Focusing properties of Si planar refractive lenses including experimental tests and theoretical analysis have been studied. Computer simulations of the X-ray wave field distribution near the focal plane have been performed for different lens designs. Comparison of the experimental results with the computer simulation allows establishing the reasons for deviation of focusing from ideal performance. The deviation of the lens vertical sidewall profile was minimized by additional correction in the lens design and special efforts in optimization of etching process. Optimized lenses were manufactured, tested at the ESRF and brought out the dramatic enhancement in focusing properties.
We report the manufacture and experimental tests of first diamond refractive lenses for hard X-ray focusing. A transfer molding technique based on diamond growth on a pre-patterned silicon mould was employed to fabricate diamond refractive lenses. Diamond films were produced by microwave plasma enhanced chemical vapor deposition. The lenses were designed for 50 cm focal length at energy 9 keV. Experimental tests were performed at the ESRF ID15 (wiggler) and ID22 (undulator) beamlines using monochromatic, "pink" and white X-ray radiation in the energy range from 6 to 40 keV. Focusing in the order of 1-2 microns was achieved. To evaluate the lens microstructure properties phase contrast imaging and diffraction techniques (SAXS and WAXS) were applied.
X-ray refractive optics is mainly concerned on a focusing devices. Another kinds of X-ray refractive devices with a new functionality, namely X-ray biprism and Michelsone echelon are considered. An experiment was fulfilled with biprism made from the synthetic diamond crystals on BM05 beamline ESRF. A computer simulation technique was developed to obtain interference patterns generated by the biprism with an account of a variety of experiment geometrical conditions, source size and absorption in biprism material. Recorded interference patterns were in a good agreement with the predicted ones for a given experimental conditions. Thus a complete description of a brightness distribution in source can be obtained by a reconstruction of the intensity distributions in interference fringes using the developed technique for investigation of synchrotron beams coherence. Possibilities of devices realisation with a extended functional capabilities by means of previously used microelectronic planar techniques are discussed.
X-ray kinoform lenses were proposed earlier as focusing devices with refractive and diffractive properties. Deep X-ray lithography technique was applied to realize kinoform lenses in thick resist layers PMMA. Created lens has rather short focal distance 20 cm at base energy 17.5 keV and full aperture 1.5mm with outermost segments 2 μm in width. Predicted performance of created lens is compared with simple parabolic lenses. Applications of kinoform lenses are considered and potentials of X-ray lithography for creation new versions of refractive focusing devices are discussed.
We demonstrate that Si planar parabolic lens with long focus distance can collimate high energy X-rays with microradian precision. A divergent beam from a wiggler at the ESRF ID15 beamline is reduced from 15 microradian down to 1 microradian. We propose a new imaging technique for direct measurements of beam divergence. It is shown experimentally that precision better than 1 mrad may be really achieved. Measurements are done at the energy range 60 - 90 keV. Contribution of source size and diffraction phenomena to the precision and ultimate sensitivity of the developed technique is discussed.
The planar microelectronics technology, involving lithography and highly anisotropic plasma etching techniques, allows manufacturing high quality refractive and diffractive lenses, which may be used in hard X-ray microprobe and microscopy applications. These silicon lenses are mechanically robust and can withstand high beat load of the white X-ray beam at third generation synchrotron radiation sources. For the first time we designed and manufactured a new type of lenses: kinoform lenses and parabolic lenses with scaled reduction of curvature radii. The theoretical background for such type of lens features is presented. Focusing properties in the terms of focus spot and efficiency of all these lenses were tested at the ESRF beamlines. Magnified imaging with planar lense was realized. Some future developments are discussed.
Microelectronics technology involving photolithography and highly anisotropic plasma etching techniques was applied to fabricate planar parabolic refractive lenses. A set of Si planar parabolic lenses with apertures from 0.5 to 1.8 mm and 200 microns deep has been fabricated especially for high energy X-rays (E > 50 keV). Focusing properties in terms of the spot size and the efficiency in the energy range from 50 to 100 keV have been studied at the ESRF ID15 beamline. Linear focusing by single lens and by two-lens system as well as two-dimensional focusing by two lenses in cross geometry has been realized. Features of refractive collimator based on a set of planar lenses have been investigated and a technique for evaluation of the beam divergence in a micro radian range has been proposed. Future applications of proposed planar lenses are discussed.
Silicon planar parabolic refractive lenses with relief depth of 100 micrometer are realized by microfabrication technique. A set of 5 planar lenses with simple parabolic profiles and equal apertures and equal focal distances is realized. This set consists of different number (from 1 to 8) of individual lenses. Lenses with minimized absorption as a set of parabolic segments are fabricated too. Focusing and spectral properties of silicon planar parabolic lenses were studied with synchrotron radiation in the x-ray energy range 8 - 25 keV at the ESRF. Linear focus spots of 1.5 micrometer width were recorded for the parabolic lenses and 1.8 micrometer for the lenses with minimized absorption. The intensity transmission of the lens with minimized absorption is two times greater than this value of simple parabolic lenses at 8 keV and in the x-ray energy range over 15 keV overcomes 90%. Spectral properties of the lenses with minimized absorption are discussed in details. Heatload properties of the silicon planar lenses are analyzed and compared with the lenses made of diamond.
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