Abstract:Lanthanum-containing cathodes are an attractive alternative to thorium tungsten cathodes because of their low work function and their comparatively low operating temperatures. A La-Mo carbonized cathode was described, which had a high thermionic emission; it was made up in a similar way to the Th-Wcathode, but possesses high emission values. The thermionic tube equipped with La-Mo carbonized cathode was designed for comparison with Th-W cathode tube. It was experimentally verified that La-Mo cathode has higher thermionic emission effectiveness and its operating temperature is about 200℃lower than that of Th-Wcathode. The emission current density of La-Mo wire satisfies for electron tubes as Th-W filament. Astable emission current has been obtained with La-Mo carbonized cathode tubes for more than 1 800 h. From the results it is clear that the emission stability of La-Mo cathode satisfies the requirements for the replacement of  Th-W filament.

Key words: cathode　rare-earth　molybdenum　thermionic emission　La2O3