Universal mask for hard x rays

Abstract

The penetrating power of x rays underpins important applications such as medical radiography. However, this same attribute makes it challenging to achieve flexible on-demand patterning of x-ray beams. One possible path to this goal is “ghost projection,” a method that may be viewed as a reversed form of classical ghost imaging. This technique employs multiple exposures of a single illuminated non-configurable mask that is transversely displaced to a number of specified positions to create any desired pattern. An experimental proof of concept is given for this idea, using hard x rays. The written pattern is arbitrary, up to a tunable constant offset, and its spatial resolution is limited by both (i) the finest features present in the illuminated mask and (ii) inaccuracies in mask positioning and mask exposure time. In principle, the method could be used to make a universal lithographic mask in the hard-x-ray regime. Ghost projection might also be used as a dynamically configurable beam-shaping element, namely, the hard-x-ray equivalent of a spatial light modulator. The underpinning principle can also be applied to gamma rays, neutrons, electrons, muons, and atomic beams. Our flexible approach to beam shaping gives a potentially useful means to manipulate such fields.