We report a multilens X-ray interferometer consisting of six parallel arrays of planar compound refractive lenses. The
main concept of new interferometer is based on the same principle such a bilens interferometer. The interference fringe
pattern produced by the multilens interferometer was described by Talbot imaging formalism. A theoretical analysis of
the interference pattern formation was carried out and corresponding computer simulations were performed. The
proposed multilens interferometer was experimentally tested at ID06 ESRF beamline in the X-ray energy range from 10
to 30 keV. Experimentally recorded fractional Talbot images are in a good agreement with computer calculations.
We present results of imaging properties of the lens-crystal system for hard x-ray radiation. The system is based on a
beryllium parabolic refractive lens placed in front of the sample, and an asymmetric silicon single crystal placed behind
the sample. The beryllium refractive lens has such advantages as small absorption and high efficiency which allow high
spatial resolution. We demonstrate a phenomenon of image formation using the Bragg reflection of focused x-ray beam
from asymmetric single crystal. For recording the magnified x-ray phase contrast image the asymmetric single crystal Si
(220) with asymmetry factor b = 1/6 was used at the x-ray energy 15 keV. The experiment was performed at the beam
line BM-5 of the European Synchrotron Radiation Facility (ESRF). The peculiarities of image transformation are
investigated both experimentally and theoretically when the focus of refractive lens is moved across and along the
optical axis. The computer program was elaborated for a simulation of image formation in the system based on the
refractive lens and the crystal with asymmetric Bragg diffraction. The algorithm is based on the FFT procedure for
making a transition from a real space to a plane wave space.n/mswo
Spatial structure of a focused beam diffracted from crystals of different thickness was studied experimentally at the
ESRF optical beamline BM5. The beam was focused by a planar parabolic refractive lens. Si (111) thick crystal and
8 μm and 50 μm thick perfect Si(111) crystals positioned between the lens and the focus were used as model samples.
The structure of the beam was analyzed at the focus of the lens by using a knife edge scan and a high-resolution CCD
camera. The broadening of the focused beam due to the extinction effect was experimentally measured and compared
with theoretical predictions. For a sufficiently thin crystal a second peak was experimentally observed which is due to
the reflection from the back surface. We found also that the spatial structure depends on whether the crystal diffracts
strongly (dynamically) or weakly (kinematically). In the later case, both surfaces of the crystal effectively reflect as
mirrors with the reduced reflectivity and the relative intensity of the two peaks is determined by absorption. Theoretical
simulations show excellent agreement with experiment.
We present the first results of collimating the synchrotron radiation beam by zone plate located at the long distance from
the source. Zone plate (ZP) has been fabricated from silicon crystal. We observe the interference fringes due to existence
of various orders of focusing. We record experimentally an amplification of synchrotron beam intensity up to four times
by means of ZP. The experimental measurements have been performed at the beam line BM-5 of the European
Synchrotron Radiation Facility (ESRF) for the energy interval from 8 to 17.5 keV. The fringes were discussed on the
base of analytical theory as well as were studied by means of computer simulation. The radial distribution of intensity is
determined as a convolution of the zone plate transmission function and the Kirchhoff propagator in paraxial
Results of the first experiment in which Bragg diffraction of a focused x-ray beam was utilized to obtain depth sensitive
structural information are presented. Silicon-on-insulator (SOI) layers of 4.5 to 25 μm thick were studied. The beam was focused by a circular zone plate. A beam stop and an order sorting aperture were used to reduce the contribution of the background radiation into diffracted intensity. Diffraction patterns were recorded by a CCD detector placed in the focus of the zone plate. Spatial distributions of the recorded intensity in the scattering plane revealed variations of the lattice constant within the layers. Incoherent scattering was observed out of the scattering plane thus providing a new method to
study diffuse scattering. Computer simulations of the intensity patterns produced by the interface between two layers with the lattice constant mismatch are presented.
Stacking technique was developed in order to increase focusing efficiency of Fresnel zone plates at high energies. Two
identical Si chips each of which containing Fresnel zone plates were used for stacking. Alignment of the chips was
achieved by on-line observation of the <i>moiré</i> pattern from the two zone plates. The formation of <i>moiré</i> patterns was
studied theoretically and experimentally at different experimental conditions. To provide the desired stability Si-chips
with zone plates were bonded together with slow solidification speed epoxy glue. Technique of angular alignment in
order to compensate a linear displacement in the process of gluing was proposed. Two sets of stacked FZPs were
produced and experimentally tested to focus 15 and 50 keV X-rays. Gain in the efficiency by factor 2.5 was
demonstrated at 15 keV. Focal spot of 1.8 μm vertically and 14 μm horizontally with 35% efficiency was measured at
50 keV. Forecast for the stacking of nanofocusing Fresnel zone plates was discussed.
We present results of study of optical properties of extremely thick refractive lens when the thickness (or length) of a compound refractive lens is comparable with its focal distance. We tested a 2D parabolic compound refractive lens composed from 300-500 elements. Each element is a bi-concave lens made from aluminum with the curvature radius <i>R</i> = 0.2 mm and thickness 1 mm. Special long holders were designed and manufactured to keep up to 500 of elements. As far as the thin lens approximation is not valid we developed and used accurate theory of long parabolic compound lens for ray-tracing analysis. The experimental measurements were performed for the X-ray energies E = 20-30 keV. The measured focus distance and effective aperture correlate with the theory.
We present results on comprehensive studies of high resolution SU-8 planar refractive lenses. Lens optical properties were investigated using coherent high energy X-ray radiation. Resolution of about 270 nm was measured for the lens consisting of 31 individual lenses at energy 14 keV. Coherent properties of the set-up permit to resolve near-focus fine structure, which is determined by tiny aberrations caused by lens imperfections close to the parabola apex. This study allows understanding as far SR deep lithography as possible can maintaine to close tolerances for lens parameters. Two-dimensional focusing crossed lenses were tested and imaging experiments in projection and imaging mode were conducted. Radiation stability test was performed and conclusions on the applicability of SU-8 lenses were done.
Experimental results of synchrotron radiation focusing by parabolic planar compound refractive lenses made of glassy carbon are presented. The lenses with the curvature radii of 5 μm and 200 μm and with the geometric aperture of 40 μm and 900 μm correspondingly were developed with various techniques of laser evaporation. The number of bi-concave elements in the compound lenses was 4, 7 and 200. The planar lenses allow one to obtain linear focuses of the lengths comparable with the depths of their parabolic profiles. Use of two lenses in the cross geometry provides a formation of 2-dimensional focus. The experiments were performed at the ESRF at the bending magnet beamline BM-5. The minimum experimental focus size was as fine as 1.4 μm, which is larger than the theoretical estimation. The reasons of the focus broadening are discussed.
Focusing of hard X-rays by refraction has been a long time been considered as unfeasible due to strong absorption and weak refraction of X-rays in matter. Recently it has been shown that compound refractive lenses can overcome the problem. It was demonstrated that the best candidates for lenses are low Z, high density materials. Linear and 2D lenses from aluminum, boron carbide, beryllium, pyrographite and Teflon were produced and tested. Focusing of 2 - 3 microns was achieved at an energy range from 9 to 30 keV. Compound refractive lenses have low sensitivity to heatload and are extremely well suited for focusing of undulator radiation. Two-plane focusing lenses have been optimized, built and installed in the white beam of the undulator on the machine diagnostic beamline of the ESRF to be used as an X-ray emittance diagnostic. The future potentials of the refractive lenses will be discussed as well.
3D computed tomographic images with micrometer resolution were made in phase-contrast mode with high energy x-rays at a third generation synchrotron source. The phase-contrast technique enables one to obtain information not only about the amplitude of the wave field behind the object and thus about the absorption, but also about the refractive index distribution inside the sample. Increasing the x-ray energy from the soft x-ray region up to 10-60 keV simplifies the experimental setup and opens the possibility to study organic samples at room-temperature and under normal pressure conditions. The projection data is recorded with a fast, high-resolution x-ray camera consisting of a 5 micrometers thin YAG scintillator crystal, a visible light microscope optics and a slow scan 1k X 1k CCD camera. The spatial resolution of phase-contrast microtomography is currently limited by the resolution of the x-ray detector to about 1-2 micrometers . First applications in biology and geophysics are shown.
Bragg-Fresnel optics shows excellent compatibility with ESRF sources and are capable of obtaining monochromatic submicron focal spots with 10<SUP>8</SUP> - 10<SUP>9</SUP> photons/sec in an energy bandwidth of 10<SUP>-4</SUP> - 10<SUP>-6</SUP> and in a photon energy range between 2 - 100 keV. Microprobe and microimaging techniques based on Bragg-Fresnel optics were realized at the ESRF beamlines.