Simulation of a non-equilibrium helium plasma bullet emerging into oxygen at high pressure (250–760 Torr) and interacting with a substrate

摘要: A two-dimensional computational study of a plasma bullet emanating from helium gas jet in oxygen ambient at high pressure (250–760 Torr) was performed, with emphasis on the interaction substrate. Power applied form trapezoidal +5 kV pulse lasting 150 ns. neutral transport model employed to predict concentration distributions and system. These were then used dynamics investigate characteristics during its propagation Upon ignition, discharge first propagated as surface wave along inner wall containing tube, exited tube well-defined ionization front (streamer or bullet). The evolved hollow (donut-shaped) feature one where maximum axis. gap between exit substrate an average speed ∼2 × 105 m/s. encountering metal substrate, formed conductive channel dielectric turned into propagating radially surface. For radial species fluxes peaked symmetry ring-shaped flux distribution observed. “footprint” plasma-surface increased either by decreasing relative permittivity insulating pressure. As system lowered 760 250 Torr, initiated earlier, increased. reverse electric field developed late stages ramp-down pulse, which accelerated electrons forming brief backward discharge.