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Magnetic trapping of neutrons

Nature volume 403, pages 62–64 (2000)Cite this article

Abstract

Accurate measurement of the lifetime of the neutron (which is unstable to beta decay) is important for understanding the weak nuclear force1 and the creation of matter during the Big Bang2. Previous measurements of the neutron lifetime have mainly been limited by certain systematic errors3; however, these could in principle be avoided by performing measurements on neutrons stored in a magnetic trap. Neutral-particle and charged-particle traps are widely used for studying both composite and elementary particles, because they allow long interaction times and isolation of particles from perturbing environments4. Here we report the magnetic trapping of neutrons. The trapping region is filled with superfluid 4He, which is used to load neutrons into the trap and as a scintillator to detect their decay. Neutrons in the trap have a lifetime of 750+330-200 seconds, mainly limited by their beta decay rather than trap losses. Our experiment verifies theoretical predictions regarding the loading process and magnetic trapping of neutrons. Further refinement of this method should lead to improved precision in the neutron lifetime measurement.

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Figure 1: Half-section view of the neutron trapping apparatus.
Figure 2: Counting rate as a function of time after the neutron beam is turned off (pooled background-subtracted data).

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Acknowledgements

We thank J. M. Rowe, D. M. Gilliam, G. L. Jones, J. S. Nico, N. Clarkson, G. P. Lamaze, C. Chin, C. Davis, D. Barkin, A. Black, V. Dinu, J. Higbie, H. Park, R. Ramakrishnan, I. Siddiqi and G. Brandenburg for their help with this project. We thank P. McClintock, D. Meredith and P. Hendry for supplying the isotopically pure helium. We acknowledge the support of the NIST, US DOC, in providing the neutron facilities used in this work. This work is supported in part by the US NSF. The NIST authors acknowledge the support of the US DOE.

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Author notes

  1. J. S. Butterworth & M. S. Dewey

    Present address: Institut Laue-Langevin, BP 156-6 rue Jules Horowitz, 38042, Grenoble, Cedex 9, France

Authors and Affiliations

  1. Harvard University, 17 Oxford Street, Cambridge, 02138, Massachusetts, USA

    P. R. Huffman, C. R. Brome, J. S. Butterworth, S. N. Dzhosyuk, C. E. H. Mattoni, D. N. McKinsey, F. E. Wietfeldt & J. M. Doyle

  2. National Institute of Standards and Technology, 100 Bureau Drive, MS 8461, Gaithersburg, 20899, Maryland, USA

    P. R. Huffman & F. E. Wietfeldt

  3. National Institute of Standards and Technology, 325 Broadway, MS898.02, Boulder, 80303, Colorado, USA

    K. J. Coakley

  4. Hahn-Meitner-Institut, Glienicker Strasse 100, Berlin, D-14109, Germany

    R. Golub & K. Habicht

  5. University of California, Los Alamos National Laboratory, PO Box 1663, Los Alamos, USA, 87545, New Mexico

    G. L. Greene & S. K. Lamoreaux

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Huffman, P., Brome, C., Butterworth, J. et al. Magnetic trapping of neutrons. Nature 403, 62–64 (2000). https://doi.org/10.1038/47444

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