The Borrmann effect in parametric X-radiation under asymmetric reflection conditions

Parametric X-radiation (PXR) of a relativistic electron traversing a single crystal plate is considered in Laue geometry. The expressions describing spectral–angular distributions of PXR formed on the atomic planes situated under arbitrary angle δ to surface of the plate (asymmetric reflection) obtained on basis of two-wave approximation of dynamic diffraction theory are used for definition of the conditions of the most pronounced manifestation of the Borrmann effect (optimal value of angle δ) are clarified. This effect leads to considerable increase of the intensity of the quasi-monochromatic tuning source of coherent X-radiation built on basis of PXR.