Characterization of the DC glow discharge in longitudinal flowing helium at atmospheric pressure

A one-dimensional self-consistent fluid model was developed to study the direct-current (DC) glow discharge in longitudinal flowing helium (He) at atmospheric pressure. Distinct dynamical features of charged particles are observed at different He flow velocities, which is accompanied by a dramatic change of spatial discharge structure. The positive He flow leads to the reduction of charged particle densities in the positive column and negative glow regions, and even makes the negative glow region disappear. The negative He flow allows for the enhancement of charged particle densities in the negative glow regions. These observations above mainly lie in the fact that the convection effects due to the He gas flow influence the transport properties of charged particles through different ways by comparing the He flow velocity with the ion drift one. These findings are of guiding significance for the improvement of the chemical activity and work efficiency of plasma source by controlling the gas flow in practical industrial fields.