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Aberration-free aspherical lens shape for shortening the focal distance of an already convergent beam

DOI: 10.1107/S1600577517011808 DOI Help

Authors: John P. Sutter (Diamond Light Source) , Lucia Alianelli (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Synchrotron Radiation , VOL 24 , PAGES 1120-1136

State: Published (Approved)
Published: November 2017

Open Access Open Access

Abstract: The shapes of single lens surfaces capable of focusing divergent and collimated beams without aberration have already been calculated. However, nanofocusing compound refractive lenses (CRLs) require many consecutive lens surfaces. Here a theoretical example of an X-ray nanofocusing CRL with 48 consecutive surfaces is studied. The surfaces on the downstream end of this CRL accept X-rays that are already converging toward a focus, and refract them toward a new focal point that is closer to the surface. This case, so far missing from the literature, is treated here. The ideal surface for aberration-free focusing of a convergent incident beam is found by analytical computation and by ray tracing to be one sheet of a Cartesian oval. An `X-ray approximation' of the Cartesian oval is worked out for the case of small change in index of refraction across the lens surface. The paraxial approximation of this surface is described. These results will assist the development of large-aperture CRLs for nanofocusing.

Journal Keywords: X-ray; lens; oval; nanofocusing; aberration

Subject Areas: Technique Development, Physics


Technical Areas: Metrology , Optics

Documents:
jsy2yi5037.pdf