Precision Measurement of the n-3He Incoherent Scattering Length Using   Neutron Interferometry
  We report the first measurement of the low-energy neutron-$^3$He incoherent scattering length using neutron interferometry: $b_i' = (-2.512\pm 0.012{statistical}\pm0.014{systematic})$ fm. This is in good agreement with a recent calculation using the AV18+3N potential. The neutron-$^3$He scattering lengths are important for testing and developing nuclear potential models that include three nucleon forces, effective field theories for few-body nuclear systems, and neutron scattering measurements of quantum excitations in liquid helium. This work demonstrates the first use of a polarized nuclear target in a neutron interferometer. 
M. G. Huber, M. Arif, T. C. Black, W. C. Chen, T. R. Gentile, D. S.   Hussey, D. Pushin, F. E. Wietfeldt, L. Yang