Formation mechanism of bright and dark concentric-ring pattern in dielectric barrier discharge

In this work, a bright and dark concentric-ring pattern is reported in the dielectric barrier discharge for the first time. The spatiotemporal dynamics of the bright and dark concentric-ring pattern is investigated by an intensified charge-coupled device and photomultiplier tubes. The results indicate that the bright and dark concentric-ring pattern is composed of three concentric-ring sub-lattices. They are bright concentric-ring structures, dark concentric-ring structures and wider concentric-ring structures, respectively. The bright concentric-ring structures and dark concentric-ring structures are alternately distributed. The bright concentric-ring structures are located at the centre of the wider concentric-ring structures. The formation of the wider concentric-ring structures is first formed from the outer edge and gradually develops to the centre. The essence of all three concentric-ring structures is the individual discharge filaments. The optical emission spectra of different sub-lattices are acquired and analyzed. It is found that the plasma parameters of the three concentric-ring sub-lattices are different. Finally, the formation mechanism of the bright and dark concentric-ring pattern is discussed.