In this paper, we propose a tunable terahertz (THz) radiation source that utilizes a free electron beam to generate THz diffraction radiation coupled with the guided modes in a cylindrical corrugated waveguide. Detailed theoretical analyses and computer simulations are conducted, and the results demonstrate the characteristics of the tunable radiation frequency. In particular, the coherent diffraction radiation excited by a prebunched electron beam is discussed both theoretically and numerically with regard to the enhancement of the radiation power and efficiency. This paper may offer attractive prospects for the development of compact and tunable radiation sources in the THz frequency regime.

Coherent diffraction; Corrugated waveguide; Diffraction radiation; Prebunched electrons; Terahertz; Terahertz radiation; Tunable radiation; Vacuum devices

--