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

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 magnetic resonance spectroscopy. In this article, we propose a W-band gyrotron, which uses a so-called multimode switching scheme to realize ultrabroadband frequency tuning capability, nearly covering about 70% of the W-band (75-110 GHz) range. The tuning strategy used to suppress mode competition and stabilize gun parameters in such an open-cavity multimode switching gyrotron is presented. Theoretical study shows that the multimode 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 multimode switching gyrotron is a promising ultrabroadband source for millimeter-wave and terahertz-wave applications.