Smith-Purcell radiation from a ribbon beam as effective THz and X-ray source

We investigate the possibility to enhance the THz and X-ray sources based on interaction between an electron beam and a grating using a ribbon beam. Making the beam ribbon, we increase the area of effective interaction between the beam and the grating, which can lead to increasing the number of photons radiated through Smith-Purcell mechanism. The theory of this process is constructed; the fully analytical description is given; the numerical analysis shows that the radiation can be enhanced considerably with use of ribbon beams instead of cylindrical one in case when transversal part of coherent form-factor plays a role.