External electric field effects in pattern formation in plasma-liquid interactions.

In this work, we present experiments using atm-DC plasma in contact with a H₂O+NaClO₄ solution, to study effects of external electric fields in the pattern structures of plasma-liquid interactions. Electric fields are modified using metallic apertures in the region between the anode liquid and the pin cathode. Diagnostics include current through the plasma, and self-emission images. Spatial distribution of emission/absorption spectroscopy are measured using a holographic imaging spectrometer (430-670nm), complemented with absorption spectroscopy (200-1100nm) provided by USB2000 spectrometer. Spatial distribution of the electric fields are studied using ANSYS Maxwell Electrostatic Solver.

Results show several variations with the inclusion of metallic apertures. We observe enhanced stability of the plasma column, showing no erratic movement and remaining in the same position. Also, using fixed saline concentration and current driving the plasma, patterns are modified showing structures similar to those obtained at different currents when no apertures are used. These results are clear indications of the effects of the electric field in the plasma-liquid interaction region. Regarding spectroscopic measurements, absorption in the measured range is observed, which can be ascribed to production of RONS in the liquid. Further effects of the electric field topology in the plasma and the production of RONS will be presented and discussed