Initiation from a point anode in a dielectric liquid

Abstract

For original paper see Kim and Hebner, ibid., vol.13, p.1254 (2006). In this discussion, the initiation of a positive streamer from the tip-electrode when a high voltage is applied to a tip-plane measurement cell filled with cyclohexane is discussed. The authors suggest that the initiating process is the formation of electron avalanches near the positive tip. In the present case the high field is concentrated around the tip anode. Fermi level of the metal electrode is energetically located in the middle of the forbidden gap of cyclohexane, electrons from molecules adsorbed at the surface of the tip and of adjacent layers can tunnel into the metal giving rise to the injection of positive charges. This process is called field ionization and has been invoked in the explanation of injection currents in liquids. In liquid cyclohexane strong incoherent scattering prevents the formation of a Rydberg state. Mean free path for electrons in cyclohexane changes by about three orders of magnitude between a thermal energy situation and one in which there is energy available to electrons due to electric fields with magnitudes like those under the conditions studied. So, our postulate was based on consideration of the dynamic properties rather than the equilibrium properties. The discussion of the model stating that the experimental results were consistent with such a model, and ended by characterizing the model as a framework in which experimental results can be reconciled. Kim and Hebner reply to the comments.