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Description
The use of a temperature gradient in the study of the dynamical diffraction of a spherical X-ray wave in the Laue geometry is due to the fact that the atomic reflecting planes in the crystal are fan-shaped, which makes it possible to control the focusing process. It was shown in [1] that in the case of a short period superlattice a smooth change in the gradient value can focus different satellites on the exit surface of the crystal, which makes it possible to determine their structure factors.
In the present work, we consider the possibility of studying the internal structure of phase objects by dynamical diffraction of a spherical X-ray wave in a crystal using a temperature gradient. If, prior to the incidence on the crystal, X-ray radiation from a point source passes through the phase object, then it acquires an additional phase. As a result of refraction at phase object inhomogeneities, the direction of radiation and the curvature of the wave front change locally. The use of a temperature gradient directed perpendicular to the crystal surface makes it possible to obtain a focal distribution of all point inhomogeneities in the phase object on the exit surface of the crystal.
The measurement process consists of moving the phase object along the direction of the diffraction vector and finding the corresponding gradient values that ensure focusing of the diffracted wave on the exit surface of the crystal. In this case, the displacement step must be smaller than the focus width in order to find the narrowest and highest intensity peak on the exit surface of the crystal.
Based on the data obtained, it is possible to find the additional phase of the wave acquired in the phase object and restore the internal structure of the corresponding section of the phase object.
Reference
- L. Levonyan and H. Manukyan. ActaCryst. (2023), A79, 14-19.
