Analysis of the Methods of Discrete and Smooth Frequency Tuning in Gyrotrons for Spectroscopy, on the Example of a Generator Operated in the 0 . 20–0 . 27 THz Frequency Range

We consider the main features of a low-power frequency-tunable gyrotron with an oversized cavity, which is designed for the purposes of nuclear magnetic resonance spectroscopy and other applications and operates in the 0.20–0.27 frequency range producing an output power of 200 W. We study the possibilities of wideband output frequency tuning by exciting a sequence of modes with similar caustics using magnetic-field variations and smooth tuning due to the excitation of modes with a great number of longitudinal variations. Aiming at widening the frequency tuning range, we also analyzed the possibility of smooth frequency tuning determined by controlled variations of the cavity temperature. Specific features of the electron-optical system of such a gyrotron is discussed, along with the possibility of increasing its efficiency by means of single-stage recovery of the residual energy of the electron beam.