Filamentation in argon microwave plasma at atmospheric pressure

Abstract

Filamentation in an argon plasma is studied using a microwave cavity at atmospheric pressure. We show that the size and gas temperature of the filaments increase with the power absorbed by the plasma. The appearance of an additional filament occurs at specific values of the absorbed power. Each new filament appears with a smaller diameter than that of its parent filament but the sum of the diameters of all filaments evolves linearly with the absorbed power. A secondary filament emerges from a set of microfilaments created by a perturbation of the electric field (a slight increase in the incident power above a threshold value). This perturbation occurs over a larger radius than that of the parent filament. By resorting to modeling, we found that the filamentation process involves either a decrease in the effective frequency for momentum-transfer collisions, i.e., a lower electron temperature, or an increase in the electron density. We could show that a small change in the relative positions occupied by two filaments in the microwave cavity requires a strong variation in the electron temperature.

Self-consistent evolution of plasma discharge and electromagnetic fields in a microwave pulse compressor

“…1,2 More recently, many experimental, theoretical, and numerical studies of the spatial structure and temporal evolution of plasma formed in the high-pressure microwave discharge have been performed. [3][4][5][6][7] Yet, the dynamics of the plasma formation at the initialnanosecond time-scale-stage of the discharge remains insufficiently understood. This is especially important for the case of discharge in a resonant cavity as there is a mutual influence of the discharge development and the process of microwave energy release from the cavity that goes out of resonance during plasma generation.…”

Nanoscience with non-equilibrium plasmas at atmospheric pressure

“…For example, cold plasmas at atmospheric pressure differ from cold plasmas under vacuum by weak laminar diffusion fluxes that are most often negligible compared to other fluxes of transfer of matter. Increasing the pressure gives rise spontaneously to plasma filaments of small dimensions [17][18][19][20]. Then, plasmas at atmospheric pressure have features that cannot be found in low-pressure plasmas.…”

Microwave-plasma synthesis of nano-sized silicon carbide at atmospheric pressure

“…The pressure was then gradually increased to atmospheric pressure where filamentation of the plasma structure occurred [29]. At this pressure the hydrogen and MTS were fed into the system.…”