Broadband operation of an X-band high-power relativistic traveling wave tube

Wide-band high-power relativistic traveling wave tubes (RTWTs) in X-band have the potential in phased-array antennas, microwave weapons, and so on. Thorough design and optimization are required to achieve wide-band amplification, especially with invariant beam voltage and interaction length. A corrugated circular waveguide is applied as the slow-wave structure for wide bandwidth. The geometric parameters of the structure are initially chosen by cold analysis and then verified by a nonlinear model and the 2D particle-in-cell simulation. The kinematic mismatch is proved to be vital to the wide-band amplification of the device. Optimization is performed so that high output powers in the bandwidth can be achieved with the same interaction length. With the beam voltage of 625 kV and the beam current of 1.92 kA, the optimized RTWT can deliver more than 100 MW from 8.43 to 9.32 GHz, and the corresponding bandwidth is similar to 10%. In the frequency range from 8.65 to 9.32 GHz, the output power and efficiency are larger than 170 MW and 14%, respectively.