The Application of the X-L Filament to Power Tubes

The properties of the X-L or thoriated tungsten filament are discussed with particular reference to the suitability of this material for use in power tubes and its advantages over other materials. Comparisons are given between pure tungsten and thoriated tungsten filaments in electron emission characteristics and effect on tube design and performance. Several power tubes containing X-L filaments are described in detail. The improvements due to the use of the X-L filament are illustrated by comparison of these tubes with older types of tubes containing pure tungsten filaments.