A synchronous-wave amplifier

The small-signal gain expression for an amplifier consisting of two resonant synchronous-wave couplers is presented and the results of an experimental investigation of such a tube are reported. Some theoretical studies of such an amplifier have been reported earlier but no experimental results have been given. The experimental tube operated at 3.00 kMc and employed a Brillouin flow beam with a dc power of 730 w. The saturation output power was 45 w. In general, the experimental results were in good qualitative agreement with the theory. The discrepancy between the theoretical gain of 13 db and the experimentally observed 8-db gain is attributed to thick-beam effects. Oscillations due to the interaction between the slow space-charge wave and the off-axis longitudinal circuit fields were observed, and it is pointed out that this effect may set some limitations on the gain that can be achieved in the sychronous-wave amplifier.