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The ever‐increasing brightness of synchrotron radiation sources demands improved X‐ray optics to utilize their capability for imaging and probing biological cells, nano‐devices and functional matter on the nanometre scale with chemical sensitivity. Hard X‐rays are ideal for high‐resolution imaging and spectroscopic applications owing to their short wavelength, high penetrating power and chemical sensitivity. The penetrating power that makes X‐rays useful for imaging also makes focusing them technologically challenging. Recent developments in layer deposition techniques have enabled the fabrication of a series of highly focusing X‐ray lenses, known as wedged multi‐layer Laue lenses. Improvements to the lens design and fabrication technique demand an accurate, robust, in situ and at‐wavelength characterization method. To this end, a modified form of the speckle tracking wavefront metrology method has been developed. The ptychographic X‐ray speckle tracking method is capable of operating with highly divergent wavefields. A useful by‐product of this method is that it also provides high‐resolution and aberration‐free projection images of extended specimens. Three separate experiments using this method are reported, where the ray path angles have been resolved to within 4 nrad with an imaging resolution of 45 nm (full period). This method does not require a high degree of coherence, making it suitable for laboratory‐based X‐ray sources. Likewise, it is robust to errors in the registered sample positions, making it suitable for X‐ray free‐electron laser facilities, where beam‐pointing fluctuations can be problematic for wavefront metrology. [ABSTRACT FROM AUTHOR]

The focusing property of an ellipsoidal monocapillary has been characterized using the ptychography method with a 405 nm laser beam. The recovered wavefront gives a 12.5 × 10.4 μ m 2 focus. The reconstructed phase profile of the focused beam can be used to estimate the height error of the capillary surface. The obtained height error shows a Gaussian distribution with a standard deviation of 1.3 μ m. This approach can be used as a quantitative tool for evaluating the inner functional surfaces of reflective optics, complementary to conventional metrology methods. [ABSTRACT FROM AUTHOR]

We report on a developed micromachined silicon platform for the precise assembly of 2D multilayer Laue lenses (MLLs) for high-resolution X-ray microscopy. The platform is 10 × 10 mm2 and is fabricated on ~500 µm thick silicon wafers through multiple steps of photolithography and deep reactive-ion etching. The platform accommodates two linear MLLs in a pre-defined configuration with precise angular and lateral position control. In this work, we discuss the design and microfabrication of the platform, and characterization regarding MLLs assembly, position control, repeatability, and stability. The results demonstrate that a micromachined platform can be used for the assembly of a variety of MLLs with different dimensions and optical parameters. The angular misalignment of 2D MLLs is well controlled in the range of the designed accuracy, down to a few millidegrees. The separation distance between MLLs is adjustable from hundreds to more than one thousand micrometers. The use of the developed platform greatly simplifies the alignment procedure of the MLL optics and reduces the complexity of the X-ray microscope. It is a significant step forward for the development of monolithic 2D MLL nanofocusing optics for high-resolution X-ray microscopy. [ABSTRACT FROM AUTHOR]

Multilayer Laue lens (MLL) is a new class of x-ray optics that offer great promise for achieving nanometre-level spatial resolution by focusing hard x-rays. Fabricating an MLL via thin-film deposition provides the means to achieve a linear Fresnel-zone plate structure with zone widths below 1 nm, while retaining a virtually limitless aspect ratio. Despite its similarity to the Fresnel-zone plate, MLL exhibits categorically distinctive focusing properties and their fabrication comes with a wide array of challenges. This article provides a comprehensive review of advances in MLLs, and includes extensive theoretical modelling on focusing performance, discussion on fabrication challenges, their current capabilities and notable results from x-ray focusing experiments. [ABSTRACT FROM AUTHOR]