Design of Klystron-Like Relativistic Backward Wave Oscillator with Triple Modulation Cavity

An X-band klystron-like relativistic backward wave oscillator (KL-RBWO) with a triple modulation cavity has been designed and analyzed using a finite-difference time-domain (FDTD)-based particle-in-cell (PIC) simulation code. This study focuses on evaluating the impact of the triple modulation cavity configuration on the fundamental harmonic current and the growth of the axial electric field, both of which play a crucial role in enhancing beam-wave interaction and optimizing energy transfer. Additionally, the variation in RF output power under different applied magnetic field strengths has been systematically investigated to determine the optimal operational conditions for maximum efficiency and stability. The results indicate that, for a magnetic field strength of approximately 2.9T, the device achieves an average RF output power of around 2.87 GW, with a power conversion efficiency of nearly 75%, pulse length of 133 ns, at an operating frequency of approximately 9.5 GHz.