Performance of the neutron polarimeter NPOL3 for high resolution measurements

Abstract

We describe the neutron polarimeter NPOL3 for the measurement of polarization transfer observables $D_{ij}$ with a typical high resolution of $\sim$300 keV at $T_n$ $\simeq$ 200 MeV. The NPOL3 system consists of three planes of neutron detectors. The first two planes for neutron polarization analysis are made of 20 sets of one-dimensional position-sensitive plastic scintillation counters with a size of 100 cm $\times$ 10 cm $\times$ 5 cm, and they cover the area of 100 $\times$ 100 $\mathrm{cm}^2$. The last plane for detecting doubly scattered neutrons or recoiled protons is made of the two-dimensional position-sensitive liquid scintillation counter with a size of 100 cm $\times$ 100 cm $\times$ 10 cm. The effective analyzing powers $A_{y;\mathrm{eff}}$ and double scattering efficiencies $\epsilon_{\mathrm{D.S.}}$ were measured by using the three kinds of polarized neutrons from the ${}^{2}{\rm H}(\vec{p},\vec{n})pp$, ${}^{6}{\rm Li}(\vec{p},\vec{n}){}^{6}{\rm Be}(\mathrm{g.s.})$, and ${}^{12}{\rm C}(\vec{p},\vec{n}){}^{12}{\rm N}(\mathrm{g.s.})$ reactions at $T_p$ = 198 MeV. The performance of NPOL3 defined as $\epsilon_{\mathrm{D.S.}}(A_{y;\mathrm{eff}})^2$ are similar to that of the Indiana Neutron POLarimeter (INPOL) by taking into account for the counter configuration difference between these two neutron polarimeters.