Grating optical diffraction radiation - Promising technique for non-invasive beam diagnostics

Two simple approaches for evaluating the transversal beam size using a slit and a grating are presented. A model for calculating the resonant diffraction radiation (RDR) characteristics from grating consisting of perfectly conducting strips spaced by vacuum gaps is developed. The proposed model allows calculating the RDR characteristics for a beam passing through a big slit between two gratings. It is noted that quasimonochromatic maxima appear in the RDR spectral-angular distribution, whose position is determined by the grating's period and observation geometry. The peak shape depends on the beam parameters. Having measured the RDR angular distribution at a fixed wavelength, one may evaluate the beam size using simple formulas obtained.