A synchrotron beam is like a jet of water from a hose: wide and awkward for fine work. To examine a tiny sample, you need a fine needle, not a hose. In the new setup, the needle is a glass capillary — a tube through which light glides, reflecting off the walls like a voice echoing down a long corridor. Such a capillary gathers divergent light and compresses it into a spot smaller than a micrometer.
Researchers at Aarhus University installed such a capillary on the ASTRID2 synchrotron in Denmark. They measured how the beam width, position, and the amount of light passing through the tube changed as the source size varied. It turned out that even if the capillary surface is not perfectly smooth, you can place an aperture to block stray rays. As a result, the beam was focused to a spot 900 nanometers wide — a hundred times thinner than a human hair.
Many modern materials (graphene, thin films, quantum dots) are so small that a regular beam simply "floods" them with light, mixing signals from neighboring regions. A narrow beam lets you look precisely at the point of interest and see how electrons behave right there. It's like switching from watering a lawn with a hose to targeted drip irrigation for each flower.
The new focusing capillary works over a wide range of photon energies — from extreme ultraviolet to soft X-rays. This is important because different materials respond to different energies. Now, on a single setup, you can study both chemical bonds and electronic structure without changing optics. And the capillary's high transparency means precious synchrotron light is not wasted.
Capillary optics work via total external reflection: X-rays graze along the wall at a very shallow angle, like a flat stone skipping across water, and are barely absorbed.
In science fiction, narrow beams are often used for ultra-precise scanning or energy transmission — for example, in "Star Wars," the Death Star's beam is assembled from many rays, though the scales there are quite different.