Visualization of electrical interaction among close-packed atmospheric pressure plasma jets

Plasma jet arrays can flexibly generate large-scale plasma in ambient air for surface treatment. Close arrangement of plasma jets inevitably induces a complex electrical interaction, which reshapes plasma plumes and destabilizes the treatment process. Understanding electrical interaction is a prerequisite for optimizing parameters in surface treatment. In this study, we employ a linear electro-optic technique to visualize the electrical interaction on the cross section perpendicular to plume trajectories. The strength of the interaction is featured by the density of the deposited surface charge. Results show that plasma jet arrays can simultaneously deposit like-charged groups onto the substrate. However, the electrical interaction is proven to behave with a tendency toward convergence rather than the repulsion caused by electrostatic interaction. It is inferred that electrons at the head of ionization waves (IWs) shield electrostatic repellence between positive charge groups. The collision ionization by electrons in the interval guides the coalescence of adjacent IWs. This study clarifies the electrical interaction between multiple jets, which is instructive for stable control of large-scale non-thermal plasmas for surface treatment.