Characterization of a cold atmospheric pressure plasma jet driven by nanosecond high-voltage pulses

Summary form only given. Atmospheric pressure plasma jets (APPJs) are widely investigated for plasma assisted medical treatments due to their versatility, granted by the diverse possible combinations of driving power supply, gas employed and source architecture. In this work, a single electrode plasma jet driven by voltage pulses with nanosecond rise time and pulse duration in the order of few tens of nanoseconds is characterized; this plasma source has been previously used for the treatment of polymer solutions to improve their electrospinnability, to increase nanoparticle dispersion and was preliminary characterized in a previous work. Here a set of diagnostic techniques is adopted to get deeper insights on the correlation between the plasma structure and the fluid-dynamic behaviour of the jet (iCCD and high-speed Schlieren imaging) and to assess the compatibility of the plasma jet for the treatment of thermo-sensible and biological materials (temperature measurements, OES and UV absolute radiometry). Depending on the operating conditions, the plasma plume presents a single front or several branched sub-fronts; comparing results from Schlieren and iCCD imaging, it is observed that branching of the plasma jet front occurs in spatial regions where the flow is turbulent. Oscillations both in light emission intensity and plume length are observed during the temporal evolution of the plasma discharge. The plasma plume spectrum, measured by OES, is characterized by N₂, N₂⁺, NO, OH spectral bands as a consequence of mixing with ambient air. Measurements of UV irradiance of the APPJ and temperature of the plasma plume, found to be compatible with biomedical applications, are also presented.