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14,104 items found (0 items not approved), displaying 13,931 to 13,940.[First/Prev] 1,390, 1,391, 1,392, 1,393, 1,394, 1,395, 1,396, 1,397 [Next/Last]

Instruments / Technical Area	Publication Details	Published
Optics	Using the Power Spectral Density method to characterise the surface topography of optical surfaces Simon Alcock , Geoff Ludbrook SPIE: Advances in Metrology for X-Ray and EUV Optics III DOI: 10.1117/12.861539 Show Abstract ▼ Abstract: Power Spectral Density (PSD) is an alternative method for specifying optical surfaces, and quantifies the contribution of each spatial regime to the total surface error. This approach naturally includes mid-range spatial frequency errors, which are often overlooked. The PSD method has recently been adopted by the Space and Astronomy industries, but has not yet received general acceptance within the synchrotron community. To assess the suitability for specifying synchrotron optics using PSD, Fast Fourier Transforms were performed on topography data from a range of optical surfaces of varying quality and manufacturing techniques. For each grade of optic, the entire regime (~100nm to ~50mm) of surface errors was measured, with overlapping bandwidths, using a micro-interferometer and a Fizeau interferometer. From this heuristic information, root-mean square "roughness" can be predicted over any desired spatial range, thus allowing direct comparison of metrology data obtained by instruments with different spatial bandwidths. We present an efficient approach for calculating 1-D and 2-D PSDs using MATLAB algorithms, and discuss analysis considerations, including "field of view" effects and instrument calibration.	Aug 2010
Optics	High efficiency nano-focusing kinoform optics for synchrotron radiation L. Alianelli , K. J. S. Sawhney , R. Barrett , I. Pape , A. Malik , M. C. Wilson Optics Express DOI: 10.1364/OE.19.011120 PMID: 21716341 Open Access Show Abstract ▼ Abstract: Modern synchrotron sources have provided for decades intense beams of photons over a large energy spectrum. The availability of improved optics and detectors has opened up new opportunities for the study of matter at the micrometre and nanometre scale in many disciplines. Whilst exploitation of micro-focused beams occurs almost daily in many beamlines, the production of beams of 100 nm is achieved on few instruments which use specialised optics. Refractive lenses, zone plates, curved mirrors, multilayers, and multilayer Laue lenses, can all focus x-rays to less than 50 nm under strict beam stability conditions. Focusing the synchrotron radiation to beam sizes smaller than 10 nm is considered the ultimate goal for the current decade. Silicon micro-technology has so far provided some of the most advanced x-ray refractive lenses; we report on design and characterisation of a novel silicon kinoform lens that is capable of delivering nano-beams with high efficiency	May 2011
Optics	ACTOP11: Fourth Workshop on Adaptive and Active X-ray & XUV Optics Kawal Sawhney , Simon Alcock Synchrotron Radiation News 24, 6 - 9 ACTOP11: Fourth Workshop on Adaptive and Active X-ray & XUV Optics DOI: 10.1080/08940886.2011.601999 Show Abstract ▼ Abstract: The fourth international workshop on Adaptive and Active X-ray & XUV Optics (ACTOP11) was held on April 4-5, 2011, at Diamond Light Source in Oxfordshire, UK. This workshop follows on from earlier, successful active optic events at SOLEIL (2006), Elettra (2008), and Osaka (2009).	Aug 2011
Optics	Automated in-situ optimization of bimorph mirrors at Diamond Light Source John Sutter , Simon Alcock , Kawal Sawhney Advances in X-Ray/EUV Optics and Components VI DOI: 10.1117/12.892719 Show Abstract ▼ Abstract: Bimorph mirrors are used on many synchrotron beamlines to focus or collimate light. They are highly adaptable because not only their overall figure but also their local slope errors can be corrected. However, the optimization procedure is complex. At Diamond Light Source, highly repeatable and accurate pencil beam measurements are used to determine a mirror's slope errors. These data are then used by automated scripts to calculate the necessary corrections. This procedure may be applied to any type of active mirror, but for hard X-ray mirrors, diffraction from the slits must be considered.	Sep 2011
Optics	X-ray wavefront modeling of Bragg diffraction from crystals John Sutter Proc Spie Advances in Computational Methods for X-Ray Optics II DOI: 10.1117/12.892697 Show Abstract ▼ Abstract: The diffraction of an X-ray wavefront from a slightly distorted crystal can be modeled by the Takagi-Taupin theory, an extension of the well-known dynamical diffraction theory for perfect crystals. Maxwell's equations applied to a perturbed periodic medium yield two coupled differential equations in the incident and diffracted amplitude. These equations are discretized for numerical calculation into the determination of the two amplitudes on the points of an integration mesh, beginning with the incident amplitudes at the crystal's top surface. The result is a set of diffracted amplitudes on the top surface (in the Bragg geometry) or the bottom surface (in the Laue geometry), forming a wavefront that in turn can be propagated through free space using the Fresnel- Huygens equations. The performance of the Diamond Light Source I20 dispersive spectrometer has here been simulated using this method. Methods are shown for transforming displacements calculated by finite element analysis into local lattice distortions, and for efficiently performing 3-D linear interpolations from these onto the Takagi-Taupin integration mesh, allowing this method to be extended to crystals under thermal load or novel mechanical bender designs.	Sep 2011
Optics	Aspherical lens shapes for focusing synchrotron beams Manuel Sanchez Del Rio , Lucia Alianelli Journal Of Synchrotron Radiation 19 DOI: 10.1107/S0909049512003020 PMID: 22514171 Show Abstract ▼ Abstract: Aspherical surfaces required for focusing collimated and divergent synchrotron beams using a single refractive element (lens) are reviewed. The Cartesian oval, a lens shape that produces perfect point-to-point focusing for monochromatic radiation, is studied in the context of X-ray beamlines. Optical surfaces that approximate ideal shapes are compared. Results are supported by ray-tracing simulations. Elliptical lenses, rather than parabolic, are preferred for nanofocusing X-rays because of the higher peak and lower tails in the intensity distribution. Cartesian ovals will improve the gain when using high-demagnification lenses of high numerical aperture.	May 2012
Optics	Diamond beamline I24: a flexible instrument for macromolecular micro-crystallography Gwyndaf Evans , Lucia Alianelli , M. Burt , Armin Wagner , Kawal Sawhney Aip Conference Proceedings 879 (836), 836-839 DOI: 10.1063/1.2436190 Show Abstract ▼ Abstract: The I24 beamline is dedicated to the measurement of diffraction data from micro-crystals of macromolecules. The optical design gives high versatility in selecting the beam size at the sample and at the detector through the use of two pairs of Kirkpatrick-Baez arranged mirrors. The end-station is similarly designed to allow the optimization of the final signal-to-noise ratio of the diffraction measurements. The layout and key properties of the optics and end-station components are presented.	Jan 2007
Optics	Measurement and analysis of active synchrotron mirrors under operating conditions John P. Sutter , Simon Alcock , Kawal Sawhney Nuclear Instruments And Methods In Physics Research Section A: Accelerators, Spectrometers, Detectors And Associated Equipment 710, 72–77 4th International Workshop on Metrology for X-ray Optics, Mirror Design and Fabrication DOI: 10.1016/j.nima.2012.10.115 Show Abstract ▼ Abstract: At the Diamond Light Source, in situ slope error measurements using the pencil-beam method have enabled X-ray mirror surfaces to be examined in their beamline environment. A surface corrugation common to several bimorph mirrors and the removal of that corrugation by repolishing were both confirmed using this method. In the same way, mirrors curved in a controlled way with bending actuators and sag compensators could also be optimized. Fits to the elastic bending of ideal beams using the Euler–Bernoulli model have been performed on the slope errors of a mechanically bent mirror in order to distinguish bender curvatures from gravitational distortion and to calculate the compensating force that most reduces the latter effect. A successful improvement of the sag compensation mechanism of a vertically focusing mirror was also achieved, aided by a previously tested method for optimizing the settings of a mirror's actuators using pencil-beam scans.	Nov 2012
Optics	Hybrid diamond-silicon angular-dispersive x-ray monochromator with 025-meV energy bandwidth and high spectral efficiency S. Stoupin , Y. V. Shvydko , D. Shu , V. D. Blank , S. A. Terentyev , S. N. Polyakov , M. S. Kuznetsov , I. Lemesh , Kiran Mundboth , Steve Collins , John Sutter , Martin Tolkiehn Optics Express 21 (25), 5518-5529 DOI: 10.1364/OE.21.030932 PMID: 24514666 Open Access Show Abstract ▼ Abstract: We report on the design, implementation, and performance of an x-ray monochromator with ultra-high energy resolution (ΔE/E ≃ 2.7 × 10−8) and high spectral efficiency using x rays with photon energies E ≃ 9.13 keV. The operating principle of the monochromator is based on the phenomenon of angular dispersion in Bragg back-diffraction. The optical scheme of the monochromator is a modification of a scheme reported earlier [Shvyd’ko et al., Phys. Rev. A 84, 053823 (2011)], WHERE a collimator/wavelength selector Si crystal was replaced with a 100-μm-thick type IIa diamond crystal. This modification provides a very-small-energy bandwidth ΔE ≃ 0.25 meV, a 3-fold increase in the aperture of the accepted beam, a reduction in the cumulative angular dispersion rate of x rays emanating from the monochromator for better focusing on a sample, a sufficient angular acceptance matching the angular divergence of an undulator source (≈ 10 μrad), and an improved throughput due to low x-ray absorption in the thin diamond crystal. The measured spectral efficiency of the monochromator was ≈ 65% with an aperture of 0.3 × 1 mm2. The performance parameters of the monochromator are suitable for inelastic x-ray spectroscopy with an absolute energy resolution ΔE < 1 meV.	Dec 2013
Optics	Optomechanical Design of a Multilayer Laue Lens Test Bed for 10-nm Focusing of Hard X-rays Deming Shu , Evgeny Nazaretski , Jungdae Kim , Hanfei Yan , Kenneth Lauer , Brian Mullany , Dennis Kuhne , Jörg Maser , Yong Chu 11th International Conference on X-ray Microscopy (XRM2012) DOI: 10.1088/1742-6596/463/1/012029 Show Abstract ▼ Abstract: A multilayer Laue lens (MLL) test bed was designed at the Argonne National Laboratory for the National Synchrotron Light Source-II (NSLS-II) project at Brookhaven National Laboratory. Argonne and Brookhaven scientists and engineers collaborated to carry out this work in order to achieve NSLS-II's R&D goals of 10-nm focusing of hard x-rays. The test-bed design was based on the experience gained from the Argonne nanopositioning system designed for the CNM/APS hard x-ray nanoprobe project and an MLL test bed at Advanced Photon Source (APS) beamline 26-ID [1-3]. Optomechanical design of the MLL test bed, as well as the preliminary test results for the alignment apparatus and sample base stages' mechanical vibration performances are presented in this paper	Oct 2013

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