Neutron lifetime measurement with the UCN trap-in-trap MAMBO II

We have measured the free neutron lifetime tau(n) by storage of ultra-cold neutrons (UCN) in a Fomblin coated UCN trap of in situ variable size. The method was initially developed by W. Mampe et al. (1989) [10] with MAMBO I and improved by the addition of a prestorage volume yielding a well defined UCN spectrum for storage in the main trap. By extrapolation to infinite trap size using the time scaling method we obtain for the free neutron lifetime tau(n) = (880.7 +/- 1.3 +/- 1.2) s. Data from different UCN spectra, trap temperatures and storage times were used for the evaluation. The present result is compared with other experimental neutron lifetime data. (c) 2010 Elsevier B.V. All rights reserved.