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Abstract: The Diamond Optics & Metrology Group and the collaborators at the STFC Central Microstructure Facility have initiated a program for the design and fabrication of in-line micro- and nano-focusing optics for synchrotron radiation beamlines. The first type of optics fabricated is a kinoform lens in silicon on the same model proposed by K. Evans- Lutterodt et al [Opt. Expr. 11 (2003) 919.]. The fabrication utilised ultra high resolution electron beam lithographic patterning of an electron sensitive SU8 polymer and deep reactive ion etching of silicon. The first test of the focusing properties was performed at the ESRF BM5 optics beamline. In this paper we present details on the design and fabrication, and discuss the test results.

Open Access

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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.

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Abstract: Additive manufacturing (AM), more commonly known as 3D printing, is a commercially established technology for rapid prototyping and fabrication of bespoke intricate parts. To date, research quality mirror prototypes are being trialled using additive manufacturing, where a high quality reflective surface is created in a post-processing step. One advantage of additive manufacturing for mirror fabrication is the ease to lightweight the structure: the design is no longer confined by traditional machining (mill, drill and lathe) and optimised/innovative structures can be used. The end applications of lightweight AM mirrors are broad; the motivation behind this research is low mass mirrors for space-based astronomical or Earth Observation imaging. An example of a potential application could be within nano-satellites, where volume and mass limits are critical. The research presented in this paper highlights the early stage experimental development in AM mirrors and the future innovative designs which could be applied using AM. The surface roughness on a diamond-turned AM aluminium (AlSi10Mg) mirror is presented which demonstrates the ability to achieve an average roughness of ~3.6nm root mean square (RMS) measured over a 3 x 3 grid. A Fourier transform of the roughness data is shown which deconvolves the roughness into contributions from the diamond-turning tooling and the AM build layers. In addition, two nickel phosphorus (NiP) coated AlSi10Mg AM mirrors are compared in terms of surface form error; one mirror has a generic sandwich lightweight design at 44% the mass of a solid equivalent, prior to coating and the second mirror was lightweighted further using the finite element analysis tool topology optimisation. The surface form error indicates an improvement in peak-to-valley (PV) from 323nm to 204nm and in RMS from 83nm to 31nm for the generic and optimised lightweighting respectively while demonstrating a weight reduction between the samples of 18%. The paper concludes with a discussion of the breadth of AM design that could be applied to mirror lightweighting in the future, in particular, topology optimisation, tessellating polyhedrons and Voronoi cells are presented.