S-Band space traveling-wave tubes employing velocity resynchronization and collector depression

Two related traveling-wave tubes, both of which demonstrate in excess of 50 percent efficiency over the design bandwidth, are introduced. Low dielectric and conductive shield loading are combined with suitable velocity resynchronization techniques to provide effective beam-circuit wave interaction. Use is made of multi-stage depressed collectors to sort the electrons according to energy, thus recovering a portion of the spent electron beam energy. Both devices utilize suitable helix phase velocity tapering to provide high basic interaction efficiencies. An extension of the extremely favorable beam-circuit wave interaction occurring just prior to saturation leads directly to improved efficiency performance. The tubes operate at moderate values of velocity parameter and possess smooth and continuous transfer characteristics across extended bandwidths. The tubes are lightweight and rugged and are consistent with space applications. Focusing is achieved using periodic permanent magnets of samarium cobalt.