This is a note written about the commend given to me by the Japanese society neutron science in 2024 on achievement of construction to operation of the pulsed neutron source at J-PARC. Addressing the most important events starting with ASTE collaboration to confirm a spallation neutron source with Hg target, how we have performed the construction of neutron source in largest scale never ever experienced. Appreciating, and fighting with critical addresses from Neutron Technical Advisory Committee, we have arrived at great completion of it. Note that all views are given from my personal view.

We have established the fundamental technology for neutron diffraction experiments under high magnetic fields by combining pulsed magnets and spallation neutron sources at Materials and Life Science Experimental Facility (MLF) in Japan Proton Accelerator Research Complex (J-PARC). This system includes a vacuum chamber, a 4 K closed-cycle refrigerator for samples, and a small pulsed coil immersed in a liquid nitrogen bath made of a stainless-steel tube. The compactness and portability facilitate easy installation at any existing beamlines for practical user applications. In this article, the history of the developments of our pulsed high magnetic field neutron diffraction is described, with a particular focus on our achievement realized at Beamline No. 10 (NOBORU) in MLF.

We have developed a compact accelerator-driven neutron analysis facility, AISTANS, optimized for neutron Bragg-edge imaging. This facility consists of an electron linear accelerator, a neutron source, and two beamlines. The parameters of the electron beam, such as energy, pulse width, and repetition rate, have been optimized. A decoupled solid-methane moderator provides a short-pulsed neutron beam, which is ideal for Bragg-edge imaging. Super-mirror neutron guide tubes installed in the first beamline enhance the neutron beam flux by 6 times at a neutron wavelength of approximately 0.4 nm compared to operation without the guides. Since the construction of AISTANS, various samples, including automobile parts, joined metals, and steels, have been measured. Furthermore, lithium-ion batteries and concrete samples have been examined since 2023.

Advanced structural materials are anticipated to play a crucial role in the next generation of technologies. To enhance the performance of these materials, it is necessary to elucidate the mechanisms underlying their strength and ductility. This study investigates the contributions of each constituent phase to the strength and ductility of low-alloyed TRIP steel using in-situ neutron diffraction during deformation. The experiments were conducted using the engineering materials diffractometer “TAKUMI” at MLF of J-PARC. Furthermore, advanced welding techniques are critical for ensuring the safe application of these materials. Friction stir welding, a solid-state joining method, produces joints with excellent mechanical properties. However, the deformation mechanisms remain largely unexplored. Thus, this study investigates the deformation behavior of friction stir welded advanced structural materials using in-situ neutron diffraction during tension. In the present paper, several results are presented from these investigations.

Cerium, one of the rare earth elements, has a 4f¹ electron and exhibits a wide variety of physical properties. Since 4f electrons are in the inner shell, direct interactions are very weak, and thus the hybridization of the 4f electrons and conduction electrons is dominant to give rise to various magnetic properties. This article describes the magnetic properties of CeTSi₃ (T = transition metal) with broken inversion symmetry, van der Waals compounds CeTe₃, and Ce₅Si₃ with a Shastry-Sutherland lattice, using neutron experiments as the main method of study.

We describe the features and applications of using pulsed beams in the neutron resonance spin echo spectroscopy, particularly the method known as TOF-MIEZE.