Practical aspects of fundamental research in thermionic conversion. Progress report, July 1, 1972--August 31, 1973

During the reporting period a system was constructed for testing advanced cylindrical cesium-vapor thermionic converters with indirectly heated emitters. Initial testing of a cylindrical diode with a platinum-clad niobium emitter in pure cesium vapor showed that pulse enhancement could not be obtained with forward pulses as in previous inert gas planar diodes, but the expected enhancement was obtained for reverse pulses. During testing, the arc drop in the unpulsed igtited mode of this converter gradually disappeared. This highly favorable result is tentatively thought to have occurred due to a new type of discharge occurring in a cavity formed by movement of the platinum cladding. A demountable cesium vapor system was also constructed for expanding the exploration of advanced converter configurations previously performed in at inert gas system. A preliminary evaluation of thermionic topping of large electric power plants was performed to illustrate the significance of advanced converter performance in a reoriented general thermionic conversion program. A summary of basic electrode requirements for advanced converter operation is also included. (auth