Looking ahead: SNS users visit to discuss next-generation target station at ORNL

 

More than 200 scientists from around the world met from October 27 to 29 at the U.S. Department of Energy’s Oak Ridge National Laboratory to provide input on the scientific instruments that would be installed at a proposed Second Target Station, or STS, at the Spallation Neutron Source.

The workshop—which was organized by ORNL’s Neutron Sciences Directorate and drew researchers from 56 universities, research institutions, and other national laboratories—aimed to define the capabilities needed to ensure the next-generation neutron source meets the biggest science challenges.

The Spallation Neutron Source is a DOE Office of Science User Facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development.

Neutron scattering is useful to scientists because it is one of the few characterization techniques that reveals where atoms are and how they move, which helps researchers understand the relationships between the structure, dynamics, and function of materials, from batteries and superconductors to polymers and enzymes. This understanding allows researchers to form predictive models that inform new material designs.

Discovery and study of future materials will require neutron techniques that do not currently exist and that complement ORNL’s two current neutron sources, the first target station at the SNS, and the High Flux Isotope Reactor. The Department of Energy has charged ORNL with understanding how a strategic investment in a new neutron facility such as the Second Target Station can meet the nation’s future science challenges and fuel major discoveries.

The SNS accelerator and the HFIR reactor produce neutron beams for instruments specially designed to study characteristics of materials. Defining the instruments for the STS was one of the key discussion topics during the ORNL workshop. Scientists used the opportunity to determine what new and innovative instruments would be possible at the new neutron source.

“(With STS) we’re hoping to answer big and important questions,” said Boris Khaykovich, workshop co-chair from Massachusetts Institute of Technology. “We’re hoping to study very complex materials with multiple levels of organization—small samples, novel materials, and samples that are difficult to make.”

The workshop was an opportunity for the research community to weigh in on the science they expect to do at the Second Target Station, what they need to do that they can’t do now, and which types of instruments are their top priorities, explained Ken Herwig, the local workshop coordinator and Instrument Technologies lead for Neutron Sciences at ORNL.

“A lot of the workshop’s excitement centered on discussing these possible instruments,” Herwig said. “The teams were charged with first reviewing the science needs of STS and secondly looking at what types of instrumentation would address those needs.”

The STS team will take those concepts and continue to develop them as they head toward a conceptual design report for the new facility.

While the existing SNS and HFIR are valuable facilities, they can’t do it all. Herwig explained, “Often we have to use multiple instruments to learn all that we need to know about a material.”

The Second Target Station will emphasize the production of long wave neutrons, which are predominantly used for soft materials and complex materials and will address complexity as a unifying science theme.

“One of the big opportunities with the STS is the chance to get more neutrons onto smaller samples,” said John Tranquada, Neutron Scattering Group Lead at Brookhaven National Laboratory and STS Workshop participant. “Rather than waiting to grow crystals that are big enough to fit into a big beam, we can have beams with higher brightness that we can focus onto small samples, allowing us to get new results out much more quickly.”

Alan Tennant, chief scientist for Neutron Sciences, explained that the ability to measure complex materials efficiently and accurately is a current gap in the field of neutron scattering.

“There are materials that fundamentally need a more powerful beam of long wavelength neutrons in order for us to characterize their structure and function,” Tennant said. “STS can make these new measurements possible.”

The workshop included presentations from ORNL staff summarizing the science need and characteristics of the Second Target Station and from science community leaders who were engaged in an effort to identify grand challenges in their fields through a series of workshops in 2014. Their presentations summarized the findings from the workshops, including how neutrons can be used to answer their most pressing questions. The presentations helped to set the stage and to define the science needs of STS.

“This meeting is about the next steps,” Tennant said. “It’s a critical step in the process of determining what the configuration should be to optimize science output. STS will ensure future U.S. economic growth and competitiveness because so much of the economy hinges on advanced materials and technologies enabled by those materials.”

More than 3,000 scientists come to ORNL each year to use the two neutron facilities, SNS and HFIR, to study materials.

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