  We demonstrate a prototype of a Focused Ion Beam machine based on the
ionization of a laser-cooled cesium beam adapted for imaging and modifying
different surfaces in the few-tens nanometer range. Efficient atomic ionization
is obtained by laser promoting ground-state atoms into a target excited Rydberg
state, then field-ionizing them in an electric field gradient. The method
allows obtaining ion currents up to 130 pA. Comparison with the standard direct
photo-ionization of the atomic beam shows, in our conditions, a 40-times larger
ion yield. Preliminary imaging results at ion energies in the 1-5 keV range are
obtained with a resolution around 40 nm, in the present version of the
prototype. Our ion beam is expected to be extremely monochromatic, with an
energy spread of the order of 1 eV, offering great prospects for lithography,
imaging and surface analysis.
