Narrow Results

Dusty plasmas are complex systems where new phenomena arise from the presence of solid dust particles inside a plasma. Dust particles acquire a negative charge by attaching free electrons and are thus trapped in the plasma. This charge loss can be drastic for the plasma equilibrium and instabilities can appear due to the strong interdependence between the dust particle cloud and the plasma. In this paper, various types of self-excited instabilities consisting in regular or chaotic oscillations, are presented. They are obtained in low pressure radio-frequency discharges where dust particles are grown by using a reactive gas or by sputtering a surface exposed to the plasma. The complex evolution scheme of these instabilities is brought to the fore thanks to various diagnostics.

Heavy loads of aerosols in the air have considerable health effects in individuals who suffer from chronic breathing difficulties. This problem is more acute in the Middle-East, where dust storms in winter and spring transverse from the neighboring deserts into dense populated areas. Discrimination between the dust types and association with their source can assist in assessment of the expected health effects. A method is introduced to characterize the properties of dense dust clouds with passive IR spectral measurements. First, we introduce a model based on the solution of the appropriate radiative transfer equations. Model predictions are presented and discussed. Actual field measurements of silicone-oil aerosol clouds with an IR spectro-radiometer are analyzed and compared with the theoretical model predictions. Silicone-oil aerosol clouds have been used instead of dust in our research, since they are composed of one compound in the form of spherical droplets and their release is easily controlled and repetitive. Both the theoretical model and the experimental results clearly show that discrimination between different dust types using IR spectral measurements is feasible. The dependence of this technique on measurement conditions, its limitations, and the future work needed for its practical application of this technique is discussed.