Characteristics of a gallium liquid metal field emission ion source

Abstract

Discusses the emission of positive ions from liquid metals under the action of high electric fields. High brightness sources are being developed with a variety of applications in mind. The basic principles of such sources are discussed and the design and experimental behaviour of a gallium source are described in detail. Measurements of the current-voltage characteristics of the source, together with the angular distribution of the beam are presented. The current-voltage behaviour is found to be in agreement with the predictions of a simple space charge model. Field ion creation mechanisms require liquid metal emitting features of submicron dimensions and this does not appear to be consistent with space-charge considerations and the best available microscopic observations. This apparent paradox can be resolved if a highly mobile emitting feature is assumed to exist.