Characteristics of electron tubes having clean electrodes

In conventional electron tubes, the grid and anode electrode surfaces become coated with materials evaporated from the cathode, so that they do not exhibit the characteristics of clean metal. It has been found that clean electrodes can be obtained in electron tubes by using active metal surfaces and high degassing and exhaust temperatures, and that they can be maintained for long periods of time by using with them only oxide-coated cathodes having a passive base metal. Tubes having clean electrodes exhibit low levels of grid and anode emission. A diode having a clean anode surface can be made to operate reliably in the emission limited region. A triode having a clean grid surface can be made to have a built-in grid bias of two volts or more. Tubes with clean electrodes have provided stable and reliable performance for long periods of time.