Experimental investigations of void dynamics in a dusty discharge

Copyright 2004 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas and may be found at http://link.aip.org/link/?PHPAEN/11/3733/1International audienceThe first electrical and spectroscopic characterizations of an instability, usually called the ‘‘heartbeat'' instability, occurring in a laboratory dusty plasma are reported. The heartbeat instability consists of successive contractions and expansions of the central dust free region observed in a dense cloud of dust particles. This cloud is formed in a radio-frequency plasma by sputtering polymer material deposited on the electrodes. The evolution of the discharge current reveals the relatively complex shape of the instability and allows one to measure its evolution as a function of gas pressure and radio-frequency power

Role of negative ions for the formation of dust particles

topical invited speaker 3 journal pages (2 columnes)International audienceThe creation of nanoparticles in reactive low temperature discharges is a rather complex multi step process that involves a great variety of different charged and uncharged species. This contribution deals with the role of negative ions in the nucleation process of nanoparticles in a reactive low temperature plasma. The contribution focus on the formation of particles in hydrocarbon discharges. In particular experiments performed in pulsed discharges demonstrate the important role of negative ions for the formation of nanoparticles. Theoretical considerations support these experimental results and show that the formation of particles can be controlled by the proper choice of the pulse frequency

Plasma based formation of polymer-graphite nanocomposites

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Dust density influence on complex plasma decay

Copyright 2008 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in AIP Conference Proceedings and may be found at http://link.aip.org/link/?APCPCS/1041/185/1International audienceIn this paper, the influence of dust particles on the plasma losses in a complex plasma afterglow is studied. It is shown that the dust particles can drastically shorten the plasma loss time by absorption-recombination onto their surfaces. The dust particle absorption frequency increases with the dust density but the dependence is not linear for high dust density. Finally, the possible use of dust absorption frequency measurements as a diagnostics for complex plasmas is mentioned and supported by comparison to existing experimental data

Low frequency instabilities during dust particle growth in a radio-frequency plasma

Copyright 2006 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas and may be found at http://link.aip.org/link/?PHPAEN/13/092103/1International audienceIn this paper, instabilities appearing in a dusty plasma are experimentally investigated. These low frequency self-excited instabilities appear during dust particle growth and are characterized by a frequency spectrum evolving during this process. The onset, the time evolution and the main characteristics of these instabilities are investigated thanks to electrical and optical measurements. Both signals show a clear evolution scheme with a well-defined succession of phases. From the beginning to the end of this scheme, regular oscillations and/or chaotic regimes are observed. Finally, instabilities stop when the dust particle size reaches a few hundreds of nanometers and a stable three-dimensional dust cloud is obtained. A dust-free region called void is then usually observed in the plasma center

Residual dust charges in an afterglow plasma

International audienceAn on-ground measurement of dust particle residual charges in the afterglow of a dusty plasma was performed in a rf discharge. An upward thermophoretic force was used to balance the gravitational force. It was found that positively-charged, negatively-charged and neutral dust particles coexisted for more than one minute after the discharge was switched off. The mean residual charge for 200 nm radius particles was measured. The dust particle mean charge is about -5e at pressure of 1.2 mbar and about -3e at pressure of 0.4 mbar