This work focuses on the investigation of the memory effect origin in atmospheric pressure Townsend discharges in nitrogen/oxidizing gas mixtures. For this purpose, an experimental approach is used on a plane-to-plane dielectric barrier discharge, using short exposure time photographs of the discharge with interference filters, synchronized with the discharge current. A segmented electrode into eight strips allows to correlate the discharge current and light emissions from different species in time and space (position along the gas flow). The results highlight the occurence of a memory effect involving oxidizing species when an oxidizing gas is added to nitrogen. A comparison of the discharge for different gas gaps, and the parallel drawn with a numerical 1-D model in pure nitrogen, suggests the importance and the predominance of this memory effect compared to the secondary electron emission by N2(A) which was considered to be the dominant mechanism up to now.

We report the experimental demonstration of plasma generation by time-reversal focusing. After a learning phase, the amplified time reversed signal built at a central frequency of 2.45 GHz injected in a low loss metallic cavity allows us to ignite and maintain a localized centimeter-sized plasma in argon at 133 Pa. The plasma spatial position is totally controlled by the signal waveform.

Nanocomposite thin films can be obtained by polymerization of a colloidal solution in a dielectric barrier discharge (DBD) at atmospheric pressure. In such a process, the dispersion of nanoparticles into the matrix is driven by the charging, transport, and deposition dynamics of the atomized colloid. This work examines the interaction of atomized TiO2 nanoparticles with ac electric fields in a plane-to-plane dielectric barrier discharge reactor. Experiments are performed with the discharge off to examine transport and deposition phenomena over a wide range of experimental conditions with a fixed particle charge distribution. Scanning electron microscopy reveals that the size distribution of TiO2 nanoparticles collected at different locations along the substrate surface placed on the bottom electrode of the DBD reactor can judiciously be controlled by varying the amplitude and frequency of the ac electric field. These results are also compared to the predictions of a simple particle motion model accounting for the electrostatic force, the gravitational force, and the neutral drag force in the laminar flow. It is found that while the initial charge distribution of atomized particles strongly influences the total deposition yield, its maximal position on the substrate, and the width of the deposited area, the initial size distribution of the particles at the entrance of the reactor mostly changes the size distribution at each position along the substrate surface.