Observation of intense bursts of terahertz synchrotron radiation at UVSOR-II

We have detected very intense bursts of terahertz synchrotron radiation at the UVSOR-II electron storage ring operated in single bunch mode. The bursts were observed in the wavelength range from 0.2 to 3.0 rnm by using a liquid-helium-cooled InSb hot-electron bolometer. The typical duration and interval of the bursts were about 200 mu s and 10-15 ms, respectively. Each burst shows the quasi-periodic structure of about 30 mu s. The peak intensity of the bursts was about 10000 times larger than that of ordinary synchrotron radiation in the same wavelength region. The extremely high intensity strongly suggests that the bursts are coherent synchrotron radiation, although the radiation wavelength was much shorter than the electron bunch length.