Short-bunch-length operating-mode design at HLS-Ⅱ storage ring for coherent terahertz radiation

Coherent THz radiation has become an important research tool in many basic science studies and applied research. A detailed simulation process for coherent THz (terahertz) radiation at the HLS-Ⅱ (Hefei Light Source-Ⅱ) storage ring with 2 mm bunch lengths was presented. The low-alpha mode and harmonic cavity mode were two methods applied here for coherent THz radiation. The related issues of short bunch length, including beam instability threshold current, radiation power, and longitudinal phase-space damping progress, were also discussed.