3-D PIC investigation of an output circuit for the relativistic klystron oscillator

Summary form only given, as follows. The relativistic klystron has been a promising HPM source for many years, and is currently under active research as a GW class tube. While considerable effort has been spent an understanding the bunching mechanism in both the amplifier and oscillator regimes, the issues for extracting HPM from a bunched intense relativistic electron beam (IREB) has received much less attention. In this research, we take advantage of the fact that we can isolate the output circuit from the rest of the source and concentrate on the physics of the IREB´s interaction with a low-Q extractor gap. Using a prescribed beam based on profiles consistent with experimental data and simulations of the modulator circuit, we investigate the relative importance of the modulation depth, harmonic content, distribution of kinetic and potential energy, and extractor impedance on the efficiency of power extraction. With this information, we identify features for successful extractor design for AFRL´s RKO.