Speaker
Description
Low n nuclei with spin are important for understanding spin-dependent portions of 3-body interactions. These three body forces account for about 5% of the nuclear biding energy, but are poorly experimentally constrained. The binding energy of $^4$He for example can only be predicted to about 1% with current theoretical calculations. The polarized n-$^3$He system can be used to probe these interactions with precision measurements of the associated cross sections. We have been following a two tiered path. First is to improve the accuracy of the n-$^3$He incoherent scattering cross section $b_i$ though neutron spin-echo measutments, and second is to attempt to measure explicitly the polarized n-$^3$He absorption cross section $\sigma_p$ (or absolute $^3$He polarimetry) which is needed for an absolute determination of b_i. Recent experiments to measure $b_i$ were performed at the SNS-NSE with data analysis ongoing, and measurements of $\sigma_p$ are planned for the spring at ISIS.
