The National Institute of Standards and Technology (NIST) Center for Neutron Research, or NCNR ranks among the best research centers of its type in the world. Delivered via beamlines to 29 major analytical instruments—some without parallel in the U.S.—its neutron probes support the research of more than 2,000 scientists and students each year.
For important jobs that range from tracking water molecules as they circulate in a fuel cell to shadowing proteins as they cross the cell membrane to measuring stresses in pipelines, neutron probes often are the tool of choice. And because neutrons reveal important properties, structures, and behaviors outside the "view" of X-rays and other probes, scientists and students from around the United States make use, each year, of the National Institute of Standards and Technology (NIST) Center for Neutron Research, or NCNR. In 2010, the NCNR served researchers from more than 140 U.S. universities, 45 U.S. industrial laboratories, and more than 30 government laboratories.
In Demand for Frontier Research
The NCNR is the most versatile source of neutrons for research in the United States. And "beam time" is in great demand. Growing numbers of industrial and university scientists are finding neutrons essential to accomplishing their research objectives. As a result, the number of scientists who use the NCNR has quadrupled over the last decade, an increase accommodated by improvements and upgrades. It is the most heavily used facility of its type in the nation, serving more scientists and engineers than any of the other U.S. neutron research facilities.
A 2002 Office of Science and Technology Policy report on the status of U.S. neutron research facilities called for increased support and improvements in the NCNR's instrumentation and its infrastructure. This recommendation was one of the report's top two priorities.
Leveraging the NCNR for Competitiveness
As part of the America Competes Act, the NCNR is nearing completion of a significant expansion of its cold neutron measurement capability. The enhancements include new neutron measurement instrumentation and reactor reliability enhancements. The capacity that will be introduced when the new cold neutron instruments are operating will allow at least 500 additional researchers to be served annually.
Planned enhancements would include the development of five new world-class research instruments, the equivalent of a 25 percent increase in measurement and other analytical capacity. The proposed initiative also includes additional funding to support more research projects at the frontiers of science and technology.
Seeing with Neutrons
Except for scheduled maintenance, the NCNR runs 24/7. In operation more than 250 days a year, the facility's 29 specialized instruments are fully subscribed, supporting a rich variety of scientific and basic technology research.
No technique can answer every question that scientists might want to ask. Still, neutrons—uncharged particles liberated from the nuclei of atoms—turn out to be uniquely revealing and versatile compared to other probes. For example, beams of neutrons:
- make excellent rulers for measuring "inner space." Depending on temperature, the length of the neutron ruler can be tuned over a range spanning from roughly the size of a single atom to the size of a molecule composed of hundreds or thousands of atoms.
- are non-destructive, highly penetrating probes.
- "see" magnetism, allowing the behavior of exotic magnets and superconductors to be detailed precisely.
- can be used to measure the energies of vibrations in molecules, waves in magnetic materials, and other exotic phenomena.
- can be used to identify almost infinitesimal amounts of material in samples ranging from shards of ancient pottery to pollutants to foods.
- can distinguish between "light" and "heavy" versions (isotopes) of hydrogen, making it possible to highlight specific regions of large biological molecules and track how these subunits change shape and location.
The broad utility of the NCNR is indicated by the productive relationships that the center has forged with a diverse set of organizations—federal agencies, businesses, and universities. For example, the Food and Drug Administration maintains an instrument for measurements and analyses that support quality assurance in its food safety program.
In addition, the National Science Foundation and NIST support a suite of neutron-scattering instruments used by university, government and industrial researchers in materials science, chemistry, biology and physics.
Examples of Technological and Scientific Impact
In a typical year, experiments conducted at the NCNR are reported in more than 300 articles in scientific journals. This new knowledge often contains the seeds of future technological innovations. It also may spawn the insights that lead to solutions to important industrial problems. Examples follow.
Toward Hydrogen-Powered Vehicles. The NCNR's neutron imaging facility, commissioned in March 2006, provides unparalleled views into the internal workings of experimental fuel cells. Specifically, the instrument can track the formation of water molecules and their subsequent travels through the fuel cells' circuitous channels. Proper water balance is fundamental to the performance, reliability, and longevity of fuel cells. Consistently achieving this balance is basic to the nation's quest to replace petroleum with hydrogen to power cars and trucks. Like its predecessor, a prototype version, the neutron imaging facility is used by U.S. automakers, prospective suppliers of fuel cells or their components, and university and government researchers.
Better Magnetic Materials. Vital to products and applications ranging from data storage to medical imaging, magnetic materials are a "sweet spot" for neutron techniques. For example, IBM researchers credit the NCNR with providing valuable research capabilities that contributed to the company's success in exploiting a phenomenon known as giant magnetoresistance. The resulting technology greatly increased data storage capacity, and it is embedded in information technology throughout the world today. Now, teams of NCNR researchers are investigating an array of exotic magnetic phenomena and experimental materials to build the basic understanding necessary to develop future generations of vastly more powerful magnetic technologies.
Ensuring Safety, Preventing Failures. As is true in people, stresses in materials may not become apparent until after they have done their damage—for example, a ruptured pipeline, a failed engine component, or a cracked train rail. Some of the stresses that contribute to structural failures may originate early on, during the forming and joining of materials. Beyond the view of surface inspection methods, such residual stresses undermine the integrity of materials and abet damaging processes such as fatigue or corrosion. The nondestructive, yet great penetrating power of neutron probes make them ideal for uncovering the causes of residual stresses at various stages in manufacturing, forming, and joining. In recent work, an NCNR team developed a thorough picture of how internal stresses arise and then increase during the manufacture of gas pipelines. Similar studies have been performed for train rails, jet engine turbine blades, automotive springs, and other structures, products, and components. Results eliminate uncertainties and are used to fine-tune processes to ensure an acceptable margin of safety.
Creating More Affordable Renewable Energy. Organic photovoltaics, which rely on organic molecules to capture sunlight and convert it into electricity have significant advantages over traditional rigid silicon cells. Organic photovoltaics start out as a kind of ink that can be applied to flexible surfaces to create solar cell modules that can be spread over large areas as easily as unrolling a carpet. They'd be much cheaper to make and easier to adapt to a wide variety of power applications, but their market share will be limited until the technology improves. Teams of scientists are using the NCNR to optimize the dispersion of organic molecules that conduct electricity within the insulating polymer matrix, thereby increasing the performance of this new class of cheap, flexible, and easy-to-make solar cells.