We report progress towards magnetic trapping: of ultra-cold neutrons (UCN)
in preparation for a neutron lifetime measurement. UCN will be produced by
inelastic scattering of cold (0.89 nm) neutrons in a reservoir of superflui
d He-4 and confined in a three-dimensional magnetic trap. As the trapped ne
utrons decay, recoil electrons will generate scintillations in the liquid H
e, which should be detectable with nearly 100% efficiency. This direct meas
ure of the number of UCN decays vs, time can be used to determine the neutr
on beta-decay lifetime. (C) 2000 Elsevier Science B.V. All rights reserved.