Absolute and global instabilities driven by Cherenkov interaction between magnetized electron beam and spoof surface plasmon polaritons

Abstract

In this study, we examine absolute and global instabilities driven by the Cherenkov interaction between a magnetized electron beam and spoof surface plasmon polaritons (SPPs) with an azimuthal mode number m. The absolute and global instabilities are induced in long and short lengths of the cylindrical corrugated waveguides (CCWs), respectively. The temporal and spatial growth rates have different dominant modes of spoof SPPs that, respectively, affect the absolute and global instabilities. In the experiment, the G-band radiation, which corresponds to the dominant mode in the spatial growth rate, is observed with the short length CCW. In the long CCW, the G-band radiation vanishes because the dominant mode in the temporal growth rate has lower frequency than the G-band cutoff frequency of the detecting system. Our results demonstrate that the instability and the multimode radiation are changed by the length of the CCW.