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Magnetic Trapping of Ultra Cold Neutrons and Determination of the Mean Lifetime of Neutrons


At the request of researchers from the Ionizing Radiation Division, SED staff joined an international team of researchers from NIST, Harvard University, Los Alamos National Laboratory, and the Hahn-Meitner-Institut in Berlin. The team proposed a new technique to trap ultra cold neutrons in a magnetic field. With this this trapping technology, the team plans to make a high precision measurement of the mean lifetime of the neutron. Along with other experimental data, the mean lifetime of the neutron allows one to test the consistency of the standard model of electroweak interactions.  Further, the mean lifetime of the neutron is an important parameter in astrophysical theories. Eventually, this method should yield a lifetime estimate with an uncertainty 10 to 100 times less than the current accepted value.


Statistical contributions include experimental planning and analysis, stochastic modeling, development of likelihood models for observed data, development and analysis of of neutron lifetime estimation algorithms, quantification of random and systematic errors.

Lead Organizational Unit:



NIST collaborators include:

  • Paul Huffman (PL),
  • Scott Dewey (PL),
  • David Gilliam (PL),
  • Kevin Coakley (SED), and
  • Grace Yang (SED).

Outside collaborators include:

  • Harvard University,
  • Los Alamos National Laboratory, and
  • Hahn-Meitner-Institut (Berlin).

Facilities/Tools Used:

NIST Center for Neutron Research

Other Organizational Unit:
Physical Measurement Laboratory


K.J. Coakley, SED

Kevin J. Coakley

Phone: 303-497-3895
Email: kevin.coakley@nist.gov
Fax: 303-497-3012