Physics with Polarized Helium 3

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Polarized noble gas samples of 3He, 21Ne and 129Xe provide tools for our multifaceted program investigating fundamental interactions at the atomic, nuclear and nucleon scale. We have advanced from the exploratory stage of four years ago, when large quantities of 3He were first polarized by spin exchange with laser optically pumped Rb, to the successful development of high precession NMR frequency spectroscopy and the realization of polarized 3He targets. With the techniques developed, we are able to measure free precession frequencies with a precision of 10-7 Hz in a one hour measurement interval and have set new limits on Lorentz Invariance violation due to Mass Anisotropy with respect to a preferred direction. A measurement of the time reversal invariance violating electric dipole moment (EDM) of Xe129 is underway. This measurement should be sensitive to the EDM at a level of 10-27 e-cm. Our study of the optical pumping and spin exchange mechanisms, theory and measurement of depolarization including ionization by the accelerator beam, the development of diode laser arrays and exploration of new light sources have made possible the practical application of polarized 3He as a target for neutron polarization and accelerator experiments. We are now in the process of building an experiment at the MIT Bates LINAC to measure the electric form factor of the neutron by quasi- elastic scattering of polarized electrons from polarized 3He. We will also demonstrate the feasibility of a scaled up target for a measurement of the neutron's spin dependent structure function by deep inelastic scattering of polarized electrons from polarized 3He at SLAC with the intent of undertaking that measurement as soon as possible.