Electrical Characterization and Imaging of the Discharge Morphology in a Small Scale Coaxial Packed Bed Dielectric Barrier Discharge

Packed Bed Dielectric Barrier Discharges (PB-DBDs) are gaining widespread attention due to direct interaction between plasma and catalyst, resulting in enhanced product selectivity in gas processing. Because of its construction most reactors does not enable a visual observation of the plasma morphology within the reactor and this limits the understanding of its electrical properties. In this contribution, a small scale coaxial DBD reactor, enabling the end-on view observation of the discharge gap, has been constructed. The primary objective is to correlate electrical measurements such as voltage-charge (V-Q) plots with the plasma morphology in PB-DBD for different pressures, gas compositions, packing materials and applied voltage amplitudes. Simultaneous imaging and V-Q plot analysis, with special attention to parasitic capacitances, result in the revision of equivalent circuit for PB-DBDs and a more accurate experimental determination of the key capacitance values, namely the cell capacity (C_cell), and effective dielectric capacity (ζ_diel). Additionally, the analysis includes the role of parasitic discharges, which can lead to the overestimation of input power. We aim to enhance the understanding of PB- DBDs, to provide sound knowledge about the power input and penetration of the flowing gas by active plasma.