B.I. Stepanov Institute of Physics, Belarus, Russia
Uppsala University, Uppsala, Sweden
University of Gothenburg, Gothenburg, Sweden
Pulsed THz FELs are typically driven by rf Linacs which produce intense electron bunches with a duration of a few picoseconds or even shorter. When the bunch duration is less than a picosecond, the wavelength of the THz light is greater than the bunch length and the FEL operates in the super-radiant (SR) regime*. In the report, we summarize our studies performed for an SR source operating in the THz frequency range. In particular, we focus on an open-type planar undulator comprising no guiding structure. Using a numerical code that supports 3D modeling of the SR dynamics as well as statistical properties of electron bunches, we analyze influence of electron bunch parameters on generated THz radiation and reveal some surprising results. More specifically, for the considered undulator configuration, we predict degradation in the angular divergence and spectral broadening of the generated radiation as the electron bunch emittance decreases. We also demonstrate how electron bunch broadening associated with the electron energy spread can eventually be suppressed.
* R. Chulkov, V. Goryashko, and V. Zhaunerchyk, Report III of the series of reports by the Swedish FEL Center and FREIA Group, http://www.diva-portal.org/smash/get/diva2:699684/FULLTEXT01.pdf.
