The effects of dielectric rods on streamer dynamics in patterned dielectric barrier discharges

Dielectric barrier discharges (DBDs) are promising tools for environmentally friendly electrified chemical conversion of various compounds into value-added products powered by excess renewable energy and based on short switch on and off times. Often, such plasmas are combined with catalytic surfaces. To improve the energy efficiency, conversion, and selectivity of such applications, knowledge-based plasma process control is the key. Conventional DBDs are often non-uniform, unstable, and their active plasma volume covers only a fraction of the reactor volume. These characteristics strongly limit plasma diagnostics, control, and efficiency. Such limitations can largely be overcome by using an advanced DBD plasma source, the patterned dielectric barrier discharge (pDBD), which combines volume and surface DBDs in a highly stable and controllable way by introducing a structured electrode surface. In this work, we combine such a pDBD with floating dielectric rods placed in the reactor volume at strategically selected positions above conical pellets immersed in one of the electrodes. Based on experimental phase-resolved optical emission spectroscopy and in a model gas mixture selected to optimize plasma stability as well as diagnostic access to the dynamics of energetic electrons, these dielectric rods are found to induce the generation of additional streamers and to guide the streamer motion in the pDBD via polarization effects. In this way, the streamer dynamics can be controlled, and the active plasma volume can be enhanced, providing potential benefits for plasma-induced conversion processes in more complex gas mixtures.