Numerical simulations of C-band three-cavity transit-time oscillator

By employing a 2.5-D PIC code, the three-cavity transit-time oscillator (TCO) is simulated numerically and the details are presented. It is found that the TCO can modulate REB, that the modulated beam can be converted to HPM, and that the frequency of microwave accords with theoretical ones. The relations between output power and span of inverse diode and that between output power and r-distance of extractor are obtained. Furthermore, the relation between output power and span of foils is presented and it accords with that of the linear theory. A 600MW, 5 GHz peak output power microwave is generated by simulation, with 400 kV electron beam voltage and 4 kA current. The start time to oscillate is about 3.5 ns. The peak efficiency is over 37%.