EMISSION OF LIQUID-METAL IN VACUUM

The destabilization of an infinite plane surface of liquid metal by a normal electric field in vacuum has been the subject of different theo retical articles: above a critical field peaks grow on the liquid surf ace. A wavelength can be attributed to the resulting pattern. The elec tric field at onset and the corresponding wavelength only depend on th e density and the surface tension of the liquid. Above this critical f ield a whole range of wavelengths are excited, each growing with a dif ferent growth time: the fastest is the dominant wavelength. We shall p resent the dynamics of the liquid viscosity and of the liquid bath dep th: it can be shown that the dominant wavelength is smaller with highe r fields but differs if the liquid film is thick or thin, inviscid or viscous. The development of the pattern involves nonlinear interaction s. While a stable deformed interface has been observed on the analogou s case of a magnetic fluid under magnetic field, experimentally we onl y found stable non-plane interface for a confined geometry where the v olume conservation makes forming the destabilization more difficult: i ndeed the critical field for the obtainment of peaks is then greater t han the value of the horizontally infinite surface. Otherwise, some pe aks emit at their apex, killing the field: thus the peaks fall, do not emit any more and the electric field is installed again; this gives a n oscillatory phenomenon. For a sufficiently large liquid bath differe nt wavelengths can be seen,depending on the electric field and the way this field was reached. For confined geometries one or two peaks grow on the surface and the critical field can be significantly higher.