Diffraction in forward direction of parametric X-ray radiation from relativistic particles of moderate energy - art. no. 663418

The analytical expressions for the difference between the classical frequency of the parametric X-ray radiation (PXR) and the Bragg frequency in the PXR reflection are derived. The difference increases proportionally to the square of the angular distance to the PXR reflection center and also the Bragg frequency always exceeds the PXR one from the same system of crystallographic planes. A possibility of the existence of PXR diffraction from electrons of moderate energy to forward direction due to PXR peak broadening in a thin crystal and also in polycrystal or mosaic crystal is described. The experiment at accelerator for observation of PXR diffracted to forward direction in textured polycrystal or mosaic crystal is proposed. Application of PXR spectral peak broadening for measurement of thin crystal thickness, crystalline grains or domains size is proposed.