Towards a Unified Model of the Low-Current Glow Discharge with a Liquid-Phase Anode

Abstract: A self-consistent model describing a glow discharge in argon with a liquid-phase (distilled water) anode is presented. The model is based on an extended hydrodynamic description of plasma and takes into account the heating of the metal cathode and liquid-phase anode, as well as the equilibrium evaporation of water molecules into the discharge gap and the kinetics of elementary processes involving them. A numerical study is performed for two key cases: the discharge initiation in a pure argon atmosphere and that with the initial presence of water molecules at a concentration corresponding to the saturated vapor pressure at an initial liquid-phase anode temperature of 293 K. For the first case, it is shown that a change in the plasma-forming ion from to the hydrated cluster ion and also a change in the dominant negatively charged particle from the electron to the OH^– ion are observed during the evaporation of water molecules. For the second case, it is shown that is the dominant positive ion over the entire time interval. The competition between electrons and OH^– ions on times up to ~0.01 s was detected for negatively charged particles. The OH^– ion becomes the dominant negatively charged particle at times larger than 1 s but the electron density remains comparable by the order of magnitude, which is critical for maintaining plasma conductivity.