Terahertz gyrotrons with quasi-regular cavities
We describe two ways of the use in high-harmonic gyrotrons of quasi-regular cavities with short irregularities formed by the widening of cavity radius. The first one is a significant improvement of the selectivity of the second-harmonic gyrotrons due to the supression of parasitic near-cutoff fundamental-harmonic waves. The second approach is aimed to solve a typical problem of weakly-relativistic high-harmonics gyrotrons, namely, the use of long cavities ensuring extremely high diffraction Q-factors and a great share of Ohmic losses. We propose a quasi-regular cavity with periodic phase correctors, where a far-from-cutoff axial mode with a decreased diffraction Q-factor is excited in a gyrotron-like regime.
A method for suppression of spurious fundamental-harmonic waves in gyrotrons operating at the second cyclotron harmonic
A typical problem of gyrotrons operating at high harmonics of the electron cyclotron frequency is the suppression of parasitic near-cutoff waves excited at lower harmonics. In this paper, a method for a significant improvement of the selectivity of the second-harmonic gyrotrons is proposed. This method is based on the use of quasi-regular cavities with short irregularities, which provide different effects on the process of excitation of the operating second-harmonic wave and the spurious fundamental-harmonic wave by the electron beam.
Design of an Optimized Resonant Cavity for a Compact Sub-Terahertz Gyrotron
Coherent sources of radiation in the sub-terahertz and the terahertz frequency range are in great demand for various spectroscopic studies (e.g. electron spin resonance spectroscopy, DNP/NMR spectroscopy etc.). The required levels of the output power as well as the needed specific spectral characteristics make the gyrotrons the most promising and high-performance devices for such applications. Recently, an initial design of a versatile second harmonic gyrotron utilizing a compact cryo-free 8 T superconducting magnet has been accomplished. In this paper we present an optimized resonator for this gyrotron. Instead of a regular (cylindrical) part as in the conventional cavities it contains an uptapered section. Such configuration offers a significant increase of the efficiency and improves the overall performance of the tube. We outline briefly the underlying theory, present and discuss the results of the numerical experiments carried out during the optimization process.