High-power industrial vacuum tubes having thoriated-tungsten filaments

Contrary to a long-standing belief, thoriated-tungsten filaments can be used as electron emitters in high-power vacuum tubes with a reliability equal to that established by low-power types. High-power types may be defined as those having unmodulated class C plate voltage ratings of greater than 5,000 volts. The use of thoriated-tungsten filaments in high-power types has been made possible by the use of new and improved materials and processing techniques. In the radio broadcast field, performance of these high-power tubes has been excellent. In the industrial field, tubes having thoriated-tungsten filaments are continuing to set new records after as much as 22 months of uninterrupted full-load service at plate voltages as high as 17,000 volts. Such performance, in addition to the lower cost of equipment components and lower cost of operation due to reduced filament-power requirements, makes these tubes very attractive for industrial applications.