Sagittal focusing inducing energy structure in medium to high energy resolution x-ray monochromators

Sagittal focusing is a widely used geometry to horizontally focus X-rays in synchrotron beamlines. Usually, two types of devices are used: toroidal mirrors combined with flat X-ray monochromators or flat mirrors combined with sagittal focusing monochromators. The former option seems to be better since the stresses caused by the bending of the second crystal in a double crystal monochromator (DCM) are avoided. In this work we explore the effect of sagittal focusing in medium to high energy resolution X-ray monochromators. Our studies are based on a theoretical explanation of experimental data acquired in two different experiments performed at the XRD2 beamline at Laboratorio Nacional de Luz Sincrotron (LNLS / Brazilian Synchrotron) and X18A at the National Synchrotron Light Source (NSLS / BNL / USA). The first experiment was carried out with a flat meridional bendable mirror followed by a DCM with the second crystal being sagitally bent. The second experiment was carried out with a flat Si 111 DCM followed by a toroidal, but meridional bendable mirror. Both setups are completed by a Si 551 4-bounce monochromator to scan the energy spectrum around 13.7 keV and 13.9 keV, respectively. The results show that the sagittal curvature induces an energy structure. Theoretical studies made by analyzing the reflecting angles in the mirror surface joined with the dynamical theory of X-ray diffraction in the 4-bounce X-ray monochromators confirm these results, which are also explored by the DuMond diagram.

[1]  P. Eng,et al.  Construction and performance of a bent crystal x‐ray monochromator , 1993 .

[2]  B. Lengeler,et al.  Focusing high-energy x rays by compound refractive lenses. , 1998, Applied optics.

[3]  Jesse W. M. DuMond,et al.  Theory of the Use of More Than Two Successive X-Ray Crystal Reflections to Obtain Increased Resolving Power , 1937 .

[4]  V. Jain,et al.  ABRASIVE-BASED NANO-FINISHING TECHNIQUES: AN OVERVIEW , 2008 .

[5]  R. Neuenschwander,et al.  High-resolution X-ray diffraction beamline at the LNLS for the study of charge, orbital and magnetic structures. , 2003, Journal of synchrotron radiation.

[6]  Augusto Marcelli,et al.  Waviness effects in ray-tracing of “real” optical surfaces , 1992 .

[7]  H. C. Kang,et al.  Nanometer linear focusing of hard x rays by a multilayer Laue lens. , 2006, Physical review letters.

[8]  Konstantine Kaznatcheev,et al.  Synchrotron X-ray tests of an L-shaped laterally graded multilayer mirror for the analyzer system of the ultra-high-resolution IXS spectrometer at NSLS-II. , 2011, Journal of synchrotron radiation.

[9]  S. Wilkins,et al.  Phase-contrast imaging using polychromatic hard X-rays , 1996, Nature.

[10]  Hans M. Hertz,et al.  Phase-contrast x-ray imaging with a liquid-metal-jet-anode microfocus source , 2007 .

[11]  S. Jacobs,et al.  Model of Magnetorheological Finishing , 1996 .

[12]  A. Authier.  Dynamical theory of x-ray diffraction , 2001 .

[13]  C. J. Sparks,et al.  X-ray monochromator geometry for focusing synchrotron radiation above 10 keV , 1980 .

[14]  C. N. Kodituwakku,et al.  Tracing X-rays through an L-shaped laterally graded multilayer mirror: a synchrotron application. , 2010, Journal of synchrotron radiation.

[15]  D. Keith Bowen,et al.  Characterization of crystal growth defects by X-ray methods : [proceedings of NATO Advanced Study Institute on Characterization of Crystal Growth Defects by X-ray Methods, held August 29-September 10, 1979, at Durham University, Durham, United Kingdom] , 1980 .

[16]  Mary Halliwell,et al.  Characterization of Crystal Growth Defects by X-ray Methods , 1981 .

[17]  O. Mitomi,et al.  Influence of fabrication errors on wölter mirror imaging performance. , 1998, Applied optics.

[18]  A. Takeuchi,et al.  X-ray imaging microscopy at 25keV with Fresnel zone plate optics , 2001 .