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Guide To NIST, July 1998
Electron Paramagnetic Resonance Facility


NIST is leading a national and international effort in electron paramagnetic resonance (EPR) dosimetry for measuring ionizing radiation. Paramagnetic centers (molecules or atoms with unpaired electrons) are produced by the action of radiation on materials. In the EPR measurement, irradiated materials are placed in a magnetic field and electron spin transitions are induced by an electromagnetic field of the appropriate frequency (typically in the GHz range). EPR is used as a non-destructive probe of the structure and concentration of paramagnetic centers. The centers created by ionizing radiation are proportional to the absorbed dose and provide a sensitive and versatile measurement method.

Capabilities: The EPR dosimetry facility is supported by three state-of-the-art X-band EPR spectrometers capable of measuring radiation effects on a wide range of materials from inorganic semiconductors to biological tissues. The data acquisition system provides full computer control of all spectrometer functions, including real-time spectral display and rapid acquisition scan to analyze rapidly decaying signals. The data acquisition system is interfaced with an advanced data analysis station for data manipulation and is capable of simulating and deconvoluting multi-component spectra.

Applications: EPR dosimetry is operable over many orders of magnitude in absorbed dose (10-2 Gy to 105 Gy) and impacts many facets of society and industry. Areas of application include:

The EPR facility also serves as a fully functional, materials research facility for analyzing radiation effects on semiconductors, optical fibers, functional polymers, and composites.

Alanine dosimeters from around the world
Availability: The EPR facility is available for collaborative research by researchers from industry, academia, and other government agencies under the supervision of NIST staff.

Contact: Marc F. Desrosiers

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Online: May 1997   -   Last update: August, 1998