The Diamond Light Source beamline I12 (JEEP) is installing a monochromator for high-energy (50-150 keV) X-rays. It consists of two highly asymmetrically cut silicon crystals diffracting in the Laue case. These crystals will be bent to increase the bandpass to several hundred eV. It is necessary to estimate the tolerances for the
angular alignment and the bending radii, and to account for gravitational and thermal distortions. A simple ray-tracing model has been developed for use with finite-element analyses. For simple cases, this model is backed by more precise wave-optical calculations.
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.
Parabolic refractive x-ray lenses with short focal distance can generate intensive hard x-ray microbeams with lateral extensions in the 100nm range even at short distance from a synchrotron radiation source. We have fabricated planar parabolic lenses made of silicon that have a focal distance in the range of a few millimeters at hard x-ray energies. In a crossed geometry, two lenses were used to generate a microbeam with a lateral size of 160nm by 115nm at 15.2keV at a distance of 47m from the synchrotron radiation source. First microdiffraction and fluorescence microtomography experiments were carried out with these lenses. Using diamond and boron as lens material, microbeams with lateral size down to 20nm and below are conceivable in the energy range from 10 to 100keV.
Fluorescence microtomography is a hard x-ray scanning microscopy technique that has been developed at synchrotron radiation sources in recent years. It allows one to reconstruct non-destructively the element distribution on a virtual section inside a sample. The spatial resolution of this microbeam technique is limited by the lateral size of the microbeam. Since recently, nanofocusing refractive x-ray lenses (NFLs) are under development that were shown to produce hard x-ray microbeams with lateral resolution in the range of 100nm. Future improvements of these optics might reduce the microbeam size down to below 20nm. Using nanofocusing lenses, fluorescence microtomography with sub-micrometer resolution was performed. As an example, the element distribution inside a small cosmic dust particle is given. Tomographic reconstruction was done using a refined model including absorption effects inside the sample.
Compound refractive lenses printed in Al and Be are becoming the key X-ray focusing and imaging components of beamline optical layouts at the 3<sup>rd</sup> generation synchrotron radiation sources. Recently proposed planar optical elements based on Si, diamond etc. may substantially broaden the spectrum of the refractive optics applicability. Planar optics has focal distances ranging from millimeters to tens of meters offering nano- and micro-focusing lenses, as well as beam condensers and collimators. Here we promote deep X-ray lithography and LIGA-type techniques to create high aspect-ratio lens structures for different optical geometries. Planar X-ray refractive lenses were manufactured in 1 mm thick SU-8 negative resist layer by means of deep synchrotron radiation lithography. The focusing properties of lenses were studied at ID18F and BM5 beamlines at the ESRF using monochromatic radiation in the energy range of 10 - 25 keV. By optimizing lens layout, mask making and resist processing, lenses of good quality were fabricated. The resolution of about 270 nm (FWHM) with gain in the order of 300 was measured at 14 keV. In-line holography of B-fiber was realized in imaging and projection mode with a magnification of 3 and 20, respectively. Submicron features of the fiber were clearly resolved. A radiation stability test proved that the fabricated lenses don't change focusing characteristics after dose of absorbed X-ray radiation of about 2 MJ/cm<sup>3</sup>. The unique radiation stability along with the high effficiency of SU8 lenses opens wide range of their synchrotron radiation applications such as microfocusing elements, condensers and collimators.
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.
We studied the feasibility to create a Bragg-Fresnel optical element through the use of silicon dioxide films grown on the silicon perfect crystal surface. In our case the Bragg-Fresnel lens structure consists of a set of silicon dioxide rectangular shape etched zones arranged by the Fresnel zone law. The stress within coated and uncoated crystal regions is opposite in sign, whether tensile or compressive. The strain in the substrate crystal lattice directly underneath discontinuities in the deposited film give rise to phase difference between waves diffracted from coated and uncoated crystal regions. This phase difference is known to be dependent on the thickness and composition of film and substrate. In this paper the focusing properties of Si/SiO<sub>2</sub> Bragg-Fresnel lenses with 107 zones and 0.3 micrometer outermost zone width were experimentally studied as a function of the silicon oxide thickness in the range of 100 - 400 nanometers. The efficiency of the focusing of hard X-rays was found to be about 16% at energy 10 keV.
Parabolic compound refractive lenses (PCRLs) are high quality hard x-ray imaging optics that can be used to image a synchrotron source onto a sample in a strongly demagnifying setup. This allows to produce an intensive microbeam with lateral extensions in the (sub-)micrometer range. Aluminium PCRLs can be operated in an energy range from about 10keV to 60keV and withstand the high heat load of the white beam of an ESRF undulator source. The microbeam properties using monochromatic and single undulator harmonic (pink) radiation are discussed, focusing on beam size, depth of field, background, flux, and gain. The large depth of focus allows to scan fairly large samples (a few millimeters in thickness) with a beam of constant lateral extension. This makes tomographic scanning techniques, such as fluorescence microtomography possible. As applications, fluorescence microtomography of plant samples with sub-cellular resolution and the mapping of trace elements in single cancer cells is shown.
Compound refractive lenses (CRL) for hard x-rays are genuine imaging devices like glass lenses for visible light. They are ideally suited for both full field and scanning microscopy with hard x-rays in the range from 2 to 100keV. They are robust and can withstand the heat load of the white beam of an ESRF undulator source. In full field microscopy, resolutions down to 300nm have been achieved so far using aluminium lenses. Resolutions below 100nm are expected for beryllium lenses currently under development. For scanning microbeam techniques, a monochromatic microbeam of 550nm by 5.5micrometers with a 1.1 10<SUP>10</SUP>ph/s (gain 1120) has been achieved with aluminium lenses at a third generation undulator source. For beryllium as lens material, a flux up to two orders of magnitude higher is expected. At planned FEL beamlines, the source size and distance from the source are favorable to microbeams produced by compound refractive lenses, and a diffraction limited microbeam is expected both horizontally and vertically. For beryllium lenses the diffraction limit can be below 100nm. A typical FEL beam size of approximately 1mm at the experiments hutch ideally matches the aperture of compound refractive lenses. Estimates of the heat load on the CRL as well as expected photon fluxes and micro beams sizes are given.
First experimental results of fluorescence microtomography with 6 micrometer resolution obtained at the ESRF are described. The set-up comprises high quality optics (monochromator, mirrors, focusing lenses) coupled to the high energy/brilliance/coherence of the ID 22 undulator beamline. The tomographic set-up allows precise measurements in the 'pencil-beam' geometry. The image reconstruction is based either on the filtered back-projection (FBT) method or on a modification of the algebraic reconstruction method (ART) but includes simplifications of the model. The quality and precision of the 2D reconstructed elemental images of two phantom sample are encouraging. The method will be further refined and applied for the analysis of more complex inhomogeneous samples.
The performance of a fixed exit double crystal monochromator in terms of stability and reproducibility of the outgoing X- ray beam becomes the crucial point at modern synchrotron beamlines dealt with the high resolution X-ray optics. Due to the high heat load the monochromator crystals have to be cryogenically cooled. The cooling loop of the second crystal may have an impact on the performance of the monochromator. We therefore suggest to use a Si<SUB>1-x</SUB>Ge<SUB>x</SUB> single crystal as the first cooled crystal of the monochromator. With that the second crystal is held at room temperature. To verify the proposed solution an experiment was performed where the lattice parameters of pure Si and SiGe crystals as a function of temperature were measured.