APS’s bright light aids scientific discovery

Using a bright light aids discovery, whether you’re searching for your keys or attempting to reveal centuries-old scientific secrets. Researchers at Argonne’s Advanced Photon Source (APS) have lifted veils from a number of secrets.

The APS’s 1,104-meter circumference storage ring, large enough to encircle a baseball park, produces the nation’s most brilliant X-ray beams for materials and biological research. This complex machine accelerates and stores a beam of subatomic particles that is the source of APS’s 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, X-rays from the APS are 1 billion times more intense than those available in the standard laboratory. This brilliance permits the examination of materials in greater detail and shorter duration, as well as the use of samples that are smaller than those required in conventional experiments.

Second, scientists at the APS can select the X-ray energy most appropriate for their experiments. With a typical laboratory X-ray tube source, only one X-ray energy is available. The ability to choose the energy permits analysis of specific elements within a sample, allowing researchers greater control of their experiments. Results of some of those experiments follow.

LEARNING TO BURN
Scientists have explored the dense core of fuel injection, essential for improving engine performance and reducing vehicle emissions. Using APS X-rays to examine the structure and atomization process of fuel sprays, researchers from Argonne’s Transportation Technology Research and Development Center and the APS can see how very small particles of the fuel mix with air to create combustion. Physical properties such as droplet size and density, spatial distribution, air-to-fuel ratio and velocity of spray particles govern the spray’s combustion behavior, which in turn determines efficiency and emissions levels. Researchers at the APS can see and measure these properties deep inside the fuel spray — information that cannot be obtained through laser, optical or other research techniques.

This work has particular application for diesel fuel. While diesel engines are much cleaner and more fuel-efficient than they were 20 years ago, they must become even more so to help reduce the nation’s dependence on overseas oil. These APS experiments will help engineers design injection system components to raise fuel efficiency and lower emissions.

UNDERSTANDING IRON IN THE EARTH’S CORE
In other research, scientists have determined the phonon density — used to measure thermal energy — of states for iron under pressures up to 153 gigapascals — equivalent to those found at the Earth’s core. Proving long-held theories for iron at these pressures opens doors to a diverse array of basic and applied investigations, including seismological interpretation, planetary science and the development of new thin-film materials such as data-storage media.

Scientists from the APS and the University of Chicago were joined by colleagues from the Carnegie Institution of Washington, University College London, and Fachbereich Physik of Germany for this research.

Previously, ultrahigh-pressure experiments using nuclear resonant inelastic scattering have been difficult to carry out due to the tiny samples required. The extreme brilliance of APS X-ray beams has removed this limitation. The new data and subsequent experiments are of obvious interest to Earth scientists and geophysicists, because iron is prevalent in the cores of several planets, including ours, where the core is a metallic alloy rich in iron and densely packed by extreme pressures.

MICROORGANISMS PROVIDE MINING SITE INSIGHT
Probing the microscopic life found in the submerged recesses of an abandoned Wisconsin lead and zinc mine, scientists from Argonne and the University of Wisconsin-Madison have found compelling evidence that microorganisms play a key role in the formation of mineral deposits.

The finding not only sheds light on biology’s role in forming some metal ores, but could help jump-start new remediation efforts for contaminated mining sites.

The microorganisms are found in natural biofilms that seem to concentrate zinc sulfide. The biofilms, found deep in an abandoned mine, are heavily populated with the bacteria, some of which help convert zinc from groundwater and sulfate or sulfuric acid — a pervasive contaminant associated with the mining of metal ores into zinc sulfide.

These results show how microbes control metal concentrations in groundwater and wetland-based remediation systems and suggest biological routes for formation of some low-temperature zinc-sulfide deposits.

MUSCLE RESEARCH TAKES WING
Researchers from the Illinois Institute of Technology and the University of Vermont used the high-brilliance X-ray beams from the APS to create high-quality patterns from the flight muscles of live fruit flies. These insects are ideal for study because they are amenable to genetic manipulation and, therefore, can be used in studies to probe specific aspects of muscle function. The experiments produced detailed, two-dimensional X-ray diffraction patterns of working muscle in a living organism and provide a new model for studying integrative biology.

Precise measurements at 1-millisecond time resolution indicate that the myofilament lattice spacing — the structure of the delicate muscles that make up the pattern in the wings — does not change significantly as the wings flap, a process called "oscillatory contraction." This result suggests that, as the wings move, the muscles that power that movement are perfectly coordinated throughout the fruit fly’s flight.

The experiments helped increase understanding of the relationship between molecular structure and muscle function in living organisms.

For more information please contact Catherine Foster