LOW GROUP-VELOCITY TRAVELING-WAVE TUBE AMPLIFIERS

We report experimental and theoretical results from research into high power X-band traveling wave tube amplifiers designed to eliminate sid ebands caused by reflections from the output of such structures. These amplifiers have a low energy velocity, such that the time it takes a wave to be reflected from the output to the input-is of the order of, or greater than, the electron beam pulse duration. The elimination of sidebands and the effects of reflections is achieved by this transit t ime isolation. The bandwidth of the output spectrum is limited by the low pass-band of the periodic structures. Such amplifiers have been op erated at power levels of up to 160 MW at 9 GHz for 50 ns pulse durati ons.