Absolute [formula omitted]He polarimetry for a double-chambered cell using transmission of thermal neutrons

Abstract

We present an absolute 3He polarimetry method based on thermal neutron transmission for a double-chambered cell. This method utilizes the fact that a 3He nucleus has a large absorption cross section and a spin dependence for thermal neutrons. The cell had a pumping chamber and a target chamber. Polarized 3He gas was produced in the pumping chamber by SEOP and then diffused into the target chamber. The 3He polarization in the target chamber was determined by comparing the neutron transmissions with the polarized and unpolarized targets. The measurement was performed at the RIKEN Accelerator-Driven Compact Neutron Source. The 3He polarization in the target chamber was determined with a statistical error of 1.8% and systematic uncertainty of 0.6%. This method can be used to obtain high-precision data of spin observables in few-nucleon scattering for the investigation of nuclear forces.