D<sub>2h</sub> superlattice patterns in dielectric barrier discharge with striped water electrode

In this work, a special striped water electrode dielectric barrier discharge device is designed. Through numerical solutions of the Laplace equation, the spatial distribution of the applied electric field is revealed to exhibit a strip-shaped nonuniform distribution featuring the alternating regions of enhanced and weakened field intensity. These field gradients play a pivotal role in governing the plasma, for the intensified regions act as preferential sites for discharge onset, directly shaping the formation and evolution of plasma structures. Using this device, a series of novel striped patterns is observed in the discharge of a mixed gas of air and argon, marking a significant advancement in pattern formation studies. Notably, four striped superlattice patterns are obtained for the first time, each displaying intricate structural hierarchies. Among them, the large and small dot honeycomb striped superlattice pattern featuring structural complexity is chosen to investigate the formation mechanisms. The pattern is composed of three substructures: small dots, large dots, and a honeycomb framework. In the experiment, the emission spectra of different substructures are measured using a spectrograph, revealing that they are in different plasma states. The spatiotemporal dynamic behaviors of the pattern are observed using a high-speed camera and two photomultiplier tubes. It is found that the discharge sequence is small dots → large dots → honeycomb framework, where the honeycomb framework is formed by the superposition of random discharge filaments. The electric field distributions at different times are simulated by solving the Poisson equation, and the result well explains the formation mechanism of the above-mentioned patterns.