X‐ray focusing using an inclined Bragg‐reflection lens

An experimental demonstration showing that a one‐dimensional focus can be produced by using the principle of inclined diffraction from a perfect crystal is presented. By machining a groove with a controlled cross‐sectional profile it is shown that it is possible to vary the out‐of‐plane deviations in a controlled manner and hence generate a focus. Also demonstrated is the use of four reflections in (−,+,+,−) dispersive geometry resulting in the cancellation of all beam‐spreading in the orthogonal direction. The experiment used an energy of 15 keV with a source‐to‐crystal distance of 13.5 m and crystal‐to‐focus distance of 4.5 m. A focus of width 0.29 mm was produced from an incident beam of width 2.7 mm. It is clear from the measurements that a better surface finish would result in a smaller focal spot.