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Bright Ideas in X-ray spectromicroscopy research at Advanced Light Source

The Advanced Light Source (ALS) is a third-generation synchrotron, a specialized particle accelerator that generates bright beams of x-rays for scientific research. It is located in a building originally designed in the 1930s by Arthur Brown, Jr.—architect of the Coit Tower in San Francisco—to house Ernest O. Lawrence’s 184-in. cyclotron.

In 1987, a $99.5 million construction project, funded by the U.S. Department of Energy’s Office of Basic Energy Sciences, began to reconfigure the building to accommodate the ALS accelerator and beamlines. Completed in 1993, the ALS is a national user facility that now attracts more than 2,000 researchers and students annually from around the world.

Electron bunches traveling nearly the speed of light, when forced into a circular path by magnets, emit bright ultraviolet and x-ray light that is directed down beamlines to experiment end stations. The ALS produces light in the x-ray region of the electromagnetic spectrum that is 1 billion times brighter than the sun. This extraordinary tool offers opportunities for state-of-the-art research in biology, chemistry, physics, and materials, energy, and environmental sciences.

Ongoing research includes semiconductors, polymers, superconductors, magnetic materials, biological macromolecules (proteins, etc.), 3-D biological imaging, chemical reaction dynamics, and atomic and molecular structure.

UC Berkeley Civil and Environmental Engineering Research Engineer Marie Jackson explains the differences between ALS's processes and more traditional microscopy practices: "In petrographic microscopy, a digital camera photographs an image through a traditional polarized light microscope; in scanning electron microscopy with energy dispersive spectroscopy compositional analyses, a focused beam of electrons scans a sample and produces a high-resolution image with information about the morphology at the micron scale and qualitative chemical analysis, mainly as major elements in atomic percent or in weight percent oxides; and in synchroton radiation applications, electromagnetic radiation emitted by high-energy particles accelerated to relativistic speeds in a magnetic field are focused on a sample to determine diverse aspects of its material characteristics at the nanoscale.

"The Scanning Transmission X-ray Microscopy analyses performed at ALS beamlines 5.3.1 and 5.3.2 (described in the American Mineralogist article) investigate the very fine scale bonding environments of aluminum and silicon (also carbon and calcium) in poorly-crystalline C-A-S-H and crystalline Al-tobermorite in relict lime clasts. The high-pressure X-ray diffraction analyses performed at ALS beamline 12.2.2 (discussed in the Journal of the American Ceramic Society article) describe mineral structure of the Al-tobermorite in a relict lime clast and its mechanical properties, computed as bulk modulus. The micro X-ray diffraction analyses performed at ALS beamline 12.2.2 (also described in the Journal of the American Ceramic Society article) show the mineral structure of Al-tobermorite and phillipsite in the cementitious matrix of the ancient seawater mortar."

X-ray spectromicroscopy also can study the hydration process in-situ (under water). This unique feature permits researchers to characterize complex reactions with very high spatial resolution (~20 nm). Together with ALS scientists, the Berkeley team is exploring the use of diffraction imaging, which can revolutionize the understanding of the early-age reactions.