Atmospheric-pressure plasma transfer across dielectric channels and tubes

Atmospheric-pressure plasma transfer refers to producing an ionization wave (IW) in a tube or channel by impingement of a separately produced IW onto its outer surface. In this paper, we report on numerical and experimental investigations of this plasma transfer phenomenon. The two tubes, source and transfer, are perpendicular to each other in ambient air with a 4 mm separation with both tubes being flushed with Ne or a Ne/Xe gas mixture at 1 atmosphere pressure. The primary IW is generated in the source tube by ns to µs pulses of ±25 kV, while the transfer tube is electrodeless, not electrically connected to the first and at a floating potential. The simulations are conducted using a two-dimensional (2D) plasma hydrodynamics model with radiation transport, where the three-dimensional tubes in the experiments are represented by 2D channels. Simulations and experiments show that the primary IW propagates across the inter-tube gap and upon impingement induces two secondary IWs propagating in opposite directions in the transfer tube. Depending on the polarity of the primary IW in the source tube, the secondary IW in the transfer tube can have polarities either the same or opposite to that of the primary IW. The speed and strength of both the primary and secondary IWs depend on the rate of rise of the voltage pulse in the source tube. The modelling results were found to agree well with the behaviour of plasma transfer observed using nanosecond intensified charge-coupled device imaging.