Monolithic two-dimensional beam compressor for hard x-ray beams

Abstract

Using asymmetric diffraction in grazing incidence or in grazing emergence it is possible to expand or compress an x-ray beam in one dimension. Combining two asymmetric diffractions with non-coplanar planes of diffraction it is possible to obtain two-dimensional beam expansion or compression. This paper reports on a monolithic two-dimensional x-ray beam compressor consisting of two non-coplanar asymmetrically inclined {311} diffractors prepared in one silicon crystal block and tested at Optics beamline BM05 at ESRF, Grenoble. The design of the x-ray beam compressor, the results of beam tracing image simulation, the experimental arrangement used for testing and the properties of the x-ray microbeams formed are presented. For the beam energy of 9.5 keV 10- and 13-times beam compression in two directions was observed. Using a metal grid in the incident beam more than 400 microbeams smaller than 10 µm and separated by less than 5 µm were obtained in the outgoing beam. A gain of up to 100 times in intensity per unit area was obtained in comparison with the x-ray beam magnifier geometry, demonstrating a real two-dimensional beam compression.

Aberrations of diffractive–refractive optics: Bragg-case sagittal focusing of multiple parabolic elements

“…This simplification may introduce some inaccuracy in the focus simulation. In this paper, we have applied a ray-tracing simulation [10] which is based on the exact theoretical description of diffraction according to the processes in inclined non-coplanar geometry, that has to be solved in the framework of a generalized dynamical diffraction theory [14]. In summary, we apply dynamical diffraction theory in the two-beam approximation, where the exact shape of the dispersion surface of the 4th order and exact boundary conditions for a crystal with arbitrarily oriented locally flat surface are considered.…”

“…This aberration is discussed analytically by using a new (more precise) formula for calculating the focusing distance, which respects the finite distance between sequential optical elements. Second, the achievable focus size will be calculated by a ray-tracing simulation method based on the dynamical theory of x-ray diffraction [10,11]. Finally, we propose a way to suppress the aberration with a slight correction to the parabolic profile.…”

Towards high-flux X-ray beam compressing channel-cut monochromators

“…The refraction effect reduces considerably the overlap of the rocking curves of the two diffractors (channel walls) and the output photon flux when the total compression (expansion) factor m = m 1 Â m 2 exceeds 10. Several solutions of this problem have been proposed (Servidori, 2002;Koryta ´r et al, 2010;A ´c ˇet al, 2010) and tested in the beam expansion mode for X-ray imaging (Koryta ´r et al, 2005;Ferrari et al, 2011;Vagovic ˇet al, 2013Vagovic ˇet al, , 2015. Here, the expansion of the beam after it has passed through an object reduces the apparent pixel size of a two-dimensional detector, enhancing the resolution of the object image.…”