Refractive X-ray Lenses Research Articles

Highly efficient 2-D nano focusing by an optical system of planar refractive lenses

A lens system of two parabolic refractive X-ray lenses giving an intensity gain over 108 for a focal spot size below 10 nm for photon energies above 10 keV is suggested.

Hard X-ray scanning microscopy with fluorescence and diffraction contrast

Based on nanofocusing parabolic refractive x-ray lenses we have developed and built a hard x-ray scanning microscope that was tested and put to use at beamline ID13 of the ESRF. It can provide a monochromatic hard x-ray nanobeam with lateral extension below 100 nm (down to 50 nm) and a flux up to 109 ph/s in the energy range from 15 to 25 keV. The microscope exploits transmission, fluorescence, and diffraction contrast to obtain local elemental and nanostructural information from the sample. Tomographic scanning yields high resolution elemental maps from the inside of an object. Coherent x-ray diffraction imaging with nanofocused illumination yields images of objects with highest spatial resolution, e. g., 5 nm in a given example.

Transmission hard X-ray microscope with increased view field using planar refractive objectives and condensers made of SU-8 polymer

Planar X-ray refractive lenses in crossed geometry providing 2D focusing are fabricated from SU-8 polymer using tilted deep X-ray lithography. The profiles of the objective lens elements are parabolic. The lens elements for the condensers were designed with a power of the surface function of 1.5, 1.7 and 2 to vary the field of views for a transmission X-ray microscope (TXM). With these lenses a TXM was set up at the ESRF beamline BM-5 for a photon energy of 15 keV. Different test nanostructures were imaged with this TXM using inline phase-contrast, with X-ray magnification factors of 29, demonstrated spatial detail resolution of 100 nm (half-period of lines and spaces) and exposure times around 10 s. Further improvement of a TXM based on the SU-8 lenses using refractive condensers with large apertures is considered with the aim to reduce exposure times.

Refractive X-ray lenses with rotation profile and curvature-radius scale reduction

Refractive X-ray optics, the physical fundamentals of which were considered by us previously [1], is presented mainly by focusing devices. Among them, an important role is played by compound lenses, the constructions of which are based on the additivity of optical forces of individual lenses. The law of additivity is experimentally proved for the X-ray range [2] by the example of a set of identical lenses having a constant curvature radius. It should be noted that the possibility of a stage-by-stage increase in the optical forces of individual lenses due to reducing the radius of circular apertures was indicated already in the first description of compound lenses [3]. Previously [4], we designed and investigated the planar lenses from silicon, where the curvature-radius scale reduction was introduced for individual lenses. The described type of planar lenses is considered nowadays [5] as most prominent for focusing the beams in the nanodimensional range. In this work, we describe the compound lenses, which were created for the first time with the curvatures-radius scale reduction and the rotation profile by the method of laser stereolithography from photopolymeric materials.

An X-ray refractive lens comprising two sections cut from a gramophone record for a portable total reflection X-ray fluorescence spectrometer

An X-ray refractive lens is assembled from two sections cut from a gramophone record. The refractive lens is placed in a portable total reflection X-ray fluorescence (TXRF) spectrometer, and it is used for collimation of the incident X-ray beams. A TXRF spectrum measured with the refractive lens is compared with that measured with a waveguide. Compared with the refractive lens, the waveguide enhances the intensities of the X-rays illuminating an analyte. Therefore, fluorescent X-ray intensities increase when using the waveguide. On the other hand, the vertical angular divergence of the incident X-ray beams is smaller when using the refractive lens, and the smaller angular divergence results in a reduction of the scattering of the incident X-rays from a sample holder. Therefore, the spectral background is reduced when using the refractive lens, resulting in an increase of the signal to background ratios of the fluorescent X-rays. Detection limits for 3d transition metals obtained with the refractive lens are sub-nanograms to a few nanograms, and the detection limits are similar to those obtained with the waveguide.

An efficient pre‐object collimator based on an x‐ray lens

A multiprism lens (MPL) is a refractive x-ray lens with one-dimensional focusing properties. If used as a pre-object collimator in a scanning system for medical x-ray imaging, it reduces the divergence of the radiation and improves on photon economy compared to a slit collimator. Potential advantages include shorter acquisition times, a reduced tube loading, or improved resolution. We present the first images acquired with a MPL in a prototype for a scanning mammography system. The lens showed a gain of flux of 1.32 compared to a slit collimator at equal resolution, or a gain in resolution of 1.31-1.44 at equal flux. We expect the gain of flux in a clinical setup with an optimized MPL and a custom-made absorption filter to reach 1.67, or 1.45-1.54 gain in resolution.

Diamond kinoform hard X-ray refractive lenses: design, nanofabrication and testing

Motivated by the anticipated advantageous performance of diamond kinoform refractive lenses for synchrotron X-ray radiation studies, this report focuses on progress in designing, nanofabricating and testing of their focusing performance. The method involves using lift-off and plasma etching to reproduce a planar definition of numerically determined kinoform refractive optics. Tests of the focusing action of a diamond kinoform refractive lens at the APS 8-ID-I beamline demonstrate angular control of the focal spot.

Highly intense monochromatic X-ray diffraction facility for high-pressure research at SPring-8

Beamline BL10XU at SPring-8, designed for X-ray diffraction experiments using diamond anvil cells at high pressure and low/high temperature, is continuously upgraded. The X-ray source, optics, and attractive experimental equipment such as simultaneous measurement systems have been optimized over the past years. The high energy and high intensity monochromatic X-ray beams emitted by an undulator source, focused using a characteristic X-ray refractive lens, have enabled us to obtain excellent counting statistics and high-resolution X-ray diffraction data even from a highly compressed sample under multi-megabar pressure. At BL10XU, low- and high-temperature conditions are achieved using a cryostat (10–300 K) and double-sided laser-heating system (1000–4000 K), respectively. Numerous results have been obtained in the fields of high-pressure materials science and mineral physics: for instance, the structural information on novel materials under pressure, including new pressure-induced structural phase transitions, the measurements of equations of states, and the phase-equilibrium data of Earth interior minerals.

Fabrication and performance of 2-D compound X-ray refractive lenses

Due to the weak refraction of X-rays in matter, a focusing or deflection of X-ray using conventional refractive optics was not feasible. However, since compound X-ray refractive lens (CXRL) with consecutive holes array was proposed, it becomes currently a noticeable issue in X-ray optics. In this paper, we report on fabrication and performance test of two types of PMMA (polymethyl methacrylate) CXRLs. Firstly, one dimensional refractive X-ray lenses of parabolic and circular shape is fabricated by LIGA process. Based on the results, we conduct a fabrication of 2-D CXRLs. Here we suggest a LIGA-self align method which doesn’t need a special align equipment and is simpler method than conventional one. Through performance tests, we show experimentally that CXRLs are novel optical components for the hard X-ray range of about 8 keV and that they have possibilities to apply the X-ray optics for micro-focusing, imaging, and lithography.

Scanning x-ray diffraction with 200nm spatial resolution

We report a scanning technique, which combines high resolution x-ray diffraction (in reciprocal space) along with a submicrometer spatial resolution (in real space). SiGe∕Si(001) Stranski–Krastanow islands served here as a well investigated model system to check the limits of the developed method. A set of refractive silicon x-ray lenses focused the x-ray beam size down to a diameter of 200nm (full width at half maximum), which enables scanning of individual micrometer-sized and even smaller islands. By illuminating diverse {111} island side facets, crystal truncation rods of different orientations were independently excited and thus became distinguishable in the scattering patterns. The reassembling of these locally resolved diffraction patterns coincides with both an integral measurement and a corresponding scattering simulation.

Measurement of side walls of high aspect ratio microstructures

In this paper, the new method of measurements is presented for the technological control of the lithographic fabrication of high aspect ratio microstructures with complex side-wall profiles. The sampling procedure includes pouring polymer glue on a substrate with the microstructures and its hardening, sectioning the polymer matrix in the depth with planes parallel to the substrate and analysis of digital optical microscope images of the planes. The measured deviations the micro structure profiles in comparison with the designed geometry are used for the further optimization of the technological design of planar X-ray refractive lenses.

Inspection of refractive x-ray lenses using high-resolution differential phase contrast imaging with a microfocus x-ray source

A refractive x-ray lens was characterized using a magnifying cone beam setup for differential phase contrast imaging in combination with a microfocus x-ray tube. Thereby, the differential and the total phase shift of x rays transmitted through the lens were determined. Lens aberrations have been characterized based on these refractive properties.

Crossed planar X-ray lenses made from nickel for X-ray micro focusing and imaging applications

X-ray refractive lenses made from nickel are ideally suited for scanning focusing microscopy and imaging using high-energy X-ray photons. They can provide minimum spot size of about 20 nm for a focused photon beam of 80 keV energy. A four-fold magnified image of a low-contrast object with a spatial resolution of 600 nm was measured at this energy for the first time. In order to further decrease the focal spot size a lens with mosaic shape was designed and its optical performance evaluated.

Development, production, and investigation of PMMA-based X-ray compound refractive lenses

Equipment and technology for producing X-ray refractive lenses from polymethyl methacrylate are described. Each single lens has a spherical profile with a radius of 2.38 mm. A compound lens is composed of 235 single lenses. The focal length of the compound lens for 14-keV X-ray photons is 4.8 m. The lenses developed thereby have been tested on the synchrotron radiation source of the Scientific and Engineering Complex at the Kurchatov Centre of Synchrotron Radiation and Nanotechnologies. The advantages and the drawbacks of the parabolic and spherical lenses are discussed.

The Compound Refractive Lens for Hard X-ray Focusing

The compound refractive X-ray lens (CRL) for focusing hard X-rays is investigated to determine the parameters such as the focal length, the focal spot size, and spatial distribution at the focal spot using a simple theoretical calculations and CRLs fabricated by the self-assembly method. The number of individual compound lenses are defined for the given focal length of 1 m. The X-ray energy of 1 to 40 keV is used in the calculations. The CRL for focusing hard X-rays which generated from the X-ray tube is fabricated by nanoparticle-polymer composite in the form of circular concaves. The self-assembly method is applied to form the nanoaluminum-poly (methly meth-acrylate) composite and carbon-polymer composite CRL lenses. Aluminum nanoparticles of 100 nm and carbon microparticles are diffused in the polymer solution then the high gravity up to 6000G is applied in it to form the concave lens shape. X-ray energy at 8 keV is used for characterization of the composite CRLs. The FWHM of intensity for the fabricated nanoaluminium composite CRL system, N=10 is measured as 1.8 mm, which would give about $70{\mu}m$ in FWHM at 1 m of the focal length.

Using of a microcapillary refractive X-ray lens for focusing and imaging

The microcapillary lens, formed by air bubbles in a hollow core glass capillary filled with epoxy, is a novel design of a compound refractive lens for X-rays. The epoxy enclosed between two air bubbles has the form of a biconcave lens and acts as a positive lens for X-rays. Each individual lens is spherical with radius of curvature equal to the inner radius of the capillary. Up to 500 individual biconcave lenses can be formed in a single capillary with diameters from 50 to 500 μm. Due to the small radius of curvatures that can be achieved, microcapillary lenses typically have shorter focal lengths than those made by compression or injection molding. For example, microcapillary lenses with a focal length about 5 cm for 8 keV X-rays and 50-micron aperture are readily available. We have produced a set of lenses in a 200-micron inner-diameter glass capillary with 100–350 individual microlenses and measured their parameters at the Stanford Synchrotron Radiation Laboratory and at the Advanced Photon Source. Our investigations have also shown that the lenses are suitable for imaging applications with an X-ray tube as a source of X-rays. A simple X-ray microscope is discussed. The microscope consists of a copper anode X-ray tube, X-ray lens and CCD-camera. The object, lens and CCD-camera were placed in-line at distances to satisfy the lens formula. It is shown that the field of view of the microscope is about 1 mm and resolution is equal to 3–5 μm.

Hard X-ray nanoprobe with refractive X-ray lenses

Hard X-ray nanoprobe with refractive X-ray lenses

Hard x-ray nanoprobe based on refractive x-ray lenses

Based on nanofocusing refractive x-ray lenses a hard x-ray scanning microscope is currently being developed and is being implemented at beamline ID13 of the European Synchrotron Radiation Facility (Grenoble, France). It can be operated in transmission, fluorescence, and diffraction mode. Tomographic scanning allows one to determine the inner structure of a specimen. In this device, a monochromatic (E=21keV) hard x-ray nanobeam with a lateral extension of 47×55nm2 was generated. Further reduction of the beam size to below 20 nm is targeted.

Hard X-ray nanoprobe with refractive X-ray lenses

C. G. Schroer, O. Kurapova, J. Patommel, P. Boye, J. Feldkamp, B. Lengeler, M. Burghammer, C. Riekel, L. Vincze, A. van der Hart, M. Kuchler HASYLAB at DESY, Notkestr. 85, D-22607 Hamburg, Germany II. Physikalisches Institut, Aachen University, D-52056 Aachen, Germany ESRF, BP 220, F-38043 Grenoble Cedex, France Department of Analytical Chemistry, Ghent University, Krijgslaan 281 S12, B-9000 Ghent, Belgium ISG, Research Center Julich, D-52425 Julich, Germany IZM, Fraunhofer Institute, Reichenhainer Str. 88, D-09107 Chemnitz, Germany

Refractive x-ray lenses

Parabolic refractive x-ray lenses are novel optical components for the hard x-ray range from about 5 keV to about 120 keV. They are compact, robust, and easy to align and to operate. They can be used like glass lenses are used for visible light, the main difference being that the numerical aperture is much smaller than 1 (of the order of 10−4–10−3). They have been developed at Aachen University and are made of beryllium, boron, aluminium and silicon. Their main applications are in micro- and nanofocusing, in imaging by absorption and phase contrast. In combination with tomography they allow for three-dimensional imaging of opaque media with sub-micrometre resolution. Finally, they can be used in speckle spectroscopy by means of coherent x-ray scattering. References to a number of applications are given.