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1.
Y. Y. Lau K. R. Chu L. R. Barnett V. L. Granatstein 《International Journal of Infrared and Millimeter Waves》1981,2(3):373-393
The operation of the gyrotron travelling wave amplifier is based on the convective cyclotron maser instability. It is found that this convective instability may become absolute (nonconvective) at a sufficiently high current level, resulting in oscillation instead of amplification. This threshold current for the transition depends sensitively on the applied magnetic field. The axial wavelength and the characteristic frequency of oscillation at the onset of absolute instability are given. It is found that momentum spread has virtually no effect on the threshold current. A small amount of resistive wall loss, however, raises the threshold current significantly. Oscillations due to partial reflection at the ends of the system are also examined. Preliminary experimental results on both types of oscillations are reported and are found to be in good agreement with the theory. 相似文献
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A simple scheme is proposed for the construction of a wide-band fast wave gyrotron travelling wave amplifier. The key features of this scheme include a contoured waveguide, a tapered magnetic field, and injection of input signals in opposite direction of the streaming electrons. Bandwidths at tens of percents, and gain at tens of decibals, are projected. 相似文献
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Chien-Lun Hung 《International Journal of Infrared and Millimeter Waves》2006,27(7):913-921
This theoretical investigation examines the feasibility of improving the stability of the coaxial-waveguide gyrotron traveling-wave
tube (gyro-TWT) by selecting the geometrical parameter C, i.e., the ratio of the outer radius to the inner radius. The effects of the geometrical parameter C on the start-oscillation currents of oscillation modes are analyzed to determine the optimum operating conditions. Simulation
results indicate that the coaxial gyro-TWT with distributed wall losses can be stably operated at a higher beam current by
optimizing C. Additionally, the saturated behaviors of the operating TE01 mode are evaluated for several C values to investigate the geometrical effects on the amplification of the coaxial gyro-TWT. Moreover, performance of the
fundamental harmonic coaxial gyro-TWT achieved with the optimized C value is predicted under stable operating conditions. 相似文献
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本文阐述了半导体激光放大器组件中,末端带高折射率类球透镜的锥形光纤耦合头对放大器芯片的外腔反馈效应,从理论上对这种耦合头的反馈效应进行了计算.为了使计算结果更接近于实际情况,在理论分析中引入了厚透镜表面的菲涅耳(Fresnel)反射及有限孔径的影响. 相似文献
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The nonlinear theory of slow-wave electron cyclotron masers (ECM) with an initially straight electron beam is developed. The evolution equation of the nonlinear beam electron energy is derived. The numerical studies of the slow-wave ECM efficiency with inclusion of Gaussian beam velocity spread are presented. It is shown that the velocity spread reduces the interaction efficiency. 相似文献
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根据8 mm回旋速调管放大器对双阳极磁控注入电子枪的要求,分析了电极形状、阳极电压、磁场、注电流对电子注横纵速度比和速度零散的影响,并进行了粒子模拟。分析表明:这些因素可归根为电场和磁场的作用,阴极附近高的电场有助于提高横纵速度比和降低速度零散;而高的磁场及低的磁压缩比将降低横纵速度比,但对速度零散影响无明显规律。在此基础上通过优化电极形状、磁场分布、电流、第一阳极电压和第二阳极电压,模拟并试制出工作电压65 kV、电流12 A、磁场1.4 T的双阳极电子枪,得到的横纵速度比值为1.4,横向速度零散为4.5%, 为8 mm回旋速调管提供了稳定高质量的电子注。 相似文献
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利用激光器、硅光电池等器件,采用光折射方法设计了激光测量水的振动频率与水波传播速度实验.本文介绍了实验原理和装置,测量了水的振动频率和水波向外传播的速度,观察了小块物体落水激起的水波情况. 相似文献
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A global design of an erbium-doped fiber and an open-loop erbium-doped fiber amplifier (EDFA) in a steady-state operation is discussed by applying genetic algorithms. Taking a signal gain and a bandwidth as objective functions, 7 parameters of the EDFA (erbium concentration, core radius, erbium-doped radius, refractive index difference, fiber length, pumping wavelength and signal power) are optimized by solving optical propagation equations, assuming a homogenous two-level active medium and a single-mode propagation. There is evidence to show that the 1480 nm pump utilized in usual EDFAs is not an optimal choice, which should be chosen around 1460 nm. The optimal core radius ranges 0.465–0.548 μm on pumping power 50–200 mW. Under different design objects and with different pumping powers, however, there are different optimal Er-doped concentrations, reflective index differences and fiber lengths. As a single fiber EDFA, 35 dB signal gain or 35 nm bandwidth is obtained with the 7 optimal parameters, 100 mW pumping power and 0.001 mW input signal power. 相似文献
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回旋行波管放大器是高功率毫米波雷达发射系统最重要的候选者.通过对回旋行波管放大器中的绝对不稳定性、回旋返波振荡以及电子注-波互作用的研究,讨论了回旋行波管的稳定性、寄生模式的抑制和工作参数的优化等问题,给出了W波段TE01模回旋行波管放大器的模拟设计结果.PIC粒子模拟结果表明,在电子注电压100kV、电流10A、工作磁场3.52T时,94GHz的基波回旋行波管放大器可获得大于250kW的输出功率、40dB的增益、大于25%的效率和约5%的带宽.
关键词:
W波段
回旋行波管放大器
模拟
设计 相似文献
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回旋行波管放大器是一种具有高功率、高频率、宽带宽的毫米波放大器,TE02模二次谐波回旋行波管放大器在保持基波回旋行波管放大器的基础上极大地减小了工作磁场,从而具有广阔的应用前景. 利用两段分布式损耗的互作用结构,有效抑制了绝对不稳定性和回旋返波振荡,避免了模式互作用电路引起的模式畸变,提高了输出功率,在一定程度上克服了谐波互作用较弱的缺点,满足了扩展功率容量和放大器长时间稳定工作的要求. 非线性模拟结果和粒子模型(particle in cell)模拟结果均表明,在工作电压为100k
关键词:
W波段
二次谐波
回旋行波管放大器 相似文献
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Gianluca Geloni Svitozar Serkez Ruslan Khubbutdinov Vitali Kocharyan Evgeni Saldin 《Journal of synchrotron radiation》2018,25(5):1335-1345
The (spectral) brightness for partially transverse coherent sources such as synchrotron radiation and free‐electron laser sources can be defined as the maximum of the Wigner distribution. Then, the brightness includes information on both coherence and wavefront characteristics of the radiation field. For undulator sources, it is customary to approximate the single‐electron electric field at resonance with a Gaussian beam, leading to great simplifications. Attempts to account for the modified spatial and angular profile of the undulator radiation in the presence of detuning due to energy spread, currently build on the simplified brightness expression derived under the assumption of Gaussian beams. The influence of energy spread on undulator radiation properties is becoming important in view of diffraction‐limited rings with ultralow emittance coming on‐line. Here the effects of energy spread on the brightness of undulator radiation at resonance are discussed, as well as relevant relations with coherence properties. 相似文献
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Kousik Mukherjee 《Optik》2011,122(10):891-895
All optical logic gates exploiting polarization independent four wave mixing in semiconductor optical amplifier (SOA), filtering property of ADD/DROP multiplexer (ADM) and non-linearity in reflective semiconductor optical amplifier (RSOA) have been proposed. The logic gates proposed are polarization independent which ensures hardware simplicity and greater speed. The all optical frequency encoded logic gates NOT, OR, NOR, AND, NAND, X-OR, X-NOR are implemented which are very useful in optical computing ad signal processing, cryptography, etc. The logic gates proposed have the advantages that there is no intensity loss dependent problem, and are polarization and temperature insensitive. 相似文献
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Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well solar cells 下载免费PDF全文
Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well(MQW) solar cells are investigated. It is found that due to the reduction of piezoelectric polarization and the enhancement of tunneling transport of photo-generated carriers in MQWs, the external quantum efficiency(EQE) of the solar cells increases in a low energy spectral range(λ 370 nm) when the barrier thickness value decreases from 15 nm to 7.5 nm. But the EQE decreases abruptly when the barrier thickness value decreases down to 3.75 nm. The reasons for these experimental results are analyzed. We are aware that the reduction of depletion width in MQW region, caused by the high resistivity of the p-type GaN layer may be the main reason for the abnormally low EQE value at long wavelengths(λ 370 nm). 相似文献
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采用LaF3∶Er,Yb纳米颗粒掺杂有机/无机杂化材料作为有源材料,制备了掩埋条形结构光波导放大器,研究了放大器在室温下的增益特性和波导中的频率上转换现象. 当抽运功率60 mW时,波导中明显可见绿色上转换发光,观测到Er3+从2H9/2,2H11/2,4S3/2,4F9/2到基态4I15/2跃迁分别对应的4个波长分别为405?nm, 520?nm, 544?nm和650?nm的发射峰,分析了其产生机理. 当输入信号光06?mW,抽运功率160 mW时,在1535?nm波长处获得15 dB/cm的相对增益.
关键词:
光波导放大器
增益
上转换 相似文献
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《中国物理 B》2021,30(7):77504-077504
In order to counteract the demagnetization caused by eddy current loss, widespread attention has been devoted to increasing the resistivity of permanent magnets. We prepared 2:17-type Sm Co magnets doped with different ZrO_2 contents and investigated the influence of the ZrO_2 content on the magnetic properties and resistive anisotropism. The results showed that not only was the resistivity of the magnet improved, but, in addition, the coercivity of the magnet was significantly increased. The microstructure was studied with TEM, which showed that ZrO_2 doping was able to cause a decrease in the lamellar phase density and the growth of cellular structures. The increased grain boundaries and Sm_2O_3 phases were favorable to the improvement of resistivity. The decrease of the lamellar phases caused a narrowing of the resistive anisotropism. The additional Cu in the center of the cellular boundaries was the main reason for the enhancement of Hcj.However, an excessive amount caused an increase of the Zr_6(Fe Co)_(23) phase and a deterioration of the cellular structure,thereby leading to a decrease in coercivity. 相似文献
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Popovics S 《Ultrasonics》2005,43(6):429-434
Earlier findings showed that the effects of moisture (liquid or free water) in hardened concrete on its behavior, especially the lesser known effects ofuneven moisture distribution, can (a) be significant, and (b) vary from property to property. This distribution, for instance whether or not the surface layer is drier than the overall average moisture content, can be characterized by the difference between the velocity of the longitudinal wave (pulse velocity) measured in the standard through-thickness manner, and the velocity of the longitudinal wave propagating on the concrete surface. The summary of earlier findings on the effects of moisture distribution is followed by a recent investigation on pulse velocity in the special case, occurring frequently in practice, when the distribution is uneven because the liquid is concentrated in cracks in the concrete. 相似文献