Hard X-rays have exceptional properties that are useful in the chemical, elemental and structure analysis of matter. Although single-nanometre resolutions in various hard-X-ray analytical methods are theoretically possible with a focused hard-X-ray beam, fabrication of the focusing optics remains the main hurdle. Aberrations owing to imperfections in the optical system degrade the quality of the focused beam 1 . Here, we describe an in situ wavefront-correction approach to overcome this and demonstrate an X-ray beam focused in one direction to a width of 7 nm at 20 keV. We achieved focal spot improvement of the X-ray nanobeam produced by a laterally graded multilayer mirror 2 . A grazing-incidence deformable mirror 3 was used to restore the wavefront shape. Using this system, ideal focusing conditions are achievable even if hard-X-ray focusing elements do not achieve sufficient performance. It is believed that this will ultimately lead to single-nanometre spatial resolution in X-ray analytical methods.Synchrotron radiation facilities produce high-quality light with wavelengths ranging from the infrared to hard-X-ray regions. The use of hard X-rays with energies higher than several kiloelectronvolts in conjunction with analysis methods such as X-ray diffraction, X-ray fluorescence, X-ray absorption and X-ray photoelectron spectroscopy offers unique advantages for the investigation of the structure, elemental distribution and chemical bonding state of advanced materials and biological samples. In these analytical methods, the resolution, signal strength and contrast must be as high as possible. In this regard, the development of a hard-X-ray focusing device is important for meeting these demands. To focus light, it is necessary to take advantage of its interactions with matter, such as diffraction, reflection and refraction. There are a variety of hard-X-ray focusing optical systems such as mirrors 4 , zone plates 5 , refractive lenses 6 and multilayer Laue lenses 7 . The minimum achievable spot size has been theoretically investigated by many researchers 8-10 , and it has been concluded that sizes below 10 nm are feasible with kiloelectronvolt X-rays. That is, hard-X-ray analytical techniques have the potential for single-nanometre spatial resolution.However, in such discussions, the imperfections of the focusing elements have not been entirely considered. Rayleigh's quarterwavelength rule 1 states that if the wavefront aberration exceeds a quarter of a wavelength, the quality of the retinal image will be significantly impaired. This rule is also applicable to simple light-focusing optical systems. The wavefront error of the focused beam distorts the shape of the intensity profile on the focal plane and spreads the beam. The short wavelength of X-rays demands unprecedented accuracy in the manufacturing of the LETTERS 1.43 nm (r.m.s.) over a 500-nm-square area, which was directly confirmed by atomic force microscopy. A phase shift occurred at the boundary between the X-rays propagating inside and outside the phase ...

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Nanofocused x rays are indispensable because they can provide high spatial resolution and high sensitivity for x-ray nanoscopy/spectroscopy. A focusing system using total reflection mirrors is one of the most promising methods for producing nanofocused x rays due to its high efficiency and energy-tunable focusing. The authors have developed a fabrication system for hard x-ray mirrors by developing elastic emission machining, microstitching interferometry, and relative angle determinable stitching interferometry. By using an ultraprecisely figured mirror, they realized hard x-ray line focusing with a beam width of 25nm at 15keV. The focusing test was performed at the 1-km-long beamline of SPring-8.

Visualizing the elemental distributions of cells and tissues is of growing importance in biology and medical science because such data deepen our understanding of the behavior of metal‐binding proteins and ions. Elemental mapping by X‐ray fluorescence analysis with a hard X‐ray nanobeam is very well suited for this purpose owing to its high sensitivity and high resolution. Using this technique, samples must be prepared without artifacts that are caused by treatments such as chemical fixation and staining procedures. In many studies of elemental mapping, sample preparation is not explicitly considered. To overcome this deficiency, we developed a cryo‐scanning X‐ray fluorescence microscope and installed it in the second experimental hutch of BL29XUL of SPring‐8. We used it to observe frozen‐hydrated cells that had been fixed by a quick‐freezing technique to preserve elemental data of the living state at an X‐ray energy of 11.5 keV. The distributions of K, Ca, Fe, Cu and Zn were successfully visualized. The distributions of these elements (especially those of K, Ca and Fe) differed from those in cells fixed with paraformaldehyde. Copyright © 2010 John Wiley & Sons, Ltd.

Intense X-ray fields produced with hard X-ray free-electron laser (XFEL) have made possible the study of nonlinear X-ray phenomena. However, the observable phenomena are still limited by the power density. Here, we present a two-stage focusing system consisting of ultraprecise mirrors, which can generate an extremely intense X-ray field. The XFEL beam, enlarged with upstream optics, is focused with downstream optics that have high numerical aperture. A grating interferometer is used to monitor the wavefront to achieve optimum focusing. Finally, we generate an extremely small spot of 30 Â 55 nm with an extraordinary power density of over 1 Â 10 20 Wcm À 2 using 9.9 keV XFEL light. The achieved power density provides novel opportunities to elucidate unexplored nonlinear phenomena in the X-ray region, which will advance development on quantum X-ray optics, astronomical physics and high-energy density science.