Simulation studies of a klystronlike amplifier operating in the 10-100 GW regime

A coaxial drift tube allows propagation of an ultra high-power relativistic electron beam (500 keV, >or=100 kA, 100 ns). The modulation of a large-diameter (12.6 cm) intense, relativistic electronic beam (500 keV, 16 kA) by an external microwave source via particle simulation is studied. The annular beam, enclosed within a coaxial drift tube, is found to be fully modulated by a low-power external RF source at a frequency of 1.3 GHz. It is shown that for such an intense beam, a highly nonlinear interaction takes place at the modulating gap, producing highly coherent bunches of electrons. This finding is similar to earlier research in which such modulations were studied for an intense beam propagating in a hollow drift tube. It is further shown that, unlike the hollow drift tube case, the coaxial configuration is easily scaled to high power. Here, a very large diameter (26 cm) intense beam (460 keV, 100 kA) is fully modulated at 1.3 GHz to obtain 31 GW of RF beam power.>