Design of a 1-THz fourth-harmonic gyrotron driven by axis-encircling electron beam

Li, Fan-Hong and Du, Chao-Hai and Zhang, Zi-Wen and Li, Si-Qi and Gao, Zi-Chao and Liu, Pu-Kun and Ma, Guo-Wu and Huang, Qi-Li and Ma, Hong-Ge and Zhang, Liang and Cross, Adrian W. (2022) Design of a 1-THz fourth-harmonic gyrotron driven by axis-encircling electron beam. IEEE Transactions on Electron Devices, 69 (6). pp. 3393-3399. ISSN 0018-9383 (

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In this article, the design of a fourth-harmonic gyrotron with 1-kW-level output power at 1 terahertz (THz) is presented. A unique advantage of this design is that, with a well-optimized magnetic-cusp large-orbit electron gun, the designed gyrotron can operate from first-harmonic to fourth-harmonic in multiple discrete bands by varying the confining magnetic field strength. By carefully balancing the competing modes, the gyrotron can be tuned to operate at six candidate modes, including TE 1,2 for fundamental harmonic, TE 2,3 and TE 2,4 for second-harmonic, TE 3,5 and TE 3,6 for third-harmonic, and TE 4,8 for fourth-harmonic interactions. As the main operating mode, the TE 4,8 can generate a peak output power of 1.68 kW, with an output efficiency of about 2.1%, and a magnetically controlled frequency tuning range of about 1.5 GHz around 1 THz. The impact of the longitudinal nonuniformity of the cavity at high-harmonic interaction was also studied. It shows that a radial tolerance of several micrometers will significantly elevate the start-oscillation current and deteriorate output performance. This design is to produce a THz source with ultra-wideband tuning capability ranging from the submillimeter-wave to 1-THz bands.


Li, Fan-Hong, Du, Chao-Hai, Zhang, Zi-Wen, Li, Si-Qi, Gao, Zi-Chao, Liu, Pu-Kun, Ma, Guo-Wu, Huang, Qi-Li, Ma, Hong-Ge, Zhang, Liang ORCID logoORCID: and Cross, Adrian W. ORCID logoORCID:;