Ceramic-insulated vacuum tubes for very-high frequency industrial heating

A new range of ceramic-insulated triodes has been designed for the highest frequencies now in use in industrial dielectric heating equipment. Output powers of from 5kW to 40 kW are available at frequencies in excess of 100Mc/s (220Mc/s below 12kW output). Tube characteristics and performance are given for one tube in the range. This can be operated with a direct anode voltage of 6kV at an anode efficiency of 80%, with an adequate grid safety factor greater than 2: 1. Mechanical features considered include the envelope, the thoriated-tungsten filament, the grid and cooling requirements. Appendices deal in some detail with the more important design considerations.