Simulation Investigation of an $X$ -Band Forward-Wave Oscillator Using Spiral Metamaterials

An ${X}$ -band forward-wave oscillator operating at 8.946 GHz and using spiral metamaterials (SMTMs) driven by a transparent cathode was developed. Particle-in-cell (PIC) simulations with the code CST show that a circular waveguide with a radius of 5.628 cm loaded with a slow wave structure (SWS) based on a hexagonal unit cell of SMTMs can support the forward wave of the TM $_{{01}}$ mode. Simulations confirm that when the ${X}$ -band forward-wave oscillator driven by a transparent cathode with six emitters powered with a voltage of 600 kV, a magnetic field of 0.58 T, and a current of 2.45 kA, the output power can be as high as 522 MW, and its corresponding electronic efficiency is 35.4%. The main purpose of this article tries to seek out a forward-wave oscillator with high output power and low start current.