Exploring Plasma Behavior in Dielectric Barrier Discharges with Non-Equal Electrode Spacing

Dielectric barrier discharges (DBDs), due to their simple structure and ease of scaling up, have been widely applied in various low-temperature plasma applications. In all previously reported volume dielectric barrier discharges—including both planar and cylindrical (or coaxial) configurations—the gap distance between the two electrodes has always been constant. In this presentation, we first report a novel DBD configuration with a non-uniform gap, formed between a wedge-shaped electrode and a planar electrode [1]. It is observed that the plasma self-organizes into striped patterns: the discharge initially occurs at the center of the wedge-shaped electrode, where the gap is narrowest, and then jumps to positions with progressively larger gaps after a characteristic delay.

Second, a non-uniform gap DBD formed between a cone-shaped electrode and a cylindrical electrode is presented. In this setup, the gap varies from 1 mm at its narrowest to 7 mm at its widest. A distinctive ladder-shaped plasma consisting of multiple plasma layers is generated within the gap. This structure arises from the propagation of ring-shaped plasma fronts from the narrow-gap region toward the wide-gap region [2].

Third, we describe a non-uniform gap DBD formed between a spiral-shaped electrode and a cylindrical electrode. Here, the discharge initiates at the point of smallest gap and propagates continuously along the spiral path, following the increasing gap distance at a velocity of approximately 10⁶ m/s [3].

Fourth, we present a DBD configuration where the left side of the structure exhibits a rapidly increasing gap from 0.5 mm to 6 mm, while the right side maintains a uniform 6 mm gap across the main discharge region. This arrangement produces a homogeneous plasma within the 6 mm main gap.

Finally, by applying an external magnetic field to a DBD system, a room-temperature air plasma jet is successfully generated.