Toward 80% Efficiency in a Super Klystron-Like Relativistic Backward Wave Oscillator With Second and Third Harmonic Coaxial-Premodulation Cavity

To further increase the beam-wave conversion efficiency, a super klystron-like relativistic backward wave oscillator (RBWO) with coaxial-premodulation (CPM) cavity is proposed. Compared with previous dual-premodulation (DPM) cavities, the CPM cavity intensifies the second and the third harmonic components, resulting in a larger fundamental harmonic current both in the slow-wave structure (SWS) and the extraction cavity, and, consequently, leads to an enhanced microwave power generation by the Cherenkov radiation and transition radiation. In the particle-in-cell simulation, an
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-band microwave with a power of 3.44 GW and record efficiency of up to 80% has been achieved.