Coherent THz radiation source driven by pre-bunched electron beam

In this paper a tunable coherent THz radiation source driven by a pre-bunched electron beam is discussed. We consider the generation of a micro-bunch train by using either the self-modulation instability observed in a plasma channel or by irradiating the photocathode with a train of femtosecond laser pulses. By changing the plasma density in the channel or separation between the laser pulses the bunch train modulation frequency can be controlled. Using the micro-bunched beam frequency-tunable coherent THz radiation can be generated using many well studied mechanisms. We present a study of THz radiation generation when a modulated beam propagates above a shallow metal grating (Smith-Purcell radiation).