The dynamics of liquid metal ion sources

The emission of ions and other charged particles from sharpened solid needles wetted with a film of liquid metal is initiated by an electrically driven redistribution of the film at the needle's apex to form a Taylor Cone. In this paper the authors examine the effect of viscous fluid flow on the properties of the emitter, in particular the transient properties during redistribution and at onset. A purely inertial treatment is found to be inadequate and viscous effects are shown to dominate. Electric stress and surface tension pressure are not equal during emission and the liquid cone is in a state of tension with steady-state conditions maintained by the process of ion emission. (author)