Estimation of coherence properties of an undulator-generated x-ray beam from near-field and far-field slit diffraction visibilities (original) (raw)

Spatial coherence measurement of X-ray undulator radiation

Optics Communications, 2001

We measure the spatial coherence function of a quasi-monochromatic 1.1 keV X-ray beam from an undulator at a third-generation synchrotron. We use a Young's slit apparatus to measure the coherence function and ®nd that the coherence measured is poorer than expected. We show that this dierence may be attributed to the eects of speckle due to the beamline optics. The conditions for successful coherence transport are considered. Ó

Experimental characterization of X-ray transverse coherence in the presence of beam transport optics

Journal of Physics: Conference Series, 2013

A simple Boron fiber based interference scheme [1] and other similar schemes are currently routinely used for X-ray coherence estimation at 3rd generation synchrotron radiation sources. If such a scheme is applied after a perfect monochromator and without any focusing / transport optics in the optical path, the interpretation of the measured interference pattern is relatively straightforward and can be done in terms of the basic parameters of the source [2]. However, if the interference scheme is used after some focusing optics, e.g. close to the X-ray beam waist, the visibility of fringes can be significantly affected by the new shape of the focused beam phase-space. At the same time, optical element imperfections still have a negative impact on the transverse coherence. In such situations, which are frequently encountered in experiments at beamlines, the quantitative interpretation of a measured interference pattern is not straightforward. Here we show that this can nevertheless be done by using partially-coherent synchrotron radiation wavefront propagation simulations. The results obtained from measurements, performed at the 32-ID undulator beamline of the Advanced Photon Source, and wavefront propagation based simulations show, in particular, that new generation 1D Beryllium Compound Refractive Lenses do not reduce the X-ray transverse coherence in any significant manner.

Experimental characterization of the coherence properties of hard x-ray sources

Optics Express, 2011

The experimental characterization of the coherence properties of hard X-ray sources is reported and discussed. The source is described by its Mutual Optical Intensity (MOI). The coherent-mode decomposition is applied to the MOI described by a Gaussian-Schell model. The method allows for a direct, quantitative characterization of the degree of coherence of both synchrotron and laboratory sources. The latter represents the first example of characterizing a low coherence hard x-ray source.

Shearing Interferometer for Quantifying the Coherence of Hard X-Ray Beams

Physical Review Letters, 2005

We report a quantitative measurement of the full transverse coherence function of the 14.4 keV x-ray radiation produced by an undulator at the Swiss Light Source. An x-ray grating interferometer consisting of a beam splitter phase grating and an analyzer amplitude grating has been used to measure the degree of coherence as a function of the beam separation out to 30 m. Importantly, the technique provides a model-free and spatially resolved measurement of the complex coherence function and is not restricted to high resolution detectors and small fields of view. The spatial characterization of the wave front has important applications in discovering localized defects in beam line optics.

Focus on X-ray beams with high coherence

New Journal of Physics, 2010

This editorial serves as the preface to a special issue of New Journal of Physics, which collects together solicited papers on a common subject, x-ray beams with high coherence. We summarize the issue's content, and explain why there is so much current interest both in the sources themselves and in the applications to the study of the structure of matter and its fluctuations (both spontaneous and driven). As this collection demonstrates, the field brings together accelerator physics in the design of new sources, particle physics in the design of detectors, and chemical and materials scientists who make use of the coherent beams produced.

Development of new apertures for coherent X-ray experiments

Journal of Synchrotron Radiation, 2009

When one performs a coherent small-angle X-ray scattering experiment, the incident beam must be spatially filtered by slits on a length scale smaller than the transverse coherence length of the source which is typically around 10 mm. The Fraunhofer diffraction pattern of the slit is one of the important sources of background in these experiments. New slits which minimize this parasitic background have been designed and tested. The slit configuration apodizes the beam by the use of partially transmitting inclined slit jaws. A model is presented which predicts that the high wavevector tails of the diffraction pattern fall as the inverse fourth power of the wavevector instead of the inverse second power that is observed for standard slits. Using cleaved GaAs single-crystal edges, Fraunhofer diffraction patterns from 3 and 5.5 keV X-rays were measured, in agreement with the theoretical model proposed. A novel phase-peak diffraction pattern associated with phase variations of the transmitted electric field was also observed. The model proposed adequately accounts for this phenomenon.

Influence of the transverse and longitudinal coherence in the dynamical theory of x-ray diffraction

Journal of Physics D: Applied Physics, 1999

We investigate dynamical diffraction phenomena of a quasi-monochromatic x-ray beam emitted by a small source at a large distance from the sample. Under certain conditions of coherence the diffraction intensity profile in a recording plane reproduces the angular profile of the rocking curve of the crystal. The coherence requirements are stronger for thicker crystals. This has been verified in experiments

Diffraction imaging: The limits of partial coherence

Physical Review B, 2012

Coherent diffraction imaging (CDI) typically requires that the source should be highly coherent both laterally and longitudinally. In this paper, we demonstrate that lateral and longitudinal partial coherence can be successfully included in a CDI reconstruction algorithm simultaneously using experimental x-ray data. We study the interplay between lateral partial coherence and longitudinal partial coherence and their relative influence on CDI. We compare our results against the coherence criteria published by Spence et al. [Spence et al., Ultramicroscopy 101, 149 (2004)] and show that for iterative ab initio phase-recovery algorithms based on those typically used in CDI and in cases where the coherence properties are known, we are able to relax the minimal coherence requirements by a factor of 2 both laterally and longitudinally, potentially yielding significant reduction in exposure time.

Spatial coherence characterization of undulator radiation

Optics Communications, 2000

The coherence properties of undulator radiation at extreme ultraviolet EUV wavelengths are measured using the Thompson-Wolf two-pinhole method. The effects of asymmetric source size and beamline apertures are observed. High spatial coherence EUV radiation is demonstrated. Projection of these same capabilities to the x-ray region is straightforward.