The 2011 Great East Japan Earthquake damaged the Japan Research Reactor 3 (JRR-3), owned by the Japan Atomic Energy Agency, leading to its shutdown. Thanks to the extraordinary efforts of many people, after nearly 10 years, in February 2021, the reactor resumed operation after meeting all the strict safety standards.

Since then, users who had to stay away from the reactor have returned under the General User Program (GUP), managed by the Institute for Solid State Physics, University of Tokyo, starting in July 2021. The number of GUP users has now returned to the pre-shutdown level.

To commemorate this milestone, a new Special Topics edition of the Journal of Physical Society of Japan presented various papers on the development of instruments at the revived JRR-3 and on condensed matter research conducted using them.

Currently, twelve university-managed neutron scattering instruments are installed at JRR-3. The papers in this Special Topics edition provide an overview of the capabilities and the upgrades made to them during the shutdown period.

Nawa et. al. detailed the GPTAS, a general-purpose triple axis spectrometer at JRR-3, explaining its upgrades (e.g., doubly focusing monochromator and analyzer) and the contributions made using it to investigate structural and magnetic properties of condensed matters.

Nakajima et. al. showcased the polarized and unpolarized neutron scattering capabilities of Polarized Neutron Triple-Axis spectrometer (PONTA) instrument at JRR-3, demonstrating its use for studies on a centrosymmetric magnetic skyrmion host Gd₂PdSi₃.

Ikeda et. al. introduced the advantages of the PATH platform, which includes the powder diffractometer HERMES, the high-momentum resolution three-axis spectrometer AKANE, polarized neutron triple axis spectrometer TOPAN, and the chopper spectrometer POLANO at JRR-3. Specifically, they highlighted the contributions to material science made using TOPAN and AKANE.

Additionally, Nambu et. al. focused on the modifications and improvements made to HERMES since JRR-3’s shutdown, noting that HERMES currently boasts the finest resolutions at low scattering angles in reactor-based neutron powder diffractometers.

Kikuchi et. al. detailed the recent development and installation of the new multiplex-type inelastic neutron scattering spectrometer, the Horizontally Defocusing Analyzer Concurrent Data Acquisition (HODACA) spectrometer, at JRR-3, featuring 70-times greater measurement efficiency than the conventional triple-axis spectrometer.

Takahashi et. al. analyzed the performance of the Four-circle Off-centered Neutron Diffractometer (FONDER) when used with the normal zero-dimensional detector or the curved two-dimensional position sensitive detector (C-2DPSD). They also discussed the potential of combining this technique with X-ray or time-of-flight (TOF) Laue diffraction techniques.

Mayumi et. al. introduced recent studies on polysaccharide hydrogels and tough ionic gels using JRR-3’s Small-angle Neutron Scattering Instrument (SANS-U), revealing the hierarchical structure of these soft materials.

Suzuki et. al. utilized JRR-3’s Multilayer Interferometer and reflectometer for Neutron (MINE2) to investigate spin interferometry with high-frequency magnetic fields using a continuous neutron beam, showcasing its capabilities for neutron spin optics research.

Furthermore, Higuchi et. al. produced iron film spin filters and tested them with ultracold neutron (UCN) spin analyzers available at JRR-3’s MINE2, for the next generation electric dipole moment (EDM) experiment.

Akiba et. al. focused on the significant improvements made to the AGNES, a direct geometry chopper-type time-of-flight neutron spectrometer, installed at the cold neutron guide of JRR-3, since the shutdown. Due to these improvements, the neutron-intensity of AGNES increased by 7.7 times in the standard mode and by 3.2 times in the high-resolution mode.

In summary, these papers showcase the immense capabilities and contributions of the instruments at JRR-3. Researchers from all over Japan are benefiting from the revival of JRR-3. Neutron scattering research is used in a variety of fields, including solid-state physics, superconductivity, topical materials, energy storage, and even in biological sciences. The neutron scattering results obtained from JRR-3 has the potential to significantly improve our lives and society. The current special issue is also expected to facilitate a new research reactor at Fukui.

We hope that more researchers will benefit from JRR-3, leading to new innovations that enhance our lives.

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