Narrowband THz generation by ultra-relativistic beam

High peak power, narrow band THz radiation can be generated by an ultrarelativistic electron beam passing through slow wave structure. In this paper we will review a series of recent experiments at Tsinghua University Accelerator Laboratory where a 31 MeV electron beam compressed to a sub-picosecond duration had been transported through dielectric loaded waveguide structures of various dimensions. Such high peak current electron beam generates wakefield, - a mix of TM0,N modes in the slow wave structure. This radiation is extracted from the slow wave structure and is characterized with interferometer. Narrowband signals in the range from 0.3 - 1.5 THz were measured with typical duration of few tens of picoseconds and few microjoules energy per pulse.