Atmospheric pressure plasma jets generated by the DBD in argon-air, helium-air, and helium-water vapour mixtures

Plasma jets are increasingly used in plasma medicine, in microelectronics and for surface treatment due to their unique properties, such as low gas temperature and high concentration of active species. This paper presents the results of a study of plasma jets generated by the atmospheric pressure dielectric barrier discharge while passing through it of argon-air, helium-air and helium-water vapor mixtures. Comparison of the plasma jets characteristics shows that the gas flow rate at which the maximum power of UV radiation is achieved increases in the series of He-H2O, He-air, Ar-air. Replacing Ar-air working mixture with He-air mixture leads to an increase in the plasma jet radiation power in similar to 3 times. The maximum overall radiation power achieved in the He-air plasma jet was 0.07 W. The emission spectra of the plasma jets were identified in the spectral region of 270-900 nm, it was found that the molecular bands of the second positive and first negative systems of nitrogen predominate in the UV region of spectrum and lines of He I or Ar I prevail in the visible region. The distributions of the radiation intensity of excited plasma species along the jet length were measured. The analysis of difference in the emission spectra of the plasma jet in pure Ar and He and in their mixtures with air, as well as in a He-H2O mixture, has been performed taking into account values of the mean electron energy and rate constants of elementary processes in the plasma calculated using the Bolsig + code. The molecular and ionic reactions responsible for emission of radiation in the UV range of spectrum are considered.