Increasing phase-velocity tapering in overvoltaged regimes for high-efficiency traveling-wave tubes

This paper deals with one of the results of a study aimed at achieving high efficiency in traveling-wave tubes. For the most part, the study has relier, for its progress, on measured data from special beam analyzing devices developed during the course of its researches. These devices made possible measurements of the spent beam current-voltage distribution, and of the spent beam r-f current modulation. The inferences drawn from these data implied that in highly overvoltaged operating regimes, a traveling-wave tube would operate most efficiently not with a recreasing phase velocity circuit in the output section of the tubes as is currently advocated by several investigators, but rather with an increasing phase velocity circuit. In addition, it was found that in these overvoltaged regimes, the measured data indicated that the small-signal behavior of the beam and circuit wave interaction was sharply at variance with the accepted small-signal theory.