Influence of the water surface on the glow-to-spark transition in a metal-pin-to-water electrode system

Abstract

The glow-to-spark transition in a pin-to-water anode electrode system is investigated and compared with a pin-to-metal-plate system with 20 ns time resolution by fast imaging and corresponding current and voltage measurements. A contraction of the anode spot and cathode spot of the glow is observed in the pin–metal-plate system leading to a narrow filamentary spark, while the anode spot on the water anode electrode remains diffuse. In the latter case only a significant radial constriction of the glow in the bulk and near the metal cathode of the discharge gap is observed which causes a broadening of the spark near the water anode. Constriction of this broadened spark channel occurs several 100 ns after spark ignition. Additionally, the influence of the conductivity of the liquid electrode on the glow-to-spark transition is investigated.