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Foreign governments are investing in the SNS. International collaborations have been a hallmark of ORNL since the early days of the laboratory's neutron research program. As the Spallation Neutron Source matures in scope and complexity, these scientific collaborations are more important than ever. As the world's foremost facility for the study of materials, the SNS will be a critical resource for the international neutron community. In return, ORNL will be the beneficiary of a vast wealth of expertise brought to the facility by thousands of visiting scientists.
"ORNL's philosophy opens our user program to international investigators and institutions on the same basis as it does to anyone else," says SNS scientist and administrator Ken Herwig. "That philosophy encourages researchers from every corner of the world to bring their most important scientific problems to the SNS. The result is a creative energy that maximizes our impact in the scientific community." Herwig notes that because visiting researchers have worked at many different facilities, they bring a range of perspectives and techniques to the research process. "Both their perspectives and their experience enrich the scientific program at SNS," Herwig says. Currently, barely three years into operation, the SNS has major collaborations with research institutions from Germany, Canada and Switzerland ORNL's German Counterpart The most extensive partnership to date has been with the German research center, Forschungszentrum Jülich. In many ways a German counterpart to ORNL, Jülich has a research portfolio that emphasizes energy, bioscience and high-performance computing. A unique collaboration with ORNL has resulted in a major contribution by Jülich to the SNS instrument suite. Drawing on its considerable experience in the design and construction of neutron instrumentation, Jülich teamed with SNS to build the Neutron Spin Echo Spectrometer The instrument will be used to study "soft matter" systems. Researchers use the instrument to delve into a wide range of biological problems, such as how proteins that can encapsulate small molecules might be adapted for delivering drugs to specific targets within the body. Herwig notes that Jülich not only funded the construction of the instrument but also its operation. "They are embedding their staff in our organization to run the instrument for the benefit of the ORNL user program," he says. In return for this unique level of commitment to the SNS, Jülich receives 20 percent of the beam time on the Spin Echo, as well as beam time on two additional instruments. Herwig observes that a fifth of the beam time on any SNS instrument is "a sizeable resource." "Jülich also funds an instrument scientist on each of the other two instruments," he adds. "Their commitment to the SNS scientific program is very significant." Herwig believes the project is a great long-term asset to the SNS. "The Germans brought 20 years of experience to a worldclass instrument in a world-class facility that will be available to thousands of users for years to come." Canada's "Big" Investment A second international instrument at the SNS is the VULCAN Engineering Diffractometer, funded by the Canadian Foundation for Innovation. CFI is an independent corporation created by the Canadian government to assist Canada's research institutions. VULCAN enables users to take measurements of the positions of atoms in materials under conditions of stress that are of particular interest to researchers focused on engineering applications. "One of VULCAN's unique assets is its sheer size," Herwig says. In contrast to instruments designed to take measurements from minute crystals, VULCAN enables researchers to place objects as large as an engine or a section of an aircraft's wing in the path of the beam. "We call it an engineering diffractometer," Herwig notes, "because VULCAN is designed specifically to look at materials that are involved in engineering-related problems. Using this instrument, we can push, pull and twist materials while they are in the neutron beam. By subjecting the materials to the same stresses and strains they experience in real-world use, we can better understand how cracks form and spread." Assisted by the world's most powerful computers, ORNL scientists use data from VULCAN to address a variety of problems associated with material degradation and failure in critical applications. In return for providing funding to build the instrument, the CFI scientists, like their colleagues from Jülich, receive a share of VULCAN's beam time, as well as beam time on SEQUOIA, an instrument that specializes in studies of magnets and hightemperature superconductors. Swiss Magnetism The Swiss have made two major contributions to the SNS research program. Both of these contributions were provided by the Paul Scherrer Institut, a research laboratory operated by the Swiss government. The first of the two contributions came in the form of an enormous magnet designed to provide unique environmental conditions for sample analysis. "We usually seek to control the environment around the sample to meet specialized conditions," Herwig says. "To address a number of scientific questions, we wanted to be able to apply a very strong magnetic field to the sample. The Swiss helped make this possible by funding the construction of a massive 16-Tesla magnet. Several of the SNS instruments were designed to produce and use beams of polarized—or magnetically identical—neutrons. Polarized neutrons enable scientists to probe magnetic structure and fluctuations in materials. Herwig explains that, "If all of the neutrons have the same initial polarization direction, we can get more information on magnetic interactions and structure than we could using an unpolarized neutron beam." The new Swiss magnet is expected to be particularly useful in the study of superconductors and nanomaterials. To ensure that the field produced by the giant magnet does not interfere with neighboring instruments, the magnet is enclosed in a second set of magnetic coils that compensate, or "jam," the magnetic field produced by the primary coils. The Swiss magnet is the first compensated magnet of this field strength to be built for a neutron beam line. Herwig says the other SNS collaboration with the Swiss is the development of key components of a new instrument called HYSPEC, scheduled to come on line in the next two years. HYSPEC will be one of the SNS instruments designed to employ a polarized beam of neutrons. The Paul Scherrer Institut is producing a specialized optical component called a supermirror polarization analyzer that will enable researchers to determine whether neutrons change their polarization as they interact with a sample. Unlike other SNS instruments used to study magnetic materials, HYSPEC can also tightly focus the neutron beam, enabling the analysis of smaller samples. This unique capability would be particularly valuable for the study of crystalline materials, such as certain esoteric superconductors that are difficult to grow in large volumes. Swiss scientists have been allocated beam time across the SNS instrument suite in return for the Paul Scherrer Institut's contributions to the SNS's research program. Demonstrating the Benefits In fewer than three years, the enormous potential of the SNS to expand the boundaries of traditional materials science and extend the reach of neutron science to new fields of study has been demonstrated. The addition of the Neutron Spin Echo Spectrometer NSE, the Paul Scherrer Institut magnet and new optical components, and the recent completion of the VULCAN diffractometer together represent major contributions by the international scientific community to America's research agenda. There is little question that the U.S. user community, as well as the scientific mission of the Department of Energy, have benefitted—in terms of both the instruments that are available and the quality and breadth of the research being conducted—from an unprecedented level of international involvement in the SNS research program. As the SNS gradually fills the complement of instruments in the first target station and plans how the 25 additional beam lines in a proposed second target station will be allocated, Herwig expects to see a continued level of international cooperation. "I expect the model of collaboration we have established to continue," he says. "Without a willingness to undertake this level of collaboration, these instruments and their wonderful capabilities would not be at the SNS. Put simply, our international partnerships extend the reach of our research program in ways we never could have imagined."
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