Contribution of field effects to the achievement of higher brightness ion sources

The use of field effects for the delivery of high brightness ion beams is considered. Two solutions have been experimentally investigated, which are intended to increase the supply function in a field ion microscope: a liquid fed field ionization source and a field desorption source. Their performances and characteristics have been compared and they suggest two different regimes of emission. The field desorption source seems however more likely to produce reliable results. Brightnesses on the source side of the order of 108 to 109 A/cm2sr are expected but much care must be devoted to the design of the electrostatic transfer optics of the gun to take full benefit of the intrinsic properties of such large solid angle emitters. (Auth.)