Microfocusing of Hard X-rays with Cylindrically Bent Crystal Monochromators

Abstract

High-energy X-ray focusing with bent-crystal monochromators is known to be hampered by so-called depth or crystal-thickness aberrations. A theoretical model of focus broadening based on the geometrical theory of X-ray diffraction in slightly deformed crystals is presented and compared with experimental data. First, it is shown that depth broadening can be avoided in the Laue geometry by an appropriate choice of asymmetry angle. Based on this finding, a monochromator for high-pressure diffraction experiments has been designed and a source-size-limited focal spot below 10 microns is observed. As a consequence of the box-shaped rocking curve of bent Laue crystals, the focus is free of long-ranging tails. Diffraction patterns of standard powder samples were recorded on imaging plates and a theoretical description of the energy-dispersion-related peak broadening is given. Finally, diffraction patterns of N2 at 180 kbar demonstrate the excellent data quality achievable with this monochromator.

Design of a 5-Station Macromolecular Crystallography Beamline at MAX-Lab

“…The outer di m ensions of the di am ond crysta l s wi l l be m m , and the crysta l s are bent m eri di ona l ly to pro vi de focusi ng i n the hori zonta l pl ane. Thi s techni que has previ ously b een used wi th sili con crysta l s [19]. Addi ti onal l y, the bendi ng i ncreases the accepted ba nd wi dth by a facto r two .…”

Three-energy focusing Laue monochromator for the diamond light source x-ray pair distribution function beamline I15-1

“…The crystals have been manufactured by Crystal Scientific (UK) Ltd (Alnwick, United Kingdom) and have been installed in a crystal cage assembly manufactured by FMB Oxford Ltd (Oxford, United Kingdom). The remaining parameters to be optimized were the asymmetry angle of the reflections and the crystal bending radius, which are determined by the two types of focusing in meridionally bent Laue crystals [1,2].…”

Fixed-exit monochromator for computed tomography with synchrotron radiation at energies 18–90 keV

“…T 2 = 2T 1 , in order to span the required energy band. However, the actual matching conditions are rather complex, and detailed calculations would be needed for each situation (Schulze et al, 1998). The present work focuses on the practical aspects of the monochromator construction, and identical crystals are used.…”

“…where s ij are the elastic compliances for a given crystal orientation and asymmetry angle (Schulze et al, 1998). The re¯ectivity curve can be calculated using the geometrical theory of diffraction from a deformed crystal (Penning & Polder, 1961;Kato, 1964;Schulze & Chapman, 1995).…”