Facility for the (p, n) polarization transfer measurement

We have designed and constructed a facility to measure the complete polarization transfer coefficient D_ij for the (p, n) reaction at intermediate energies. The facility consists of a beam swinger dipole magnet used for angular distribution measurements and a 100 m tunnel for the neutron energy measurement by the time-of-flight method. Typical neutron energy resolution is about 1.85 MeV for 290 MeV neutrons including a contribution of 1 MeV due to the target thickness. The background associated with this tunnel system was carefully investigated and found to be negligibly small. A dipole magnet for the neutron spin rotation is installed in the neutron flight path to measure the longitudinal polarization as well as the induced polarization. The neutron polarimeter which consists of 6 planes of the two-dimensional position-sensitive neutron detectors with a size of 1 m × 1 m × 0.1 m has been constructed. Its effective left-right analyzing power 〈A^eff_y〉 has been calibrated at 194, 290 and 384 MeV. The figure-of-merit value defined by 〈A^eff_y〉² × ∈_DS at 290 MeV is 4.05 × 10^-4, where ∈_DS is the double scattering efficiency.