Performance of the neutron polarimeter NPOL2 for ( [formula omitted], [formula omitted]) polarization transfer measurements

Abstract

A high performance neutron polarimeter NPOL2 has been constructed to measure polarization transfer observables D ij for neutron kinetic energies of T n = 150–400 MeV. The NPOL2 system consists of 6 planes of two-dimensional position-sensitive neutron detectors with a size of 1 × 1 × 0.1 m 3. Neutron polarization is determined from the azimuthal distribution of the elastic n + p scattering in the scintillator material. The effective analyzing powers ( A y;eff ) of NPOL2 have been calibrated by using the polarized neutrons from the 0° 2H( p , n )pp reaction at T p = 146, 228, 296, 346 and 392 MeV as well as by using the polarized neutrons from the 0° 6Li( p , n ) 6Be(g.s.) reaction at T p = 228 MeV. The A y;eff values of NPOL2 have reasonable values, typically 0.223 ± 0.012 and 0.132 ± 0.004 for ( n ,n) and ( n ,p) channels, respectively, at T n = 291 MeV. The figure-of-merit value defined as ε D.S.( A y;eff ) 2 is over 4 × 10 −4 for the wide neutron kinetic energy region of T n = 200–400 MeV, where ε D.S. is the double scattering efficiency.