Focusing, collimation, and beam expansion of high-energy X-rays with diamond refractive lenses

Diamond is extremely well suited for synchrotron X-ray refractive optics. The effectiveness of diamond refractive lenses, fabricated by pulsed laser ablation, is demonstrated here for the focusing, collimation, and expansion of high-energy, undulator-source X-ray beams in the 40-70 keV photon energy range. The design of the lens elements and their mounting scheme allow the convenient feature of stacking both one-dimensionally and two-dimensionally focusing elements together in a self-aligning manner within the same holder for astigmatic manipulation, when needed. The CuCrZr alloy frames embedding the diamonds are suitable for thermal management, while possessing hardness. Collimating lenses, placed following a high-heat-load monochromator, are employed to increase the throughput of a subsequent narrow-angular-acceptance high-energy-resolution monochromator, after which the X-rays are focused to deliver a beam to coherent diffraction experiments on a long beamline. Also motivated and proposed is the concept of a convex beam-expander, which might seem counterintuitive given that it has higher attenuation on-axis. However, for high-energy X-rays from a low-emittance source on a long beamline, convex diamond beam-expanders could be practical. A proof-of-principle test result of this idea is presented.