The X-ray beam expander for advanced synchrotron sources based on Si planar compound parabolic refractive lenses (CRLs) with aperture of 10 micron was considered. The lenses were fabricated by using MEMS technologies including a lithography and a deep silicon etching for CRLs pattern generation in the hard mask and the pattern transfer into silicon wafer down to 40 μm, respectively. To minimize an influence of the manufacturing errors on the CRLs optical properties special control and metrology of the geometrical parameters of the lenses were proposed and applied. The errors influence on the X-ray beam expander parameters was considered theoretically and the related computer simulations were performed.
The X-ray planar compound refractive lenses (CRLs) made of monocrystalline silicon by a lithography and plasma deep Si etching (Bosch process) were considered. The CRL is a planar structure of biconcave parabolic refractive surfaces etched into silicon wafers down to 70 μm. The geometrical parameters of the parabolic lens structures were measured by different SEM-based methods and compared with CAD data. The influence of the manufacturing errors on the CRLs optical properties was discussed. The approaches for the improvement of the lens manufacturing techniques were proposed.
The optical system consisting of X-ray refractive axicon lenses and traditional parabolic lenses is considered. Such lenses combination makes it possible to flexibly adjust the size of the focused ring-shaped beam produced by axicons changing their number in the optical system. It was theoretically shown that the considered lens system is analogous to the X-ray refractive parabolic axicon. The axicons were made from polycrystalline aluminum by a pressing technique. The optical properties of the presented beam-shaping lens have been experimentally tested at the European Synchrotron Radiation Facility (ESRF). The obtained results are fully consistent with theoretical calculations. Additionally, the numerical experiment was carried out to demonstrate the influence of the axial symmetry of the optical scheme as a whole and axicons conical shape distortion on the focused annular beam. Future possible applications of the axicon are discussed.
Recently we demonstrated the phase-sensitive X-ray imaging technique based on the bilens interferometer. The essence of the method consisted of scanning a sample, which was set upstream of the bilens across the beam of one lens of the bilens, and recording changes in the interference pattern. This optical scheme involves fine-tuning the position of the sample on the optical axis, while a small deviation can lead to some distortion of its reconstructed phase profile. In this work, the advanced optical layout is considered. Knowing that the bilens generate two diffraction-limited focal spots, the sample can be placed in the focal plane of the bilens CRLs. In this case, the small size of the focused beams provides excellent phase sensitivity and high spatial resolution allowing to avoid possible distortions of the phase profile completely. The capabilities of both optical schemes were studied theoretically and experimentally.
A novel interferometric approach where the X-ray amplitude splitting interferometer based on the compound refractive lens was used to visualization of thin layers with a thickness of several nanometers applied to the surface of the membrane. The functional capabilities of the proposed technique were theoretically studied and experimentally demonstrated on the example of the gold strip 8 nm thick deposited on the 1000 nm Si3N4 membrane. The corresponding numerical simulations were performed. It was shown that the interference pattern is very sensitive to small thickness deviations of the gold layer, resulting in the ability to accurately determine not only its average thickness but also to reconstruct its cross-section profile with a nanometer resolution.
We are proposing an X-ray reflecto-interferometry technique using an x-ray microfocus laboratory source for thin-film structure research based on compound refractive lenses. The idea of this technique is to use a very simplified experimental setup where a focused X-ray beam reflected from parallel flat surfaces creates an interference pattern in a wide angular range. Due to this, the interference pattern can be obtained in a single shot without the need to rotate the specimen or the detector. The applicability of this technique has been demonstrated using the MetalJet Excillium microfocus laboratory source, which has GaKα emission line at 9.25 keV. A series of interference patterns for Si3N4 membranes and the experimentally obtained film thickness are in good agreement with the declared characteristics. The main advantages and future possible of the reflecto-interferometry technique are discussed.
The requirement for the high-quality optics for the 4th generation synchrotrons is becoming particularly urgent nowadays. We present a laboratory complex “SynchrotronLike” designed for the X-ray optics tests and development of the X-ray optical techniques before their use on the synchrotron sources. This complex consists of four main parts: 1) microfocus Xray source MetalJet D2+ 70kV, 2) detector module that contains X-ray spectrometer and three X-ray cameras with different resolution and field of view, 3) Micro-Optics Test Bench for X-ray optics tests and development of the X-ray optical techniques, 4) X-ray Single Crystal Diagnostics Endstation for the X-ray diffraction microscopy experiments. This complex was successfully used for the preliminary tests of the X-ray refractive lenses made from polymer, epoxy, and diamond. Moreover, the ultracompact X-ray transfocators, diamond monochromators, and beam-splitters for the 4th generation synchrotron sources were also tested on the “SynchrotronLike”. The unique parameters of our laboratory source, such as high brightness and high beam coherency make it possible to implement versatile experimental synchrotron techniques. Consequently, we managed to get excellent results in the X-ray reflecto-interferometry and X-ray microradian diffraction. The results of the latter technique are presented in this paper.
A new X-ray Reflecto-Interferometry (XRI) technique is proposed and realized for thin-film characterization. The XRI employs refractive optics that produce a converging fan of radiation, incident onto a sample surface, and a high-resolution CCD detector, which simultaneously collects the reflecto-interferogram over a wide angular range. The functional capabilities of the new method were experimentally tested at the ESRF ID06, and ID10 beamlines in the X-ray energy range from 14 keV to 22 keV. The free-standing Si3N4 membranes with different thickness were studied. The main advantages and possible future applications of the proposed reflecto-interferometry are discussed.
We present a study of optical properties of the bilens interferometer, where there is a space (Si bulk volume) between two compound refractive lenses (CRL). This design was proposed by analogy with the well-known Billiet bilens for the visible light. It was experimentally shown that under the conditions of partial absorption of X-ray radiation by the bilens, the generated interference pattern has a double period for several central fringes instead of pattern with a constant period. It was shown by computer simulation of such peculiar interference patterns that this phenomena is due to the additional interference between the rays focused by bilens and rays transmitted through the Si material between lenses in bilens. This fact encourages us to propose a new design for bilens and multilens interferometers, in which there is no spacing between CRLs. The proposed design is the lens arrays in the interferometer are arranged in a chessboard pattern, i. e. the arrays are shifted relative to each other by the distance equal to half-length of the single lens.
The optical system consisting of an X-ray parabolic axicon and traditional parabolic refractive lenses is considered. Such lenses combination makes it possible to flexibly adjust the size of the focused ring-shaped beam produced by axicon changing the number of the parabolic lenses in the optical system. The optical properties of the presented beam-shaping lens have been studied theoretically and experimentally tested. Based on the complex optical function of the lens a new approach to the phase-contrast imaging which takes advantage of the traditional X-ray microscopy and the unique optical properties of the parabolic refractive axicon was presented. Additionally, the computer simulation approach based on a Fast Fourier Transform wave optics computation was described as well as the corresponded numerical calculations of the considered optical transformations were performed. The simulation results are in good agreement with experimental ones.
2D parabolic X-ray compound refractive lens was manufactured by laser micro-machining of a single-crystal diamond.
The lens consists of parabolic half lenses with apertures of 1 mm and parabola apex radii of 200 μm. It has been tested at
the synchrotron undulator source (ID06, ESRF) and at a laboratory setup using MetalJet X-ray tube with a liquid-gallium
jet as the anode. X-ray imaging and focusing modes were used. Unique optical and thermal properties of singlecrystalline
diamond lenses allow them to be applied as focusing, imaging and beam-conditioning elements at high-heat
flux beams of today and future X-ray sources.
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