Computer simulation of the effect of focusing X rays by means of refractive-diffractive lens

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Abstract

The features of focusing X rays using a refractive-diffractive lens (RDL), which is a system of two asymmetrically reflecting crystals with asymmetry factors, the product of which is equal to unity, and a refractive lens with a large focal length, are theoretically studied. Crystals make it possible to shorten the focal length of the lens by b2 times, where b is the asymmetry factor of the second crystal. A detailed numerical simulation of the effect of radiation focusing using the RDL has been performed. The universal computer program XRWP was used which is created to calculate the effects of coherent X-ray optics. Analytical formulas are obtained for the optimal aperture and radius of curvature of the lens, as well as for the width of the radiation spectrum that can be focused.

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About the authors

V. G. Kohn

National Research Centre “Kurchatov Institute”

Author for correspondence.
Email: kohnvict@yandex.ru
Russian Federation, Moscow

References

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Supplementary files

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2. Fig. 1. Experimental diagram: 1 – point source, 2 – slit limiting the beam, 3 – first crystal expanding the beam, 4 – lens focusing the beam, 5 – second crystal compressing the beam, 6 – focus, i.e. the place where the beam becomes a secondary source.

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3. Fig. 2. Distribution of the relative radiation intensity in empty space in the region near the focal point using the RDL. Photon energy 17.58 keV, distances from the RDL to the source and focus z0 = z1 = 2.24 m, silicon crystals, 220 reflection, asymmetry factors b equal to 1/20 and 20 for the first and second crystals. Beryllium lens, R = 1 mm, A = 2 mm.

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4. Fig. 3. Distribution of the relative radiation intensity in empty space in the region near the focal point using the RDL with the same parameters as in Fig. 2, except for z0 = 50 m, z1 = 1.15 m.

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5. Fig. 4. Dependence of the optimal values ​​of the aperture A (1) and the radius of curvature of the surface R (2) of the lens on the parameter M = z1/z0 at a fixed distance zt = z0 + z1 = 4.48 m. All other parameters are the same as in Fig. 2.

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6. Fig. 5. The energy spectrum of the radiation focused with the help of RDL, i.e. the x-coordinate integral intensity in focus as a function of the photon energy for the RDL parameters, as in Fig. 2.

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