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

Contact Kevin Coakley
Statistical Engineering Division
Information Technology Laboratory
303-497-3895
kevin.coakley@nist.gov
Impetus/How Project Began 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.
Objective(s) 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.
FTE This information is not available.
Timeline/
Milestones
FY97. Developed numerical integration algorithm to simulate trajectories of marginally trapped neutrons.
FY98. Phase 1 statistical planning study completed for case of stationary background signals.
FY99. Feasibility of magnetic trapping demonstrated. Statistical analysis of data from first generation experiment completed.
FY00. Phase 2 statistical planning study completed. Construction of likelihood models and associated estimation algorithms for unbinned event time data and for binned event time data.
FY00. Phase 3 statistical planning study completed for case of nonstationary background. Optimal background correction strategies determined.
NIST Involvement NIST collaborators include:
  • Paul Huffman (PL),
  • Scott Dewey (PL),
  • David Gilliam (PL),
  • Kevin Coakley (SED), and
  • Grace Yang (SED).
Outside Involvement Outside collaborators include:
  • Harvard University,'
  • Los Alamos National Laboratory, and
  • Hahn-Meitner-Institut (Berlin).
What Work Has ITL Done See the timeline above.
What Work Has Been Done By Collaborators The collaborators have demonstrated feasibility of magnetic trapping method in a first generation experiment.
What Developments Have Occurred and How Has the Project Changed During the development of the first generation experiment, the experimental strategy for detecting neutrons was refined so as to reduce the background signal. In the second generation experiment, the signal to noise ratio of the experiment will be increased by using a bigger magnet. Statistical planning software facilitated the design of the second generation experimental apparatus.
Publications or Artifacts The following publications are related to this project.

P.R.Huffman, C.R. Brome, J.S.Butterworth, K.J.Coakley, M.S.Dewey, S.N.Dzhosyuk, D.M.Gilliam, R.Golub, G.L.Greene, K.Habicht, S.K.Lamoreaux, C.E.Mattoni, D.N.McKinsey, F.E.Wietfeldt, and J.M.Doyle. "Magnetic Trapping of Ultracold Neutrons," Nature, 403, 62-64 (2000).

P.R.Huffman, C.R. Brome, J.S.Butterworth, K.J.Coakley, M.S.Dewey, S.N.Dzhosyuk, D.M.Gilliam, R.Golub, G.L.Greene, K.Habicht, S.K.Lamoreaux, C.E.Mattoni, D.N.McKinsey, F.E.Wietfeldt, and J.M.Doyle. "Progress Towards Magnetic Trapping of Ultracold Neutrons," Nuclear Instruments and Methods A. 440(3), 522-527 (2000).

K.J. Coakley. "Statistical Planning for a Neutron Lifetime Experiment Using Magnetically Trapped Neutrons", Nuclear Instruments and Methods in Physics Research A, 406, pp. 451-463 (1998).

K.J. Coakley. "Neutron Lifetime Experiments Using Magnetically Trapped Neutrons: Optimal Background Correction Strategies", submitted to Nuclear Instruments and Methods in Physics Research A.

G.L. Yang and K.J. Coakley, "Likelihood Models for Two-Stage Neutron Lifetime Experiments", submitted to Physical Review C, in review.

How Industries Have Benefited From NIST's Work Nothing to report at this time.
Acknowledgements of the ITL's Effort ITL's involvement is acknowledged through coauthorship of publications.
Future Related Activities Systematic error analysis related to imperfect background correction and random timing errors in measurement system. Further theoretical investigation of statistical estimation algorithms for neutron lifetime estimation. Statistical analysis of data from planned second generation experiment.
Additional Information A more detailed write-up of this project is in the SED annual report (yellow book).

Date created: 6/5/2001
Last updated: 6/21/2001
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