Diffraction of virtual and real photons

Parametric X-ray radiation associated with the diffraction of virtual photons and the diffraction of X-rays described as the diffraction of real photons are studied experimentally. The diffracted radiation was generated by a 7 MeV beam of electrons and an X-ray tube respectively. Both diffraction mechanisms occur in a tungsten powder. The processes have been compared excluding three key parameters: the attenuation in the target, the background of the diffracted signal and the spectrum of the incident radiation. Remarkable differences between the diffraction mechanisms of virtual and real photons are observed. The ratio between the PXR peak and the XRD peak decreases when the peak energy increases.