Forward diffracted parametric X radiation from a thick Tungsten single crystal at 855 MeV electron energy

Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 &mgr;m thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (101)[bar above final 1] plane at a Bragg angle of 3.977°. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward diffracted PXR may be employed to diagnose bending radii of lattice planes in large area single crystals.