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![[Figure 1]](fd5003fig1mag.jpg)
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Figure 1
Evolution of transparent concave lenses for the focusing of X-rays. The pioneering experiments were performed using circular holes drilled into a substrate (Snigirev et al., 1996  ) as shown in (a). Single (b) or stacks of parabolic lenses provide better focusing properties (Lengeler, Schroer, Tuemmler et al., 1999) and the kinoform version of these objects, (c), (d) (Aristov et al., 2000) and (e) (Snigireva et al., 2001), provide larger apertures owing to reduced absorption. The LP lens (f) approximates the parabolic material distribution stepwise (step h) with linear segments (Cederström et al., 2000). The focal distance is tunable as h can be varied. Note that for the sake of clarity this lens is drawn with a very exaggerated inclination. The prism array (g) is the Fresnel version of the latter lens with increased aperture. The array (h), which also has the appropriate curvature for ideal focusing, is discussed in this report. The lenses in (a) and (b) have already been realized with radial symmetry for two-dimensional focusing. All other devices are linear devices, which provide two-dimensional focusing only in a crossed pair. |
![[Figure 1]](fd5003fig1.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
