Investigations on a 0.5-THz Ultrabroadband, Continuously Frequency-Tunable Gyrotron

Continuously frequency-tunable terahertz (THz) gyrotrons are attractive for modern applications. Nevertheless, it is challenging to generate a broadband, continuously frequency-tunable range for a single-mode operation gyrotron. In this article, a frequency-tuning scheme based on multimode switching and axial mode transition is employed to effectively enhance the frequency-tunable capacity of a THz gyrotron. A 0.5-THz broadband, continuously frequency-tunable gyrotron with four operating modes TE $_{5,7,q}$ , TE $_{10,5,q}$ , TE $_{3,8,q}$ , and TE $_{1,9,q}$ ( $q = 1, 2, 3\ldots $ ) working successively has been theoretically investigated in detail and the principle of the operating mechanism is proposed in this article. By means of changing the operating magnetic field and the beam energy, the four operating modes are excited successively. Numerically calculated results show that a 10-GHz level continuous frequency tuning range is obtainable. The frequency can be tuned from 500.3 to 510.8 GHz successively. Meanwhile, the output power always remains at hundreds of watts level, which is typically favorable for modern applications. Besides, the corresponding magnetron injection gun (MIG) is optimized to meet the requirements of the broadband frequency-tunable gyrotron. The electron beam quality versus the operating voltage or the operating magnetic field has also been studied. The principle could benefit the development of broadband, frequency-tunable THz gyrotrons.