Performance of neutron polarimeter SMART-NPOL

The neutron polarimeter SMART-NPOL has been constructed at the RIKEN Accelerator Research Facility for measuring polarization correlations of proton–neutron systems. The SMART-NPOL system consists of 12 parallel neutron counter planes of two dimensionally position-sensitive plastic scintillators with a size of 60×60×3.0cm3. Polarimetry measurements were made using the analyzing power of the H1(n⇒,n)H1 reaction occurring in the plastic scintillators. The effective analyzing power of SMART-NPOL was measured with polarized neutrons from the zero-degree Li6(d⇒,n⇒) reaction with an incident deuteron energy of 135MeV/A. The effective analyzing power thus obtained was 0.26±0.01stat±0.03syst0.26±0.01stat±0.03syst and the double scattering efficiency was 1.1×10-31.1×10-3.