Observation of the ionization wave and the shock wave ahead of the plasma jet generated in the plasma focus discharge

An ionization wave travelling ahead of the shock wave of the plasma jet, propagating in residual gas (nitrogen) of the plasma focus discharge, is detected by the laser-interferometry method at the plasma focus. Radial and axial distributions of electron densities of the shock wave and plasma jet are measured.     

Axial structure of plasma column sustained by non‐symmetric electromagnetic surface wave

This article presents the results of theoretical study of the axial structure of gas discharge that is sustained by a non‐symmetric electromagnetic surface wave (SW) with azimuth wavenumber m = –2. The phase and attenuation characteristics of the wave, and the spatial wave field structure were studied as well. The wave considered propagates along the magnetized slightly nonuniform in axial direction plasma column and sustains it. The influence of external magnetic field value and finite plasma column radius on the discharge stability, on the plasma density axial profile and on the SW properties has been studied in the case of the diffusion regime of gas discharge sustaining.     

Determination of the wave number of an electromagnetic wave propagating in high-frequency jet discharge plasma

The measurements of the amplitude-phase characteristics of the electromagnetic field in a high-frequency jet discharge burning in air and argon have been performed. Experimentally obtained radial distributions of the radial component of the electric field gave the base to determine the value of the wave number of an electromagnetic wave which propagates in the HF jet discharge plasma. The axial distribution of the radial component of the electric field has been calculated from the model of a jet discharge channel formed as a finite-length electric line.     

脉冲放电产生螺旋流注的等离子体特性研究

通过脉冲放电方式产生三维螺旋形的等离子体放电通道,在高速摄像机拍摄下观察到放电通道中的发光电离体以流注形式沿螺旋轨迹快速传播.建立电磁模型解释螺旋放电的形成机制,对造成对称性破缺及影响其手性性质的极向电场进行分析.研究表明,螺旋放电产生的放电通道存在两种不同的手性特征,而脉冲重复频率等放电参数及边界条件对螺旋流注的传播特性存在影响.脉冲电源驱动的电磁场在介质管内所形成的波模是极向电场形成的一个重要来源,当极向电场与轴向电场强度相近时则形成螺旋流注放电.     

Plasma characteristics and broadband electromagnetic wave absorption in argon and helium capacitively coupled plasma

A one-dimensional self-consistent calculation model of capacitively coupled plasma(CCP) discharge and electromagnetic wave propagation is developed to solve the plasma characteristics and electromagnetic wave transmission attenuation.Numerical simulation results show that the peak electron number density of argon is about 12 times higher than that of helium, and that the electron number density increases with the augment of pressure, radio frequency(RF) power, and RF frequency. However, the electron number density first increases and then decreases as the discharge gap increases. The transmission attenuation of electromagnetic wave in argon discharge plasma is 8.5-d B higher than that of helium. At the same time, the transmission attenuation increases with the augment of the RF power and RF frequency, but it does not increase or decrease monotonically with the increase of gas pressure and discharge gap. The electromagnetic wave absorption frequency band of the argon discharge plasma under the optimal parameters in this paper can reach the Ku band. It is concluded that the argon CCP discharge under the optimal discharge parameters has great potential applications in plasma stealth.     

Electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

We analyze the electromagnetic interaction between local surface plasmon polaritons （SPPs） and an atmospheric surface wave plasma jet （ASWPJ） in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two- dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.     

Numerical investigation of subcritical microwave discharges in a high-pressure gas

Subcritical microwave streamer discharges are investigated using a two-dimensional model that describes gas-dynamic processes in the ideal gas approximation and a self-consistent electromagnetic field in the wave approximation and takes into account the minimum required number of kinetic processes (such as ionization, attachment, recombination, diffusion, and electric conduction). The initial conditions imitate the initiation of a discharge from a small cavity with a reduced gas density and an arbitrarily small degree of gas ionization. The possibility of describing streamer discharges without reference to ionizing hard radiation is confirmed.     

Chaotic electron trajectories in electromagnetic wiggler free-electron laser with a guide magnetic field

Summary The Hamiltonian for an electron travelling through a large-amplitude backward electromagnetic wave, an axial guide magnetic field and radiation field is formulated. Poincaré surface-of-section plots show that this Hamiltonian is non-integrable, and leads to chaotic trajectories. Equilibrium conditions are derived in the limit where the radiation field approaches zero. Compared to conventional FEL, the total energy of the system at pondermotive resonanceE _c is large, while the electron's critical energy γ_c is low for electromagnetic wiggler FEL. Moreover, the threshold wave amplitude (A _r=A _c) of beam chaoticity is found at lower values of the radiation field amplitude compared to magnetostatic wiggler FEL. Previous features confirmed that electromagnetic wiggler FEL can operate more coherently and more efficiently at moderated particle's energy compared to magnetostatic wiggler FEL.     

高功率微波与等离子体相互作用理论和数值研究

研究高功率微波与等离子体的相互作用,对于微波放电和电磁兼容研究均具有重要意义.基于波动方程、等离子体的流体力学方程以及波尔兹曼方程,建立高功率微波脉冲与等离子体相互作用的理论模型,并结合等离子体的特征参数,采用时域有限差分方法分析了等离子体电子密度和高功率微波传输特性的变化.结果表明,由于高功率微波的电子加热作用,等离子体中的非线性效应明显,发生击穿使得等离子体电子密度增大,从而导致微波的反射增强,透过率降低.所提出的模型和相关结果对于高功率微波和电磁脉冲防护具有指导意义.     

Electrodynamic Model of the Gas Discharge Sustained by Azimuthal Surface Waves

Results of studying an electrodynamical model of the plasma producer based on azimuthal surface waves (ASW) propagation both in a cylindrical metal waveguide filled by magnetoactive plasma and along metal cylindrical antenna placed into the plasma are presented. Parameters of these gas discharges are studied in the two frequency ranges where propagation of the ASW is possible and also are compared. The value of plasma density that can be achieved by this producer is calculated. The spatial distribution of the wave electromagnetic fields, dependencies of their penetration depth into plasma and angular discharge length on the discharge parameters are studied analytically and numerically. Advantages of the operation in the both frequency ranges are indicated. Possibility of resonant absorption of the ASW energy due to their conversion into the bulk upper hybrid mode is examined as well.     

等离子体微带开关特性

 提出一种基于微放电等离子体的微带开关。它是以“时变等离子体”取代微带线射频微机电开关的“金属悬臂”,利用等离子体的导体或介质特性使电磁波沿其表面进行传输或截止,从而实现微带线上电磁波传输的动态控制。等离子体微带开关的基本结构包括用以隔断电磁波的微带间隙和产生片状等离子体的放电装置。放电产生时,电磁波因等离子体导体性通过开关,形成“开”状态;放电停止后,电磁波被微带间隙反射,形成“关”状态。利用CST软件仿真研究了等离子体开关特性,结果表明：这种开关的带宽由等离子体密度决定,隔离度由间隙决定,而工作插损与等离子体密度和电子碰撞频率有关。等离子体位形（宽度、厚度等）对于开关性能也非常重要。     

电离层与电波通信

介绍了等离子体电波传播折影响，阐述了电磁波在等离子体中的截止现象，这就是电离层作为地面上短波无线电通信的反射层的原理，同时指出了截止频率与短波最大通信频率的差别及其相互间的关系。     

电子回旋共振放电电离特性的PIC/MCC模拟

A theoretical and computational model is presented to study the ionization of the argon electron cyclotron resonance(ECR)microwave discharge using a quasi-three-dimensional electromagnetic particle-in- cell plus Monte Carlo collision method.The interaction between the charged particles and microwave fields are described by the electromagnetic mode of particle-in-cell method.The collision processes are treated with Monte Carlo method.The simulation code is the original work.The results of the particle simulation for the ECR discharge of argon gas which include the microscopic features of charged particles and the electromagnetic characteristics of the ECR discharge plasma,and also the transient phenomena have been presented.     

The influence of the axial heterogeneity of the plasma of high-frequency torch discharge on its electrodynamic characteristics

Measuring results for axial distribution of gas temperature of high-frequency torch discharge burning in the air at atmospheric pressure are presented. The distribution of electric field over the discharge axis was calculated based on the model of discharge in the form of heterogeneous electric line of finite length. It is shown that the experimentally observed linear character of electric field change along the discharge axis is conditioned by its axial heterogeneity.     

磁化等离子体填充螺旋线的色散方程

利用等离子体流体理论和纵向场分量法，结合螺旋线的导电面模型，对在有限磁场作用下，填充等离子体的螺旋线进行了严格的场分析. 在给出各区域电磁场分量表达式的基础上，利用螺旋线的边界条件，导出了磁化等离子体填充螺旋线中电磁波传播所满足的色散方程，并对所导出的色散方程进行了讨论. 关键词： 有限磁场 等离子体 螺旋线 色散方程     

四注行波管周期永磁聚焦系统的优化设计

根据电子注参数、布里渊磁场公式及周期聚焦系统轴向磁通密度峰值经验公式,计算出永磁聚焦系统轴向峰值磁通密度,利用Ansoft Maxwell 3D软件建立了四注行波管周期永磁聚焦系统仿真模型,对模型结构尺寸进行了参数化分析,研究了周期永磁聚焦系统结构尺寸对聚焦系统通道内磁通密度的影响,确定了磁聚焦系统结构最佳尺寸配合,优化设计出了四注行波管周期永磁聚焦系统。其电子注通道中心轴线上轴向磁通密度峰值B_z=309 mT,横向磁通密度B_t=2.86 mT,B_t/B_z=0.92%。     

任意纵向磁场中等离子体-腔漂移通道电磁波的解析解

 从麦克斯韦方程和双成分等离子体粒子在外部轴向磁场的线性化运动方程出发,推导出了任意纵向磁场中等离子体介电张量和等离子体-腔漂移通道的电磁波的解析解。结果表明在一般情形下,在位于外部均匀纵向磁场的等离子体波导中,不存在分离的轴对称E波和H波。在此基础上进一步得到轴对称波的具体解析式。单波近似下的结果和俄罗斯全俄电技术研究所M.A.Zavjalov等的结果一致。     

Electromagnetic radiation sources based on a low-inductive extended z-discharge

Model sources of electromagnetic radiation based on a low-inductive extended z-discharge are studied experimentally and numerically. The discharge is initiated by a high-voltage pulse generator through a long transmission line. It is shown that using a sliding discharge traveling wave, one can provide electrical breakdown of long discharge gaps in a wide range of initial gas pressure and produce a plasma pinch at moderate voltages of the generator. A new nonpinch mechanism of radiation generation is discovered in the soft X-ray range of the spectra. This mechanism offers a higher efficiency of conversion of electrical energy to the energy of an inverted medium.     

Fine Structure of the Local Alfven Resonances in Cold Plasma Placed in Bumpy Magnetic Field

Unlike in the case of an axial magnetic field, in which each mode of electromagnetic wave excited by an external source propagates independently, ripples in a bumpy magnetic field cause the wave to propagate as a wave envelope that contains also satellite harmonics in addition to the main harmonic. The influence of this multimodity on the distribution of electromagnetic waves within the local Alfven resonance regions is studied and compared for the following three cases. In the first case, Alfven resonance takes place for a main harmonic of the wave. In the second case, Alfven resonance occurs in the same region for two main harmonics which are coupled due to the plasma periodic axial inhomogeneity. Alfven resonance for a satellite harmonic is considered in the third case.