9501312 Snow A neutron polarizer for low energy neutrons will be developed for use in fundamental symmetry tests, including tests of time reversal invariance and weak interaction coupling constants. The latter will be used to test the unitarity of the matrix describing weak transitions between the different quark- lepton sectors, which in turn tests the fundamental assumption of three generations of quarks and leptons. The polarizer will be based on neutron interactions with optically-pumped polarized helium-three. Experiments will be conducted at the National Institute of Standards and Technology research reactor. Research in this area will advance our understanding of the electroweak interaction and fundamental neutron physics, both high priority activities in contemporary nuclear physics. This project represents development, construction, and utilization of major state-of-the-art equipment and the education of graduate and undergraduate students and postdocs.***