Storage of ultracold neutrons in the magneto-gravitational trap of the UCNτ experiment

D. J. Salvat, E. R. Adamek, D. Barlow, J. D. Bowman, L. J. Broussard, N. B. Callahan, S. M. Clayton, C. Cude-Woods, S. Currie, E. B. Dees, W. Fox, P. Geltenbort, K. P. Hickerson, A. T. Holley, C. Y. Liu, M. Makela, J. Medina, D. J. Morley, C. L. Morris, S. I. PenttiläJ. Ramsey, A. Saunders, S. J. Seestrom, E. I. Sharapov, S. K.L. Sjue, B. A. Slaughter, J. Vanderwerp, B. Vorndick, P. L. Walstrom, Z. Wang, T. L. Womack, A. R. Young

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28 Scopus citations

Abstract

The UCNτ experiment is designed to measure the lifetime τn of the free neutron by trapping ultracold neutrons (UCN) in a magneto-gravitational trap. An asymmetric bowl-shaped NdFeB magnet Halbach array confines low-field-seeking UCN within the apparatus, and a set of electromagnetic coils in a toroidal geometry provides a background "holding" field to eliminate depolarization-induced UCN loss caused by magnetic field nodes. We present a measurement of the storage time τstore of the trap by storing UCN for various times and counting the survivors. The data are consistent with a single exponential decay, and we find τstore=860±19 s, within 1σ of current global averages for τn. The storage time with the holding field deactivated is found to be τstore=470±160 s; this decreased storage time is due to the loss of UCN, which undergo Majorana spin flips while being stored. We discuss plans to increase the statistical sensitivity of the measurement and investigate potential systematic effects.

Original languageEnglish
Article number052501
JournalPhysical Review C - Nuclear Physics
Volume89
Issue number5
DOIs
StatePublished - May 23 2014
Externally publishedYes

Funding

FundersFunder number
National Science FoundationPHY-0969490, PHY-1068712
U.S. Department of EnergyDE-FG02-97ER41042, 2015LANLE9BU
National Science Foundation
Directorate for Mathematical and Physical Sciences1005233, 0969490

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