Theory of filamentary plasma array formation in microwave breakdown at near atmospheric pressure

Summary form only given. Recently reported observations of filamentation during breakdown of near-atmospheric pressure gas by high power microwaves are explained using a one-dimensional fluid model coupled to a theoretical model of wave reflection, transmission, and absorption in an arbitrary profile plasma slab. Simulation results are consistent with experimental observation, showing the evolution of the plasma filaments spaced slightly less than one quarter wavelength (0.57 mm), the sequential discrete light emission propagating back toward the source, and the diffusion and decay of the plasma. Fig. 1 shows the normalized transverse electric field E², the normalized excitation rate k_exc, and the normalized electron density n_e. The excitation starts at the location where the field strength is near maximum (Fig.1.(a)), a new plasma filament develops (Fig.1.(b)), and it starts to absorb the field (Fig.1.(c)). Finally the new filament reflects the field (Fig.1.(d)) due to its high density. The model allows examination of many features not easily obtained experimentally, including dependence on field strength and frequency, pressure, and gas composition, which influence electron temperature and control the breakdown and emission properties.