Terahertz Large-Orbit High-Harmonic Gyrotrons at IAP RAS Features

We describe high-harmonic gyrotrons with axis-encircling electron beams developing on the basis of two (80 keV pulsed and 30 keV Cw) experimental setups. Selective operation at the second (0.267 THz) and at the third (0.394 THz) cyclotron harmonics were observed in the 30 keV gyrotron. Quasi-regular cavities with periodic phase correctors are designed to improve the operation at the third harmonic, as well as to achieve the fourth-harmonic operation at frequencies of up to 0.65 THz. At the pulsed gyrotron setup, a sectioned cavity with a decreased diffractive Q-factor was experimentally tested.