Radiation Regimes of Subterahertz Multiwave Cherenkov Generator

A numerical simulation of a multiwave Cherenkov generator with a diffraction reflector in the subterahertz (112–114 GHz) frequency range has been performed using a 2.5D hybrid electromagnetic PIC code. A tubular beam with an electron energy of 180–490 keV and a current of 1–30 kA was injected into an electrodynamic system with a diameter of 36.4 mm. Two regimes were found in numerical experiments. With electron energy near 280 keV, a high (88%) efficiency of bringing radiation power forward was obtained. With electron energy near 250 keV, a power self-modulation regime was found. In the multiwave Cherenkov generator, for the first time, a transition was found from stable generation at a power of 6.8 MW to stable generation at a power of 800 MW through self-modulation and chaotic power oscillations with an increase in beam current. In this case, the ratio of the beam current to the starting generation current varied from 1.3 to 16.7.