WORLD’S SHARPEST X-RAY BEAM DEVELOPED

BERLIN (TIP): Scientists have successfully generated the world’s sharpest x-ray beam which is ten thousand times thinner than a strand of hair. This fine beam of x-ray light barely 5 nanometres in diameter, created by researchers led by Professor Tim Salditt from the University of Gottingen, allows focusing on smallest details. “Instead of a common lens, we use a so-called Fresnel lens which consists of several layers,” said coauthor Dr Markus Osterhoff. The central support is a fine tungsten wire with the thickness of only a thousandth of a millimetre. Around the wire, nanometre-thin silicon and tungsten layers are applied in an alternating way. The physicists then cut a thin slice from the coated wire. “This slice has 50 to 60 silicon and tungsten layers, comparable to growth rings of a tree,” said team member Florian Doring. “And the layer thicknesses have to be extremely precise,” Christian Eberl added. The wire slice with a size of only about two thousandth of a millimetre is used as a lens. However, it does not diffract light like a glass lens but scatters it like an optical grid generating a pattern of bright and dark patches. The thickness of the layers is selected in such a way that the bright areas of the diffraction pattern coincide at the same spot.