Energy loss of light ions with allowance for the presence of metastable particles in the ion beam

The change in the average ion charge due to the presence of particles in metastable states in beams of helium-like ions has been studied. The charge distributions and average charges have been calculated for ions with nuclear charges Z = 3?7 and a velocity of 3.65 au in nitrogen. The previously obtained data on the cross sections of loss and capture of electrons by metastable ions and ions in the ground state were used in the calculations. It is shown that the presence of metastable particles in ion beams leads to an increase in the average charge and energy loss for all considered ions.     

Compressive and Rarefactive Waves in Dust Plasma with Non-thermal Ions

The governing equation of the dust fluid with non-thermal ions and variable dust charge on dust particles in hot dust plasmas is obtained. Both the compressive and rarefactive waves in this system are investigated. They can be determined by plasma parameters including the temperatures of dust fluid, ions and electrons, as well as the non-thermal parameter of ions, and the number densities of the dust particles, the ions and the electrons, etc.     

Ultrahigh charging of dust particles in a nonequilibrium plasma

Charging of dust particles in a plasma with the two-temperature energy distribution of electrons has been studied. It has been shown that the dust-particle potential divided by the electron temperature decreases with increasing electron temperature in the plasma with cold ions. Owing to this behavior, the potential of the dustparticle surface increases with the electron temperature more slowly than the linear function and is lower than the electron temperature (divided by the elementary charge) for T _e > 5.5 eV in hydrogen and for T _e > 240 eV in argon. The fraction of fast electrons at which these electrons begin to contribute to the charge of dust particles has been determined. It has been shown that the charge of micron particles can reach 10⁶ elementary charges. The effect of the cold and thermal field emission on the charge of dust particles has been analyzed. The possibility of obtaining ultrahigh charges (to 10⁷ elementary charges on dust particles with a radius of 50–100 μm irradiated by a 25-keV 1-mA electron beam has been demonstrated.     

Kinetic simulations of argon dusty plasma afterglow including metastable atom kinetics

The afterglow of a dusty plasma of rf discharge in argon is simulated by the particle-in-cell-Monte Carlo collision (PIC-MCC) method. The experimental observation that heavy dust contamination of plasma leads to an anomalous increase in the electron density at the beginning of afterglow is explained by release of electrons from the dust surface. Under the assumption that the floating potential of particles is in equilibrium with plasma conditions, the fast cooling of electrons in afterglow plasma due to a rapid escape of hot electrons from the volume leads to a decrease in the magnitude of the floating potential and hence to a loss of charge by dust. The intensive desorption of electrons from nanoparticles is the origin of anomalous behavior of the electron density. At the next stage of afterglow, when the electrons become cool, the plasma decay is defined by ambipolar diffusion. The effect of metastable argon atoms is also considered. Additional ionization due to metastable atom collisions affects the electron temperature but does not change the behavior of the electron density qualitatively.     

Theoretical analysis for transmission of Gaussian and sine time irradiance of electromagnetic beam in collisional dusty plasmas

A theoretical model of propagation of Gaussian and Sine time irradiance of an electromagnetic beam in collisional dusty plasma has been done in the present analysis. It contains equilibrium of dust charge, particle density, and energy of plasma ingredients having charge neutrality. Ionization of neutral particles, recombination of free electrons with ions, adsorption and emission of electrons from dust grain surface, and binary collisions between plasma components are also considered in this treatment. Time varying behaviour of modified electron temperature and collision frequency has been illustrated numerically as a function of dust densities. Also, the comparative analyses of variation of beam waist parameter with the dimensionless length of transmission for both the Gaussian and Sine time irradiance are involved in this model as a function of distinguishable time width, collision frequencies, and dust densities under the condition that the size of dust nebulous is greater than the electrons mean free path for the adsorption on the dust grain surface. The observed results are significant for the applications in industry and astrophysics.     

Effect of particle size distribution on the polarity of triboelectric charging in granular insulator systems

Triboelectric charging occurs in granular insulating systems even when all particles are composed of identical material. A simple model is used here to address triboelectric charging in such systems. The basis of the model is the existence of electrons trapped in high-energy states, which can be released during collisions with another particle and transferred to the other particle. This model shows that triboelectric charging in insulator systems composed of particles of identical material can be attributed to a distribution of particle sizes, such that smaller particles tend to charge negatively and larger particles tend to charge positively. This polarity of charging has been observed in field studies of sand storms, dust devils and volcanic plumes, and most laboratory experiments on triboelectric charging in granular systems.     

Potential profile near the virtual cathode in presence of charged dust

In this work, concept of virtual cathode and its existence in dusty plasma has been studied by theoretical and numerical analysis. Using basic equations of charge dust, ions, and electrons, the non‐monotonic behaviour of the potential in presence of charged dust has been calculated and plotted as a function of dust density. It has been found that there is a change in potential between cathode and sheath potential and subsequently changes the threshold wall temperature as compared to that of without dust conditions. The threshold wall temperature has been increased due to the ability of micro‐particles acquiring electron charge and hence, reducing potential at the wall. Further, for different values of α (depends on dust density); threshold temperature remained the same for observed virtual cathode. Hence, behaviour of potential has been plotted as a function of α with increasing wall temperatures for two dust charge values (1 and 1,000). Considering no dust charge, it has been observed that, at lower dust density, double layer like structure is formed near the emissive wall. But this double layer structure gets diminishes with increasing dust density. Hence, below a threshold dust density, virtual cathode near to the emissive wall is not possible. While for Z_d = 1,000, the formation of virtual cathode appeared even at very small dust density. However, irrespective of variation of potential difference near the wall and existence of virtual cathode at different emission regime the threshold wall temperature remains same. Effect of dust potential dependency on threshold wall temperature has also been discussed in this study.     

Theoretical model for the effect of dust grains on self‐filamentation of a gaussian electromagnetic beam in a fully ionized plasma

A theoretical model for the effect of dust grains on the self‐filamentation of a Gaussian electromagnetic beam propagating in a fully ionized plasma has been developed by employing the energy balance of the plasma constituents, perturbed electron and ion concentrations, and temperature. In this model, neutral atom ionization, re‐integration and accumulation of electrons and ions, photoelectric emission of electrons from the surface of dust grains, as well as elastic and charging collisions have also been considered. The effective dielectric constant in the presence of dust grains has been constructed. The effect of temporal growth of dust grains on various plasma parameters for different values of the dust density has been explored. The variation of the beam width with the normalized channel of propagation has been observed for distinct dust densities and dust charge states. It is observed that the non‐linearity induced by the effective dielectric constant in the presence of dust grains increases the self‐filamentation of the beam, thus enhancing the effective critical power with the dust density. Some of the outcomes of our approach are in line with experimental observations. These outcomes may be useful for explaining space and laboratory plasma experiments as well as for future studies in complex plasmas.     

A particle-in-cell simulation of dust charging and shielding in lowpressure glow discharges

The transport of particles (“dust”) in low pressure electrical glow discharges is being studied in regard to its role in contaminating silicon wafers during plasma etching and deposition. Particles (10 s nm-μm) negatively charge in glow discharges and, to first order, appear to be massively large negative ions around which sheaths develop. The forces on particles in plasmas include electrostatic (drift of charged particles in electric fields) and viscous ion drag. The latter force is momentum transfer from ions to particles by either collisions or orbital motion. This force critically depends on the charge on the particle and the shape of the sheath surrounding the particle. In this work, we report on a pseudoparticle-in-cell (PIC) simulation of the transport of electrons and ions in the vicinity of dust particles in low pressure glow discharges. The simulation produces the electrical charge on the dust particle, the sheath structure around the dust particle and the orbital dynamics of the ions. A companion molecular dynamics simulation uses these parameters to produce ion-dust and electron-dust particle cross sections for momentum transfer and collection. Results will be discussed for charge, sheath thickness, cross sections and viscous ion drag forces on dust particles as a function of radius and plasma parameters     

Ionization Potential Depression in Hot Dense Plasmas Through a Pure Classical Model

The ionization potential of an ion embedded in a plasma, lowered due to the whole of the charged particles (ions and electrons) interacting with this ion, is the so‐called plasma effect. A numerical plasma model based on classical molecular dynamics has been developed recently. It is capable to describe a neutral plasma at equilibrium involving ions of various charge states of the same atom together with electrons. This code is used here to investigate the ionization potential depression (IPD). The study of the IPD is illustrated and discussed for aluminum plasmas at mid and solid density and electron temperatures varying from 50eV to 190eV. The method relies on a sampling of the total potential energy of the electron located at an ion being ionized. The potential energy of such electron results from all of the interacting charged particles interacting with it. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dust-ion-acoustic shock waves due to dust charge fluctuation

A dusty plasma system containing Boltzmann electrons, mobile ions and charge fluctuating stationary dust has been considered. The nonlinear propagation of the dust-ion-acoustic waves in such a dusty plasma has been investigated by employing the reductive perturbation method. It has been shown that the dust charge fluctuation is a source of dissipation and is responsible for the formation of the dust-ion-acoustic shock waves. The basic features of such dust-ion-acoustic shock waves have been identified. The implications of our results in space and laboratory dusty plasmas are discussed.     

Adiabatic dust-acoustic solitons

We investigate the existence of adiabatic dust-acoustic solitons in a dusty plasma consisting of adiabatic dust particles along with Boltzmann distributed electrons and ions. It is shown that the presence of adiabatic dust particles decreases the magnitude of the soliton amplitude.     

Nonlinear dust-ion-acoustic waves in a multi-ion plasma with trapped electrons

A dusty multi-ion plasma system consisting of non-isothermal (trapped) electrons, Maxwellian (isothermal) light positive ions, warm heavy negative ions and extremely massive charge fluctuating stationary dust have been considered. The dust-ion-acoustic solitary and shock waves associated with negative ion dynamics, Maxwellian (isothermal) positive ions, trapped electrons and charge fluctuating stationary dust have been investigated by employing the reductive perturbation method. The basic features of such dust-ion-acoustic solitary and shock waves have been identified. The implications of our findings in space and laboratory dusty multi-ion plasmas are discussed.     

Theory of mach cones in magnetized dusty plasmas with strongly correlated charged dust grains

A theory for the formation of Mach cones in a magnetized dusty plasma with strongly correlated charged dust grains has been presented. We use the electron and ion susceptibilities for weakly correlated magnetized electrons and ions as well as the strongly correlated unmagnetized dust grain susceptibilities which are obtained by means of the quasilocalized charge approximation and a generalized hydrodynamic model. The plasma dielectric response of the present system reveals the parametric regimes for which Mach cones in a strongly coupled laboratory dusty magnetoplasma can be formed. We suggest conducting experiments in radiofrequency dusty plasma discharges with superconducting magnets for verifying the theoretical prediction of Mach cones that is made herein.     

Dust in Plasma II. Effects of Secondary Electrons: Ionization and Surface Emission

In this second paper, the effect of secondary electrons on the charge and potential of a dust particle immersed in plasma has been studied. The processes of electron‐induced ionization and those of photo‐electron and secondary electron emission from the particle surface as a function of primary electron temperature have been taken into account. Starting from temperatures as low as 6 eV in an Ar plasma, ionization produces an extra ion flux to the dust surface comparable to that of the ion charge exchange effect. For what concerns the surface emission, results show that a transition from negative to positive dust charge/potential takes place, and that the transition regime is characterized by a non‐monotonic behavior of the electric potential around the particle. In the case of photoelectric emission, the dust charge and potential are monotonic decreasing functions of the electron temperature, while in the case of emission induced by primary electrons a minimum charge/potential is reached before they grow towards positive values. In no case multiple dust charge states have been observed due to the presence of the potential well attached to the particle surface. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dust-electron-acoustic shock waves due to dust charge fluctuation

The nonlinear propagation of the dust-electron-acoustic waves in a dusty plasma consisting of cold and hot electrons, stationary and streaming ions, and charge fluctuating stationary dust has been investigated by employing the reductive perturbation method. It has been shown that the dust charge fluctuation is a source of dissipation, and is responsible for the formation of the dust-electron-acoustic shock waves in such a dusty plasma. The basic features of such dust-electron-acoustic shock waves have been identified. It has been proposed to design a new laboratory experiment which will be able to identify the basic features of the dust-electron-acoustic shock waves predicted in this theoretical investigation.     

On the role of dust in the cometary plasma

The cometary coma consists of neutral gas, plasma, and dust grains. The dust grains can influence both the neutral and charged coma’s constituents. Usually, the presence of dust particles in a plasma results in additional losses of both electrons and ions due to the plasma recombination on the particle surfaces. Solar radiation makes the impact of dust even more complicated depending on the solar flux, the dust number density, the photoelectric properties of the dust particles, the dust particle composition, the distribution of the sizes, etc. We propose a simple kinetic model evaluating the role of dust particles in the coma plasma chemistry and demonstrate that this role can be crucial, resulting in a nontrivial behavior of both the electron and ion densities of the plasma. We show that a coma’s dust particles can be negatively as well as positively charged depending on their composition. These opposite charges of the grains can result in fast coagulation of dust particles, thus, forming complex aggregate shapes of cometary grains. The text was submitted by the authors in English.     

Neutron yield when fast deuterium ions collide with strongly charged tritium-saturated dust particles

The ultrahigh charging of dust particles in a plasma under exposure to an electron beam with an energy up to 25 keV and the formation of a flux of fast ions coming from the plasma and accelerating in the strong field of negatively charged particles are considered. Particles containing tritium or deuterium atoms are considered as targets. The calculated rates of thermonuclear fusion reactions in strongly charged particles under exposure to accelerated plasma ions are presented. The neutron generation rate in reactions with accelerated deuterium and tritium ions has been calculated for these targets. The neutron yield has been calculated when varying the plasma-forming gas pressure, the plasma density, the target diameter, and the beam electron current density. Deuterium and tritium-containing particles are shown to be the most promising plasmaforming gas–target material pair for the creation of a compact gas-discharge neutron source based on the ultrahigh charging of dust particles by beam electrons with an energy up to 25 keV.     

The Dielectric Tensor for Magnetized Dusty Plasmas with Superthermal Plasma Populations and Dust Particles of Different Sizes

We present general expressions for the components of the dielectric tensor of magnetized dusty plasmas, valid for arbitrary direction of propagation and for situations in which populations of dust particles of different sizes are present in the plasma. These expressions are derived using a kinetic approach which takes into account the variation of the charge of the dust particles due to inelastic collisions with electrons and ions, and features the components of the dielectric tensor in terms of a finite and an infinite series, containing all effects of harmonics and Larmor radius, and is valid for the whole range of frequencies above the plasma frequency of the dust particles, which are assumed to be motionless. The integrals in velocity space which appear in the dielectric tensor are solved assuming that the electron and ion populations are described by anisotropic non-thermal distributions characterized by parameters κ _∥ and κ _⊥, featuring the Maxwellian as a limiting case. These integrals can be written in terms of generalized dispersion functions, which can be expressed in terms of hypergeometric functions. The formulation therefore becomes specially suitable for numerical analysis.     

Nonlinear ion-acoustic waves in magnetized plasmas in presence of energetic electrons and positively charged dust

A theoretical investigation has been carried out for exploring different features of ion-acoustic solitary and shock waves in a three-component magnetized plasma containing a mixture of thermal and nonthermal (energetic) inertialess electrons, warm inertial ions, and positively charged stationary dust particles. The standard Korteweg-de Vries (Burgers) equation has been derived by employing the reductive perturbation method, and its solitary (shock) wave solution has been derived and examined analytically as well as numerically. The latter exhibits characteristic properties (amplitude, width, speed, and polarity) of the ion-acoustic solitary and shock waves. It has been shown that the ion-acoustic solitary and shock waves are significantly modified by different plasma parameters (viz. parameter measuring the ratio of dust charge density to ion charge density, parameter measuring the fraction of energetic electrons, parameter measuring ion or electron temperature, and the external magnetic field). The present investigation may help in understanding the physics of various nonlinear phenomena formed in many space plasma systems, (viz. earth's mesosphere, solar wind, and cometary tails) and laboratory devices (laboratory experiments of Samarian et al., Phys. rev. E. 64 , 056407 [2001] and of Fortov et al., New J. Physics 5 , 102 [2003]).