Simulation of the Second and Third Harmonic Cavity Relativistic Klystron Amplifier with a Genetic Algorithm in S-band

In order to high efficiency, a second and third harmonic cavity was introduced into the S-band relativistic klystron amplifier (RKA) which was simulated with a genetic algorithm in this article. Through multi-objectives and multi-parameters optimization, we have attained multiple high-efficiency RKAs. An RKA selected with the results above was simulated in AJDISK again, and an efficiency of 79 %, a gain of 56 dB, an output power of 56 MW, and a total interaction length of 857 mm were attained when the beam voltage and current, and input power are 500 kV, 140A, and 140 W, respectively. It is essential to the fabrication and growth of the high-efficiency RKA.