Plasma production in electrically conducting liquids

Abstract

The production of plasmas in saline solution at low voltage (here 225 V) is investigated. It is confirmed that this is associated with vapour layer formation on the electrode surface. The plasmas occur once the vapour layer has completely covered the electrode and reached a thickness of approximately 0.3 mm. There are several aspects of this specific environment that may influence the breakdown characteristics of the vapour layer. These include the high electric fields, approaching 107 V m−1, in the vapour layer, the presence of sodium and chlorine on the electrode surface and sodium in the vapour layer. There are generally plasmas of different character in each pulse. They can be broadly classified as of short (a few μs) or long (up to 500 µs) duration. The presence of sodium in the vapour layer is hard to explain and the possible sudden vaporization of the saline solution is considered. Vapour layer and plasma production is faster and occurs at lower voltages with negative polarity pulses. An understanding of the phenomena exhibited in the production of plasmas in saline solution is important in determining their potential new applications in areas such as plasma medicine.