A Compact THz Source: 100/200 GHz Operation of a Cylindrical Smith–Purcell Free-Electron Laser

We report first operation in the terahertz regime of a cylindrical grating Smith-Purcell free-electron laser. Propagation of an annular electron beam in proximity to a cylindrical grating causes strong electron bunching due to a beam-surface wave interaction. Electromagnetic radiation results from the bunching (fundamental) and, at bunch harmonics, the Smith-Purcell effect. In the experiment, over 2.5 kW was generated at 100 GHz (fundamental) and over 100 W at 200 GHz (Smith-Purcell). The results illustrate the potential of this configuration for generation of high-power terahertz radiation.