Production and analysis of lithium ion beams in the low electron volt region.

Abstract

A lithium ion source capable of delivering low energy, monoenergetic beams of rectangular cross section, has been developed for use in the study of low-energy atomic, ionic, and molecular impact phenomena. An analysis of the spatial and energy distribution of the ion beams extracted from the source was made over the range of ion energies from 1.2 ev. to 100 ev, with particular attention given to beams with energies less than 25 ev. The experimental equipment and procedures are described. For the beams of low energy the intensity of the beam was limited by the space charge. The beam intensity in this space charge limited condition was approximately one third of the theoretical limit. Total beam —8 intensities ranged from a few times 10" amps at the lowest energies to a few times 10" amps at the higher energies with corresponding energy spreads of 1 .1 eV to * 0*3 eV. Typical beam dimensions are 1.0 cm by 2.0 cm at a distance of 5.0 cm from the gun with an aperture 0.47 cm by 1.5 cm.