Particle simulation of a high-power gyrotron oscillator

A self consistent and time-dependent particle code has been developed to simulate the beam-wave dynamics in a gyrotron oscillator. The code is first applied to investigate the effect of the self-consistent field profile on the scaling of the cavity-filling rate with beam current. The fixed-field theory predicts that the transient-wave growth rate depends linearly on the beam current. The simulation results agree with the theoretical prediction at low beam currents. As the beam current increases, the modified field profile changes the nature of the gain scaling from linear to nonlinear. At higher beam currents, the excited wave is observed to exhibit the behavior of the modulated oscillation, due to unequal couplings to the forward- and backward-going waves by the beam. Associated with such amplitude modulation is a periodic variation of the self-consistent field profile. At still higher beam currents, the system becomes chaotic, showing the effect of periodic doubling. Simulation results are presented for the efficiency, the self-consistent field profile, and the scaling of the transient growth rate with the beam current     

Mathematical simulation of high-power laser systems

The energetic, spectral, and time characteristics of a high pressure CO₂ laser at high pumping level are studied. It is shown that in the free generation regime high power radiation pulses R~ 10^–8 sec in duration with a multifrequency spectrum can be obtained. Laser output characteristics are presented as functions of gas pressure, pumping energy, and resonator parameters.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 15–20, June, 1981.     

Nonlinear nonequilibrium processes in a silicon switch of high-power microwave radiation

The nonlinear dynamic interaction of high-power microwave radiation with a high-purity compensated silicon sample, driven or not by a laser pulse initiating nonequilibrium photoconductivity, has been investigated numerically. It is shown that this effect can be used in semiconductor switches of the phase of electromagnetic waves in the presence of strong thermal self-action of microwaves. Original Russian Text ? G.G. Denisov, Vl.V. Kocharovsky, M.L. Kulygin, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 1, pp. 98–102.     

Nonlinear processes in the optical medium of a high-power neodymium laser

The article is devoted to an analysis of the nonlinear processes that arise when powerful beams propagate in the optical medium of an Nd laser and influence its output parameters. A review is presented of the methods of theoretically describing the processes of temporal and spatial self-focusing, and experimental data are cited that illustrate the character of the course of the self-focusing in the generators and amplifiers of a high-power laser. Possible methods of suppressing self-focusing in a laser installation are considered.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 103, pp. 84–117, 1978.     

Computer simulation of collective phenomena in a turbulent plasma

A short review of the results of one- and two-dimensional computer investigations of strong Langmuir turbulence is given. The main topics of interest are the following: formation of high energetic electron tails; ion sound turbulence accompanying collapse and plasmons' conversion; modulation instability (MI) in X,Y-geometry for $\text{T}{}_{\mathrm{e}}\text{T}{}_{\mathrm{i}}\text{? 1}$ and $\text{T}{}_{\mathrm{e}}\text{T}{}_{\mathrm{i}}\text{?1}$; MI in transverse magnetic field. The case of the “forced” collapse (quasicollapse) in presence of an external pump $\text{E}{}_{\mathrm{<mtext>ext</mtext>}}\text{=}\text{E}{}_{\mathrm{<mtext>ox</mtext>}}\text{Cos}\text{ω}{}_{\mathrm{o}}\text{t}$ is considered.     

S波段宽带大功率连续波耦合腔行波管3维模拟设计

 使用3维PIC粒子模拟软件定量分析了耦合腔行波管的大信号注波互作用行为。使用完整的仿真模型完成了S波段连续波管型的设计,达到如下设计指标：工作频率2.0~2.3 GHz,输出功率4.3 kW,频带内增益波动±0.7 dB。提出了使用大介电常数微扰介质棒减小耦合阻抗计算误差的方法,研究了行波管的冷腔特性,给出了色散、耦合阻抗等参数。     

S波段宽带大功率连续波耦合腔行波管3维模拟设计

使用3维PIC粒子模拟软件定量分析了耦合腔行波管的大信号注波互作用行为。使用完整的仿真模型完成了S波段连续波管型的设计,达到如下设计指标：工作频率2.0~2.3 GHz,输出功率4.3 kW,频带内增益波动±0.7 dB。提出了使用大介电常数微扰介质棒减小耦合阻抗计算误差的方法,研究了行波管的冷腔特性,给出了色散、耦合阻抗等参数。     

Nonlinear stability of incoherence and collective synchronization in a population of coupled oscillators

A mean-field model of nonlinearly coupled oscillators with randomly distributed frequencies and subject to independent external white noises is analyzed in the thermodynamic limit. When the frequency distribution isbimodal, new results include subcritical spontaneous stationary synchronization of the oscillators, supercritical time-periodic synchronization, bistability, and hysteretic phenomena. Bifurcating synchronized states are asymptotically constructed near bifurcation values of the coupling strength, and theirnonlinear stability properties ascertained.     

Nonlinear dynamics and collective excitations of spin-1 magnets

The Poisson brackets for macroscopic parameters are obtained and nonlinear dynamic equations of spin-1 magnets are derived. Two types of magnetic exchange Hamiltonians corresponding to two Kazimir invariants of SU(3) group are introduced. Thermodynamics of spin-1 magnets is studied and the flux densities of additive integrals of motion are found in terms of exchange energy density. The momentum of magnons is introduced and the corresponding dynamic equation is derived. The spectra of spin and quadrupole waves of magnets with various symmetry of equilibrium state with respect to time inversion are found.     

高功率激光装置中局部波前畸变的非线性传输

 根据高功率激光装置中强激光束传输的特点,建立了描述光束通过光学元件时引入的局部波前畸变模型,并利用纹波传输的线性化处理方法,研究了带有局部波前畸变的高强度光束的传输规律。以一个连续的非增益激光介质为例,用该模型进行数值模拟,给出了不同空间尺度的局部波前畸变的频谱分布、不同空间频率的纹波引起的振幅非线性增长曲线、不同B积分的非线性增益随光束传输距离的变化曲线,光束振幅非线性增益达到最大时光束的传输距离和标准传输距离不同时由局部波前畸变引入的振幅分布。研究表明为了防止光学元件损坏,应避免光学元件表面出现半径为0.5~2.0 mm的局部瑕疵。     

Computer simulation of nonlinear coupling of high-power microwaveswith slots

Numerical calculations are used to determine the effects of air breakdown on the coupling of intense microwave pulses passing through enclosed slot apertures. The calculations are based on Maxwell's equations and a set of electron-fluid equations. Variations in the energies of microwaves transmitted through slot apertures as a function of incident-field intensity and aperture size are addressed. Results show that air-breakdown threshold energies in apertures have a functional dependence on pressure similar to that of air-breakdown threshold energies in the atmosphere     

高功率超声脉冲激励下金属板的非线性振动现象研究

对高功率超声脉冲作用下金属板中的超谐波、次谐波、准次谐波以及混沌等非线性振动现象进行了实验和理论研究.在实验中,高功率超声换能器产生脉冲调制的高频振动激励金属板产生非线性振动,利用激光测振技术测量不同尺寸和不同固定方式下金属板复杂的非线性振动情况,并对其进行了时序分析、频谱分析以及相空间分析.根据实验条件,提出包含非线性接触阻尼的振动-碰撞动力学模型,用以研究强超声振动-碰撞作用下的板非线性振动机制,并进行了相应的理论计算.计算结果表明,超声换能器的变幅杆与金属板之间的间歇性高频碰撞作用是金属板强非线性振 关键词： 非线性板振动 强超声脉冲激发 振动-碰撞动力学     

Wave optics simulation approach for high-power laser beam combination

A numerical wave optics approach for simulating multiplex super Gaussian beam combination in high-power laser facility is presented. The approach involves the application of a sequence of random phase screens and von Karman turbulence phase to an initial beam field and the summation of the intensity results. The analytical and numerical calculation results have been given to illustrate the properties of the resulting far-field pattern after coherent, incoherent and spatially coherent combination, and some of that are compared with experimental results. The approach can be used for modeling and evaluating applications such as high-power laser shooting that might utilize different beams combining approach.     

高功率高效率三次谐波二维数值模拟研究

对大口径、高功率情况下的三次谐波转换 ,选择 KDP晶体 Type / Type 匹配角度失谐的三倍频方案 ,并从非线性三波耦合方程组出发 ,采用离散傅立叶变换和四阶龙格 -库塔 ( R-K)积分方法 ,编制了二维模拟三次谐波转换的计算程序。计算了各种晶体厚度和不同失谐角条件下 ,二、三次谐波的转换特性和效率。并对入射基频光为六阶超高斯分布时的三倍频器进行了优化 ,三倍频转换效率达80 % ,此时具有较大的动态范围和较高的三倍频转换效率     

加载静电压的同轴回旋管放大器的非线性模拟

对一种工作频率为0.14 THz的小轨道同轴回旋管放大器进行非线性模拟,结果表明:通过加载外部静电压的方法,可将回旋管放大器的饱和输出功率提高19%,而且电子束横向与纵向速率比以及横向速度离散对输出功率都没有明显影响,从而可以有效提高回旋管放大器性能. 关键词： 回旋管放大器 静电场 静电离心聚焦系统 饱和功率     

时变等离子体高功率微波频率上转换的粒子模拟

基于电磁波与时变介质相互作用能够实现电磁波频率上转换的原理,通过粒子模拟(PIC)方法对电磁波与时变等离子体薄层相互作用进行模拟,实现了频率由2.45 GHz提升至130 GHz,功率转化效率约为0.39%。探究了等离子体参数(包括等离子体密度、有限的等离子体上升时间以及等离子体薄层厚度)对频率上转换的影响。模拟结果验证了等离子体密度决定上转换频率,与理论结果相符。模拟结果表明,等离子体薄层厚度越大,得到的上转换波的能量越大;等离子体的上升时间越小,上转换波的转换效率和频谱纯度越高。采用等离子体密度21020 cm-3,等离子体厚度1 cm,等离子体上升时间0.04 ns 可以得到可观的130 GHz上转换波输出。