Oversized coaxial relativistic extended interaction oscillator with gigawatt-level output at Ka-band

Abstract

In this paper, an oversized coaxial relativistic extended interaction oscillator (OCREIO) with gigawatt-level output at the Ka-band is proposed. We adopt a four-gap buncher cavity and a three-gap output cavity to increase the power capability and improve the electronic efficiency of the OCREIO. The beam-loading conductance for each mode existing in the buncher cavity is derived based on a small-signal theory. The beam-wave interaction and power capability for the 2π/3 and π modes exciting in the buncher cavity are analyzed. The operation mode 2π/3 is chosen by considering the beam-loading conductance and power capability. In addition, an improved method is proposed to mitigate the electric field intensity of the buncher cavity so as to moderate velocity modulation. The weak velocity modulation offers enough distance to make density modulation, thereby obtaining a relatively high fundamental harmonic current amplitude. Our study on the device performance of the proposed OCREIO, using the particle-in-cell simulation code CHIPIC, predicts an output power of 922.7 MW and a high electronic efficiency of 32.9% at 30.5 GHz, as well as the relatively less time of frequency-lock of self-oscillation <20 ns. The simulated results of the proposed OCREIO motivate us to practically develop the device in the near future.