Mirrors for Sharply Focusing X-Rays

Piezoelectric deformable mirror with dimorph structure (Source: S. Matsuyama et al. / NPG)

Piezoelectric deformable mirror with dimorph structure (Source: S. Matsuyama et al. / NPG)

A research team in Japan has now succeeded in developing high precision X-ray deformable mirrors that can be configured as necessary. They are the first to have achieved the formation of three types of X-ray focused beams, which differ in focused spot size, without changing the experi­mental setup. These findings constitute a consi­derable step towards developing a multi­functional X-ray microscope, which will be able to perform a variety of microscopic analyses in one device.

X-ray analysis is applied in many fields such as medicine, industry and research. By sharply focusing X-rays it is possible to conduct high-sensitivity and high-resolution analysis. So far, however, X-ray analysis and X-ray micro­scopes are lacking the flexi­bility of electron microscopes as one device is merely capable of sending a fixed set of focused beams thereby limiting the range of uses of the device. The research team centering around Kazuto Yamauchi and Satoshi Matsu­yama both at Graduate School of Engineering, Osaka University, success­fully developed deformable mirrors that can be configured as necessary. By combining four of these mirrors, a new X-ray focusing system, in which the focused spot size is controllable, was developed. This removes the necessity of having to change experiment setups, including the position of the sample. The adaptive focusing system were developed at the large-scale synchro­tron facility SPring-8, located at Harima Science Garden City, Hyogo prefecture, where the world’s brightest radiation light is created.

With the new system it is now possible to create light collection optical systems, which differ in numerical aperture, an index indicating the ability of a lens or mirror to focus light, just by changing the confi­guration of the deformable mirrors. Changing the numerical aperture allows for a controlling of the focused spot size close to the diffraction limit of a lens or mirror, that is the limit of its ability to focus light because light is being diffracted. The researchers developed an X-ray wave front measuring technique with which to determine mirror configuration errors with high precision and control deformation with an accuracy of 2nm. The research team conducted this procedure with precision for three optical systems with different numerical apertures.

The results of this research will contribute to the development of a multi­functional X-ray microscope that is able to perform a variety of X-ray/X-ray-microscopic analyses by forming optimal beam sizes for each analysis. Especially in the development of advanced X-ray sources such as X-ray free electron lasers of which exist only two in the world (Japan and America) and ultra-low emittance radiation sources, an inter­nationally compe­titive research field to develop the next gene­ration radiation source, these research results will contribute to the intro­duction of new and effective styles of conducting experiments. (Source: Osaka Univ.)

Reference: S. Matsuyama et al.: Nearly diffraction-limited X-ray focusing with variable-numerical-aperture focusing optical system based on four deformable mirrors, Sci. Rep. 6, 24801 (2016); DOI: 10.1038/srep24801

Link: Dept. of Precision Science and Technology, Osaka University, Japan

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