A high efficient X-band klystron-like RBWO

A high efficient X-band klystron-like relativistic backward wave oscillator is studied. By adding a drift tube after the first period of the slow wave structure, the energy spread of the electrons decreases effectively, and the fundamental harmonic current reaches maximum in the extracting cavity. Utilizing a trapezoid resonant reflector with a ridge, the depth of pre-modulation could be adjusted continuously. As a result, the beam-wave interaction is promoted greatly and the efficiency reaches 65%.