Planar Compound Refractive Lenses Research Articles

Submicron Focusing of X-rays by Silicon Planar Compound Refractive Lenses

Submicron Focusing of X-rays by Silicon Planar Compound Refractive Lenses

A New Method for Determining the Size of a Synchrotron Radiation Beam in the Focus of a Compound Refractive Lens

A new method is proposed for determining experimentally the size of a synchrotron radiation beam in the focus of planar compound refractive lenses. The method consists in measuring the angular divergence of radiation after the focus using Bragg diffraction in a perfect crystal during its rotation. This method determines the beam size, which depends only on the focusing properties of the lenses in use, in contrast to other currently applied methods. The efficiency of the proposed approach has been experimentally demonstrated using nanofocusing planar silicon lenses as an example.

On the theory of synchrotron radiation nanofocusing with planar compound refractive lenses.

Two new methods of computer simulation of synchrotron radiation nanofocusing with planar compound refractive lenses (PCRLs) are presented. The methods are based on the results of analytical theory. In contrast to previous works, the new methods take into account the PCRL aperture. It is especially important at high photon energies, when absorption is low and the calculations based on analytical theory, i.e. without taking into account the aperture, give incorrect results. A computer program was created and specific results were obtained for a silicon PCRL having an aperture of 50 µm, element length of 102 µm and minimum thickness of 2 µm. For an energy of 50 keV and number of elements 300, it focuses the beam to 31 nm size at a distance of one and a half times its length. Analysis of the calculation accuracy for the proposed methods is performed, as well as a demonstration of the capabilities of the computer program.

Adaptable refractive correctors for x-ray optics

Advances in x-radiation sources put greater demands on x-ray optics. Fabrication errors in optical elements lead to deformation of the radiation wavefront, which prevents diffraction-limited imaging of the source. A new adaptable x-ray phase compensator using refracting elements has been developed, fabricated, and tested. The compensator makes a sinusoidal correction to the x-ray wavefront with variable amplitude, period, and phase. The adaptable compensator was used to correct two planar compound refractive lenses and a Kirkpatrick–Baez mirror system on an x-ray beamline. Wavefront measurements showed a reduction in the rms wavefront error by a factor of seven for the lenses and three for the mirror system, reducing rms wavefront errors down to of order $ \lambda /100 $λ/100. This concept could be used with optics on existing x-ray beamlines to enable diffraction-limited focusing.

30-Lens interferometer for high-energy X-rays.

A novel high-energy multi-lens interferometer consisting of 30 arrays of planar compound refractive lenses is reported. Under coherent illumination each lens array creates a diffraction-limited secondary source. Overlapping such coherent beams produces an interference pattern demonstrating strong longitudinal functional dependence. The proposed multi-lens interferometer was tested experimentally at the 100 m-long ID11 ESRF beamline in the X-ray energy range from 30 to 65 keV. The interference pattern generated by the interferometer was recorded at fundamental and fractional Talbot distances. An effective source size (FWHM) of the order of 15 µm was determined from the first Talbot image, proving the concept that the multi-lens interferometer can be used as a high-resolution tool for beam diagnostics.

Theory of an X-ray interferometer in the form of an array of planar compound refractive lenses

The results of theoretical analysis of the interference pattern created by an X-ray multilens interferometer in the case of an arbitrary number of planar compound refractive lenses are presented. The full widths at half maximum of the resonance peaks in the transverse and longitudinal directions relative to the direction of synchrotron radiation are calculated at distances corresponding to the fractional Talbot effect. A relation between the widths is shown to exist that is very close to the width relation in the case of focusing by a single lens. A difference between the fractional and full Talbot effects is discussed, and the necessary conditions for the transverse and longitudinal coherence of radiation are analyzed, the satisfaction of which guarantees that undistorted interference peaks will be observed experimentally.

Fabrication of polycrystalline diamond refractive X-ray lens by femtosecond laser processing

X-ray planar compound refractive lenses were fabricated from a polycrystalline diamond plate grown by chemical vapor deposition, by precise through cutting with femtosecond laser pulses. The lens geometry and the surface morphology were investigated with optical and scanning electron microscopy, while the material structure modification was analyzed by Raman spectroscopy. The results of the preliminary lens test at 9.25-keV X-rays are presented.

X-ray multilens interferometer based on Si refractive lenses.

We report a multilens X-ray interferometer consisting of six parallel arrays of planar compound refractive lenses, each of which creates a diffraction limited beam under coherent illumination. Overlapping such coherent beams produces an interference pattern demonstrating substantially strong longitudinal functional dependence. The interference fringe pattern produced by multilens interferometer was described by Talbot imaging formalism. 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. The experimentally recorded fractional Talbot images are in a good agreement with computer simulations.

High energy X-ray nanofocusing by silicon planar lenses

Optimizing the lens design and improving the technological process, we manufactured X-ray planar compound refractive lenses with vertical sidewalls up to 70 microns deep. The lens surface roughness in the order of 20 nm was attained. The minimal thickness of the material between two individual lenses of 2 μm was realized. The optical tests of the new planar lenses were performed at the ESRF BM05 and ID15 beamlines. The technological breakthrough allows reaching the nanometer focusing. The resolution below 200 nm was measured in the energy region of 15–80 keV. The best resolution of 150 nm was demonstrated at 50 keV X-rays.

X-ray parabolic lenses made from glassy carbon by means of laser

Parabolic planar compound refractive lenses (CRLs) made from glassy carbon by means of laser ablation are presented. They have radii of curvatures of 5 and 200μm and geometric apertures of 40 and 900μm, respectively. The numbers of biconcave elements in the CRLs were 4, 7, and 200. The planar lenses allow formation of a linear focus of length comparable with the depths of their profiles. Usage of two CRLs in a crossed geometry provides formation of two-dimensional focus. The lenses were tested at the European Synchrotron Radiation Facility at the bending magnet beam line BM-5. The minimum experimental size of the focus has been achieved as 1.4μm.

Planar parabolic X-ray refractive lens made of glassy carbon

Experimental results of synchrotron radiation focusing by parabolic planar compound refractive lenses, made of glassy carbon, are presented. The lenses with the curvature radius of 5 and 200 μm, and with the geometric aperture of 40 and 900 μm were developed. The number of bi-concave elements in the compound lenses was from 4 to 200. The experiments were performed at the ESRF at the bending magnet beamline BM-5. The minimum size of the focus was observed as 1.4 μm.

The INE-beamline for actinide research at ANKA

The Institut für Nukleare Entsorgung (INE) at the Forschungszentrum Karlsruhe is presently constructing and will commission and operate an x-ray spectroscopy beamline dedicated to actinide research at the new synchrotron source ANKA. One great advantage of the INE-Beamline is that on-site, in situ actinide research is possible for studying, e.g., solid-water interface chemical reactions, which are not possible at other facilities. The design is for a multi-purpose beamline, i.e., a number of methods (XAFS, surface sensitive and spatial resolved techniques) are possible on one and the same sample. Planned is a safe and flexible containment concept for activities up to 106 times the limit of exemption. The design will allow spectroscopic investigations using photon energies from the K edge of S (2477 eV) to the Rh K-edge (23 220 eV). The optics include collimating and focusing mirrors for a sub-mm beam dimension at the sample position. A later upgrade is planned to install auxiliary μ-focusing optics (e.g., a single bounce elliptical monocapillary or planar compound refractive lenses). The monochromator at the INE-Beamline is a Lemonnier type double-crystal x-ray monochromator (DCM), built at the Universität Bonn, Physikalisches Institut. The pressure inside the small diameter (380 mm) vacuum housing is ∼106 mbar, allowing fast changes of crystals, avoiding long pumping times. Multi-layer mirrors can be used in the DCM for wide band-pass experiments, e.g., for x-ray fluorescence analysis measurements. Installation of beamline components has been completed in October 2003. Operation begin is targeted for 2004.