Search

We will review the current status and perspectives of x-ray mirror design, fabrication, and metrology to respond to the demand for optics for next generation light sources. The presentation will be based on our own experience, as well as on materials and discussions from two recent meetings: the International Workshop on X-ray Mirror Design, Fabrication, and Metrology (September 22-24, 2009, Osaka University, Suita, Osaka, Japan), and the EuroFEL Workshop on Photon Beamlines and Diagnostics (June 28-30, 2010, DESY, Hamburg, Germany).

Metrology plays an important role in surface figuring with subnanometer accuracy. We have developed relative angle determinable stitching interferometry for the surface figuring of elliptical mirrors, in order to realize hard x-ray nanofocusing. In a stitching system, stitching angles are determined not by the general method using a common area between neighboring shots, but by the new method using the mirror’s tilt angles measured at times when profile data are acquired. The high measurement accuracy of approximately 4 nm (peak-to-valley) was achieved in the measurement of a cylindrical surface having the same curvature as the elliptically designed shape to enable hard x-ray nanofocusing. [ABSTRACT FROM AUTHOR]

A numerically controlled elastic emission machining (EEM) system has been developed to fabricate ultraprecise optical components, particularly in x-ray optics. Nozzle-type EEM heads, by which a high shear-rate flow of ultrapure water can be generated on the work surface, have been newly proposed to transport the fine powder particles to the processing surface. Using this type of EEM head, the obtainable spatial resolution in figure correction can be changed by selecting the suitable aperture size of the nozzle according to the required spatial frequency. As a result of test figuring, 1 nm level peak-to-valley (p-v) accuracy is achieved throughout the entire spatial wavelength range longer than 0.3 mm. In addition, the microroughness of the processed surface is certified to also be approximately 1 nm (p-v). [ABSTRACT FROM AUTHOR]

Abstract: A laterally- graded multilayer mirror, which has a multilayer film on a curved surface substrate, is one of the candidates of focusing elements producing an ultimate hard-X-ray beam. Aberration, which multilayer mirrors natively have, should be seriously considered when we challenge several nanometer-size X-ray beams. X-rays, inserting a multilayer structure, are reflected at a relatively large angle by the effect of interferences among X-rays slightly reflected on each boundary. However, if focal points of X-rays reflected at bottom boundary and uppermost surfaces might be different, the X-rays are not allowed to be focused at the same point. This is due to refractions inside the multilayer film. Now, there is no rigorous numerical method to determine clearly the behavior of such reflection of X-rays. In this study, we code a ray-tracing simulator to analyze such aberration effect and carry out several simulations. The results conclude that aberration of an ideal laterally- graded multilayer mirror has insignificant effects on the focused beam size. [Copyright &y& Elsevier]

Abstract: In the third- and coming fourth-generation synchrotron radiation facilities, X-rays having both high brightness and high coherency can be utilized. Such X-rays require high accuracy in the reflective optics. In this study, we developed an ultra-precise measurement instrumentation for tangentially long X-ray mirrors using a Fizeau interferometer. In the system, the mirror figure is measured by stitching the subaperture profiles measured by the relative-angle determinable stitching interferometry, which we developed previously. High measurement accuracy of approximately 2nm (peak to valley) was achieved in the measurement of a 400mm-long aspherical surface. [Copyright &y& Elsevier]

Abstract: A method for evaluating the two-dimensional photon density distribution in focused hard X-ray beams is proposed and demonstrated in a synchrotron experiment at SPring-8. A synchrotron X-ray beam of 11.8keV is focused to a spot by Kirkpatrick–Baez mirrors. The two-dimensional intensity distribution of the focused beam is derived by monitoring the forward diffracted intensity from an isolated silver nanocube with an edge length of positioned in the beam waist, which is two-dimensionally scanned. Furthermore, the photon density of X-rays illuminated onto the nanocube is estimated by utilizing coherent X-ray diffraction microscopy. This method is useful for evaluating the photon density distribution of hard X-ray beams focused to a spot size of less than a few micrometers. [Copyright &y& Elsevier]

Abstract: We describe a method for characterizing sub-10-nm X-ray beams using knife-edge scanning with dark-field geometry. Beam profile measurement by the conventional dark-field method is simulated numerically, and the signal intensity is found to depend strongly on the incident angle of the beam components. A numerical procedure to correct the dependence and to determine the actual beam profile is presented. [Copyright &y& Elsevier]

Abstract: We propose an optical profilometer system for evaluating mirrors that are used for hard X-ray nanofocusing. A surface metrology system designed for these mirrors to focus to a size of 10nm is required to ensure a precise measurement of a large curvature with a vertical accuracy of 1nm and a lateral resolution less than 0.1mm. The surface metrology system is based on a stitching interferometer that can determine stitching angles between adjacent local surface profiles. Local surface profiles and stitching angles are detected simultaneously by using two types of optical interferometers, a microscopic interferometer and a large-scale interferometer, respectively. We developed a nanofocusing mirror that has approximately the same surface curvature as a sub-10-nm focusing mirror, to examine the measurement accuracy of the developed surface metrology system. As a result of a performance assessment of the measurement instrument, we achieved measurement reproducibility and reliability of less than peak-to-valley height of 4nm by measuring the focusing mirror. In addition, we achieved focusing performance of a full width at half maximum 27nm at 7keV using the mirror at SPring-8. We verified that the metrology system can be used to measure sub-10-nm focusing mirrors. [Copyright &y& Elsevier]

Abstract: A new X-ray microprobe system for trace heavy element analysis using ultraprecise X-ray mirror optics of 300mm long working distance has been developed at beamline 37XU of SPring-8. A focusing test has been performed in the X-ray energy range 20–37.7keV. A focused beam size of 1.3μm (V)×1.5μm (H) has been achieved at an X-ray energy of 30keV, and a total photon flux of the focused beam was about 2.7×1010 photons/s. Micro-X-ray fluorescence (μ-XRF) analysis of eggplant roots has been carried out using the developed microprobe. It is clearly observed in the XRF images that cadmium is highly accumulated in the endodermis, exodermis and epidermis of roots. This study demonstrates the potential of scanning microscopy for heavy elements analysis in the high-energy X-ray region. [Copyright &y& Elsevier]