Spatial characteristics of nanosecond pulsed micro-discharges in atmospheric pressure He/H2O mixture by optical emission spectroscopy

Atmospheric pressure micro-discharges in helium gas with a mixture of 0.5% water vapor between two pin electrodes are generated with nanosecond overvoltage pulses. The temporal and spatial characteristics of the discharges are investigated by means of time-resolved imaging and optical emission spectroscopy with respect to the discharge morphology, gas temperature, electron density, and excited species. The evolution of micro-discharges is captured by intensified CCD camera and electrical properties. The gas temperature is diagnosed by a two-temperature fit to the ro-vibrational OH(A(2)sigma(+)-X-2 pi, 0-0) emission band and is found to remain low at 425 K during the discharge pulses. The profile of electron density performed by the Stark broadening of H- alpha 656.1-nm and He I 667.8-nm lines is uniform across the discharge gap at the initial of discharge and reaches as high as 10(23) m(-3). The excited species of He, OH, and H show different spatio-temporal behaviors from each other by the measurement of their emission intensities, which are discussed qualitatively in regard of their plasma kinetics.

Automated summary

This study investigates atmospheric pressure micro-discharges in helium gas with a mixture of 0.5% water vapor using time-resolved imaging and optical emission spectroscopy. The temporal and spatial characteristics of the discharges, including discharge morphology, gas temperature, electron density, and excited species, are analyzed. The findings provide insights into the evolution of micro-discharges.