GEC Student Excellence Award Finalist Presentation - Surface charge dynamics at the liquid/gas phase boundary of an argon bubble in water at varying conductivities.

Interactions at the atmospheric plasma-liquid interface intersect physical and biochemistry, physics, and materials science, introducing highly reactive species that can operate at room temperature. To investigate the effects of different electrical parameters on the electric breakdown at the liquid/gas boundary, an argon bubble was floated between two electrodes and excited by 18 kV HV pulses of varying pulse-widths, submerged in water with conductivities ranging from 2 to 1300 µS/cm of NaCl.



The bubble/electrode orientation is modeled as a capacitive dielectric barrier discharge (DBD). However, increasing the salinity of the solution results in an ever-increasing lossy dielectric. This impacts the capacity for surface charges to accumulate at the phase boundary and determines whether the bubble undergoes return-stroke emission, a characteristic of a DBD. In cases of deionized water, we demonstrate that for both nanosecond and microsecond pulses, the initial discharge emission decays while the pulse is still active, and only re-emerges at the fall of the pulse with the return-stroke current. The introduction of ions to the solution, on the other hand, results in the absence of such behavior, requiring increased electric fields to reach breakdown.