How are neutrons useful?

Neutrons are powerful probes of the structure and dynamics of materials ranging from molecules inserted into membranes mimicking cell walls to protons migrating through fuel cells. The unique properties of neutrons (shown below) can be exploited by a variety of measurement techniques to provide information not available by other means. They are particularly well suited to investigate all forms of magnetic materials such as those used in computer memory storage and retrieval. Atomic motion, especially that of hydrogen, can be measured and monitored, like that of water during the setting of cement. Residual stresses such as those inside stamped steel automobile parts can be mapped. Neutron-based research covers a broad spectrum of disciplines, including engineering, biology, materials science, polymers, chemistry, and physics.

The NCNR's neutron source provides the intense beams of neutrons required for these types of measurements. In addition to the thermal energy neutron beams from the heavy water or graphite moderators, the NCNR has a large area liquid hydrogen moderator, or cold source, that provides intense neutron beams for the only cold neutron facility presently operating in the U.S.

There are currently 28 experiment stations: six provide high neutron flux positions for irradiation, and 22 are beam facilities most of which are used for neutron scattering research. The following pages show a schematic layout of the beam facilities. More complete descriptions of instruments can be found at www.ncnr.nist.gov.

The NCNR supports important NIST research needs, but is also operated as a major national user facility with merit-based access made available to the entire U.S. technological community. Each year, over 1700 research participants from all areas of the country, from industry, academia, and government use the facility for measurements. Beam time for research to be published in the open literature is without cost to the user, but full operating costs are recovered for proprietary research. Access is gained mainly through a peer-reviewed, web-based proposal system with beam time allocated by a Beam Time Allocation Committee twice a year. For details see www.ncnr.nist.gov/beamtime.html.

The National Science Foundation and NIST co-fund the Center for High Resolution Neutron Scattering (CHRNS) that operates six of the world's most advanced instruments. Time on CHRNS instruments is made available through the proposal system. Some access to beam time for collaborative measurements with the NIST science staff can also be arranged on other instruments.

Last modified 01-March-2007