激光等离子体中相干Thomson散射的实验研究

在“星光 II”装置上进行了相干 Thomson散射实验。实验中以 0 .3 5μm激光为作用束 ,以 0 .53 μm激光作为探针光束 ,散射光采用反射式收光系统配光谱仪、条纹相机和CCD记录 ,得到较高时间和空间分辨散射光谱 ,分析得出时间变化的激光等离子体参数 ZTe和 ui。     

激光等离子体中相干Thomson散射的实验研究

在“星光II”装置上进行了相干Thomson散射实验。实验中以0.35μm激光为作用束,以0.53μm激光作为探针光束,散射光采用反射式收光系统配光谱仪、条纹相机和CCD记录,得到较高时间和空间分辨散射光谱,分析得出时间变化的激光等离子体参数和ui。     

Scattering of a Bounded Electron Beam by Plasma Waves which are Self-Consistently Excited by the Beam

The nonlinear stage of the beam plasma instability of a bandlike electron beam in unbounded plasma is examined. It is shown that such an interaction is responsible for the extreme beam electron scattering that can be observed in experiments in the absence of an external magnetic field.     

Collective Scattering of Electromagnetic Waves from a Relativistic Magnetized Plasma

Recently, laser and microwave scatterings have become one of the important diagnostic means for plasma. Laser and microwave correlative scattering spectrum is determined by particle-density fluctuations in a weak turbulent plasma. In a relativistic plasma, on the basis of complete electromagnetic interaction between particles, a general expression for particle density fluctuations and spectra of laser and microwave scattering from a magnetized plasma are derived. The laser and microwave scattering spectra provide information on electron density and temperature, ion temperature, resonance and nonresonance effects.     

Analysis of Scattering Properties from an Infinite Plasma Cylinder

In this paper, the scattering characteristics of an infinite plasma cylinder are studied theoretically by using the method of eigenfunction expansion. The backscattering cross sections of plasma cylinder in the transverse magnetic (TM) polarization case are calculated in detail. Effects of different parameters on the backscattering cross section are illustrated. Some errors in determining the complex wave number in plasma, as appeared in literatures published previously, are also rectified.     

Observation of Potential Relaxation Instability in a Bounded Discharge Plasma

A potential relaxation instability (PRI), which causes a periodic motion of a potential jump and plasma expansion accompanying a high-density fluctuation level (?60 percent), is observed in a bounded discharge plasma. The instability is found to create a high electron drift velocity and a spatial growth of density and potential fluctuations, and to accelerate a test wave. An additional supplement of a plasma into the boundary suppresses the instability. At the same time, the fluctuation decreases (<5 percent) and the frequency difference of the wave spectrum between nth and (n - 1) th (n is an integer) higher harmonics decreases as the frequency increases. However, when the potential relaxation instability is excited, this frequency difference keeps constant.     

Thomson Scattering Applied to a Noisy Radiative Plasma

Thomson scattering with a 1.5 ms long pulse mode 20 J ruby laser has been applied to a radiative argon plasma with electron densities n_e from 2.5 10¹⁹ m^?3 to 1.5 10²⁰ m^?3 and an electron temperature T_e of about 3 eV. Photon counting techniques have been used. The accuracy of n_e and T_e to be reached is about 5% after 10 shots. The signal to noise ratio S/N has been optimized by the use of optical filters and a special purpose grating. The effects of these elements on S/N have been calculated. The entrance angle, transmission and quantum efficiency have also been optimized. A comparison between 5 possible laser systems, including a normal mode and a Q-switched mode ruby laser, has been carried out.     

Analysis of Electromagnetic Scattering from Plasma Antenna Using CG-FFT Method

A gaseous plasma column as an efficient radiator of electromagnetic waves is well known. This paper presents the scattering analysis of a plasma antenna using the conjugate gradient fast Fourier transform (CG-FFT) method. Radar cross sections (RCS) of designed plasma antenna for different plasma parameters are computed mainly. Numerical results show that the plasma antenna with appropriate parameters can offer lower RCS than the metal one. It is evident from the observed scattering characteristics that the plasma antenna can be regarded as a rod of imperfect conductor with losses.     

Potential Surface Waves in a Warm Nonisothermal Plasma Bounded by Metal

The dispersion properties of potential surface waves (SW), propagating at a warm nonisothermal plasma-metal boundary across the external magnetic field are studied in this paper. The existence of potential SW is shown to be possible in frequency ranges, where electromagnetic SW do not exist. The influence of transverse plasma density inhomogeneity on dispersion properties of the SW considered is studied as well.     

双向隐形传态方案及安全性分析

基于位函数的引入与介质参量无关,将各向异性目标内外的电场展为级数形式,得到了任意各向异性目标n阶散射场、目标内场的递推表达式,给出了介电常量张量的变换关系,在平面波任意入射的条件下,并给出了传播单位矢量与极化单位矢量的一般关系.以磁化冷等离子体为例,给出了一阶散射场的具体表达式,并对二阶散射场引起的误差进行了评估.在THz波段和光波段,对所得结果进行了部分仿真.结果表明:微分散射对电波频率和极化状态等因素的影响较为敏感,介电常量张量的非对角元素对散射的影响不大,当波长与目标尺寸一定时,仿真结果不仅适用于THz波段,对其它波段也成立.     

激光在相对论磁化等离子体中的集体散射

激光在完全电解等离子体中集体散射截面等于单个电子的汤姆逊散射截面乘以结构因子，结构因子由电子密度涨落确定。在考虑电粒子间电磁相同作用基础上，给出激光在相对论磁化等离子体中散射的结构因子谱的解析表示式。     

磁化冷等离子体球的太赫兹散射特性

基于位函数的引入与介质参量无关,将各向异性目标内外的电场展为级数形式,得到了任意各向异性目标n阶散射场、目标内场的递推表达式,给出了介电常量张量的变换关系,在平面波任意入射的条件下,并给出了传播单位矢量与极化单位矢量的一般关系.以磁化冷等离子体为例,给出了一阶散射场的具体表达式,并对二阶散射场引起的误差进行了评估.在THz波段和光波段,对所得结果进行了部分仿真.结果表明:微分散射对电波频率和极化状态等因素的影响较为敏感,介电常量张量的非对角元素对散射的影响不大,当波长与目标尺寸一定时,仿真结果不仅适用于THz波段,对其它波段也成立.     

Nonlinear Theory of the Plasma Wave Excitation in a Bounded Beam-Plasma System

The excitation of symmetric and antisymmetric plasma waves by a beam layer that moves within a homogeneous plasma enclosed by a metallic wall was dealt with theoretically. Investigations were carried out for the magnetic field free case and for a magnetized electron beam. In the latter case, the beam electrons are assumed to be unable to move in the perpendicular direction. The theoretical model bases upon an extension of the well known single wave theory to a two-dimensional beam-plasma system. Special emphasis should be paid to the fact that the perpendicular wave profile of the excited waves was determined self-consistently. Energy and momentum balance equations are derived for this system. The theoretical method outlined in this paper which is based on a Green's-function technique can be extended easily to three-dimensional systems or to beam-plasma systems with other boundary conditions. The main features of the saturation process of the basic unstable wave types are discussed. Several interesting effects were found in the magnetic field free case: (i) numerical solutions describe an increasing steepening of the wave amplitudes in perpendicular direction near the center of the system for the symmetric potential wave; (ii) for the antisymmetric wave, a smoothing tendency was found in the development of the perpendicular wave potential profile; (iii) spatial separation of the slow and fast beam electrons was observed; (iv) it is shown for the antisymmetric potential wave type that, under certain conditions, a very efficient beam particle retardation mechanism occurs which is connected with a strong reduction of the formation of a fast particle group; (v) generally it was shown that the conversion of the kinetic energy of the beam electrons into the plasma wave energy may be more effective as compared with the case of the magnetized beam.     

Gravitational Wave Detection by Bounded Cold Electronic Plasma in a Long Pipe

We intend to propose an experimental sketch to detect gravitational waves (GW) directly, using an cold electronic plasma in a long pipe. By considering an cold electronic plasma in a long pipe, the Maxwell equations in 3+1 formalism will be invoked to relate gravitational waves to the perturbations of plasma particles. It will be shown that the impact of GW on cold electronic plasma causes disturbances on the paths of the electrons. Those electrons that absorb energy from GW will pass through the potential barrier at the end of the pipe. Therefore, crossing of some electrons over the barrier will imply the existence of the GW.     

Light Scattering by Human Blood Plasma

Transmission of laser radiation in human blood plasma diluted with physiological solution is studied. Comparison with scattering in pure physiological solution is made. General and individual optical characteristics of blood plasma from different patients are established.     

Floating Potential of an Electron Emitting Collector that Terminates a Bounded Plasma System

Potential formation in one‐dimensional bounded plasma system terminated by a floating, electron emitting collector is studied by a fully kinetic one‐dimensional model and particle‐in‐cell (PIC) computer simulation. As the electron emission from the collector is gradually increased, the floating potential of the collector and the electric field at the collector both increase quite strongly. When the critical emission is reached, the electric field becomes zero. If the emission is increased further, the electric field changes sign and becomes positive and a virtual cathode is formed in front of the collector. The floating potential of the collector also increases, but much more slowly, than below the critical emission level. If the ratio between the temperatures of the emitted and of the bulk electrons is high enough, the floating potential of the collector may even exceed the zero potential of the source, but in this case the simulation becomes unstable, when the positive ions start to flow back from the collector towards the source. Simulation results obtained below the critical emission level are in very good agreement with the model, provided that the particle densities obtained from the simulation are normalized correctly. In this case the potential and electric field profiles found from the PIC simulation match almost perfectly to the profiles obtained from the numerical solution of the Poisson equation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the Nonlinear Resonances in Bounded Crossed Fields Plasma

On the basis of the two-component MHD and a full electromagnetic treatment, nonlinear resonances of bounded plasma placed in crossed external a.c. electric and constant magnetic fields are found.     

Transverse Rutherford Scattering of Electron-Ion Collision in a Uniformly Magnetized Plasma

Rutherford scattering formula plays an important role in plasma classical transport. It is urgent to investigate influence of magnetic field on the Rutherford scattering since the high magnetic field has been widely used in nowadays magnetic confinement fusion, inertial confinement fusion, and magneto-inertial fusion. In order to elucidate the magnetic field effect in a concise manner, we study the electron-ion collisions transverse to the magnetic field. The scattering angle is defined using th...     

Enhanced Raman Scattering of Elliptical Laser beam in a Collisional Plasma

This paper presents the Enhanced Raman scattering of a elliptical laser beam in a collisional plasma. We have considered the mechanism of non‐uniform heating of carriers along the wave‐front, which is important in collisional plasma. The nonlinearity arising through non‐uniform heating leads to redistribution of carriers, which modifies the background plasma density profile in a direction transverse to pump beam axis. This modification in density effects the incident laser beam, plasma wave and back‐scattered beam. Non‐linear differential equations for the beam width parameters of pump laser beam, plasma wave and back‐scattered beam are set up and solved numerically. Numerical results predict the effect of self‐focusing of waves on the back‐scattered beam (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)