Neutrons can pass through dense metal while remaining sensitive to hydrogen, lithium and other light elements. That makes them valuable for looking inside engines, batteries, plants and archaeological objects without cutting them open. The problem has always been control. Neutrons interact so weakly with matter that they are difficult to bend, focus or collect into a sharp image. Most neutron imaging systems therefore work without a lens. Scientists at the Paul Scherrer Institute have now demonstrated an achromatic neutron lens that can focus a broad range of neutron wavelengths at nearly the same point. Published in Nature Communications, the work points toward true neutron microscopy and sharper imaging inside complex equipment. The lens combines a nickel Fresnel zone plate with a diamond compound refractive lens. Together, the elements correct the wavelength-dependent blur that has limited earlier neutron optics. Design and components of the neutron achromat. (CREDIT: Nature Communications) A beam that refuses to behave Neutron beams are usually polychromatic, meaning they contain many wavelengths. Each wavelength bends differently through a conventional lens, so one may …