Spin exchange pumped 3He targets: progress and prospects

Polarized 3He has been used as a spin filter for neutron polarization, as a target to probe neutron structure, and in combination with 129Xe for precision measurement of fundamental physics. Spin exchange pumped masers of one and two species have run for weeks and allow CW measurement with precision trending as steeply as τ−32. At SLAC, a program of experiments has studied the neutron spin-dependent structure function in deep inelastic scattering, exploiting the large neutron polarization in a polarized 3He target. Data from the most recent experiment provide new precise data with Bjorken x down to 0.014. Among the conclusions is the need to consider Q2 dependence in interpretation of the data and determination of sum rules (sums over the full range in x).