Submillimeter-wave large-orbit gyrotron

We develop a thermionic-emission electron-optical system forming a dense beam of electrons moving along helical trajectories round the axis of a gyrotron cavity. The maximum beam current is 4 A and the pitch-factor of electrons is 1.0 for a particle energy of 250 keV and a pulse duration of 10 µs. Using such a beam in a gyrotron operated at the third cyclotron harmonic, we obtain single-mode oscillation with a power of 10 µs in the TE_3,8 and TE_3,9 modes with frequencies 371 and 414 GHz, respectively.