Electric field components within a micro-scaled DBD measured by Stark shifting and splitting of helium lines

Abstract

Abstract Atmospheric pressure dielectric barrier discharges (DBDs), such as the micro cavity plasma array (MCPA), have emerged as promising technologies for the conversion of volatile gases. These conversion processes' effectiveness can be enhanced by integrating catalytically active surfaces. To deepen the understanding of the plasma-catalyst interaction, it is crucial to study the transport dynamics of charged species to the catalytic surface, which, due to collisions with neutrals, also directly affects the transport of reactive species to the catalyst. Thereby the transport of the charged species is in particular influenced by the electric field perpendicular to the catalytic surface. 
However, experimental data on the component-wise electric field strength within DBDs are rare. To address this issue, we performed polarized optical emission spectroscopy (OES) on the shifting and splitting of the allowed 492.19 nm (1D→1P0) and forbidden 492.06 nm (1F0→1P0) helium line pair. This diagnostic approach requires a non-radially symmetric geometry, which leads to an adapted reactor design of the MCPA allowing the side-on observation of the discharge. The discharge operates in pure helium at atmospheric pressure, utilizing a triangular excitation voltage with a frequency of 15 kHz and an amplitude of 600 V. We performed phase-resolved measurements of the electric field components with a temporal resolution of 1 µs. Our results revealed an electric field strength of approximately 22 kV cm-1 for the component perpendicular to the dielectric surface, while the component parallel to the dielectric surface is about 5 kV cm-1 larger during the decreasing potential phase of the applied voltage.