Accession Number : AD0437153


Title :   A LOW ENERGY ALKALI ATOM BEAM SOURCE


Corporate Author : STANFORD RESEARCH INST MENLO PARK CA


Personal Author(s) : Lorents, Donald C ; Black, Graham


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/437153.pdf


Report Date : Feb 1964


Pagination or Media Count : 36


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.


Descriptors :   *ION BEAMS , *LITHIUM , ALKALI METAL COMPOUNDS , ATMOSPHERE ENTRY , EXCITATION , GAS IONIZATION , INSTRUMENTATION , ION BOMBARDMENT , ION SOURCES , LITHIUM COMPOUNDS , PARTICLE BEAMS , SPACE CHARGE


Subject Categories : Particle Accelerators


Distribution Statement : APPROVED FOR PUBLIC RELEASE