了理论和模拟研究. 给出了该类回旋管的起振电流、耦合系数以及注波互作用效率等重要参数, 并在此基础上设计了一只工作频率为0.4 THz, 工作模式TE₃₃模三次谐波波瓣波导谐振腔回旋管, 其电子注参数为1.0 A, 40.5 kV, 横纵速度比1.5,互作用区引导磁场为5.09 T, 输出功率达到3.3 kW.     

A Theory of the Orotron with an Inclined Electron Beam

A linear and non-linear theory of the orotron with an electron beam inclined with respect to the surface of a periodic structure is presented. The beam inclination provides the possibility of the effective interaction of all particles of thick electron beam with slow evanescent harmonic of the cavity mode. On the basis of obtained analytical expression for the orotron starting current, the possibility to increase the device frequency up to 600 GHz is discussed. According to numerical simulations, the inclination of the beam allows increasing significantly both the electron efficiency and the output power of the device. The project of low-voltage orotron with the operating frequency of 100 GHz and output power of 10 W is proposed.     

重复脉冲强流电子束源长时间稳定运行实验研究

 简要阐述了脉冲变压器型重复脉冲强流电子束加速器CHP01的组成、主要特点及工作原理,利用设计的重复脉冲强流电子束源进行了长时间运行实验研究,实验结果达到：在100 Hz重复频率下连续运行5 s,脉冲变压器能稳定输出电压1.15 MV,强流束二极管输出电压超过800 kV、束流7 kA、脉冲宽度45 ns,阴极电子发射密度超过10 kA/cm²,且运行稳定可靠。利用该电子束源进行了X波段类周期慢波结构微波器件实验研究,在50 Hz重复频率下连续运行5 s,输出微波功率超过1 GW,脉冲宽度大于25 ns。     

Application of a scanning electron microscope in simulating a beta-emission-induced current

The current induced by emission from a thin ⁶³Ni layer is simulated with allowance for the real spectrum of ejected electrons and their angular distribution in Si and GaN. The calculated results are compared with simulation data obtained for a monoenergetic electron beam perpendicular to the semiconductor detector. For both Si and GaN, the ratio between the currents induced by the SEM beam and β emission from ⁶³Ni is demonstrated to be almost completely independent of the diffusion length, if the electron-beam energy of a scanning electron microscope (SEM) is appropriately selected.     

Linear Study of a Large-orbit Coaxial-waveguide Cyclotron Autoresonance Maser Amplifier

A linear theory based on Maxwell-Vlasov equations and the Laplace transform is presented to describe the large-orbit coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier. A 35-GHz, TE_5,1-mode large-orbit coaxial-waveguide CARM amplifier is specifically analyzed. Good agreement between the linear theory and the nonlinear simulations is found in the exponentially growing region of the wave. Results show that the operating magnetic field and the electron-beam energy and average radius substantially affect the power, and especially, a small beam current may be unsuitable to a large-orbit CARM amplifier operation.     

一种新型缓变倒向场大回旋电子枪

提出了一种新的利用缓变倒向场获得大回旋电子注的设计方法,在分析缓变倒向场中电子的运动规律和引起偏心与速度零散的各种原因的基础上,设计了一支大回旋电子枪.与传统设计思路不同,这种大回旋电子枪既不追求形成薄的管状电子束,又不追求突变的倒向磁场,因而极大降低了制管工艺和结构复杂性;阴极发射带可以位于倒向点前的轴向磁场幅值渐减区域,通过控制各条轨迹起始点的正则角动量差异,并利用多种不利因素的相互抵消作用来减小偏心与速度零散.模拟计算结果与理论分析一致,表明通过微调电磁场使各种不利因素相互抵消可以显著提高大回旋电子 关键词： 缓变倒向场 大回旋电子枪 偏心 速度零散     

行波管电子枪数值模拟设计的判定

 提出了采用数值软件模拟法进行行波管电子枪设计时对电子注质量好坏的判断准则：电子枪应具有更好的阴极表面电子发射密度均匀性、电子注层流性、注腰位置附近电子注径向密度分布均匀性及某百分比电子注包络曲线的光滑性等。利用编写的软件对某行波管电子枪进行数值模拟设计时,不断调整电子枪的结构,应用以上设计准则,通过对电子注质量进行判定和比较,得到了相对更符合设计要求的电子枪结构。