Date of Original Version
The neutron lifetime has been measured by counting the neutrons remaining in a fluid-walled bottle as a function of the duration of storage. Losses of neutrons caused by the wall reflections are eliminated by varying the bottle volume-to-surface ratio. The result obtained is τβ=887.6±3 s.
W. Mampe, P. Ageron, C. Bates, J. M. Pendlebury, and A. Steyerl. (1989). "Neutron lifetime measured with stored ultracold neutrons." Physical Review Letters, 63(6), 593. Available at: http://dx.doi.org/10.1103/PhysRevLett.63.593