Development of High Energy Resolution Inelastic X-ray Scattering Instrument for Materials Research and Education

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

With this award from the Instrumentation for Materials Research program State University of New York at Stony Brook in partnership with several other universities and Argonne National Laboratories will build an optimized, high-resolution inelastic x-ray scattering beamline at the Advanced Photon Source. The instrument will be completely dedicated to this technique, and as such will be the only general-purpose meV resolution x-ray scattering spectrometer in the United States. It will serve a large community of users working on many different problems: dynamics of matter at very high pressure, picosecond dynamics of soft condensed matter and biological systems, high temperature superconductivity, etc. It will be of high system resolution of 0.8 meV (FWHM), and be able to probe a large range of wave vectors, up to several inverse Angstrom. The design is dictated by the desire to reach sub meV energy resolution. This requires the use of diced (segmented) crystals in backscattering geometry for analyzers, a novel nested monochromator to produce a very clean resolution function, and a cryogenically cooled monochromator for maximum x-ray flux. The analyzers must be located eight to ten meters away from the sample, which dictates a large hutch and novel spectrometer designs. The instrument will be available to members of the collaborative access team (CAT) as well as to a broad group of independent investigators. For the hundred years since their discovery, x-rays have enhanced our understanding of the invisible world. The most familiar example is direct imaging of specimens ranging from the cardiac arteries of a beating human heart to pipeline welds and airplane baggage. The technique has enabled us to understand and control how the fundamental principles of how atoms fit together to make molecules, the materials of our daily lives (minerals, steel, semiconductors), and the fundamental elements of life (DNA and proteins). All of these techniques depend on using x-rays in one way or another to take snapshots of a sample. This award from the Instrumentation for Materials Program to SUNY Stony Brook supports the development of an emerging technique involving the use of x-rays to measure dynamics (motion) of atoms on time scales that are inaccessible to other techniques. Among the problems to be studied are sound waves in solids at conditions in the core of the earth, the way that liquids freeze, and the way that proteins fold once they are formed. Many of the most interesting applications require measuring the energy of the x-ray to a precision of one part in thirty million. This requires very special instrumentation, and the very intense source of x-rays available at the Advanced Photon Source. There is currently no such dedicated beamline in the US. The instrument will serve a broad community access team users, with a planned strong outreach program to involve people who are not technical experts in x-ray optics. Furthermore, it is planned to be the most intense and highest resolution inelastic x-ray scattering station in the world.