Analysis of illumination coherence properties in small-source systems such as synchrotrons (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.
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.
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.
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.
Coherence-enhanced synchrotron radiology: Refraction versus diffraction mechanisms
Journal of Applied Physics, 1999
Tests performed in different regimes reveal the interplay of two edge-enhancement mechanisms in radiological images taken with coherent synchrotron light. The relative weight of the two mechanisms, related to refraction and to Fresnel edge diffraction, can be changed in a controlled way. This makes it possible to obtain different images of the same object with complementary information.
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.
Coherence-enhanced synchrotron radiology: simple theory and practical applications
Journal of Physics D: Applied Physics, 2002
The advanced characteristics of synchrotron x-ray sources make it possible to implement radiology with powerful and innovative approaches. We review in simple terms the conceptual background of such approaches, then we present a number of selected examples. The practical tests concern life-sciences specimens as well as materials-science systems.
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.
Retrieving the complex degree of spatial coherence of electron beams
Optik, 2008
We discuss the applicability of a recently developed method for two-dimensionally retrieving the complex degree of spatial coherence of laser beams, in both amplitude and phase, to the case of the electron beam provided by the source of an electron microscope. Obtaining an electron beam with the highest possible coherence is critical for successful holography experiments. Therefore, the accurate measurement of the complex degree of spatial coherence is highly desirable. The method consists of the following three steps: recording of the beam spot, determining its centered-reduced moments and inserting them as coefficients of a series. This procedure is simple, fast and of higher performance than conventional procedures such Fourier analysis or Young interferometry. Experimental results are presented.
A Synchrotron-Based Fourier-Synthesis Custom-Coherence Illuminator
AIP Conference Proceedings, 2004
Scanning illumination systems provide for a powerful and flexible means for controlling illumination coherence properties. Here we present a synchrotron-based scanning-mirror Fourier synthesis illuminator that enables sources with intrinsically high spatial coherence, such as undulators, to be used in situations demanding less coherence. The application considered here involves microfield extreme ultraviolet (EUV) lithography, however, the same methods are applicable to conventional microscopy as well as coherence-imaging techniques. This flexible illuminator allows the coherence to be tuned in situ enabling the illumination to be tailored to the specific pattern being imaged. The effectiveness of the system is demonstrated through a variety of lithographic print experiments. These include the use of resolution enhancing coherence functions, which enable the printing of 50-nm line-space features using a lithographic optic with a NA of 0.1 and an operational wavelength of 13.4 nm. MOTIVATION Extreme ultraviolet (EUV) lithography 1 remains the top candidate for the technology to be used for the 32-nm generation of nano-electronics expected to enter volume production in 2009. Achieving this target requires early availability of systems capable of these resolutions and finer. Although not under serious consideration for manufacturing applications, synchrotron radiation provides a convenient well-characterized debris-free source ideal for such advanced research systems. The problem with synchrotron radiation, however, is the poor match between its intrinsic coherence properties and those required of a lithographic tool. Although particularly true for undulator radiation, 2 in practice, this statement also holds for bend-magnet radiation. The ultimate imaging performance of any optical system depends not only on the quality of the imaging optics, but also in large part on the coherence properties of the illumination. 3 Additionally, the ideal illumination is pattern specific, making controllable illumination coherence a valuable attribute to general-purpose imaging systems. 4 Here we describe a synchrotron-based scanning illumination system with programmable coherence. Moreover, these coherence control capabilities are achieved without scatter plates or source-shaping apertures, making the system very efficient. The implementation and specific motivation described here is related to synchrotron-based EUV lithography, however, the method is relevant to a much broader class of instruments and wavelengths. For example, the methods described here are also relevant to imaging microscopes working in virtually any wavelength range.