Partial coherence and imperfect optics at a synchrotron radiation source modeled by wavefront propagation (original) (raw)
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Wavefront propagation simulations for beamlines and experiments with "Synchrotron Radiation Workshop
Journal of Physics: Conference Series, 2013
An overview of the basic principles, the approach to fully-and partially-coherent synchrotron radiation wavefront propagation simulations, implemented in the "Synchrotron Radiation Workshop" (SRW) computer code, and simulation examples for different types of sources, including undulator and wiggler, different beamlines and experiments, are presented. Recent developments, such as the support of parallel calculations, which considerably increase the efficiency of partially-coherent wavefront propagation calculations, are described.
Journal of synchrotron radiation, 2014
X-ray beamlines in modern synchrotron radiation sources make extensive use of grazing-incidence reflective optics, in particular Kirkpatrick-Baez elliptical mirror systems. These systems can focus the incoming X-rays down to nanometer-scale spot sizes while maintaining relatively large acceptance apertures and high flux in the focused radiation spots. In low-emittance storage rings and in free-electron lasers such systems are used with partially or even nearly fully coherent X-ray beams and often target diffraction-limited resolution. Therefore, their accurate simulation and modeling has to be performed within the framework of wave optics. Here the implementation and benchmarking of a wave-optics method for the simulation of grazing-incidence mirrors based on the local stationary-phase approximation or, in other words, the local propagation of the radiation electric field along geometrical rays, is described. The proposed method is CPU-efficient and fully compatible with the numeric...
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.
Analysis of illumination coherence properties in small-source systems such as synchrotrons
Applied Optics, 2002
Modern synchrotron beamlines often take the form of critical illumination systems, where an incoherent source of limited spatial extent is re-imaged to an experimental plane of interest. Unique constraints of synchrotron sources and beamlines, however, may preclude the use of the simple Zernike approximation for calculating the object-image coherence relationship. Here, we perform a rigorous analysis of the object-image coherence relationship valid for synchrotron beamlines. The analysis shows that beamline aberrations have an effect on the coherence properties. Effects of various low-order aberrations on the coherence properties are explicitly studied.
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.
Journal of Synchrotron Radiation, 2014
A new method for beamline simulation combining ray-tracing and wavefront propagation is described. The 'Hybrid Method' computes diffraction effects when the beam is clipped by an aperture or mirror length and can also simulate the effect of figure errors in the optical elements when diffraction is present. The effect of different spatial frequencies of figure errors on the image is compared with SHADOW results pointing to the limitations of the latter. The code has been benchmarked against the multi-electron version of SRW in one dimension to show its validity in the case of fully, partially and non-coherent beams. The results demonstrate that the code is considerably faster than the multi-electron version of SRW and is therefore a useful tool for beamline design and optimization.
AIP Conference Proceedings, 2016
An aberration calculation method which was developed by Lu [1] can treat individual aberration term precisely. Spectral aberration is the linear sum of these aberration terms, and the aberrations of multi-element systems also can be calculated correctly when the stretching ratio, defined herein, is unity. Evaluation of focusing mirror-grating systems which are optimized according to Lu's method, along with the Light Path Function (LPF) and the Spot Diagram method (SD) are discussed to confirm the advantage of Lu's methodology. Lu's aberration terms are derived from a precise wave-front treatment, whereas the terms of the power series expansion of the light path function do not yield an accurate sum of the aberrations. Moreover, Lu's aberration terms can be individually optimized. This is not possible with the analytical spot diagram formulae.
Physical Review Special Topics - Accelerators and Beams, 2014
For the European x-ray free electron laser (XFEL) a split-and-delay unit based on geometrical wavefront beam splitting and multilayer mirrors is built which covers the range of photon energies from 5 keV up to 20 keV. Maximum delays between Δτ ¼ AE2.5 ps at hν ¼ 20 keV and up to Δτ ¼ AE23 ps at hν ¼ 5 keV will be possible. Time-dependent wave-optics simulations have been performed by means of Synchrotron Radiation Workshop software for XFEL pulses at hν ¼ 5 keV. The XFEL radiation was simulated using results of time-dependent simulations applying the self-amplified spontaneous emission code FAST. Main features of the optical layout, including diffraction on the beam splitter edge and optics imperfections measured with a nanometer optic component measuring machine slope measuring profiler, were taken into account. The impact of these effects on the characterization of the temporal properties of XFEL pulses is analyzed. An approach based on fast Fourier transformation allows for the evaluation of the temporal coherence despite large wavefront distortions caused by the optics imperfections. In this way, the fringes resulting from time-dependent two-beam interference can be filtered and evaluated yielding a coherence time of τ c ¼ 0.187 fs (HWHM) for real, nonperfect mirrors, while for ideal mirrors a coherence time of τ c ¼ 0.191 fs (HWHM) is expected.
Journal of Synchrotron Radiation, 2014
We present a method to characterize the spatial coherence of soft X-ray radiation from a single diffraction pattern. The technique is based on scattering from non-redundant arrays (NRA) of slits and records the degree of spatial coherence at several relative separations from one to 15 microns, simultaneously. Using NRAs we measured the transverse coherence of the X-ray beam at the XUV X-ray beamline P04 of the PETRA III synchrotron storage ring as a function of different beam parameters. To verify the results obtained with the NRAs additional Young's double pinhole experiments were conducted and show good agreement.