THE EFFECTS OF FLOW IMPEDANCE ON THE CURRENT-VOLTAGE CHARACTERISTICS OF LIQUID-METAL ION SOURCES

By incorporating the flow impedance into the space-charge model of Mai r, the current-voltage curves of high impedance liquid-metal ion sourc es can be fitted to this modified model for an assumed liquid film thi ckness that decreases with voltage and/or for assumed values of the ch ange in cone half-angle. The new model strongly suggests that what lim its the current in high-impedance sources (and eventually in all sourc es) is a decrease in film thickness with voltage. Coupled to this effe ct is a self-shaping of the liquid emitter; the higher the flow impeda nce of an ion source the more pronounced is this self-shaping.