Nuclear reactions of light nuclei provide valuable information about dynamics of strongly-interacting quantum few-body systems as well as basic properties of nuclear forces such as heavy-meson exchanges, many-body forces, isospin dependences, and so on. High-performance neutron beams in combination with active-target technique will enable one to make precise experiments of neutron-induced few-nucleon reactions. In this article the current status and the future prospect of the few-nucleon physics studied with neutrons are discussed.

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In this article the performance of the polarized neutron reflectometer PORE at KENS is reported and how the experience will be utilized for design of the new reflectometer and science activities at J-PARC.

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A chiral molecule-based ferrimagnet, [Cr (CN)₆][Mn (S)-pnH(H₂O)](H₂O), with T_c=38, was newly synthesized in order to investigate the effect on the magnetic structure of the chiral molecules. The magnetic structure was analyzed by the difference pattern between 50K and 4K with neutron powder diffractometer. Several magnetic reflections are clearly observed, but satellite peak from a long-period structure was not observed. From the intensity analysis of magnetic reflections, it was concluded that the magnetic space group (Shubnikov group) was P2₁2₁2₁, and magnetic moments of Cr and Mn atoms were aligned antiparallel each other along the direction near the α-axis. Our result implies that the long-period magnetic structure, if exists, is not a helical structure but a conical one.

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Development of the neutron spin filter (NSF) based on polarized gaseous ³He is under way at KEK. ³He nuclei have a large neutron absorption cross section depending on the spin direction. A neutron spin filter is possible with polarized ³He nuclei. Gaseous ³He is polarized by the spin exchange optical pumping (SEOP) method. ³He cells made of sapphire and quartz glass have been prepared and tested. Spin relaxation times of more than 100 hours are regularly observed for quartz glass cells. ³He polarizations have been measured with a pulsed neutron beam at KENS to be 63% for a sapphire cell and 54% for a quartz glass cell. With these cells, neutron polarizations of 86% and 74% were obtained, respectively, at thermal energy. In this article, the up-to-date status of the development is reported as well as general properties of the SEOP-NSF.

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Soft matters, which are comprised of various systems such as polymers, membranes, micelles, liquid crystals, gels, colloids, supercooled liquids, multi-component liquids, etc, commonly form hierarchical self-assembled structures with a special scale ranging between nm to μm, and time scale ranging between pico second to hours. A task of small-angle scattering for the next generation is to realize in-situ or real-time observations on the self-assembled structures covering ultrasmall angle region of q<10^-3Å^-1. For this purpose, our research groups at Tokai develop two spectrometers of small-angle neutron scattering (SANS-J and PNO). The focusing devices of sextupole permanent magnet and MgF₂ biconcave lenses are installed on a pin-hole small-angle scattering spectrometer SANS-J. With these focusing devices, we aim to achieve the q-resolution q_min=10^-4Å^-1 and/or the intensity gain (×10, possibly). The q-resolution q_min=10^-4Å^-1 is complementary with that of a double crystal ultrasmall-angle scattering spectrometer PNO, which can cover a q-range down to q≅10^-5Å^-1. In this paper, we shortly describe our upgrade plan to achieve the focusing polarized neutron small-angle scattering spectrometer SANS-J-II.

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