Explosive Electron Emission From Liquid-Metal Cathodes

Since the discovery of explosive electron emission (EEE) 40 years ago, the overwhelming majority of investigations of this phenomenon have been performed with solid-state metal cathodes. At the same time, liquid-metal (LM) pool point cathodes, by virtue of some favorable properties, allow one to perform more reliable physical experiments. The peculiarities of LM cathodes are related to the features of the formation of an emitting protrusion under the action of a strong electric field. The high stability of this process in space and in time for a cathode repetitively operating under the conditions of clean high vacuum and moderate voltages (10-30 kV) ensures highly reliable experimental data. This paper is a review of the studies of the EEE from LM point cathodes. The features of the formation of an emitting protrusion and of the initiation of explosive emission at the protrusion tip, the erosion characteristics of LM point cathodes, the features of the generation of the droplet fraction in cathode erosion, and the characteristics of the explosive-emission plasma flow are considered sequentially. Original results of highly space- and time-resolved observations of the near-cathode region are also presented. Examples of practical implementation of this type of cathode are given.