Storage of ultracold neutrons in the UCN$\tau$ magneto-gravitational trap
Abstract
The UCN$\tau$ experiment is designed to measure the lifetime $\tau_{n}$ 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 provide a background "holding" field to eliminate depolarization-induced UCN loss caused by magnetic field nodes. We present a measurement of the storage time $\tau_{store}$ 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 $\tau_{store}=860\pm19$ s: within $1 \sigma$ of current global averages for $\tau_{n}$. The storage time with the holding field deactiveated is found to be $\tau_{store}=470 \pm 160$ 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.
- Publication:
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arXiv e-prints
- Pub Date:
- October 2013
- DOI:
- 10.48550/arXiv.1310.5759
- arXiv:
- arXiv:1310.5759
- Bibcode:
- 2013arXiv1310.5759S
- Keywords:
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- Physics - Instrumentation and Detectors;
- Nuclear Experiment
- E-Print:
- 6 pages, 5 figures