Production of active species in cold helium–air plasma jets

Evaluation of the composition of chemically active species produced in the plasma bullet mode of cold atmospheric-pressure helium–air plasma jets is performed. Distributions of species densities along the jet, both in the region of streamer propagation and in the relaxation zone, are given. Dominating channels for the production of major active species (O, OH, NO, O₃) are revealed. Effects of variation of the governing parameters (the frequency and amplitude of applied voltage pulses, the content of air in the helium–air mixture, the air humidity) on the plasma composition are discussed. (paper)