A LOW ENERGY ALKALI ATOM BEAM SOURCE
Abstract
A method of obtaining beams of alkali atoms in the eV energy range has been developed. The energy range and beam intensities make this a useful tool for studying ionizing reactions of importance in re-entry physics. The source has been used to produce a lithium atom beam but can be used equally well with any other alkali. Lithium ions emitted thermally from a betaeucryptite source are accelerated and focused into a ribbon beam by an electric field designed to compensate for the space charge field. Beams with current densities near the theoretical space charge limit have been attained at mean energies of 2 eV and above with a total energy spread of =0.3 eV. The Beta-eucryptite source emits impurity ions of Na and K, but at temperatures above 1000 C the impurity ions comprise less than 0.2% of the beam. The ion beam traverses at right angles a high-density collimated thermal lithium vapor beam issuing from an oven. Neutralization of the ion beam occurs by charge transfer interactions between the ions and vapor atoms and conversion efficiencies of 10-20% are easily attained. The vapor beam is frozen out on the cooled walls of the chamber which surrounds the charge transfer region so that the fast atom beam which emerges is not contaminated by any appreciable thermal flux.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1964
- Accession Number
- AD0437153
Entities
People
- Donald C. Lorents
- Graham Black
Organizations
- SRI International