An ion implantation is disclosed that includes an ionization chamber having a restricted outlet aperture and configured so that the gas or vapor in the ionization chamber is at a pressure substantially higher than the pressure within an extraction region into which the ions are to be extracted external to the ionization chamber. The vapor is ionized by direct electron impact ionization by an electron source that is in a region adjacent the outlet aperture of the ionization chamber to produce ions from the molecules of the gas or vapor to a density of at least 10.sup.10 cm.sup.-3 at the aperture while maintaining conditions that limit the transverse kinetic energy of the ions to less than about 0.7 eV. The beam is transported to a target surface and the ions of the transported ion beam are implanted into the target.