Reflection and Transmission of Ion Acoustic Waves from a Plasma Discontinuity

We calculate transmission and reflection coefficients for an ion acoustic wave incident from the upstream direction upon a plasma discontinuity of width much less than the wavelength. In the limit of an infinitely strong discontinuity there is complete in phase reflection.     

Nonplanar Ion Acoustic Solitary Waves in a Two-Electron Temperature Plasma

Linear and non-linear properties of ion acoustic wave （IAW） propagating in a two-electron temperature plasma are investigated from both analytical and numerical perspectives by employing the fluid theory. A one-dimensional modified Korteweg de Vries equation is derived for the IAW using the reductive perturbative technique in a nonplanar geometry. It is observed that the ion acoustic soliton in a two-temperature plasma admits rarefactive （dip like） solitons. In the limit that the cold electron population goes to zero, it is observed that the ion acoustic soliton yields compressive （hump like） solitons. The variation of the ion acoustic soliton with different plasma parameters is also shown. The present investigation may be beneficial to explain some aspects of ion acoustic rarefactive solitary structures observed in space environments where two-electron temperature plasmas have been observed.     

Modulational Instability of Dust Ion Acoustic Waves in a Collisional Dusty Plasma

The modulational instability of dust ion accoustic waves in a dust plasma with ion-dust collision effects is studied.Using the perturbation method,a modified nonlinear Schroedinger equation contains a damping term that comes from the effect of the ion-dust collision is derived.It is found that the inclusion of the ion-dust collision would modify the modulational instability of the wave packet and could not admit any stationary envelope solitary waves.     

Modulational Instability of Dust Ion Acoustic Waves in a Collisional Dusty Plasma

The modulational instability of dust ion acoustic waves in a dust plasma with ion-dust collision effects is studied. Using the perturbation method, a modified nonlinear Schrodinger equation contains a damping term that comes from the effect of the ion-dust collision is derived. It is found that the inclusion of the ion-dust collision would modify the modulational instability of the wave packet and could not admit any stationary envelope solitary waves.     

Phase Velocity of Acoustic Waves in a Non-Equilibrium Plasma

The phase velocity of acoustic waves was calculated for a non-LTE plasma and compared with that of a plasma in Saha-equilibrium. Several special cases of a non-equilibrium plasma were investigated. In the most general case the plasma parameters of a non-LTE plasma also depend on the geometry of the plasma (due to ambipolar diffusion and reabsorption of resonance line radiation). Especially, the case of a cylindric symmetric plasma column was treated here, because the most plasmas occuring in experiments have this geometry. Therefore, the investigation was also performed in detail for the propagation of acoustic waves in the center line of a cylindric plasma column. Numerical results are given for a hydrogen plasma.     

Phase-Drift-Suppression in Heterodyne Detection Using Coherent Light Source

The validity of the phase-drift-suppression method (PDSM) using coherent light sources of a single-mode laser diode (LD) or multimode Nd:YAG laser has been experimentally shown. PDSM can enhance the stability of an output signal in heterodyne detection using higher order harmonics. In the Michelson interferometer, the fundamental and second harmonics in heterodyne beat signals were detected by two lock-in amplifiers, and the computed signal intensity (CSI) was obtained in the computer as an output signal. Relations between the stability of CSI and modulation indexes in sinusoidal phase modulations were measured. The CSI stability was enhanced about twice by PDSM using a single-mode laser diode, and from 4 times to 9 times using a multimode laser.     

Weak Ion Acoustic Double Layers in a Warm Plasma

The analytic solutions of the weak ion acoustic double layers in warm unmagnetized and magnetized plasma have been presented with the fluid equation for ions and an arbitrary equation of state for the hot electrons. It has been shown that double layers solutions exist for both magnetized and unmagnetized plasmas when two Boltzmann model for electrons are considered. The potential, the thickness and the velocity of such type of double layers have been calculated and compared with those for the cold plasma.     

Nonlinear Longitudinal Strain Waves in a Solid Exposed to Pulsed Laser Radiation

The propagation of longitudinal strain waves in a solid with quadratic nonlinearity of elastic continuum was studied in the context of a model that takes into account the joint dynamics of elastic displacements in the medium and the concentration of the laser-induced point defects. The input equations of the problem are reformulated in terms of only the total displacements of the medium points. In this case, the presence of structural defects manifests itself in the emergence of a delayed response of the system to the propagation of the strain-related perturbations, which is characteristic of media with relaxation or memory. The model equations describing the nonlinear displacement wave were derived with allowance made for the values of the relaxation parameter. The influence of the generation, relaxation, and the strain-induced drift of defects and the flexoelectricity on the propagation of this wave was analyzed. It is shown that, for short relaxation times of defects, the strain can propagate in the form of both shock fronts and solitary waves (solitons). Exact solutions depending on the type of relation between the coefficients in the equation and describing both the shock-wave structures and the evolution of solitary waves are presented. In the case of longer relaxation times, shock waves do not form and the strain wave propagates only in the form of solitary waves or a train of solitons. The contributions of the finiteness of the defect-recombination rate and the flexoelectricity to linear elastic moduli and spatial dispersion are determined.     

Propagation and Diagnostic of Ion Acoustic Waves in a Low Pressure Argon Discharge

In a dc argon discharge column of pressure 5 × 10^?4 torr, ion acoustic waves are studied experimentally. Plasma parameters obtained from the phase velocity of waves are compared with the Langmuir probe measurements. The wave diagnostic method yields the electron temperature lower than the probe method by a factor of 3…?5, if the atomic argon ion is assumed as a dominant ion species. The axial profiles of ion drift velocity show the presence of ions flowing toward the anode along the potential drop in flont of it. Also it is found that the surface condition of the cathode sensitively affects the propagation of ion acoustic waves through the changes in discharge parameters.     

Obliquely Propagating Electron Acoustic Shock Waves in Magnetized Plasma

Obliquely propagating electron acoustic shock waves in plasma with stationary ions, cold and superthermal hot electrons are investigated in magnetized plasma. Employing reductive perturbation method, Korteweg-de Vries-Burgers equation (KdVB) is derived in the small amplitude approximation limit. The analytical and numerical calculations of the KdVB equation show the variation of shock waves structure (amplitude, velocity, and width) with different plasma parameters. Particle density (α), superthermal parameter (κ), electron temperature ratio (??), kinetic viscosity (η₀), obliqueness (k_z), and strength of magnetic field (ω_c) significantly modify the properties of the shock waves structures. The present investigation is useful to understand dissipative structures observed in space or laboratory plasma where multielectrons population with superthermal electrons are prevalent.     

Influence of Non-Maxwellian Particles on Dust Acoustic Waves in a Dusty Magnetized Plasma

In this paper an investigation into dust acoustic solitary waves(DASWs) in the presence of superthermal electrons and ions in a magnetized plasma with cold dust grains and trapped electrons is discussed. The dynamic of both electrons and ions is simulated by the generalized Lorentzian(κ) distribution function(DF). The dust grains are cold and their dynamics are studied by hydrodynamic equations. The basic set of fluid equations is reduced to modified Korteweg-de Vries(mKdV) equation using Reductive Perturbation Theory(RPT). Two types of solitary waves, fast and slow dust acoustic soliton(DAS) exist in this plasma. Calculations reveal that compressive solitary structures are possibly propagated in the plasma where dust grains are negatively(or positively) charged. The properties of DASs are also investigated numerically.     

0.53μm激光辐照金盘靶的光散射机制研究

报道了０．５３μｍ高功率激光辐照金盘靶产生的受激拉曼散射光光谱和散射光谱能量角分布，由散射光角分布计算的散射光能量与实验通过打靶透镜测得的受激拉曼散射能量不符，而且角的分布的实验结果与受激布里渊散射理论也不符。     

A Novel Laser Heterodyne Technique for the Measurement of Electron Density in Gas Discharges: Application to a TEA CO2 Laser Plasma

We describe a novel intracavity laser heterodyne technique for the measurement of electron density in gas discharges. The method produces time-resolved data from a single pulse and we have used it to monitor electron densities in a TEA laser discharge with a typical CO2 laser gas mixture. Good agreement was found between the measured electron density and its value calculated from current density and drift velocity. A maximum value of 5 × 1013 cm-3 was observed.     

激光等离子体的声学诊断研究

提出了利用激光等离子体声波对高功率激光与材料相互作用过程进行了诊断的方法。实际测量了波长０．５３μｍ激光与几种金属材料相互作用的过程，其结果与采用春它方法得到的结果基本吻合。     

Effect of Second Nonthermal Ion on the Characteristics of Dust Acoustic Solitary Waves in a Magnetized Dusty Plasma with Variable Dust Charge

The nonlinear dust acoustic solitary waves in a magnetized dusty plasma with nonthermal ions and variable dust electric charge is studied analytically. Using reductive perturbation method the Zakharov‐Kuznetsov (ZK) equation is derived and effect of nonthermal coefficient, external magnetic field, and variable dust electric charge on the amplitude and width of soliton in dusty plasma is investigated. With increasing the rate of dust charge variation with respect of plasma potential, the amplitude of generated solitary waves in magnetized dusty plasma increases to a constant magnitude while its width decreases. Increasing the nonthermal ions coefficient leads to a noticeable decrease in the amplitude of solitons while the width of soliton increases. The amplitude of generated solitary waves in such a dusty plasma is independent of applied external magnetic field but we will have more localized solitons with increasing the external magnetic field strength. It is found that solitons are strongly influenced by the direction of external magnetic field. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

腔内倍频调Q激光器中脉冲光场的时间不稳定性研究

以腔内倍频调Q激光器工作原理为基础,研究了多种形式抽运光分布的情况下倍频光的脉冲形状以及脉冲持续过程中光场分布的时间不稳定性,分析了倍频光光束质量随时间的变化规律.发现腔内倍频调Q激光器输出的倍频光光场分布在脉冲的持续过程中并不稳定,呈持续变化.对高斯型抽运的情况研究发现,减小腔长会使脉冲光场分布的不稳定性减小;而增加...     

固体激光光折变自适应光外差探测技术研究

依据光折变晶体中自抽运与互抽运相位共轭共存的特性，提出了一种新型的光折变自适应光外差探测系统，并利用相干性较差的固体激光器进行了自适应光外差探测的实验研究。该系统具有结构简单、干扰和外差探测灵敏度高等优点，在光通信、激光雷达等许多领域内都具有重要的实用价值。     

Propagation of Plasma Generated by Intense Pulsed Ion Beam Irradiation

Taking the calculation results based on the established two-dimensional ablation model of the intense-pulsed-ionbeam （IPIB） irradiation process as initial conditions, we build a two-dimensional hydrodynamic ejection model of plasma produced by an IPIB-irradiated metal titanium target into ambient gas. We obtain the conclusions that shock waves generate when the background pressure is around 133 mTorr and also obtain the plume splitting phenomenon that has been observed in the experiments.