Ryskin Nikita M. RussiaSaratovSaratov State University, 410012, Russia, Saratov, Astrakhanskaya street, 83RyskinNM@info.sgu.ru Author's articles On the Theory of Synchronization of a Two-Mode Electron Maser with a Hard Excitation Simulation of a Sub-THz Traveling Wave Tube with Multiple Sheet Electron Beam