Thursday, June 8, 2006, 10:00 am — NSLS-II Seminar Room, Bldg. 817
: Refractive x-ray lenses have been recently shown to be able to efficiently generate hard x-ray beams with a lateral extension well below 100nm. In particular, a hard x-ray beam (E = 21keV) was focused down to 47 x 55 nm^2 (flux 1.7 10^8 ph/s) at short distance from an undulator source [1]. Based on these optics, a hard x-ray scanning microscope is currently being built at the ESRF. In view of the application of refractive optics at future sources, the question is addressed of what is the smallest spot size that hard x rays can be focused to using refractive optics [2]. This question is linked to the limitation of the refractive power per unit length of the optic along the optical axis at a given aperture. A thick refractive x-ray lens is considered, whose aperture is gradually (adiabatically) adapted to the size of the beam as it converges to the focus. These adiabatically focusing lenses (AFLs) are shown to have a relatively large numerical aperture, focusing hard x rays down to a lateral size of 2 nm (FWHM). Although there is not a sharp fundamental limit for the focal size, atomic resolution seems to be out of range for these optics.
[1] C. Schroer, et al., APL 87, 124103 (2005)
[2] C. Schroer, B. Lengeler, PRL 94, 054802 (2005)
Hosted by: Kenneth Evans-Lutterodt
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