Broadband Terahertz FEL Utilizing Resonant Coherent Diffraction Radiation

Abstract

Accelerator-based THz radiation has been expected to realize a high power broad-band source. With a low emittance and short-bunch electron beam at a high repetition rate, a scheme of coherent-diffraction-radiation in an optical cavity layout is proposed. It can greatly enhance the efficiency of the radiation by the stimulated radiation process between bunches. We give an introduction of the principle of this process. We performed an experiment at cERL in KEK. A sharp resonance signal of THz which indicates broad-band stimulated radiation correlating with beam deceleration was observed while scanning the round-trip length of the cavity. It proves the efficient beam-to-radiation energy conversion due to the stimulated radiation process.