Final shape and formative time of protrusions on liquid-metal cathodes

This paper presents new results of the study on the formation of protrusions on the surface of liquid-metal cathodes of the capillary and needle types. The problems associated with the shaping and growth time of a protrusion are considered in relation to the dimensions of the liquid-metal pool on the cathode top, the length of the needle extension, and the value and waveform of the voltage applied to the gap. It has been shown that the time of growth of a protrusion can be shortened by an order of magnitude and simultaneously its stability can be increased by applying to the gap an additional dc voltage, close in magnitude to the threshold voltage at which electrohydrodynamic instability develops at the liquid-metal surface.