The Design of High-Power Traveling-Wave Tubes

This paper discusses the problems involved in designing traveling-wave tubes in the range of pulsed powers of the order of a megawatt. Suitable circuits are described, together with their advantages and limitations. In general, the all-metal structures described are capable of dissipating high average powers, have good impedances at the required voltages (100-kv range), but at a sacrifice in bandwidth. Nevertheless, this class of traveling-wave tube is useful where bandwidths of 10 to 20 per cent, not obtainable from klystrons of equivalent power outputs, are of interest. The problems of tube construction and tube design are discussed. Results of tests on an experimental model tube are described, showing good agreement with available theory. A gain uniformity of 3 db over a 9 per cent bandwidth, with power outputs of 300 kw pulsed have been obtained using attenuators of nonoptimum design. Better performance should be obtainable with further improvements in beam focusing and coupler design. Higher power levels with same effliciency should be possible, by designing the tube to operate at higher potentials.