A high efficiency 200 watt, 12 GHz traveling-wave tube

A 12 GHz-coupled-cavity tube with PPM focusing is described which incorporates a double step velocity taper and a novel multi-stage collector with radiation cooling for efficiency enhancement. The tube achieves saturated power output of 240 watts over a bandwidth of 85 MHz with 35 dB gain and an overall efficiency of 56%. The multi-stage collector includes nine active beam collection stages and features electrostatic beams velocity sorting with automatic suppression of secondaries. Upon leaving the output coupler, the spent beam is expanded in a refocusing section to reduce space charge effects and radial velocity components before entering the multi-stage collector. Collector efficiencies of 81% have been, obtained at saturation. The refocusing section and multi-stage collector is based on a NASA-Lewis Research Center design.