Brilliant X-Rays Reveal the Unknown

Discoveries at Argonne’s Advanced Photon Source (APS) over the past year have ranged from new insights into the human immune system to detection of an ancient forgery (see separate stories).

The 1,104-meter-circumference storage ring of the APS is large enough to house a baseball park. It produces the nation’s most brilliant X-ray beams for biological and materials science research. This complex machine accelerates and stores a beam of electrons that is the source of APS X-ray beams.

The APS produces its X-rays using synchrotron radiation, a source that differs in two fundamental ways from conventional laboratory X-ray generators. First, the synchrotron source is much more intense. The intensity from the APS is a billion times greater than that available in the standard laboratory. The source’s brilliance permits both the examination of materials in greater detail and in shorter times and the use of samples that are smaller than those required for experiments with conventional X-ray sources. Second, scientists at the APS can precisely select the energies of their X-ray beams. With a typical laboratory X-ray tube, only one X-ray energy is available. The ability to choose the energy lets scientists focus their research on specific elements within a sample.

Of course, no matter how remarkable the machine, its worth is shown in the research performed on it. At the APS, that research is done by scientists as part of collaborative access teams, or CATs. They design and build their own instrumentation and detection devices housed at research stations located along the X-ray beam’s path. CATs are like small research institutes in their own right. They must provide the know-how, money and effort to design, build and operate the X-ray experiment stations.

CAT members conduct their experiments using about 75 percent of the scheduled beamtime. They also make their experimental facilities available to “independent investigators,” X-ray experimenters with interesting projects who are not affiliated with CATs. Each CAT focuses its research in specific disciplines, such as materials science, chemistry, physics, biology, X-ray instrumentation, or geological, soil and environmental sciences.

In 1999, researchers from universities, medical schools, companies, U.S. national laboratories and research institutions around the world joined Argonne researchers to use the APS. The four newest CATs are SGX-CAT, dedicated to solving the structures of potential drug targets, HP-CAT, which looks at materials under high pressure, SER-CAT, a consortium of south-eastern universities performing structural biology research, and COM-CAT, a commercial facility funded by the State of Illinois.

Operated by the San Diego-based Structural GenomiX, SGX-CAT uses the X-rays focused by the beamline to produce images of proteins and potential drug targets with atomic level precision. The July 2000 CAT signing was attended by Secretary of Energy Bill Richardson. Research is expected to be underway in 2001.

HP-CAT comprises the Carnegie Institution of Washington, Lawrence Livermore National Laboratory and the University of Nevada, Las Vegas. Researchers study the way properties of materials can be radically altered under extreme pressure. Understanding and possibly predicting those changes can help improve many construction and industrial processes, and add new dimensions to studies in fundamental physics, chemistry, earth and planetary sciences, and materials science and technology.

The projects undertaken by the Southeast Regional CAT will range from the discovery of new molecular structures and drug designs to protein engineering and materials science. Their research will benefit from the APS’s ability to reveal crystal structures too small to be studied effectively with X-ray sources at most universities. Members of SER-CAT are the universities of Alabama (at Birmingham and Huntsville), Georgia, Kentucky, Missouri, North Carolina, South Carolina, Tennessee and Virginia, as well as the National Institutes of Health. Others involved in the SER-CAT include Florida State University, Emory University, Georgia Tech, Duke University, Clemson University, North Carolina State University, Vanderbilt University and St. Jude Children’s Research Hospital.

COM-CAT, funded by the State of Illinois’ Department of Commerce and Community Affairs, is available to commercial firms throughout the state. This new service is available for the first time in the year 2000. It will be useful to high-technology firms needing detailed information about materials structures.

Previously, users of synchrotron X-ray radiation had to either invest heavily in the construction of experimental equipment or plan months in advance to obtain access to the needed facilities. Now, COM-CAT offers Illinois’ industrial researchers rapid access to the benefits of synchrotron radiation and provides analytical services on a fee for service basis. Because of the high intensity of APS X-rays, spectra or diffraction patterns can be obtained rapidly, permitting the study of large numbers of samples typical of manufacturing process development.

For more information please contact Catherine Foster at 630-252-5580

Next: Lasers Light Up the Future of Synchrotron Light Sources