Propagation of discharges inside a micro-channel within a lossy dielectric

Abstract

Low temperature plasma interacting with porous dielectrics plays a significant role in the plasma-material industry. As plasma is capable of penetrating into a micro-channel and further inducing a forward ionization wave (FIW) and a restrike therein, their propagation properties remained poorly understood. This Letter establishes a 2D fluid model to study the propagation velocity of the two discharges inside the micro-channel within a lossy dielectric, highlighting its dependence on the permittivity (εr) and conductivity (σ) of the surrounding bulk dielectric. For the FIW, which propagated as a bulk streamer, increasing εr and σ reduced velocity; higher wall capacitance prolonged local charging times, while increased conductivity introduced resistive leakage that weakened the driving electric field. For the surface-hugging restrike, increased εr also slowed the restrike via capacitive loading, but its high plasma density rendered its velocity significantly less sensitive to permittivity changes than the FIW. Conversely, wall conductivity severely suppressed restrike speed and intensity by dissipating the accumulated surface charges essential for its propagation. Theoretical frameworks on the velocity of FIW and restrike were built, respectively, linking material properties and geometry to propagation properties.