Effect of Gas Mixture on Plasma Jet Discharge Morphology

The morphology of plasma emission from a streamerlike atmospheric pressure plasma jet initiated inside a glass capillary has been measured with a high spatial resolution for a gas flow of pure helium and He with a 5% Ar admixture using 5-ns time-gated intensified charge-coupled device imaging. In the pure helium plasma jet, emission remains annular and converges gradually along the core gas-air interface. With a 5% argon admixture, however, the plasma emission is initially annular inside the glass capillary but converges to the flow axis within 5 mm outside the capillary tip.