Measurement of the coherence of synchrotron radiation (original) (raw)
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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.
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.
Journal of Synchrotron Radiation, 1998
The lateral coherence length is of the order of 100 µm at the `long' (145 m) ID19 beamline of the ESRF, which is mainly devoted to imaging. Most of the optical elements located along the X-ray path can thus act as `phase objects', and lead to spurious contrast and/or to coherence degradation, which shows up as an enhanced effective angular size of the source. Both the spurious contrast and the coherence degradation are detrimental for the images (diffraction topographs, tomographs, phase-contrast images) produced at this beamline. The problems identified and the way they were solved during the commissioning of ID19 are reported. More particularly, the role of the protection foils located in the front end, the beryllium windows, the filters and the monochromator defects (scratches, dust, small vibrations) is discussed.
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.
SPIE Proceedings, 2014
A full wave propagation of X-rays from source to sample at a storage ring beamline requires simulation of the electron beam source and optical elements in the beamline. The finite emittance source causes the appearance of partial coherence in the wave field. Consequently, the wavefront cannot be treated exactly with fully coherent wave propagation or fully incoherent ray tracing. We have used the wavefront code Synchrotron Radiation Workshop (SRW) to perform partially coherent wavefront propagation using a parallel computing cluster at the Diamond Light Source. Measured mirror profiles have been used to correct the wavefront for surface errors.
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
Review of Scientific Instruments, 2000
Based upon a method of Hanbury-Brown and Twiss, while considering the nonstationary characteristics of synchrotron radiation ͑SR͒, a novel optical intensity interferometer was constructed to extract the true two-photon correlation of soft x-ray SR. This intensity interferometer consists of an optical vacuum chamber, which includes a wire scanner, a beam divider, and a grating monochromator with a coherence time modulator, and of an electric correlator which completes the multiplication of two broadband electric currents. The technique of coherence time modulation, together with the two bandpass filters in the correlator, play an essential role to cancel a huge trivial correlation, which arises from the accidental coincidence between a pair of divided pulses being largely enhanced by the finite slow time response of the detection system compared to the coherence time of the photon. A preliminary performance test was conducted, and the results exhibit satisfactory functions of this interferometer.
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.
Two-beam interference of long wavelength synchrotron radiation
2001
The synchrotron radiation emitted from the NSLS VUV ring is found to contain significant spectral structure at long wavelengths (λ > 0.5mm), suggesting multiple beam interference effects. A predominant pattern occurs as a result of direct radiation interfering with radiation reflected from the curved outer wall of the electron beam dipole chambers. This structure appears for both normal incoherent synchrotron radiation emission and coherent emission, the latter resulting from an instability-driven density modulation within the electron bunch