Application of the Epithermal Polarized Neutron Beam at ANNRI in J-PARC

Abstract

Accurate Neutron-Nucleus Reaction measurement Instrument (ANNRI) is installed at the one of the beamlines in MLF in J-PARC, and nuclear reaction measurements have been conducted using the three types of γ-ray detectors, Ge, NaI, and LaBr. Recently, a ³He spin filter to polarize neutrons has become available in ANNRI, and several experiments have been performed using the produced polarized neutrons. Significant differences in the measured cross section and γ-ray emission depending on the direction of the neutron polarization were observed in the ¹¹⁷Sn(n,γ)¹¹⁸Sn reaction. A γ-ray polarimeter was also developed, and the circular polarization of emitted γ-rays was successfully measured at ANNRI for the ³²S(n, γ)³³S reaction using the polarized neutrons.