This is the article for the distinguished contribution award for the neutron science in 2020. I focused the history of the development of neutron community in Japan. Also, I will show the development of equipment of structural science by using neutrons, in which I have contributed.

Neutron reflectivity has emerged as a powerful and important technique for the study of soft materials surfaces and interfaces. The selectivity and sensitivity afforded by deuterium/hydrogen labeling makes the technique particularly attractive for application to characterization of surface and interface. This paper provides an introduction of applications of neutron reflectivity to analyses of structure in polymer thin films and buried interface of polymer brushes.

At the end of May in 2008, the first neutron was produced successfully at a spallation neutron source in Japan Proton Accelerator Research Complex (J-PARC) Materials and Life Science Experimental Facility (MLF), the following June, SuperHRPD recorded the world's highest resolution of Δd/d = 0.0353(3)%. We used the existing Sirius vacuum scattering chamber at the KENS facility to complete the commissioning as quickly as possible. During the summer shutdown in 2009, a replacement to a new vacuum scattering chamber was carried out. The new vacuum chamber was designed and installed successfully, with ingenuity to allow for efficient construction in a small experimental building for BL08 and technical issues to achieve even higher resolution and low background.

For the production of the high-intensity pulse neutrons, a 3-GeV proton-beam transport facility (3NBT) had constructed to deliver the high-intensity proton beam to Material Life Science Experiment Facility (MLF) at J-PARC. In order to construct a facility using the beam intensity of about 200 times in Japan when the construction has started, various research and developments (R&Ds) were carried out such as magnets withstanding under the high radiation fields and the beam shape flattening technique based on nonlinear beam optics to mitigate the damage on the neutron production target. As a result of R&Ds, it was demonstrated that MLF can continuously produce high-intensity pulse neutrons using 1-MW proton beam without any issues for long duration.

We investigate incommensurate magnetic fluctuations in Sr₂RuO₄ by inelastic neutron scattering using the chopper spectrometer AMATERAS. Below T_c, we found the spin resonance at Q = (0.3, 0.3, 0.5) with energy of the superconducting gap 2Δ. This result strongly indicates that the superconducting gap of Sr₂RuO₄ has horizontal line nodes.