Smith–Purcell effect for angles of order γ−1 on the grating with spaced strips

The diffraction radiation (DR) has been considered at small emission angle in the optical and infrared region when a particle moves parallel and close to a conducting target consisting of the number of strips spaced by vacuum gaps. The maximum values of spectral–angular intensity distribution of DR is concentrated in the angular range comparable to γ −1 . The evolution of the spectral–angular distribution of DR intensity depending on the strip width and number of strips has been considered. The theoretical model to calculate the intensity of this radiation has been developed. On the basis of this model the spectra of resonant diffraction radiation (RDR) have been calculated for the Smith–Purcell geometry. The principal possibility of Smith–Purcell effect (SPE) experimental investigation in optical region has been shown. The comparison with undulator radiation (UR) has been carried out.