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Near-100% Bragg reflectivity of X-rays


Ultrahigh-reflectance mirrors are essential optical elements of the most sophisticated optical instruments devised over the entire frequency spectrum. In the X-ray regime, super-polished mirrors with close to 100% reflectivity are routinely used at grazing angles of incidence. However, at large angles of incidence, and particularly at normal incidence, such high reflectivity has not yet been achieved. Here, we demonstrate by direct measurements that synthetic, nearly defect-free diamond crystals reflect more than 99% of hard X-ray photons backwards in Bragg diffraction, with a remarkably small variation in magnitude across the sample. This is a quantum leap in the largest reflectivity measured to date, which is at the limit of what is theoretically possible. This accomplishment is achieved under the most challenging conditions of normal incidence and with extremely hard X-ray photons.

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Figure 1: X-ray Bragg diffraction diagram, X-ray Bragg reflectivity from a thick diamond crystal, and a colour map of averaged Bragg reflectivities for all allowed Bragg reflections and photon energies.
Figure 2: Reflectivity of X-rays as a function of photon energy E in Bragg backscattering from the (13 3 3) atomic planes in diamond (EH = 23.765 keV).
Figure 3: Absolute reflectivity.
Figure 4: Scheme of the experimental set-up for reflectivity measurements with highly monochromatic X-rays.


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The authors are grateful to Kwang-Je Kim (APS) for stimulating interest and discussions. We are indebted to V. Denisov, S. Polyakov and M. Kuznezov (TISNCM) for help in growing and characterizing the diamond crystals. D. Shu (APS) is acknowledged for the development of the 13.9 keV high-resolution X-ray monochromator crucial for the present studies. A.H. Said and D. Walko (APS) are acknowledged for the beamline support. Thanks go to X. Huang (APS), B. Raghothamachar and M. Dudley (SUNY) for supporting the white beam topography studies at beamline X19C of the National Synchrotron Light Source. The authors are indebted to R. Lindberg (APS) for reading the manuscript and providing valuable suggestions. Work was supported by the US Department of Energy (DoE), Office of Science, Office of Basic Energy Sciences (contract no. DE-AC02-06CH11357). Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the DoE (contract no. DE-AC02-98CH10886). This work is dedicated to the memory of Uwe van Bürck.

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Y.S. planned, organized, and performed the experiments, analysed the data and wrote the paper. S.S. built the 13.9 keV high-resolution monochromator, and performed reflectivity experiments and white beam topography studies of diamonds. V.B. and S.T. organized the manufacture of synthetic diamonds, and synthesized, processed and characterized the diamond crystals.

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Correspondence to Yuri Shvyd'ko.

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The authors declare no competing financial interests.

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Shvyd'ko, Y., Stoupin, S., Blank, V. et al. Near-100% Bragg reflectivity of X-rays. Nature Photon 5, 539–542 (2011).

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