Liquid-metal ion sources. Ionization mechanism

Electron microscopic analysis of liquid-metal emitters and extractors ''frozen'' in a high-voltage field at the moment of ion production is carried out. Microcusps of 1-3 μm diameter, craters of 5-80 μm diameter and spherical particles of the liquid metal vapor condensate are observed at the emitter surface. There is a great number of plane craters of 5-10 μm diameter. During operation of the liquid metal source the electric field extracts microcusps with the ''Taylor cone'' in the basis from the liquid surface. When reaching the threshold voltage the heads of microcusps tear off and move onto the extractor. On the extractor from liquid drops new points are extracted by the electric field which are exploded by autoelectron current, and hence, dangerously explosive plasma is produced. Electrons emitted by plasma bombard the points on the emitter, evaporate them to form craters and ionize the vapor. The mass spectrometer separates ions produced on the extractor and emitter. It is found that ion current generated by the liquid metal source has the pulsed character. The pulse amplitude is about 1 mA, pulse duration is about 10-6 sec