Kovshov Y. Interaction of electron beam with the fields of THz clinotrons with increased stability

Object of the study – Formation and propagation of a nonrelativistic intensive sheet electron beams and the beam-wave interaction processes in THz clinotrons. Purpose – Physical features of beam-wave interaction revealing in oversized electromagnetic systems of THz clinotrons. Research Methods and Apparatus – 3-D simulation of electron beam trajectories and the simulation of beam-wave interaction, optical interferometry in measurements of surface roughness, precise equipment in measurements of electromagnetic radiation parameters. Results and novelty –Theoretical model of beam-wave interaction in clinotron oscillator considering high-frequency ohmic losses caused by both the surface roughness and thermal heating of the grating structure has been developed. The theoretical model of THz clinotron considers the reflections and transformation of electromagnetic waves at the edges of slow-wave structure connecting with waveguides and electron velocity spread along the beam thickness. Developed theoretical model allows us to explain the effect of the resonant excitation of THz clinotrons as well as both the enhancement of radiation power and the excitation of multimode operation in THz clinotrons in the case of the application of nonsymmetrical electron-optical system, that was experimentally studied in the frequency range from 100 to 400 GHz in clinotrons containing either conventional slow-wave structure or multistage grating. The power and frequency stabilization loops for THz clinotrons were developed using both in-house designed high-voltage power supply and the proportional-integral-differential control scheme, that resulted in experimentally achieved output power stability of 0.5% and the frequency stability of 5 MHz for 300 GHz clinotron with the output power of 100 mW. Field of application –DNP NMR spectroscopy, THz-vision, THz-tomography, physical electronics.