Cylindrical magnetoacoustic solitons in plasma

Nonlinear cylindrical magnetoacoustic perturbations in a plasma are considered in the framework of the two-liquid collisionless electromagnetic model. The method of power expansion in a small parameter in extended space-time coordinates is used to obtain the cylindrical Korteweg-de Vries equation that describes nonlinear radial cylindrical waves. An approximate solution to this equation has the form of a cylindrical magnetoacoustic compression soliton.     

Topological solitons in active optical cavities: Fundamental properties and possible applications

Fundamental properties of topological spatial solitons existing in active cavities with high (above 100) Fresnel numbers, laser and/or parametric amplification, and saturated absorber were numerically and experimentally studied. Writing and erasing of bi- and tristable laser solitons (fundamental solitons [1, 2] and vortex solitons [3]) using an external control light pulse were considered in various regions of the laser cross section. The existence of optical domain walls (separated phase domains which are in antiphase) in the form of expanding spiral waves and the localized domain soliton rotating about the Neel defect (in this connection, we called it the “Neel soliton”) in active cavities with mixed laser and parametric amplification was shown in a numerical experiment for the first time. We proposed potential possibilities of using topological solitons in optical data processing, storage, and transmission.     

Laser-induced plasma by two-color excitation

With a superposition of a nanosecond infrared-laser pulse and its second harmonic, the threshold of plasma formation in gasses as well as the energy transfer efficiency from the laser field to the plasma can be significantly improved in comparison to purely monochromatic radiation. We present experimental results in air at pressures between 0.4 and 3 bar; in this pressure range, the threshold energy for the superposition is reduced by ≈30% as compared to that of pure infrared radiation, while the energy transfer slope efficiency is equal to the IR efficiency at high pressures and somewhat less at lower pressures. Possible mechanisms responsible for this effect are discussed.     

Electromagnetic envelope solitons in magnetized plasma

A multiple scales technique is employed to solve the fluid-Maxwell equations describing a weakly nonlinear circularly polarized electromagnetic pulse in magnetized plasma. A nonlinear Schrödinger-type (NLS) equation is shown to govern the amplitude of the vector potential. The conditions for modulational instability and for the existence of various types of localized envelope modes are investigated in terms of relevant parameters. Right-hand circularly polarized (RCP) waves are shown to be modulationally unstable regardless of the value of the ambient magnetic field and propagate as bright-type solitons. The same is true for left-hand circularly polarized (LCP) waves in a weakly to moderately magnetized plasma. In other parameter regions, LCP waves are stable in strongly magnetized plasmas and may propagate as dark-type solitons (electric field holes). The evolution of envelope solitons is analyzed numerically, and it is shown that solitons propagate in magnetized plasma without any essential change in amplitude and shape.     

Magnetoacoustic solitons in pair-ion fullerene plasma

ABSTRACT

The propagation of magnetoacoustic (fast magnetohydrodynamic) waves in pair-ion (PI) fullerene plasma is studied in the linear and nonlinear regimes. The pair-ion (PI) fullerene plasma is theorized as homogeneous, magnetized, warm and collisionless. Employing multi-fluid magnetohydrodynamic model, the dispersion relation is obtained and wave dispersion effects which appear through ion inertial length are discussed. Using reductive perturbation technique (RPT), the Korteweg–de Vries (KdV) equation is derived and its solution for small but finite amplitude magnetoacoustic solitons propagating in the direction perpendicular to the external magnetic field is presented. The compressive magnetoacoustic soliton (i.e. positive potential pulse) propagating with super Alfvénic speed is obtained in magnetized PI fullerene plasma. The variations in the amplitude and width of the magnetoacoustic soliton structures are also illustrated by using numerical values of the plasma parameters such as ions' density, temperature difference between fullerene ions and magnetic field intensity, which have been taken from the PI plasma experiments already published in the literature.     

Ultrashort relativistically strong solitons in plasma

An equation that describes a reflectionless propagation of non-one-dimensional relativistically strong wave packets in plasma has been studied. A family of three-dimensional solitons is found and their stability is analytically justified. The dynamics of soliton formation and their interactions have been numerically simulated.     

激光等离子体闪光高速摄影法实验研究

 通过对激光等离子体进行诊断,可以获取激光等离子体重要的参数和演变规律。使用高速CCD对激光等离子体闪光进行拍摄,研究了不同激光能量下激光诱导空气击穿产生的等离子体的形状、大小、颜色以及激光等离子的发展变化特性。实验表明：等离子体在空间上呈发光液滴状,且逆着激光束的方向膨胀。随着激光能量的增大,等离子体在水平方向和竖直方向的尺寸逐渐增大,增大趋势逐步变小。     

Oblique magneto-acoustic solitons in a rotating plasma

Weakly nonlinear magneto-acoustic waves propagating at an arbitrary angle to the external magnetic field in a rotating plasma are considered. A model equation (Ostrovsky's equation with positive dispersion) is derived from a set of basic magneto-hydrodynamic equations. Stationary solutions of this equation are obtained numerically and analyzed in detail theoretically. These include solitary-type solutions (solitons with monotonic and oscillating tails), complex multisolitons (bound states of coupled single solitons), as well as periodic waves. We emphasize that the positive dispersion, in contrast to the negative one, gives rise to solitary waves within the framework of Ostrovsky's equation.     

Relativistic electromagnetic solitons in the electron-ion plasma

We present the results of the investigation about the ion motion influence on relativistic soliton structure, and show that in the case of moving multinode solitons the effect of the ion dynamics results in the limiting of its amplitude. The constraint on the maximum amplitude corresponds to either the ion motion breaking in the low-node-number case, or to the electron trajectory self-intersection in the case of high-node-number solitons. The soliton breaking leads to the generation of fast ions, and provides a novel mechanism for the ion acceleration in the plasma irradiated by the high-intensity laser pulses.     

基于自吸收量化的激光诱导等离子体表征方法

为了表征激光诱导等离子体的定量特征参数,提出了一种谱线自吸收量化的方法,通过获得分析元素谱线的半高全宽来量化谱线自吸收程度,进而得到等离子体的特征参数,包括电子温度、元素含量比以及辐射物质的绝对数密度.与传统激光诱导击穿光谱定量分析方法相比,新方法由于计算过程与谱线强度弱相关,所以分析结果基本不受自吸收效应的影响,同时也无需额外的光谱效率校准.基于铝锂合金的实验结果表明,该方法能够实现精确的相对定量分析和等离子体的特性诊断.     

Discrete solitons in the bigraphene with adsorbed atomic hydrogen

The propagation of discrete solitons in the bigraphene waveguides was calculated according to the Anderson model. An effective equation analogous to the classical sine-Gordon formula was obtained. The dependence of energy distribution between the waveguides of the graphene bilayers with adsorbed atomic hydrogen on the initial pulse width was studied.     

Laser-induced liquid tin discharge plasma and its EUV spectra

Laser-induced discharge plasmas(LDPs) have the potential to be inspection and metrology sources in extreme ultraviolet(EUV) lithography. An LDP EUV source was developed to avoid tin electrode erosion in which a tin pool was used as a cathode. A CO_2 pulse laser was focused on the liquid tin target surface, and then a breakdown occurred in a very short time. The voltage-current characteristics of the discharge oscillated, lasting for several microseconds, and an RLC fitting model was used to obtain the inductance and resistance. An intensified chargecoupled device(ICCD) camera was used to investigate the dynamics of LDP, which can explain the formation of a discharge channel. The EUV spectra of laser-induced liquid tin discharge plasma were detected by a grazing incident ultraviolet spectrometer, compared with a laser-produced tin droplet plasma EUV spectrum. To explain the EUV spectrum difference of laser-induced liquid tin discharge plasma and laser-produced tin droplet plasma,the collision radiation(CR) model combined with COWAN code was used to fit the experimental EUV spectrum, which can estimate the electron temperature and density of the plasma.     

Electrostatic dust-acoustic envelope solitons in an electron-depleted plasma

A standard nonlinear Schrödinger equation has been established by using the reductive perturbation method to investigate the propagation of electrostatic dust-acoustic waves, and their modulational instability as well as the formation of localized electrostatic envelope solitons in an electron-depleted unmagnetized dusty plasma system comprising opposite polarity dust grains and super-thermal positive ions. The relevant physical plasma parameters (viz., charge, mass, number density of positive and negative dust grains, and super-thermality of the positive ions, etc.) have rigorous impact to recognize the stability conditions of dust-acoustic waves. The present study is useful for understanding the mechanism of the formation of dust-acoustic envelope solitons associated with dust-acoustic waves in the laboratory and space environments.     

Dust-acoustic solitons in quantum plasma with kappa-distributed ions

Arbitrary amplitude dust-acoustic (DA) solitary waves in an unmagnetized and collisionless quantum dusty plasma comprising cold dust particles, kappa (κ)-distributed ions and degenerate electrons are investigated. The influence of suprathermality and quantum effects on the linear dispersion relation of DA waves is investigated. Then, the effect of κ-distributed ions and degenerate electrons on the existence domain of solitons is discussed in the space of (M, f). The comparison of the existence domain for higher and lower values of κ shows that suprathermality results in propagation of solitons with lower Mach number, and the quantum effects, lead to a higher values of Mach number. The existence domain of solitons for nondegenerate κ-distributed electrons is considered for comparison with effect of degenerate electrons. Also, we found that the Sagdeev potential well becomes deeper and wider as ε _F???i decreases, as for lower κ values, the influence of quantum effects on the Sagdeev pseudopotential profile is smaller.     

Formation of cavities in a Z pinch plasma

Technical Physics - The spatial structure and dynamics of the plasma in a high current vacuum spark discharge are studied via pulsed shadowgraphy. The formation of cavities in the neck plasma at...     

激光诱导等离子体碘甲烷裂解动力学过程

采用色散荧光谱和时间分辨光谱方法,研究了532 nm强激光场诱导等离子体作用下碘甲烷分解动力学过程.通过对所得色散荧光谱归属,确定了碘甲烷分解的主要荧光产物粒子:CH3I 、CH3、CH2、CH、C、H、C 、C2 、I 、I2 ;通过时间分辨光谱分析,讨论了荧光产物粒子的形成动力学机理,归结出了碘甲烷分解所经历的主要过程为"共振多光子激发电→CH3I 解离→库仑爆炸脱氢→电子碰撞激发或电离→次级碰撞电离"的物理过程.所得结果将对其他多原子分子的强激光场作用下激光诱导等离子体分解动力学过程的研究具有参考价值.     

激光诱导等离子体碘甲烷裂解动力学过程

采用色散荧光谱和时间分辨光谱方法，研究了532nm强激光场诱导等离子体作用下碘甲烷分解动力学过程。通过对所得色散荧光谱归属，确定了碘甲烷分解的主要荧光产物粒子：CH3I+、CH3、CH2、CH、C、H、C+、C2+、I+、I2+；通过时间分辨光谱分析，讨论了荧光产物粒子的形成动力学机理，归结出了碘甲烷分解所经历的主要过程为“共振多光子激发电离→CH3I+解离→库仑爆炸脱氢→电子碰撞激发或电离→次级碰撞电离”的物理过程。所得结果将对其他多原子分子的强激光场作用下激光诱导等离子体分解动力学过程的研究具有参考价值。     

非均匀尘埃等离子体中孤子的传播

运用约化摄动法研究了非均匀尘埃等离子体中孤子的传播情况. 在低阶近似下, 对于小的、但有限振幅的长波振动, 当分界面不连续变化时,孤子在不连续点的反射波与透射波均可由 KdV 方程来描述, 并给出了低阶近似情况下, 对于小的、但有限振幅的长波振动, 当入射波为单孤子时, 反射孤子与透射孤子的个数及其大小;当分界面是有限长度并连续变化时,对于小的、但有限振幅的长波振动, 尘埃声孤波由KdV型方程来描述,并由此给出了准孤子振幅、传播速度等参量在传播过程中的变化. 关键词： 尘埃等离子体 孤子 KdV方程 约化摄动法     

Propagation of ion acoustic solitons in plasma density gradients

Experimental observations of propagation of ion acoustic solitons in a plasma with density gradients are presented. Soliton amplitude and velocity change as $\text{N}\text{x}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and $\text{N}\text{x}{}^{\mathrm{<mtext>-1</mtext><mtext>2</mtext>}}$ respectively where Nx is the local density.     

On the envelope solitons in a relativistic ion-acoustic plasma

Summary Nonlinear Schr?dinger equation describing the envelope solitons is deduced in the case of ion-acoustic relativistic plasma, without taking recourse to the usual reductive perturbation theory. The methodology is that of Friedet al. (1973), which in some sense can be considered to be an extension of the effective (pseudo) potential theory. Amplitude and velocity of the solitary wave are obtained in terms of the physical parameters of plasma.

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Riassunto Si deriva l'equazione di Schr?dinger non lineare che descrive i solitoni dell'involucro nel caso del plasma relativistico a onde ioniche, senza fare ricorso all'usuale teoria di perturbazione riduttiva. La metodologia è quella di Friedet al. (1973) che si può considerare in qualche modo come un'estensione della teoria efficace di (pseudo) potenziale. Si ottengono l'ampiezza e la velocità dell'onda solitaria nei termini dei parametri fisici del plasma.

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Резюме Выводится нелинейное уравнение Шредингера, описывающее огибающие солитоны в случае релятивистской плазмы, без использования обычной теории возмущений. Методология аналогична методологии фрейда и др. (1973), которая в некотором смысле представляет обобщение теории эффективного (псевдо) потенциала. Получается вмплитуда и скорости одиночной волны в терминах физических параметров плазмы.