Efficiency improvement by means of electron-beam bunching enhancement in a two-stage traveling-wave tube

This paper describes a novel two-helix 1 Gc traveling-wave tube designed to increase electronic efficiency by means of enhanced bunching of the electron beam. The tube incorporates a jump in electron beam velocity as well as a phase jump of the circuit wave, both adjustable for optimum tube performance. An efficiency with collector and first helix at the same potential of 44% has been measured in two-stage operation compared to 26% in single stage operation. Further improvements are expected by employing collector depression techniques. The saturated output power in the two-stage regime was 8 watts, representing a gain of 28 db. The harmonic content at saturation was extremely low, being less than 2% of the total output power.