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We studied the propagation of small-amplitude dust ion acoustic (DIA) solitary waves in four-component relativistic plasma comprised of nonthermal electrons, mobile positively charged ions, positron beam and negatively charged massive dust particles. By using the reductive perturbation method, the Korteweg–de-Vries (KdV) nonlinear wave equation is derived numerically. In this work, we have elucidated the role of energetic positron beam in the relativistic plasma and analyzed the existence region for ion-acoustic (IA) solitary wave formation. It is found that for certain plasma parameters, the propagation of both compressive and rarefactive solitary waves is possible. Here, the injecting streaming positron beam in plasma gives rise to the increase in the phase velocity (Mach number) and reaches up to the hypersonic regime of flow velocity. It is observed that the initial increase in relativistic factor of positron beam , as well as temperature ratio of the positron beam to electrons decrease the characteristic features (the amplitude) of the compressive solitary wave potential profiles. On the other hand, on increasing dust grain charge , positron beam concentration ratio as well as nonthermal electrons concentration result in enhancement of the amplitudes of IA solitary wave potential profiles. The findings of this work can be more helpful in understanding the Earth's upper atmosphere (Aurora region of the ionosphere) as well as the space plasmas. [ABSTRACT FROM AUTHOR]

In this study, the physics of sheath formation in a collisional two-electron temperature plasma in the presence of an oblique external magnetic field has been investigated. At first, a comparative study among the fluid electron model, Boltzmann electron model, and the non-extensive electron model has been carried out and a suitable range of non-extensive parameter q has been predicted. In the latter part, a collisional two-electron temperature plasma is considered. Both the hot and cold electron densities are described using the non-extensive distribution, whereas cold ions are described by the fluid equations. The properties of the sheath are investigated in different collisional regimes by varying the non-extensive parameter (q) and the hot to cold electron densities and temperatures. The magnetic field inclination angle is varied in the limit 1° ≤ α ≤ 5°. It is observed that electron distribution significantly deviates from Boltzmann distribution for nearly parallel magnetic field. Moreover, collision enhanced flux deposition for highly magnetized case is a significant finding of the study. The results obtained in this study can enhance the understanding of plasma–matter interaction processes where multiple electron groups with near parallel magnetic field are found. [ABSTRACT FROM AUTHOR]

The average equilibrium charge of submicron sized silver particles, collected during a finite time of transit through a magnetically confined plasma is reported. The fine, almost spherical particles with uniform size are produced in an evaporation chamber. The average charge of the particles was found to be about 1.4x10[sup 2] electronic charges. This result is compared with theoretical predictions. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The effect of external magnetic field on the Langmuir probe measurement and dust charging are studied in low-pressure hydrogen plasma. The experiment is performed in a dusty plasma device where plasma is created by the hot cathode filament discharge technique. A strong Strontium ferrite magnet is used inside the plasma, near the dust zone. The plasma parameters are measured at different distances from the magnet with the help of Langmuir probe system. It is observed that even at "low magnetic field case," where reL ≥ rP, riL 〉〉rP; the electron collection by the probe deviates strongly from the actual value, until reL ≥ 10rP. The observations of electron energy probability function show that at higher magnetic field, the Langmuir probe collects only the higher energy electrons compared to the low energy electrons. Both Quasi-neutrality condition and capacitance model are used separately to calculate the charge accumulated on the dust grain. Introducing the reduction factor on quasi-neutrality condition, it is observed that the influence of magnetic field on dust charge is almost negligible for "low magnetic field" case. The dust charge calculated from quasi-neutrality condition matches well with the experimentally observed dust current results, within the experimental error range. However, capacitance model deviates from the experimental results at higher magnetic field. [ABSTRACT FROM AUTHOR]

In this study the effect of hydrogen addition on the formation and properties of soliton in direct-current (DC) argon plasma is theoretically investigated. By coupling fluid equations with Poisons equation for such multi-component plasma, the Mach number and amplitude of the soliton are determined following pseudo potential method. Addition of hydrogen in argon discharge leads to the decrease of electron, Arþ ion density while a reverse trend was observed for ArH+ and hydrogen like ions. It was found that presence of hydrogen like ions in argon plasma affects the formation of soliton with its amplitude significantly decreases as concentration of hydrogen increases. On the other hand, increase in ion to electron temperature ratios of the lighter ions in the discharge also has a significant influence on the amplitude and formation of soliton. The inverse relation between solitons width and amplitude is found to be consistent for the entire range of study. [ABSTRACT FROM AUTHOR]

The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10-4 millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (∼pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains. [ABSTRACT FROM AUTHOR]

The effect of the electrostatic confinement potential on the charging of dust grains and its relationship with the plasma parameters has been studied in an electrostatically plugged multicusp dusty plasma device. Electrostatic plugging is implemented by biasing the electrically isolated magnetic multicusp channel walls. The experimental results show that voltage applied to the channel walls can be a controlling parameter for dust charging. [ABSTRACT FROM AUTHOR]

The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust. [ABSTRACT FROM AUTHOR]

A modified mode of plasma production in a double plasma device is presented and plasma parameters are controlled in this configuration. Here plasma is produced by applying a discharge voltage between the hot filaments in the source (cathode) and the target magnetic cage (anode) of the device. In this configuration, the hot electron emitting filaments are present only in the source and the magnetic cage of this is kept at a negative bias such that due to the repulsion of the cage bias, the primary electrons can go to the grounded target and produce plasma there. The plasma parameters can be controlled by varying the voltages applied to the source magnetic cage and the separation grid of the device. [ABSTRACT FROM AUTHOR]

Dust grains are produced by evaporation of silver in an experimental setup consisting of a dust chamber, a plasma chamber, and a deflection chamber. Due to differential pressure between the dust and plasma chambers, the dust grains move upward and after passing through plasma they become negatively charged. These charged dust grains are then deflected by a dc field applied across a pair of deflector plates in the deflection chamber. Both from the amount of deflection and also from the floating potential, the number of charges collected on the dust grains is calculated. As the gas pressure is changed, the plasma density and the electron temperature changes. Dust charge is then calculated at each value of pressure from the deflection and floating potential. It is found that the electron temperature has a profound effect in the accumulation of charge on dust grains. [ABSTRACT FROM AUTHOR]

An experimental study has been performed into the variation of charge on dust grains with change in the ambient plasma conditions. A dust beam containing submicron sized silver grains was passed through plasma. The dust grains were charged by the plasma particles as well as by primary electrons from the filament. An increase in the filament current increased both the plasma density and the number density of the primary electrons. The grain charge was found out both from the deflection of the dust grains and also from the floating potential. The experimental observations shows that the secondary emission caused by the primary electrons significantly influenced and played a prominent role in the establishment of charge on the grains. [ABSTRACT FROM AUTHOR]

The dust–ion–acoustic (DIA) solitary wave (SW) propagation in a magnetized dusty plasma consisting of mobile positive and heavy negative ions, nonthermal electrons and positrons is presented. By using reductive perturbation technique, three dimensional Zakharov–Kuznetsov (Z–K) equation is derived and the solution is obtained by using the tan-hyperbolic method. Here, the dust grain charging process by plasma constituents is represented by the equation following orbital motion limited (OML) theory. The characteristics features of solitary wave amplitudes arising due to different plasma parameters such as ions mass ratio, nonthermal parameters of electrons and positrons, temperature ratio of electrons and positrons, ions density ratio, and dust density ratio are analyzed. In this analysis, the influence of nonthermal electrons on solitary wave amplitude variation is observed as more significant than that of nonthermal positrons. The findings of this work can be helpful in understanding D, E, and F regions of the Earth's ionosphere, its mesosphere region, solar photosphere, and Titan's ionosphere. [ABSTRACT FROM AUTHOR]

Experimental results on effect of adding argon gas to hydrogen plasma in a multi-cusp dusty plasma device are reported. Addition of argon modifies plasma density, electron temperature, degree of hydrogen dissociation, dust current as well as dust charge. From the dust charging profile, it is observed that the dust current and dust charge decrease significantly up to 40% addition of argon flow rate in hydrogen plasma. But beyond 40% of argon flow rate, the changes in dust current and dust charge are insignificant. Results show that the addition of argon to hydrogen plasma in a dusty plasma device can be used as a tool to control the dust charging in a low pressure dusty plasma. [ABSTRACT FROM AUTHOR]

The sheath formation in a weakly magnetized collisionless electronegative plasma consisting of electrons and negative and positive ions has been numerically investigated using the hydrodynamic equations. The electrons and negative ions are assumed to follow the Boltzmann relation. A sheath formation criterion has been analytically derived. This paper focuses on studying the sheath structure by varying the electronegativity. It has been observed that the presence of negative ions has a substantial effect on the sheath structure. The observations made in the present work have profound significance on processing plasmas, specifically in the semiconductor industry as well as in fusion studies. [ABSTRACT FROM AUTHOR]

The effect of working gas pressure and dust charging on electron energy probability function has been studied for hydrogen plasma in a multi-dipole dusty plasma device. A cylindrical Langmuir probe is used to evaluate the plasma parameters and electron energy probability function (EEPF) for different working pressures. For lower energy range (below 10 eV), the EEPF follows a bi-Maxwellian shape at very low pressure (6 x 10-5 mbar), while elevating the working pressure up to ~2 x 10-3 mbar, the shape of the EEPF transforms into a single Maxwellian. Some dip structures are observed at high energy range (ε > 10 eV) in the EEPF of hydrogen plasma at all the working conditions. In presence of dust particles, it is observed that the shape of the EEPF changes due to the redistribution of the high and low-energy electron populations. Finally, the effect of working pressure on charge accumulation on dust particles is studied with the help of a Faraday cup and electrometer. From the observations, a strong influence of working pressure on plasma parameters, EEPF and dust charging is observed. [ABSTRACT FROM AUTHOR]

In this study, the effect of magnetron target on different plasma parameters of Argon/Hydrogen (Ar - H2) direct current (DC) magnetron discharge is examined. Here, Copper (Cu) and Chromium (Cr) are used as magnetron targets. The value of plasma parameters such as electron temperature (kTe), electron density (Ne), ion density (Ni), degree of ionization of Ar, and degree of dissociation of H2 for both the target are studied as a function of input power and hydrogen content in the discharge. The plasma parameters are determined by using Langmuir probe and Optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. The obtained results show that electron and ion density decline with gradual addition of Hydrogen in the discharge and increase with rising input power. It brings significant changes on the degree of ionization of Ar and dissociation of H2. The enhanced value of electron density (Ne), ion density (Ni), degree of Ionization of Ar, and degree of dissociation of H2 for Cr compared to Cu target is explained on the basis of it's higher Ion Induced Secondary Electron Emission Coefficient (ISEE) value. [ABSTRACT FROM AUTHOR]

A nonlocal theory has been developed to study the effect of a flow profile on the stability of low frequency drift-type instability in an inhomogeneous, dusty plasma. The representative experimental values for the plasma parameters show that, due to the presence of dust particles, the well-known stability of the drift wave in a sheared slab geometry does not hold. However, a radially varying transverse (to the equilibrium magnetic field) velocity field is found to play a key role in stabilizing this instability. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]