Structural Engineering of Impregnated Dispenser Cathodes

Targeted research efforts focusing on the properties and structure of impregnated dispenser cathodes (IDCs) have been monitored. The data are summarized in terms of scale structural hierarchy in inorganic materials to develop principles for controlling their formation in the design of high-emission and long-life IDCs. The performance of IDCs of different types is modeled using the materials science triad 'chemical composition a dagger" structure a dagger" properties' and the concept of structural hierarchical levels in IDCs. Basic structural levels in IDCs are determined: electronic, nanostructured, mesoscopic, microscopic, and macroscopic. Their structural elements are analyzed: electrons, emitter layer, film coating, matrix and emission material, and cathode structure. It is found out that the electronic level is the key one in the hierarchy of IDC structural levels; its effectiveness depends on the nanocrystalline, mesoscopic, and microscopic levels. The principles of structural engineering are developed for the design of high-emission and long-life IDCs and for the control of their formation at nanostructured and microscopic levels by variation in the chemical composition and structure.