Characterization of spatial coherence of synchrotron radiation with non-redundant arrays of apertures (original) (raw)
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Comparison of Non-Redundant Array and Double Pinhole Coherence Measurements with Soft X-rays
2006
Experiments on the future Linac Coherent Light Source (LCLS) and other Free Electron Lasers will need to be performed on a single-shot basis. The double pinhole method of measuring spatial coherence requires a separate measurement, with a different pinhole separation distance, for each length scale sampled. This limits its utility for LCLS. A potential alternative uses a Non-Redundant Array (NRA) of apertures designed to probe the coherence over the range of length scales defined by their physical extent, in a single measurement. This approach was tested by comparing diffraction patterns from soft xrays incident on double pinhole and NRA absorption mask structures. The double pinhole fringe visibility data serve as discrete reference points that verify the continuous spectrum of the NRA coherence data. The results present a quantitative analysis of the double pinhole coherence measurements and a qualitative comparison to the NRA images.
Physical Review B, 2012
We report on the study of hard x-ray diffraction by slits from the Fresnel to the Fraunhofer regime. The dark spot, i.e., the position where a minimum of intensity is found in the center of the diffraction pattern, is clearly observed. By progressively tuning the degree of coherence of the incident beam, the effect of partial coherence on the diffraction patterns is studied. We show that the transverse coherence length can be deduced with a good accuracy from the visibility of fringes in the Fraunhofer regime. We also show that a good estimation of the transverse coherence length can be obtained from measurements in the Fresnel regime. The measurements are discussed in the framework of the Gaussian Schell-model. A high degree of coherence is reached at the sample position for a beam size of a few micrometers and allows high-quality coherence experiments.
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
Spatial coherence of synchrotron radiation
Recent Research Developments in Optics, vol.3, 2003
Theory and measurement of spatial coherence of synchrotron radiation beams are briefly reviewed. Emphasis is given to simple relationships between electron beam characteristics and far field properties of the light beam.
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.
Optics Express
We present a systematic 2D spatial-coherence analysis of the soft-X-ray beamline P04 at PETRA III for various beamline configurations. The influence of two different beam-defining apertures on the spatial coherence properties of the beam is discussed and optimal conditions for coherence-based experiments are found. A significant degradation of the spatial coherence in the vertical direction has been measured and sources of this degradation are identified and discussed. The Fourier-analysis method, which gives fast and simple access to the 2D spatial coherence function of the X-ray beam, is used for the experiment. Here, we exploit the charge scattering of a disordered nanodot sample allowing the use of arbitrary X-ray photon energies with this method.
Intensity interferometry of single x-ray pulses from a synchrotron storage ring
Physical review letters, 2014
We report on measurements of second-order intensity correlations at the high-brilliance storage ring PETRA III using a prototype of the newly developed adaptive gain integrating pixel detector. The detector records individual synchrotron radiation pulses with an x-ray photon energy of 14.4 keV and repetition rate of about 5 MHz. The second-order intensity correlation function is measured simultaneously at different spatial separations, which allows us to determine the transverse coherence length at these x-ray energies. The measured values are in a good agreement with theoretical simulations based on the Gaussian Schell model.
Measurement of the coherence of synchrotron radiation
Journal of Synchrotron Radiation, 1998
The ®rst-order spatial (transverse) coherence of synchrotron radiation has been measured using a Young's interferometer at BL28A (a helical-undulator beamline) of the Photon Factory, KEK. The range of the photon energy is about 70±180 eV. The visibility of the fringe was found to depend largely on the electron emittance and the intrinsic photon emittance. In principle, it is possible to gain knowledge of the very small electron emittance, of the order of 10 À10 m rad, without disturbing the electron beam in the storage ring.
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.