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Q&A: Sleuthing with Neutrons

Paul Langan is the associate laboratory director for neutron sciences at Oak Ridge National Laboratory. He came to ORNL in April 2011 as a senior scientist and director of the Center for Structural Molecular Biology. In October of that year he became founding director of the Neutron Sciences Directorate's Biology and Soft Matter Division. In each role Langan has partnered with other ORNL directorates to build strong multidisciplinary research programs that exploit the neutron scattering capabilities at ORNL.

Langan’s most recent research accomplishments have been in applying neutrons to study enzyme mechanism and drug binding, developing novel technologies and computational methods for neutron macromolecular crystallography, integrating neutron scattering with high-performance computing, and providing a detailed understanding of the cellulose and lignin components of cellulosic biomass.

What about neutrons makes them so interesting across a range of disciplines?

Neutrons are an essential probe for materials research because they provide unique information. In particular they have energies that are well matched to studying huge ranges of length and time scales.

Unlike photons and electrons, which are other essential probes for materials, neutrons are fundamental particles that interact through the strong nuclear force and are therefore sensitive to light elements and isotopes. They are uncharged and therefore highly penetrating, which allows the use of complex sample chambers to look at materials under extreme conditions. Because they are neutral, that means they don’t cause direct radiation damage, which is important for studying functioning biological samples. Finally, they have spin and are therefore sensitive to magnetism.

Our users and staff are using these unique characteristics of neutrons for cutting-edge research. For example, they are studying the synthesis of a new type of diamond thread material that is formed at high pressures, which could have important industrial application in transportation or aerospace manufacturing. These diamond-like threads could be the first member of a whole new class of tunable nanomaterials. They are nondestructively studying parts built through additive manufacturing to improve the reliability of the manufacturing process. They have recently used neutrons to reveal the earliest structural formation of the disease type of the protein huntingtin, and that research is moving forward to study protein malformation responsible for Alzheimer's and Parkinson's diseases. They are studying a number of proteins that are important drug targets against several diseases such as AIDS and cancer, so that better drugs can be made. And they are using neutrons to study the intranozzle fluid dynamics of fuel injectors while they operate. These are just a few examples from the hundreds of experiments that researchers carry out each year at the Spallation Neutron Source and the High Flux Isotope Reactor.

The primary mission of the Neutron Sciences Directorate is to deliver the scientific tools that provide solutions to U.S. energy challenges that make up the core missions of the DOE Office of Science. The scientific breakthroughs that will transform our future are accelerated by the availability of advanced research user facilities like SNS and HFIR. Neutron beams suitable for scattering experiments cannot be generated in small-scale academic or industrial laboratories; thus large-scale user facilities are the only means of providing neutron beams to the scientific community to access their unique possibilities. We are using our neutron facilities to address four science priority areas: quantum materials, materials synthesis and performance, soft molecular matter, and biosciences. A couple of years ago we described what our plan is to further develop our neutron facilities so that they can have higher impact in these priority areas of science, our “strategic science plan.”

As a neutron scientist yourself, what science challenges do you think neutrons can address?

I don’t see myself as a neutron scientist, but as a scientist who uses neutrons along with other complementary experimental methods to answer questions and solve problems. Researchers define a scientific problem and then use whatever experimental methods are best matched to solve that problem. Neutron scattering is one of these experimental methods, but it is an essential one, because neutrons see things that others can’t. I see addressing and solving big science challenges as central to our mission. We met with science leaders from across the country last year to help define what some of those grand scientific challenges are. The workshops sought to outline the most pressing challenges in the fields of quantum materials, biosciences, soft molecular matter, materials synthesis and performance, engineering systems, and modeling and simulation. With those challenges defined, we are able to see clearly what further neutron technologies and innovations we will have to develop at Oak Ridge in order to solve the most important science problems over the next few years. We will be able to address some grand challenges at our present two neutron sources: HFIR and the first target station at the SNS. However, other emerging challenges will require the construction of a second target station at the SNS, one that is optimized for looking at complexity in matter and hierarchical systems.

Gaining a predictive understanding of complex systems is a major challenge in all of our science priority areas that is likely to increasingly dominate the next decade. Oak Ridge is really well positioned to make an impact not only because we have world-leading neutron sources, but also because we have powerful high-performance computing resources. Computing is needed to interpret the results from neutron experiments on complex systems, so I would like to work towards using neutrons and computing as a new integrated tool that can be applied with high impact across a range of different research problems. Construction of the second target station is part of a facilities road map that we have developed that will position Oak Ridge in the world as a truly unique center for neutron science.

What’s the future of neutron science at ORNL?

HFIR and SNS are world-leading neutron scattering facilities—in my opinion they are also two of our nation’s most significant technological achievements. I’m very proud of that. But I don’t think we’ve reached our full potential yet. The mission of this organization—the reason we’re here—is to deliver high-impact science. Our biggest scientific breakthroughs and technical successes lie in the future. That’s what motivates me. HFIR provides the world’s brightest beams of continuous cold neutrons. SNS provides the world’s most intense beams of pulsed neutrons. Together the SNS and HFIR provide neutron scattering instruments that enable science across a large range of different areas of science. I see Oak Ridge becoming a place where the best scientists want to come and work with us because they know we have the best neutron tools to solve the most important research problems that we face as a nation. We can make a difference to our nation’s industrial competitiveness, our health and well-being, and also the major challenges we face in energy and security.