Refractive x-ray focusing with modified phonograph records

We present a novel design of a refractive x-ray lens. It is shown that a lens with a simple saw-tooth profile will have the same focusing properties as one with parabolic surfaces. The lens can be made in two symmetric pieces, and be fabricated with a standard record-cutting machine at a very low cost. Furthermore, the focal length for a given energy can be adjusted by a simple mechanical procedure. A prototype in vinyl with a focal length of 20 cm for 25 keV x-rays has been manufactured. Measurements in a table-top setup with a conventional x-ray tube are in good agreement with calculations based on geometrical optics and ray-tracing simulations.