We have experimentally investigated the properties of microdischarges originating in asymmetric surface dielectric barrier discharges fed by a high-voltage sinusoidal low-frequency drive. Devices exploiting such a configuration are currently proposed as plasma actuators, because they induce a directed airflow in the gas surrounding the surface. Light emission and electric current associated with individual microdischarges have been recorded with high temporal resolution. A statistical analysis of the dataset was performed to correlate microdischarge properties with the voltage phase and to spot peculiarities arising from the actual breakdown mechanism in such a configuration. In particular, we demonstrated the asymmetry between the two different semi-cycles of the discharge, which could affect plasma actuator efficiency. Differences arising in the multiplicity, amplitude, temporal duration as well as in the spatial pattern of the discharge emitting region also permitted identifying several different groups of microdischarges, presumably playing different roles in both the discharge dynamics and airflow induction.

An experimental characterization of the properties of asymmetric surface dielectric barrier discharges used as plasma actuators was performed. Optical emission spectroscopy was used to measure the radiated power and some plasma parameters such as the electron and vibrational temperature. Electrical characterization of the discharge was executed by recording individual current pulses with high temporal resolution, and collecting a large dataset of these events. Statistical analysis performed on them allowed one to correlate microdischarge (MD) properties with the voltage phase and to spot differences arising from the actual breakdown mechanism in such asymmetric configurations. In particular, the asymmetry between the two different half-cycles of the discharges was characterized, and it was found that it directly influences plasma actuator efficiency. Differences arising in the multiplicity, amplitude and temporal duration of the MDs were investigated. Some effects connected with the dielectric material and high voltage supply properties were evaluated and correlated with the induced velocity provided by the plasma actuators.

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A wide bandwidth current probe based on a Rogowski coil was proposed to work down to the nanosecond time scale. It was then used to record the discharge current pulses that characterize the streamer regime of the plasma in a dielectric barrier discharge device. Indeed such plasmas are often made up of intermittent and highly localized structures such as streamers or microdischarges. Characteristics and performances of the probes are discussed together with a few results concerning their application to investigate dielectric barrier discharges and the temporal structure of different pulses of the electrical current.

A novel plasma source suitable for controllable nanostructured thin film deposition processes is proposed. It exploits the separation of the process in two distinct phases. First precursor dissociation and radical formation is performed in a dense oxidizing plasma. Then nucleation and aggregation of molecular clusters occur during the expansion into vacuum of a supersonic jet. This allows a superior control of cluster size and energy in the process of film growth. Characterization of the plasma state and source performances in precursor dissociation have been investigated. The performances of this new Plasma Assisted Supersonic Jet Deposition technique were demonstrated using organic compounds of titanium to obtain TiO₂ thin nanostructured films