Investigation Of Super-square Grid State Pattern In Ac-Driven Gas Discharge

Various discharge modes, such as square, hexagon, superlattice, and like-glow discharge, have been observed in ac-driven gas discharge by using the dielectric barrier discharge device.The spatio-temporal dynamics of superlattice patterns has been measured by optical method. At first, the transitions between different hexagon patterns and square patterns have been investigated. The glow background occurs in the pattern transitions as the increase of the applied voltage and the flat appears in the curve of discharge density with the discharge power. The increase of the discharge current results from the increase of the filaments and the pulses in every half period. The influences of the surface charges on above processes are discussed. Then, the variations of the discharge characteristics with gas flux have been investigated. It is found that the breakdown voltage, current pulses, and spatial distribution of the discharge present complex behaviors. The velocity of the filament increases with the increase of the gas flux.Finally, grid state patterns have been found in ac-driven gas discharge for the first time. The spatial and temporal characteristic of the super-square grid state pattern has been measured. It is found that the super-square grid state pattern is an interleaving of three sublattice patterns, whose filaments discharge simultaneously and the appearance is changed alternately, by measuring the spatio-temporal correlations between discharge filaments. Several kinds of defects have been observed in the super-square grid state. Phase transition from square pattern to super-square grid state and the formation of defects in this transition have been analyzed according to the measurement results of the discharge characteristics of the filaments.These results are useful for the study of the spatio-temporal dynamics in DBD and the pattern formation in nonlinear systems.