Theoretical Study of a ${W}$ -Band-Covering Frequency-Tunable Gyrotron

Abstract

The gyrotron has already demonstrated the capability of generating high-power coherent electromagnetic (EM) radiation at high frequencies and finds application in fusion plasma heating and in magnetic resonance spectroscopy. In this paper, we propose a W-band gyrotron which uses a so-called multi-mode switching scheme to realize ultra-broadband frequency tuning capability, nearly covering about 70% of the W-band (75GHz to 110GHz) range. The tuning strategy used to suppress mode competition and stabilize gun parameters in such an open-cavity multi-mode switching gyrotron is presented. Theoretical study shows that the multi-mode switching gyrotron can generate a frequency tuning range much wider than a conventional step-tuning gyrotron or a single-mode tuning gyrotron. In addition, another technology that uses a slot-assisted circuit to select only axis-symmetrical TE operating modes is presented. Using such a circuit a tuning range of about 25 GHz in the W-band is obtainable. The proposed multi-mode switching gyrotron is a promising ultra-broadband source for millimeterwave and terahertz-wave applications.