Electrostatic waves in a paired fullerene-ion plasma

Three kinds of electrostatic modes are experimentally observed to propagate along magnetic-field lines for the first time in the pair-ion plasma consisting of only positive and negative fullerene ions with an equal mass. It is found that the phase lag between the density fluctuations of positive and negative ions varies from 0 to pi depending on the frequency for ion acoustic wave and is fixed at pi for an ion plasma wave. In addition, a new mode with the phase lag about pi appears in an intermediate-frequency band between the frequency ranges of the acoustic and plasma waves.     

Sheath characteristics in plasma carrying finite mass negative ions and ionization at low frequency

The sheath characteristics are investigated in a collisional environment by considering three electronegative plasmas, namely CF₄, Oxygen, and C₆₀ plasmas. Specifically, positive ion velocity, electrostatic potential, charged species densities and net space charged density are examined inside the sheath region with the variation of collisional parameter, mass ratio of negative to positive ions, temperature ratios of electrons to positive ions and electrons to negative ions, non-neutrality parameter and negative ion density. Collisional cross-section is assumed to have a power-law dependence, and both the cases of constant mobility and constant collisional cross-section are discussed and compared. In order to introduce the concept of finite mass of negative ions, both kinds of ions are considered to be governed by their fluid equations, where contribution of ionization, attachment, and detachment is also taken through the continuity equations.     

Electrostatic double layers in a warm negative ion plasma with nonextensive electrons

The electrostatic double layer (DL) structures are studied in negative ion plasma with nonextensive electrons q-distribution. The extended Korteweg–de Vries (EKdV) equation is derived using a reductive perturbation method. It is found that both fast (compressive) and slow (rarefactive) ion acoustic (IA) DLs can propagate in such type of plasmas. The effects of various plasma physical parameters; such as nonextensivity of electrons, presence of negative ions, temperature of both positive and negative ions and different mass ratios of positive to negative ions on the formation of DL structures are discussed in detail with numerical illustrations.     

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.     

Kadomtsev–Petviashvili equation for dust ion-acoustic solitons in pair-ion plasmas

Using the reductive perturbation method, we have derived the Kadomtsev-Petviashvili (KP) equation to study the nonlinear properties of electrostatic collisionless dust ion-acoustic solitons in the pair-ion (p-i) plasmas. We have chosen the fluid model for the positive ions, the negative ions, and a fraction of static charged (both positively and negatively) dust particles. Numerical solutions of these dust ion-acoustic solitons are plotted and their characteristics are discussed. It is found that only the amplitudes of the electrostatic dust ion-acoustic solitons vary when the dust is introduced in the pair-ion plasma. It is also noticed that the amplitude and the width of these solitons both vary when the thermal energy of the positive or negative ions is varied. It is shown that potential hump structures are formed when the temperature of the negative ions is higher than that of the positive ions, and potential dip structures are observed when the temperature of the positive ions supersedes that of the negative ions. As the pair-ion plasma mimics the electron-positron plasma, thus our results might be helpful in understanding the nonlinear dust ion acoustic solitary waves in super dense astronomical bodies.     

The Kadomtsev-Petviashvili equation for dust ion-acoustic solitons in pair-ion plasmas

Using the reductive perturbation method,we have derived the Kadomtsev-Petviashvili(KP) equation to study the nonlinear properties of electrostatic collisionless dust ion-acoustic solitons in pair-ion(p-i) plasmas.We have chosen the fluid model for the positive ions,the negative ions,and a fraction of static charged(both positively and negatively) dust particles.Numerical solutions of these dust ion-acoustic solitons are plotted and their characteristics are discussed.It is found that only the amplitudes of the electrostatic dust ion-acoustic solitons vary when the dust is introduced in the pair-ion plasma.It is also noticed that the amplitude and the width of these solitons both vary when the thermal energy of the positive or negative ions is varied.It is shown that potential hump structures are formed when the temperature of the negative ions is higher than that of the positive ions,and potential dip structures are observed when the temperature of the positive ions supersedes that of the negative ions.As the pair-ion plasma mimics the electron-positron plasma,thus our results might be helpful in understanding the nonlinear dust ion acoustic solitary waves in super dense astronomical bodies.     

Collisionless plasma expansion and fast ion generation at plasma-vacuum boundary

Collisionless plasma expansion into a vacuum is investigated by computational treatment of a system of Vlasov equations for both ions and electrons coupled by a selfconsistent field. High-velocity low-density mass expansion is observed as a result of an electrostatic acceleration of ions.     

平行板静电场法离子引出的对称收集

离子引出的研究在AVLIS工程中有重要的意义，离子引出量和引出时间直接关系到整个系统 的离子收集效率. 在静电场中，由于等离子体屏蔽效应的存在，等离子体电位要高于正、负 极板的电位，而且在靠近正、负极板的两侧均存在鞘层. 理论模拟表明在正极板一边也可以 引出离子. 选取铯（Cs）作为实验对象，研究静电场对Cs等离子体的离子引出，使用安装在 两个极板上的法拉第筒收集离子引出信号. 实验结果表明，正极板确实可以引出离子，随着 外加电压的升高，从正极板一边引出离子的比率降低. 关键词： AVLIS 离子引出 等离子体     

Electron and positron nonthermality effects on the formation of damped solitons in collisional multi-component plasmas

Electrostatic damped field characteristics in non-thermal fast positron and electron plasma having fluids of positive and negative pair ions have been discussed when collisional frequencies parameters are taken into account. The damped and forced form of Kadomtsev-Petviashvili (DKP) equations have been obtained. The plasma parameters effects of electron density ratio, the negative ionic density ratio, the pair ionic charge ratio, the density of positron ratio, the collisional frequencies, ion mass ratio and the fast non-thermality on the electrostatic damped and forced field formations, as observed in D-F -ionosphere and laboratory experiments have been investigated.     

Multipole-Bound Molecular Negative Ions

 Within the framework of a simple electrostatic model, as compared to recent experimental results, we here discuss the stability of very weakly bound molecular negative ions. In contrast with the case of conventional valence anions, the excess electron is then located in a very diffuse orbital and is mainly bound by electrostatic dipolar, quadrupolar, and polarization forces, at large distances from the neutral molecular core. By fitting a single repulsion parameter of the model to the available experimental data, it is possible to make quantitative predictions of the excess-electron binding energies in these species. Critical values of the dipole moment, quadrupole moment or polarizability required for the observation of stable multipole-bound negative ions are predicted and compared to available experimental data and ab initio calculations. Received October 24, 2001; accepted for publication November 16, 2001     

Electrostatic Ion-Cyclotron Waves in a Plasma with Negative Ions

The dispersion relation for electrostatic ion-cyclotron (EIC) waves in a plasma containing a fraction of negative ions is derived from the fluid picture. Two wave modes are generally possible. Some of their features are investigated.     

Generating monoenergetic heavy-ion bunches with laser-induced electrostatic shocks

A method for efficient laser acceleration of heavy ions by electrostatic shock is investigated using particle-in-cell (PIC) simulation and analytical modeling. When a small number of heavy ions are mixed with light ions, the heavy ions can be accelerated to the same velocity as the light ions so that they gain much higher energy because of their large mass. Accordingly, a sandwich target design with a thin compound ion layer between two light-ion layers and a micro-structured target design are proposed for obtaining monoenergetic heavy-ion beams.     

Ion confinement by electrostatic potential well in magnetic multipole device

An effective confinement of fast ions is achieved by a negative electrostatic potential well produced by injection of electrons into a surface magnetic multipole device.     

Wake potential with mobile positive/negative ions in multicomponent dusty plasmas

We employ the test charge approach to calculate the electrostatic potential for a test charge in a multicomponent dusty plasma, whose constituents are the Boltzmann distributed electrons, mobile positive and negative ions, and immobile positive/negative charged dust particles. By using the modified dielectric constant of the dust-ion-acoustic (DIA) waves, the Debye screening and wake potentials are obtained. It is found that the presence of mobile negative ions significantly modify the DIA speed and the wake potential. The present results are relevant to polar mesosphere and microelectronic in the context of charged particle attraction and repulsion.     

Numerical and experimental studies of collection efficiency of an ion electrostatic collector for a mini-volume electrical PM detector

The experimental efficiency was numerically and experimentally studied for collecting negative and positive ions in a coaxial cylindrical electrostatic collector for a mini-volume electrical PM detector. The commercial computational fluid dynamics software package COMSOL Multiphysics™ was used to predict the behaviors of the flow and electric fields as well as the particle trajectories in the collecting zone of the ion collector. In the experiment, the ions were generated by a corona-needle ionizer with concentrations greater than 10¹³ ions/m³, the positively and negatively applied voltages at the inner electrode ranged from 0 to 45 V and the ion flow rates ranged from 1 to 5 L/min. For these ion flow rates, 1–5 L/min, the ion precipitates due to space charge and diffusion effects ranged from 92 to 97 % for positive ions and 91–97 % for negative ions. The total collection efficiency of the collector increased to 100% at collection voltages larger than 5, 20 and 40 V respectively for the ion flow rates of 1, 3 and 5 L/min for both positive and negative ions. Numerical calculation results of the ion trajectory in the collecting zone of the collector; showed good agreement with the experimental results of the total collection efficiency and can be used to support the bettering of designing in order to refine an ion collector after the charger or ionizer in a mini-volume electrical aerosol detector. Finally, this shows that this ion collector was proven to be particularly useful as an electrostatic collector for positive and negative ions after the charger or ionizer in a mini-volume electrical aerosol detector.     

离子光学系统简单数值计算方法在反射式飞行时间质谱仪中的应用

简要阐述了求解离子光学系统电场结构分布以及带电粒子在该电场中运行轨迹的通用数值计算方法,分析了在保证计算精度的前提下,节省磁盘空间、提高计算速度的PC级计算机上优化算法,并提出一种寻找最佳超松弛因子的可行性方法.在PC级计算机上应用该计算方法对一台无栅网结构高分辨率反射式飞行时间质谱仪进行计算,给出了电场分布、粒子飞行轨迹和设定各种不同条件对电场进行优化的结果.根据计算结果调整的反射式飞行时间质谱仪达到了其优化工作状态,所测得的质谱分辨率显著提高.     

盐离子对蛋白质带电特性的影响

本文应用分子理论,研究盐离子对蛋白质带电特性的影响,理论模型考虑蛋白质与阴离子的结合作用。研究发现,由于蛋白质与阴离子的结合,距离蛋白质表面附近处的阴离子被吸附在了蛋白质表面,在距离蛋白质表面附近区域,阴离子分布较少。通过计算体系中的静电势,我们发现,在距离蛋白质表面附近,静电势呈现了较大的负值,带正电荷的阳离子感受到静电吸引,会出现在距离蛋白质表面附近的区域,这会使得在距离蛋白质表面附近的区域,阳离子数目增多。这样,在不同阴离子浓度、以及阴离子与蛋白质不同结合能条件下,阴离子会在不同程度上影响蛋白质的带电特性、影响体系中的静电特性。通过考察不同结合能条件下,蛋白质表面电荷面密度随阴离子浓度的变化关系还发现,较大的结合能会使得阴离子与蛋白质结合增快,蛋白质表面会呈现从正电荷态向负电荷态的转变。理论结果符合实验观测,由此表明,盐离子与蛋白质的结合导致蛋白质表面带电特性的改变,是盐离子影响蛋白质带电特性的本质。     

Radial focusing of ion beams in a mass analyzer with an electrostatic lens and a sector-shaped inclined-wall magnetic prism

The ionic and optical properties of an inclined-wall magnetic mass analyzer with electrostatic direction focusing of ions in a nonuniform (r ^?1) magnetic field were studied. A condition for ion focusing in the radial plane was derived, and the basic parameters of the mass analyzer were determined.     

Compensation of the volume charge of ions in a time-of-flight mass analyzer

A method of forced compensation of the volume charge of ions leading to considerable deterioration of the dispersion characteristics of a time-of-flight mass analyzer with a sector electrostatic field is described. It is shown that recompensation of the voluem charge also deteriorates the resolution of the instrument.     

Nonlinear Structures in an Ion-Beam Plasmas Including Dust Impurities with Nonthermal Nonextensive Electrons

The properties of dust ion acoustic waves are investigated in an unmagnetized multicomponent plasma system consisting of ion beam, charged positive and negative ions, electrons obeying nonthermal-Tsallis distribution and stationary negatively charged dust grains by the conventional Sagdeev pseudopotential method, through which the condition for existence of several nonlinear structures is analyzed theoretically. The dispersion relation for electrostatic waves is derived and analyzed and an expression of the energy integral equation is obtained. It is reported here that our plasma model supports solitions, double layers and supersoliton solutions for certain range of parameters. Finally, the effects of different physical plasma parameters on these nonlinear structures are studied numerically. The present theory should be helpful in understanding the salient features of the electrostatic waves in space and in laboratory plasmas where two distinct groups of ions and non-Maxwellian distributed electrons are present.