GRAPHICAL METHOD FOR OPTIMIZATION OF CESIUM-SURFACE IONIZER MATERIALS
A graphical method is proposed for the optimization of cesium ionizer material, structure, and operating point. Proper selection of the ionizer material, its structure and work function, and the design point optimizes the propellantutilization efficiency, power efficiency, and, to some extent, life of the cesium-ion engine. The method is illustrated by optimization of the design point for a solid tungsten ionizer using exponential and linearized plots and by selection of optimum material based on preliminary experimental critical temperature curves and theoretical neutral fraction curves. (auth)
Single crystals of tin iodide (SnI2) have been grown in silica gels. A detailed microtopographical study of {100} faces have been described. Horizontal striations are predominant on these faces for most of the crystals, while few of them show vertical striations. The horizontal striations are associated with the two-dimensional nucleation theory whereas the vertical striations relate to the growth fronts. Growth layers modified by the presence of misaligned microcystals have been illustrated. The natural etch pits on {100} faces of the crystal are attributed to the dissolution of crystals in the acid set gel. In the light of these observations, the mechanism of the development and growth of these faces have been assessed and the implications are discussed.