  The spectral and angular properties of diffracted transition radiation (DTR)
and parametric radiation (PXR) in the ultrasoft X-ray region generated by the
periodic structure upon interaction with a relativistic electron beam with
energy of 5.7 MeV are numerically studied using a sample of the periodic
structure [Mo/Si]50, known as a multilayer X-ray mirror. Based on calculations,
an experimental approach is proposed to separate and identify the contributions
of PXR and DTR. The ultrasoft X-ray radiation can be used to eliminate coherent
effects occurring in the optical range when diagnosing the submicron electron
beam size.
