Optical Emission Spectroscopy Investigation of a 1-atm DC Glow Discharge With Liquid Anode and Associated Self-Organization Patterns

Optical emission spectroscopy is used to study a 1-atm dc helium glow discharge with a liquid anode to obtain insight into the physical mechanisms underlying observed plasma self-organization at the liquid surface. Plasma column conditions such as gas temperature, electron density, and species composition were determined by means of optical emissions spectroscopy techniques and correlated with the appearance and structure of anode patterns over a broad burning voltage range with fixed flow rate and liquid conductivity. The discharge column was stratified from a species standpoint with the attachment near the liquid surface containing more sodium and water emission, while near the cathode, the predominant emission was from nitrogen and helium. The experiment suggested a complex interplay between the transport of liquid phase species and the actual composition of the plasma, suggesting the importance of processes such as localized boiling and perhaps physical sputtering.