Title screen

[References: p. 756 (11 tit.)]

We suggest using the Smith-Purcell effect frommicrobunched beams modulated after passing theundulators in FELs as an extra source of monochromaticradiation. We investigate theoretically characteristics ofSmith-Purcell radiation in THz and X-ray frequencyregions for two types of distribution of the particles in thebeam. The expression for spectral-angular distribution ofsuch radiation is obtained and analyzed, both for fully andpartially modulated beams. The intensity of Smith-Purcellradiation is shown to be able to increase both due to theperiodicity of the beam and the periodicity of the target.The numerical results prove that such radiation source canbe an effective instrument for different FEL users,supplementary for the main FEL source.