Alkali Metal Ion Sources

Abstract

The development of alkali metal ion sources has been greatly accelerated in the past decade because of the interest in these ions in basic research and more important because of cesium ion engine development for space propulsion. Three techniques used to generate alkali metal ions are described. The porous tungsten surface ionization source, highly developed for electric propulsion, has generated ion beams of over 1 amp of cesium and is being used to produce other alkali metal ions. The electron bombardment engine, or low‐pressure discharge source, has produced high currents of Cs+, Na+, and Hg+ and is used to generate other ions. The liquid metal hydrodynamic spray technique, also studied as an electric propulsion thruster, is used to produce high current densities from a very small source and generates some molecular ions. The operational levels of the various engines and their modification for use as laboratory ion sources are described.