Simulation study on high frequency characteristics of X-band high power relative klystron amplifier

An X-band high power relativistic klystron amplifier is studied using a 2.5 dimensional PIC code MAGIC in this paper. The presented klystron is composed of five nose-cone removed pillbox cavities, including an input cavity, three middle cavities, and an output cavity. The absorption of the injected microwave is studied, and the gaps of idler cavities are optimized according to the fundamental harmonic modulated current when an electron beam propagates through every cavity. Finally, after optimization of the guiding magnetic field, the output microwave is obtained with an average power of 105 MW when the diode voltage is 520 kV, beam current 460 A, the guiding magnetic field 0.4 T and the seeding power 1 kW. The efficiency reaches 43.5% with a gain of 50 dB, when the fundamental current modulation depth reaches 162%.