Now, The Science
The SNS seeks to integrate a variety of scientific disciplines.
Just months after a single keystroke produced the research facility's first neutrons in the spring of 2006, the Spallation Neutron Source became the world's most powerful neutron source, a feat achieved while operating at only about 10 percent of its design power. Two years later, the SNS continues to explore new scientific dimensions, measured in the sheer magnitude of neutron flux and in the quality, breadth and vision of some of the most ambitious programs ever contemplated in the materials sciences.
The scientific community has no shortage of superlatives to describe the efforts required to get the massive $1.4 billion project funded, built and in the business of producing groundbreaking research. The efforts, indeed, are ongoing. Researchers increased the power of the SNS proton beam to an unprecedented one megawatt in the fall of 2009.
"On the facility development side of the house, we have come a very long way," says SNS director Ian Anderson. "Zero kilowatts to one megawatt is an incredible distance to have covered. We accomplished what we said we would do all the way through, despite considerable challenges along the way."
"Earlier this year we were within reach of the megawatt level," Anderson says. The machine was running reliably at 870 kilowatts when we made a few modifications designed to enable us to reach the megawatt milestone. Suddenly a problem occurred with the stripper foils used to create protons from the accelerator's hydrogen ion beam. Having never encountered that reaction, we reduced the machine's power, providing an opportunity to examine the process while allowing our science programs to continue uninterrupted."
Anderson believes the experience illustrates one of the challenges of running a major user facility like the SNS, where the unique needs of an international science program must be balanced with an expectation to reach operational milestones, like increased power levels, that are part of the project's commitment to the Department of Energy. Despite these expectations, running reliably and maintaining a high level of scientific output remain the primary goals for the SNS.
Producing the Science
The SNS has long been expected to have a major influence in areas traditionally associated with neutron science. As the capabilities of the SNS become increasingly apparent, scientists are realizing that this influence will also extend to fields such as biological sciences and soft matter, where using neutrons as research tools is a relative novelty. The facility's expanding significance is a result of both a quantum leap in beam power and the diversity of experimental instruments deployed or planned for the target station's 24 beam lines.
"Neutron science is a technique that can be used to study a virtually unlimited variety of materials," Anderson says. "We encourage our scientists to engage with their colleagues in other fields at ORNL and in the user community. This familiarity helps direct improvements in instrumentation and capabilities toward the needs of a broader range of science programs and keeps the SNS at the forefront of research."
Even as the SNS matures, its scientific highlights are already numerous. One such highlight is the experimental results related to the newly discovered iron arsenide family of superconductors. Novel research at the facility's ARCS spectrometer has advanced understanding of so called "unconventional" superconductivity, a precursor to a similar understanding of the basic mechanisms that give rise to superconductivity.
Unlocking the door to superconductive materials holds the long-term potential for developing a suite of technologies that could significantly reduce energy consumption. ORNL is in the unusual position of having both the facilities to synthesize these materials and the neutron scattering capabilities needed to study their structure and how they work.
Enhanced fuel cell technology is among the areas of focus for new materials. The Backscattering Spectrometer at the SNS is being used to explore ionic liquids used as membranes in proton fuel cells. The liquids have demonstrated the ability to function at relatively high temperatures, conditions under which standard "Nafion" membranes would have become completely dry.
Recent work on the SNS Magnetism Reflectometer has demonstrated that thin films of metal oxides can become magnetic when combined with paramagnetic films. This development has implications for the enhancement of data storage devices such as memory chips in phones and computers.
New polymers are yet another goal of SNS researchers. The facility's Liquids Reflectometer examines the structure and movement of individual molecules in "self-healing polymers." When these polymer mixtures are damaged, one polymer moves quickly to the surface—"healing" the damage—while the remaining polymers keep the structure stable. Understanding how these materials function and controlling their behavior have wide-ranging applications in the development of lubricants and biomaterials, such as medical implants and antimicrobial agents.
Other polymer–related research employs the SNS's Liquids Reflectometer to focus on the shifting structure of pH-dependent polymer films. These films go through a series of changes related to the acidity of their environment, leading toward the day when they may be used by pharmaceutical companies to encapsulate drugs. When the films migrate to a point where the acidity is different, such as the stomach, they would break down and release the drug.
To the surprise of some, biology is one of the areas in which the SNS is expected to have the greatest impact. The facility's high-intensity neutron flux enables researchers to understand the structure and function of protein crystals and biological membranes in much more detail than was previously possible.
Anderson points out that SNS researchers are also working with bio-inspired polymer membranes using the Liquids Reflectometer. "They are attempting to mimic the function of biological membranes by attaching polymers to substrates and making them functional. The ability to design and build instrumentation that can peer into the structure of membranes and see how they interact with proteins will have a major impact on the field."
Still another discipline being reshaped by the SNS is the study of materials under extreme conditions, including high pressure, extreme temperatures and intense magnetic fields. Anderson observes that, "Most of the time, scientists are not interested in whether materials function at room temperature. They would prefer to understand their properties under conditions in the real world."
Bolstered by unprecedented beam power, the SNS instruments can simulate real world conditions inside an automobile engine, deep in the earth's crust, or in the structure of an aircraft wing.
Burden of Expectations
In some respects, the SNS has already exceeded expectations. Against the backdrop of cost overruns and unmet schedules that have plagued similar projects, the ability to build one of the world's largest and most complex science facilities on time, on budget and on scope was, in many respects, a historic achievement. The rapid pace with which researchers ramped up the beam power toward the one megawatt threshold intensified further the sense that the SNS would fulfill its scientific promise.
Yet even as scientists pass these milestones, they are aware that their significance is short-lived. The true value of the SNS will lie in its ability to answer fundamental questions that cannot be answered anywhere else in the world. In particular, the SNS must be viewed as a center for neutron science, with capabilities that open up new horizons in disciplines across the physical and biological sciences.
Ian Anderson and his team are fully aware of both their potential and the burden of expectations. Having delivered a facility of unmatched quality, the SNS team is now committed to nothing less than producing the science that can literally reshape the world.
Web site provided by Oak Ridge National Laboratory's Communications and External Relations