Magnetic Tops in Dusty Plasmas

Paper contains the results of investigation of separate dust granules mechanical state. Observations were performed in high optical resolution. Magnetic induction varied up to 400 G. Motion of particles of different shapes was studied separately. These shapes were: ideally spherical, spherical with defects and non‐spherical. The peculiar physical features of fast rotating dusty granules (tops) were observed. They are the emergence of magnetic moment of rotating charged granule and the orientation change of magnetic moment at magnetic field superimposition. The effects observed in magnetic field are supplied with qualitative interpretation (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ion Heating in Dusty Plasma of Noble Gas Mixtures

Ion heating in dusty plasma of noble gas mixtures is studied by the observation of dust particles in stratified glow discharge. The particles and their formations can be used as a “contact‐free” probe of the ion flows. It is shown that under condition of experiments transition of dust particles into crystalline state in pure gases occur at much lower pressures in comparison to the case of gas mixtures. This observation is also supported by the evaluation of “effective” kinetic temperature of dust particles as defined from the velocity distribution function at the same set of discharge parameters. Absolute value of temperature of dust component in the mixture of helium and argon indicates important role of argon ionization process (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the formation of shock and soliton in a dense quantum dusty plasma with cylindrical geometry

Excitation of nonlinear waves in a quantum dusty plasma with various effects is analyzed when the geometry is cylindrical.This introduces the effect of finite boundary conditions on the solitary waves so generated. it is observed that the nonlinear equation deduced is cylindrical KP–Burger type leading to the generation of Shock Wave. Different situations which arises in various parameter regions are considered separately and the form of the nonlinear excitations are obtained explicitly.     

Shear Viscosity of Dusty Plasma Obtained on the Basis of the Langevin Dynamics

Shear viscosity of dusty plasma was calculated on the basis of the Langevin dynamics. Shear viscosity is considered as a function of many parameters and buffer plasma pressure is among them. Complicated dependence of viscosity on plasma pressure is considered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Head on collision of a planar shock wave with a dusty gas layer

The head-on collision of a planar shock wave with a dust-air suspension is studied numerically. In this study the suspension is placed inside a conduit adjacent to its rigid end-wall. It is shown that as a result of this collision two different types of transmitted shock waves are possible, depending on the strength of the incident shock wave and the dust loading ratio in the suspension. One possibility is a partially dispersed shock wave, the other is a compression wave. The flow fields resulting in these two options are investigated. It is shown that in both cases, at late times after the head-on reflection of the transmitted shock wave from the conduit end-wall a negative flow (away from the end-wall) is evident. The observed flow behavior may suggest a kind of dust particle lifting mechanism that could shed new light on the complex phenomenon of dust entrainment behind sliding shock waves.      

Experimental and theoretical investigations of absorbance spectra for edge-plasma monitoring in fusion reactors

This present paper deals with the spectral characterization of dusty plasmas such as those produced during ITER fusion experiments. Such plasma formed in a small radio frequency plasma reactor with acetylene was characterized using in situ Fourier transform infrared (FTIR) absorption spectroscopy and laser scattering, and ex situ transmission electron microscopy (TEM). The plasma absorbance spectra thus obtained in the visible and infrared wavelengths exhibit special features associated with the dust particle growth which absorbs and scatters IR light. This experimental absorbance behavior is reproduced using a dedicated radiation modeling based on the Mie theory and the Monte Carlo simulation. The bimodal distribution assumed for particle sizes brings the model-determined optical properties closer to the experimental dust absorbance than the normal and uniform distributions. Dust formation mechanism is further discussed comparing the experimental and simulated absorbance.     

Manifestation of polarization effects in dusty plasma

This paper is devoted to a detailed analysis of polarization effects in dusty plasma (DP). They are shown to lead to a nonmonotone decay of the self-consistent potential near the macroparticle, which may result in the formation of regular structures in the DP.     

Physisorption kinetics of electrons at plasma boundaries

Plasma-boundaries floating in an ionized gas are usually negatively charged. They accumulate electrons more efficiently than ions leading to the formation of a quasi-stationary electron film at the boundaries. We propose to interpret the build-up of surface charges at inert plasma boundaries, where other surface modifications, for instance, implantation of particles and reconstruction or destruction of the surface due to impact of high energy particles can be neglected, as a physisorption process in front of the wall. The electron sticking coefficient s_e and the electron desorption time τ_e, which play an important role in determining the quasi-stationary surface charge, and about which little is empirically and theoretically known, can then be calculated from microscopic models for the electron-wall interaction. Irrespective of the sophistication of the models, the static part of the electron-wall interaction determines the binding energy of the electron, whereas inelastic processes at the wall determine s_e and τ_e. As an illustration, we calculate s_e and τ_e for a metal, using the simplest model in which the static part of the electron-metal interaction is approximated by the classical image potential. Assuming electrons from the plasma to loose (gain) energy at the surface by creating (annihilating) electron-hole pairs in the metal, which is treated as a jellium half-space with an infinitely high workfunction, we obtain s_e≈10^-4 and τ_e≈10^-2 s. The product s_eτ_e≈10^-6 s has the order of magnitude expected from our earlier results for the charge of dust particles in a plasma but individually s_e is unexpectedly small and τ_e is somewhat large. The former is a consequence of the small matrix elements occurring in the simple model while the latter is due to the large binding energy of the electron. More sophisticated theoretical investigations, but also experimental support, are clearly needed because if s_e is indeed as small as our exploratory calculation suggests, it would have severe consequences for the understanding of the formation of surface charges at plasma boundaries. To identify what we believe are key issues of the electronic microphysics at inert plasma boundaries and to inspire other groups to join us on our journey is the purpose of this colloquial presentation.