SIMULATIONS OF THE CURRENT AND TEMPERATURE-DEPENDENCE OF LIQUID-METAL ION-SOURCE ENERGY-DISTRIBUTIONS

Of great importance to the study and application of liquid metal ion sources (LMIS) are the energy distributions of the emitted ions and their variations with source parameters. Excellent data now exist for a wide range of operating conditions but the understanding of energy distributions remains incomplete. The present paper aims to demonstrate that high frequency oscillations in the position of the ion-emitting feature (assumed here to be a jet-like cusp) can give rise to distortions of the energy distribution curves. Such distortions are observed experimentally at high temperatures and currents. Characterisation of the jet oscillations is made in terms of droplet emission from the tip; other parameters are derived from a semi-impirical approach. Energy distribution shapes are determined by the waveform of the oscillation; complete results are presented for a simplified waveform and the effects of other waveform characteristics are discussed.