The Effect of the Charge Fluctuation of Dust Particles onn Ion—acoustic wave Excited Through Ionization Instability

The effect of the charge fluctuation of dust particles on ion acoustic wave(IAW) excited through ionization instability was investigated.The hydrodynamic equations and linear time-dependent perturbation theory served as the starting point of theory,by which the dispersion relatioin and growth rate of the IAW were given.By comparing the results with the case of constant dust charges,it was found that the charge fluctuation of dust particles reduces the instability of the wave mode.     

The Effect of the Charge Fluctuation of Dust Parti-cles on Ion-acoustic Wave Excited Through Ionization Instability

The effect of the charge fluctuation of dust particles on ion acoustic wave (IAW) excited through ionization instability was investigated. The hydrodynamic equations and linear time-dependent perturbation theory served as the starting point of theory, by which the dispersion relation and growth rate of the IAW were given. By comparing the results with the case of constant dust charges, it was found that the charge fluctuation of dust particles reduces the instability of the wave mode.     

强流脉冲离子束模型及辐照靶材能量沉积的模拟研究

强流脉冲离子束(IPIB)及其在靶材中沉积的能量是研究束流与靶材作用的基础.根据三束材料改性国家重点实验室从俄罗斯引进TEMPⅡ型加速器实测的磁绝缘二极管(MID)的加速电压波形及法拉第杯检测到的MID焦点处离子流密度波形,对其进行拟合得到高斯脉冲分布模型,以此为基础采用Monte Carlo方法模拟了离子在铝靶内沉积的能量,得到了一个脉冲内靶材内沉积的能量的时空演化规律.计算了单能离子束以20°～40°角入射铝靶情形.不同能量的单能H+束和C+束以一定角度入射时的最大射程比垂直入射时都要小,表面处单位长度沉积的能量随入射角的增加而增多.IPIB入射铝靶时变化规律同单能离子束.同时对H+和C+二维入射靶材情况也进行了模拟研究.     

粒子最可几分布方法中值得注意的问题

本文评述了统计力学中粒子最可几分布方法,强调了玻尔兹曼无关粒子的最可几分布数具有宏观统计平均值意义,对明确划分宏观量与微观量的界线有积极意义。     

程序升温脱附的动力学公式最大热导率推导方法

在程序升温脱附的实验中,有两种实验方法,一种尽可能避免再吸附,另一种在吸附脱附平衡条件下实现,两种实验的理论公式数学形式是一致的。(见公式(1))本文基于化学反应可以增大热导率的思想,以脱附速度最大,热导率也必然增至最大的方法,导出了两种实验条件下都能成立的公式。     

Sheath Structures of Strongly Electronegative Plasmas

The sheath structures of strongly electronegative plasmas axe investigated on basis of the accurate Bohm criterion obtained by Sagdeev potential. It is found that the presheath transition between the bulk plasma and the sheath almost does not exist there, and that distributions of electrons, negative and positive ions in the sheath form a pure positive ion sheath near the boundary of the electrode. Furthermore, the density distribution of space net charge has a peak near the sheath edge, the spatial potential within the sheath falls faster, and the sheath thickness becomes thinner.     

Three-Dimensional Dust Crystal

Dust plasmas have received considerable attention in recent years due to the fact that a kind of crystal could be established, which is a typical example of an ideal material. In this system, the dust particles are often confined upon a three-dimensional sheath of an axissymmetric concave electrode, where the axial electrostatic force balances the gravitation and the radial electrostatic force keeps the dust from running away horizontally. In this paper, a threedimensional sheath structure is simulated through a liquid model, and the movement of the dust particles is simulated via the dynamic method. The crystals are obtained self consistently. The effect of both the electrode size and the mass of dust particles on the crystals are discussed. The simulation result demonstrates that two kinds of dust crystals could be established by varying the sheath diameter, and some proper conditions are necessary for the formation of a double layer dust crystal.     

Effects of Ion Temperature on Collisionless and Collisional RF Sheath

A numerical two-fluid simulation of the non-ionized radio frequency （rf） sheath model, has been carried out. This model is ＂global＂ and thus applicable to the sheath, pre-sheath and plasma regions, In the model all variables in the ion force balance equation, including the electrical force, ion pressure and neutral particle friction, are considered. The model is solved through a finite difference scheme and sheath characteristics are obtained. The effects of the ion temperature on both the collisionless and collisional sheath characteristics are discussed. Then it is concluded that 1） the model is in a good agreement with Bohm Theorem; 2） the ion temperature has significant effects on the rf sheath characteristics. The effects are far more significant on a collisional rf sheath than on a collisionless sheath.     

Dynamics of Dust in a Plasma Sheath with Magnetic Field

Dynamics of dust in a plasma sheath with a magnetic field was investigated using a single particle model. The result shows that the radius, initial position, initial velocity of the dust particles and the magnetic field do effect their movement and equilibrium position in the plasma sheath. Generally, the dust particles with the same size, whatever original velocity and position they have, will locate at the same position in the end under the net actions of electrostatic, gravitational, neutral collisional, and Lorentz forces. But the dust particles will not locate in the plasma sheath if their radius is beyond a certain value.     

Configuration of 2D Finite Clusters in Plasma Sheath

Finite clusters with a small number of charged particles immersed in a plasma environment have been numerically simulated with a dynamic method. Finite Coulomb clusters are systems of a small number of charged particles, N = 1 to 100, confined by a potential produced by plasma 2D-sheath. Under the action of net force each particle is in an equilibrium position and together they form finite Coulomb clusters. The results of our study show the configuration of Coulomb clusters do not depend on their initial state. After theoretically studied and tested by using the Monte Carlo technique we also prove the system energy is the determinant parameter of the configuration. In addition, the effect of the external magnetic field on the cluster configuration is analyzed.