多成分电负性碰撞等离子体的鞘层玻姆判据

采用双流体模型研究了多成分的电负性碰撞等离子体鞘层的玻姆判据,讨论了一维稳态情形下不同的带电粒子对鞘层玻姆判据的影响。采用拟牛顿法,得到了数值解。结果表明：玻姆判据存在上限和下限。二次电子发射系数越大,离子的马赫数越大;负离子的含量越多,离子的马赫数越小。鞘层中离子的温度、离子与中性粒子的碰撞以及离子的带电量对玻姆判据的上下限的取值都有一定的影响。     

Parameters of a multicomponent laser-induced plasma

Technical Physics - We report on the results of analysis of parameters of a laser-induced plasma, which were obtained using emission diagnostics of a laser torch plasma from a CuInSe2...     

Generalized Landau superfluidity criterion

An analysis of experimental data shows that, in addition to phonon-roton excitations in superfluid helium, there necessarily exist at least one branch of elementary excitations whose energy spectrum strongly depends on temperature. On this basis, the Landau superfluidity criterion is generalized for several branches of elementary excitations, taking into account that the critical velocity should vanish during the phase transition of liquid helium from the superfluid state to the normal state.     

The Bohm criterion for a dusty plasma sheath

The formation of the sheath in a dusty plasma is investigated. The Bohm criterion is derived for two different cases: (a) when electrons are in thermodynamic equilibrium and dust grains provide the immobile, stationary background and (b) when both electrons and ions are in thermodynamic equilibrium and dust grains are moving. In the first case, Bohm criterion gets modified due to the fluctuation of the charge on the grain surface. In the second case, the collisional and Coulombic drag play important role in determining the Bohm criterion.     

Self-consistent expansion of a multicomponent plasma into a vacuum

The problem of the one-dimensional collisionless expansion of a multicomponent plasma into a vacuum is considered. In the hydrodynamic approximation, an approximate analytical solution for an arbitrary set of ion species with masses M₁,..., M_n and charge numbers Z₁e, Z₂e,..., Z_ne is found by using the technique of self-similar variables employed by Gurevich, Pariiskaya, and Pitaevskii for the case of single-species ions. A numerical iterative algorithm is developed in which the analytical solution is used as a first approximation.     

Distribution functions of a slightly nonideal multicomponent plasma

A regular perturbation theory technique is constructed using the plasma parameters of the equilibrium Bogolyubov-Born-Green-Kirkwood-Yvon (BBGKY) equation chain for a multicomponent plasma in which higher order terms are small at all admissable interparticle distances, in contrast to the Debye equations. As a result, two correlation radii appear in a charge-asymmetric plasma: the Debye radius D and 2 D. The divergence of correlation functions characteristic of Debye splitting is eliminated in any order of the perturbation theory. For the proposed theory to be applicable the plasma parameter must be limited more severely, the deeper the depth of the potential well which appears upon approach of oppositely charged ions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 53–58, May, 1988.     

Dynamics in a multicomponent plasma near the low-frequency cutoff

The distinctive feature of a multicomponent plasma is found to be a first order rotation of the light ion fluid with a characteristic frequency, Omega(r). A resonance at omega=Omega(r) results in plasma oscillation with unique properties. Coupling of the fast rotation time scale with the slow magnetosonic time scale leads to a nonlinear Schro dinger equation for the system and suggests the possibility of strong structural turbulence at MHD scales.     

Weak electron acoustic double layers in a multicomponent plasma

Formation of electron acoustic double layers in a magneto-plasma with two ion species is investigated. The existence of double layers propagating almost perpendicular to the magnetic field in a plasma with two distinct ion species and cold electron is discussed.     

Exact solution for the generalized Bohm criterion in a two-ion-species plasma

For a weakly collisional two-ion species plasma, it is shown that the minimum phase velocity of ion acoustic waves (IAWs) at the sheath-presheath boundary is equal to twice the phase velocity in the bulk plasma. This condition provides a theoretical basis for the experimental results that each ion species leaves the plasma with a drift velocity equal to the IAW phase velocity in the bulk plasma [D. Lee et al., Appl. Phys. Lett. 91, 041505 (2007)10.1063/1.2760149]. It is shown that this result is a consequence of the generalized Bohm criterion and fluid expressions for the IAW phase velocities.     

电负性等离子体磁鞘的玻姆判据

采用流体模型研究了电负性等离子体磁鞘的玻姆判据,讨论了负离子以及磁场对鞘层玻姆判据的 影响.研究结果表明:负离子的存在促进离子进入鞘层;而磁场强度、角度以及离子进入鞘层的状态将共同决定 离子马赫数的取值.     

尘埃等离子体鞘层的玻姆判据

采用流体方程和自洽电荷变化模型研究了尘埃等离子体鞘层的玻姆判据. 讨论了离子临界马赫数和尘埃粒子临界马赫数随尘埃密度变化的关系, 以及尘埃表面势随尘埃密度变化的趋势. 由于鞘边尘埃粒子的存在, 离子必需以大于声速的速度进入鞘层; 随尘埃密度的持续增加, 离子的临界马赫数增加到一个最大值后开始逐渐减小. 数值计算得到的结果满足Sagdeev势的定性分析. 关键词： 等离子体 鞘层 玻姆判据     

斜磁场作用下碰撞电负性等离子体鞘层的玻姆判据

采用流体模型研究了外加斜磁场作用下的碰撞电负性等离子体鞘层的玻姆判据, 讨论了负离子和磁场对鞘层玻姆判据的影响. 研究结果表明: 在电负性鞘层中, 正离子更容易进入鞘层, 负离子的存在只能影响离子马赫数取值的下限; 而外加磁场可以使离子马赫数的取值范围整体发生移动.     

Observation of Peregrine solitons in a multicomponent plasma with negative ions

The experimental observation of Peregrine solitons in a multicomponent plasma with the critical concentration of negative ions is reported. A slowly amplitude modulated perturbation undergoes self-modulation and gives rise to a high amplitude localized pulse. The measured amplitude of the Peregrine soliton is 3 times the nearby carrier wave amplitude, which agrees with the theory. The numerical solution of the nonlinear Schr?dinger equation is compared with the experimental results.     

Large amplitude solitary waves in a multicomponent plasma with negative ions

When the concentration of negative ions is larger than a critical value, a small compressive pulse evolves into a subionic wave train and a large pulse develops into a solitary wave. The threshold amplitude and velocity of the solitary waves are measured and compared with predictions using the pseudopotential method.     

斜磁场中碰撞等离子体鞘层的玻姆判据

采用双流体模型研究了斜磁场作用下的碰撞等离子体鞘层的玻姆判据,讨论了磁场对鞘层玻姆判据的影响.结果表明:玻姆判据存在上限和下限,磁场强度、角度以及离子进入鞘层的状态都对离子马赫数的取值范围有影响.     

Effect of multicomponent dust grains in a cold quantum dusty plasma

By employing the quantum hydrodynamic model for electron-ion-dust plasma,we derive a dispersion relation of the quantum dusty plasma.The effects of the dust size distribution on the dispersion relation in a cold quantum dusty plasma are studied.Both analytical and numerical results are given to compare the differences between the dusty plasma by considering the dust size distribution and the mono-sized dusty plasma.It is shown that many system parameters can significantly influence the dispersion relation of the quantum dusty plasma.     

Propagation of waves in a multicomponent plasma having charged dust particles

Propagation of both low and high frequency waves in a plasma consisting of electrons, ions, positrons and charged dust particles have been theoretically studied. The characteristics of dust acoustic wave propagating through the plasma has been analysed and the dispersion relation deduced is a generalization of that obtained by previous authors. It is found that nonlinear localization of high frequency electromagnetic field in such a plasma generates magnetic field. This magnetic field is seen to depend on the temperatures of electrons and positrons and also on their equilibrium density ratio. It is suggested that the present model would be applicable to find the magnetic field generation in space plasma.     

Local modes in structures with multicomponent plasma

The dispersion relations of a surface plasmon are determined for the case where two- and three-dimensional plasmas coexist, which is typical of topological insulators. Local plasma modes originating from two- and one-dimensional defects in multilayer superlattices and quantum-wire superlattices are investigated.     

Acceleration of a multicomponent plasma in the cathode region of a vacuum arc

A general solution to the problem of the steady-state spherical expansion of a current-carrying multicomponent plasma into a vacuum is derived. It is shown that, in vacuum arc discharges, the main force accelerating the cathode material, which becomes a plasma at distances of 1 to 300 μm from the cathode surface, is the electron pressure gradient force maintained by Joule heating. It is established that ions of different charges move with the same hydrodynamic velocity, which is uniquely determined by the mass and mean charge of the ions and the maximum electron temperature in the cathode region.