X-ray ring-focusing mirror

Mirrors used in synchrotron radiation facilities can reflect X-ray beams ideally owing to recent advancements in ultraprecise fabrication technologies. Flat mirrors can change the direction of an X-ray beam without distorting its wavefront. Elliptically figured mirrors can focus X-rays onto a spot with nanometer dimensions. The intensity distribution of a reflected X-ray beam is determined, and thus can be controlled, by the shape of the employed mirror. This study proposes, fabricates, and evaluates a ring-focusing mirror that can produce an X-ray beam with a ring-shaped intensity profile. This ring-shaped X-ray beam could be created and observed at the soft X-ray beamline BL25SU at the SPring-8 synchrotron radiation facility, Japan. The increase in the freedom of X-ray mirror shapes will lead to the development of various analytical methods and optical systems in the X-ray region.