Improvement of Stability of High Cyclotron Harmonic Operation in the Double-Beam THz Gyrotrons

A double-beam scheme of a short-wavelength gyrotron operating at the second cyclotron harmonic is studied both within the framework of the averaged self-consistent approach and using 3-D particle in cell simulations. The analysis shows that the introduction of an additional generating electron beam allows drastically increasing the operating current of a second-harmonic gyrotron with the simultaneous suppression of self-excitation of spurious modes at the fundamental harmonic. As a result, the radiated power of a double-beam gyrotron exceeds the power of a single-beam gyrotron by a factor of four. The developed concept makes it possible to realize high-power (several hundred watts) single-mode gyrotrons in the 0.7-1.0-THz frequency range.