Collisional contribution to stimulated scattering in plasmas

The influence of collisions on stimulated Brillouin scattering in magnetized plasmas is discussed. It is shown that new effects occur when the magnitude of the electron quiver velocity exceeds the electron thermal velocity.     

高速摄影在流体动力学不稳定性研究中的应用

用高速摄影技术研究了高压气体膨胀驱动空气-水界面的瑞利-泰勒不稳定性,获得了空气-水界面的不稳定性清晰图像,得到气炮尖顶运动速度及湍流混合层高度增长速度与时间关系曲线。在横式激波管上用高速纹影诊断技术研究了激波作用空气-SF6界面的里克特迈耶-梅什科夫不稳定性,初步获得了实验图像,可清晰显示混合区变化过程。     

超声波辅助提取-HG-ICP-AES法测定中草药雷公藤中可溶态Sb(Ⅲ)和Sb(Ⅴ)

本文建立了用超声波辅助提取,氢化物发生-电感耦合等离子体原子发射光谱法测定中草药雷公藤中可溶态Sb(Ⅲ)和Sb(Ⅴ)的分析方法。研究了超声波辅助提取的影响因素、锑形态分离的最佳pH值、仪器工作条件对锑氢化物发生的影响及五价锑的还原条件,探讨了共存离子对锑测定的干扰及消除方法。Sb(Ⅲ)和Sb(Ⅴ)的检出限分别为0.3和2.4 μg·L-1, 相对标准偏差分别为3.9%和4.5%,样品加标回收率为93%～105%。     

脉冲激光烧蚀碲镉汞材料的等离子体发射谱

脉冲激光辐照处于不同背景气压下的Hg0.8Cd0.2Te材料表面,用时间和空间分辨诊断技术探测了激光照射后产生的等离子体发射谱,根据所获得的飞行时间谱测量了等离子体中粒子的出射速度,结果表明粒子速度随着出射距离的增加迅速减小,且背景气压对出射速度有很大的影响,而激光能量对粒子速度的影响不大。另外根据谱线的展宽计算了等离子体中的电子密度,结果表明,电子密度在激光辐照样品后的短时间内迅速减小,且电子密度最大的位置不是出现在靶的表面而是在距表面一定距离处。     

Nonlinear ion-acoustic structures in a nonextensive electron–positron–ion–dust plasma: Modulational instability and rogue waves

The nonlinear propagation of planar and nonplanar (cylindrical and spherical) ion-acoustic waves in an unmagnetized electron–positron–ion–dust plasma with two-electron temperature distributions is investigated in the context of the nonextensive statistics. Using the reductive perturbation method, a modified nonlinear Schrödinger equation is derived for the potential wave amplitude. The effects of plasma parameters on the modulational instability of ion-acoustic waves are discussed in detail for planar as well as for cylindrical and spherical geometries. In addition, for the planar case, we analyze how the plasma parameters influence the nonlinear structures of the first- and second-order ion-acoustic rogue waves within the modulational instability region. The present results may be helpful in providing a good fit between the theoretical analysis and real applications in future spatial observations and laboratory plasma experiments.     

实验室天体物理研究进展

近年来,随着高功率激光实验装置的广泛应用,成像技术和模拟分析技术水平的进一步提高,实验室天体物理研究取得了一些新的重要进展,如激光等离子体实验中对流等离子体磁场结构,冲击波中磁场的湍流放大效应,实验室模拟原恒星喷流中磁场的准直效应和太阳风与偶极磁场之间相互作用等方面的研究。这些研究加深了人们对原恒星以及Herbig—Haro天体喷流、超新星遗迹冲击波、地球磁层中磁场活动等天体物理现象的理解。文章对上述几个方向进行了介绍,并对未来研究方向做一些展望。     

Energy analysis of protons emitted from Nd:YAg laser-generated plasmas

Hydrogenated targets have been irradiated in vacuum with the pulsed Nd:YAg laser at intensities of the order of 10¹⁰ W/cm². The laser-generated plasma, produced by the interaction with the solid, emits protons and other ions along the normal to the target surface. Ion collectors and ion energy analyzer were used to measure the current, the angular emission and the energy distributions of the emitted protons. Time-of-flight measurements, Coulomb–Boltzmann-distributions and the fits of experimental data were also used in order to evaluate the equivalent ion plasma temperature and the ion acceleration developed in the non-equilibrium-pulsed plasma.     

Effects of Higher-Order Relativistic Nonlinearity and Wakefield During a Moderately Intense Laser Pulse Propagation in a Plasma Channel

Using a variational approach, the propagation of a moderately intense laser pulse in a parabolic preformed plasma channel is investigated. The effects of higher-order relativistic nonlinearity (HRN) and wakefield are included. The effect of HRN serves as an additional defocusing mechanism and has the same order of magnitude in the spot size as that of the transverse wakefield (TWF). The effect of longitudinal wakefield is much larger than those of HRN and TWF for an intense laser pulse with the pulse length equaling the plasma wavelength. The catastrophic focusing of the laser spot size would be prevented in the present of HRN and then it varies with periodic focusing oscillations.     

Laser Ablation Inductively Coupled Plasma Mass Spectrometry: Principles and Applications

Abstract

The application of laser ablation inductively plasma mass spectrometry (LA‐ICP‐MS) to the determination of major, minor, and trace elements as well as isotope‐ratio measurements offers superior technology for direct solid sampling in analytical chemistry. The advantages of LA‐ICP‐MS include direct analysis of solids; no chemical dissolution is necessary, reduced risk of contamination, analysis of small sample mass, and determination of spatial distributions of elemental compositions. This review aims to summarize recent research to apply LA‐ICP‐MS, primarily in the field of environmental chemistry. Experimental systems, fractionation, calibration procedures, figures of merit, and new applications are discussed. Selected applications highlighting LA‐ICP‐MS are presented.     

Potential distribution around a test charge in a positive dust-electron plasma

The electrostatic potential caused by a test-charge particle in a positive dust-electron plasma is studied, accounting for the dust-charge fluctuations associated with ultraviolet photoelectron and thermionic emissions. For this purpose, the set of Vlasov–Poisson equations coupled with the dust charging equation is solved by using the space–time Fourier transform technique. As a consequence, a modified dielectric response function is obtained for dust-acoustic waves in a positive dust-electron plasma. By imposing certain conditions on the velocity of the test charge, the electrostatic potential is decomposed into the Debye–Hückel (DH), wake-field (WF), and far-field (FF) potentials that are significantly modified in the limit of a large dust-charge relaxation rate both analytically and numerically. The results can be helpful for understanding dust crystallization/coagulation in twocomponent plasmas, where positively charged dust grains are present.