Development of a Polarizer/Adiabatic Spin-Flipper for Ultra-Cold Neutrons

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This grant supports the development of an instrument to polarize ultra-cold neutrons (UCNs) and to control the direction of UCN polarization through an adiabatic fast passage (AFP) procedure. The magnitude of the polarization produced, either parallel or antiparallel to the quantization axis, by this apparatus should be 0.999 percent or greater, representing roughly an order of magnitude improvement over neutron polarization schemes available at present. Construction of this instrument constitutes the primary Princeton contribution in the development of a series of experiments probing the fundamental properties of the neutron and neutron beta-decay. The first measurement in this series is a determination of the angular distribution of emitted electrons following the decay of polarized neutrons. The difference between the emission rate parallel to the neutron spin and the rate anti-parallel to the neutron spin, the "beta-asymmetry," can be used to find the value of the axial form-factor for semi-leptonic weal interactions of the nucleon and also to determine one of the elements of the Cabibbo-Kobayashi-Maskawa matrix. The success of this experiment depends critically on the availability of an instrument to polarize and flip UCN spins.