Self-Consistent Nonlinear Simulation of a Severed Slotted Gyro-TWT

The behavior of a two-stage slotted Gyro-TWT amplifier is evaluated with a self-consistent nonlinear slow-timescale simulation code. The effects of the sever position and the lengths of the first section, sever, and the second section on beam-wave interaction are discussed in this paper. And the influences of the magnetic field and the electron beam's velocity spread on efficiency, gain and bandwidth are also simulated and discussed in detail. The electron beam we employ encircles around the axis of the wave guide.     

Nonlinear Analysis of Coaxial Gyro-Travelling-Wave-Tube Amplifier

A set of nonlinear self-consistent equations in the electron guiding center coordinates is derived for the study of the behavior of the coaxial gyro-travelling-wave-tube (gyro-TWT) amplifier. It is found that the input signal grows faster and gets saturated earlier with the increasing of b/a (ratio of the inner to outer radius). Using an electron beam of 90kV, 10A and velocity ratio of 1.0 with 3% axial velocity spread, 275kW peak output power is obtained by calculation over the frequency range of 31.22–33.52GHz, the gain, efficiency and bandwidth are 47.4dB, 30.5% and 7.5%, respectively.     

Nonlinear Analysis of Elliptical Waveguide FEM Amplifier

A set of nonlinear three-dimension equations for the FEM amplifier with elliptical waveguide and planar wiggler is derived. Based on these equations, a universal numerical simulation program is developed independently. The characterisitics of this FEM including the evolution of power, saturation efficiency and bandwidth are investigated. Electron momentum spread and wiggler taper are also considered.     

A coaxial Gyro-TWT

The theory of a coaxial waveguide interaction structure for probable application in gyro-TWTs is presented. Relevant dispersion and gain are computed and appreciated. The basic motive behind the coaxial insertion is addressed and results are discussed     

Nonlinear Analysis on FEM Amplifier with Circular Groove Guide

FEM amplifier with a novel circular groove guide is proposed and researched both in three-dimensional nonlinear theory and numerical computation in this paper. Efficiency and bandwidth of the FEM are studied including electron beam emittance.     

Nonlinear Investigation of a Coaxial-Waveguide Cyclotron Autoresonance Maser Amplifier

A nonlinear approach is presented to simulate the coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier. Simulation shows an interesting result that the efficiency of a coaxial-waveguide CARM amplifier may be increased from 7.5% to 33.9% by tapering the magnetic field.     

半导体光放大器非线性失真特性实验研究

对半导体光放大器（SOA）用于1 310 nm残留边带幅度调制（AM-VSB）视频光信号放大时的非线性失真特性进行了实验研究.分析了非线性失真机理.给出了当输入光信号波长位于SOA增益谱下降沿且输入光信号功率较大时,SOA所引入的非线性失真主要由其增益随输入光信号功率变化而波动所造成的结论和对应表达式.提出了减小非线性失真的方法.设计了适合于AM-VSB视频光信号放大的SOA并用于有线电视（CATV）系统实验.研究结果表明,在300 mA的工作电流下,SOA在载频647.25 MHz处引入的组合二阶互调失真（CSO）在－42 dB～－38 dB之间,并随输入光信号功率的增加而变大.     

封闭圆内开缝圆自然对流的非线性特性研究

本文通过数值计算对封闭圆内开缝圆自然对流的非线性特性进行了研究。数值计算以整个流场为计算区域,采用非稳态数学模型和具有QUICK差分格式的SIMPLE算法。计算结果表明,在不同参数下流动和换热存在稳态定常解、周期性振荡解、拟周期性振荡解和非周期性振荡解。稳态定常解的相图是一个点;周期性振荡解的相图是一个极限环,对应功率谱含一个基频及其谐波;拟周期性振荡解的相图为环面,对应功率谱含两个不相关的频率及它们的线性组合频率;非周期性振荡解的功率谱为无规则的宽带连续谱。     

Nonlinear Study on FEM Amplifier with a Novel Elliptic-Groove Guide

FEM amplifier with a novel elliptic-groove guide is proposed and three-dimensional nonlinear theory for the elliptic-groove guide FEM amplifier is developed. A set of coupled nonlinear differential equations is derived and the characteristics of this FEM amplifier are numerically analyzed in detail including the evolution of power, efficiency and bandwidth. The effects on saturation efficiency due to electron momentum spread and wiggler taper are also studied.     

基频倍频光群速度对超短脉冲三倍频的影响分析

在超短脉冲的谐波转换过程中, 由于不同波包之间的群速度失配的存在, 非线性晶体的有效厚度、转换效率及带宽等将相互制约, 不能获得理想结果。基于耦合波方程, 在平面波和小信号近似条件下推导出了关于基频、倍频光群速度关系的解析表达式。通过对200 fs超短脉冲在II类KDP晶体中的混频过程的模拟分析, 发现在满足相位匹配的前提下, 三次谐波转换效率随着基频、倍频光群速度倒数的差值的平方呈现出指数衰减的关系, 与理论结果吻合。得出的关于基频光、倍频光群速度的表达式, 作为三倍频群速度匹配关系式的必要补充, 对寻找合适的色散晶体和选择有效的匹配措施, 实现宽带三次谐波转换具有理论指导意义。     

回旋行波管输出窗单端口测量去嵌入技术

射频夹具去嵌入技术通过将测量回路等效为网络级联的思想来实现,通常工作频率低于6 GHz。基于误差模型参数修正原理,利用工作在Q波段回旋行波管输出窗的S参数进行验证,证明了该方法在微波测量去嵌入上具有很高的准确度,并给出了射频夹具去嵌入无法直接用于微波测量去嵌入的原因。回避了射频夹具去嵌入用于微波测量去嵌入的谐振问题,详细介绍了误差模型参数修正原理及具体实施方式,对于微波波导测量去嵌入具有一定的借鉴意义。     

Optimization of Vane-Parameters for Gain-Frequency Response of Vane-Loaded Gyro-TWT

This paper discusses an analytical method to study the effects of the vane-parameters on the gain-frequency response of an azimuthally periodic vane-loaded cylindrical waveguide interaction structure for the gyro-traveling wave tube (gyro-TWT) amplifier in the small-orbit TE₀₁ waveguide mode configuration. The vane-loaded gyro-TWT enables the higher gain than that of the smooth-wall device. An optimum choice of the vane dimensions causes a change in the frequency corresponding to the peak-gain.     

超短脉冲在单块晶体中的三次谐波理论模拟

讨论了群速度失配、自相位调制和交叉相位调制、晶体厚度、基波的频率啁啾等因素对超短脉冲单块晶体的三次谐波转换效率、三倍频光脉冲形状以及频谱的影响.结果表明：群速度延迟使三倍频光脉冲展宽；自相位调制和交叉相位调制会降低转换效率,并使三倍频光脉冲形状发生畸变；晶体厚度对三倍频光脉冲频谱展宽有着较大的影响；合适的基频光频率啁啾可以减小三倍频光脉冲的畸变,并有效地提高三倍频转换效率.     

Effect of Air Gap on Dual-Tripler Broadband Third-Harmonic Generation

We experimentally study the effect of the air gap on conversion efficiency and the spectrum of generated third-harmonic pulses in the dual-tripler broadband third-harmonic generation scheme. The experimental results are in good agreement with predictions that the 4-cm air gap is equivalent to a full cycle of phase mismatch among the three interacting pulses （i.e. the fundamental, second-harmonic and third-harmonic pulse）. The experimental results also show that the spectrum of the third-harmonic pulse is sensitive to the air gap. We also point out that the air gap effect can be ignored when the dual-tripler system is located in 1000 Pa atmosphere. These results will guide the design of the broadband third-harmonic generation system in high power lasers.     

超短脉冲三倍频中特殊群速度组合的分析

基于非线性耦合波理论,对比分析了超短脉冲三倍频过程中不同的特殊群速度组合模式下的谐波转换特性(转换效率和带宽等).利用分步傅里叶变换和四阶Runge-Kutta积分算法,对脉宽150 fs左右的超短脉冲在KDP晶体中的I类混频过程进行数值模拟,结果表明:三波包"不等速匹配"模式下的综合谐波转换性能(转换效率达到50%和转换带宽达到2 nm)整体要优于其他特殊群速度匹配模式;"三波包不等速"模式更有利于三波包间能量之间的耦合及转换.这一结论为进一步提高超短脉冲三倍频的转换效率及带宽具有理论指导意义.     

一种新型冲击磁铁的理论分析和模拟计算

在国际上已有的冲击磁铁方案不能完全满足BEPCⅡ储存环注入系统对冲击磁铁宽均匀场区、高均匀度和低束流阻抗的设计要求的情况下,提出了一种新型冲击磁铁的设计思想.理论分析和瞬态OPERA程序模拟计算的结果表明,在Δx=±20mm的范围内,中心平面上场的均匀性为±0.6%,y=5mm的平面上场的均匀性为±0.7%,y=10mm的平面上场的均匀性为±2.9%,均优于BEPCⅡ储存环注入对冲击磁铁的设计要求.MAFIA程序模拟计算的束流阻抗Z/n(eff)小于0.022Ω,小于设计要求的0.025Ω.     

回旋行波管多模稳态理论及初步应用

建立了一种回旋行波管的多模稳态理论.利用该理论研究了输入功率和引导中心半径变化对回旋返波振荡的抑制作用,发现两者单独作用都在一定程度上可以减弱返波振荡,但两者的共同作用对改善工作模式输出性能和稳定性更有效.     

Particle Simulation of a 35-GHz Third-Harmonic Low-Voltage Complex Cavity Gyrotron

A self-consistent particle simulation code has been developed for the research of a 35-GHz third-harmonic Low-voltage complex cavity gyrotron. Aided with microcomputer we use FORTRAN to simulate the process of interaction between electron beam and electromagnetic field. About 7000 macro particles are included at the same time. In the program many useful physical graphs are accessible for the further research of this kind of gyrotron such as the field profile, electrons distribution in various spaces, output power, efficiency and et al. Such simulation results may be helpful to the optimization of devices operation parameters     

三次谐波系统在混沌状态下光场的统计特性

数值分析了三次谐波系统在混沌状态下光场的统计特性。三次谐波混沌状态下光场统计服从超泊松分布,谐波光场涨落皆大于基波光场涨落,这种光场涨落随系统最大李亚普诺夫指数增大而无规律地发生起伏变化。