Development of Scatterless Hybrid Slits Led to New High Flux Single Aperture SAXS Design

Cyrus R. Safinya, University of California-Santa Barbara, DMR 0619171

A simple hybrid design allowed us to produce scatterless aperture slits for small angle x-ray scattering and high resolution x-ray diffraction. The hybrid slit consists of a rectangular single crystal substrate (e.g Si or Ge) bonded to a tapered high density metal base. The single crystal tip is oriented far from any Bragg peak position with respect to the beam and hence produces no slit scattering commonly associated with conventional metal slits. A new, high performance single-aperture optical design has been developed for small angle x-ray scattering instruments. Based on the scatterless slits, the reduction of apertures in the system led to dramatically increased intensity as well as improved low angle resolution. A 3-fold flux increase was observed compared to a 3 slit set-up, enabling us to collect high quality SAXS data from microtubules with only 20 min exposure.

This broadly applicable design concept can be adopted to significantly boost the performance of a large number of existing and future SAXS instruments, providing enhanced nanoscale characterization capability in broad areas of research.

Figure (A, B) Schematic design of the scatterless hybrid slits. The tapered design is crucial for scatterless performance. (C, D) 2D SAXS data (20 min exposure) from a microtubule sample and corresponding intensity plots compared to a 10min exposure data at SSRL. All relevant structure details are well developed in the in-house data.

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Reference: Y. Li , R. Beck, T. Huang, M.C. Choi, M. Divinagraci, “Scatterless Hybrid Metal-Single Crystal Slit for Small Angle X-ray Scattering and High-resolution X-ray Diffraction”, J. Appl. Crystallography, accepted, 2008

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X-RAY BEAM

MRI: Development of an Ultra-High Resolution Small Angle X-Ray Scattering Instrument for Characterizing Supramolecular Assemblies

Cyrus R. Safinya, University of California-Santa Barbara, DMR 0619171

Education: The multidisciplinary research team is comprised of undergraduate and graduate students, and postdocs, with backgrounds in materials, physics and engineering. Participants are educated in x-ray instrumentation science and SAXS methods for nanoscale characterization of supramolecular assemblies, gaining essential skills fpr successful careers in a broad range of areas including nanoscience and nanotechnology, polymer physics and chemistry, chemical and biomedical engineering. Pictured (right): Postdoctoral researcher Roy Beck (Materials and Physics) working with graduate student Joanna Deek (Chemistry) to set up a SAXS measurement.

Outreach: The PI’s personally participate in multiple outreach programs at UCSB for undergraduate and high school teacher research internships. We actively recruit and encourage undergraduate students to work on this project to gain valuable first hand research experience. Co-PI Li worked closely with UCSB mechanical engineering undergraduate students Nicholas Judy and Eric Walsh (pictured to the right at Mechanical Engineering Senior Project Fair with mentor Co-PI Li) to design and fabricate many mechanical components for the new SAXS instrument.