Phase-Locking of Second-Harmonic Gyrotrons for Providing MW-Level Output Power

We propose the method of providing megawatt (MW)-level output power in continuous wave (CW) or long-pulse second-harmonic (SH) gyrotrons using phase-locking by a weak external monochromatic signal. Typically, the power of harmonic gyrotrons is hindered due to excitation of spurious fundamental-harmonic modes at the front of the accelerating voltage and the beam current. Injection of a seeding signal at the operating SH mode (priming) can suppress the spurious generation during the startup process. Within the frame of a self-consistent multimode model, we demonstrate the applicability of this approach to provide ~1-MW radiation in a 230-GHz SH gyrotron with the high-order TE_34,14 operating mode which is standardly unattainable for harmonic operation.