Laser stripping experiment of 400 MeV H beam in J-PARC

Harada, Hiroyuki; Saha, P. K.; Yoneda, Hitoki*; Michine, Yurina*; Onoda, Genki*; Yamada, Ippei; Shibata, Takanori*; Sato, Atsushi*; Kinsho, Michikazu

JPS Conference Proceedings (Internet), 45, p.011133_1 - 011133_8, 2026/06

https://doi.org/10.7566/JPSCP.45.011133

In high-intensity proton accelerators, negative hydrogen ions are charge-exchanged to protons by a carbon foil installed at the injection point of a ring accelerator. While this injection method can produce a high-intensity proton beam, it is a destructive method in which beams are passed through the foil, which leads to a short lifetime of the foil itself and to high radiation of the injection devices. Therefore, we proposed a non-destructive laser stripping injection scheme and develop for laser stripping experiment. In this study, a long-distance laser optical path of 70 m was newly constructed for the experiment. In this presentation, an overview of the laser stripping injection will be presented and the construction of the optical path, which is important for the execution of this experiment, will be reported. In addition, future experimental plans and prospects will be discussed.

Development of UHV transfer case for sample transport using NEG coating

Morohashi, Yuko; Kamiya, Junichiro; Warigai, Keiichi*; Takeishi, Kenichi; Kobata, Masaaki; Yoshigoe, Akitaka; Tsuda, Yasutaka; Fukuda, Tatsuo; Yamada, Ippei; Chiba, Daisuke

JPS Conference Proceedings (Internet), 45, p.011126_1 - 011126_10, 2026/06

https://doi.org/10.7566/JPSCP.45.011126

A new Non-Evaporable Getter (NEG) coating has been developed for J-PARC's advanced vacuum systems, addressing performance degradation due to repeated atmospheric exposure. The new technique removes oxide films from the interior of titanium vacuum chambers before applying the NEG coating, using titanium's getter function to maintain lower pressures even after repeated exposure. A lightweight, compact prototype transfer case was designed to transport nanomaterial samples between analyzers while maintaining ultra-high vacuum (UHV) conditions. Tests between J-PARC and SPring-8 confirmed successful transport of NEG-coated (Ti, Zr, V) surfaces and silicon wafers without oxidation. Future improvements will focus on enhancing the design for commercial use and applying it to J-PARC's future accelerator vacuum systems.

Tuning optical properties of densified silica glass via high pressure and ultrafast laser excitation

Tsubone, Misora*; Shimotsuma, Yasuhiko*; Kono, Yoshio*; Kakizawa, Sho*; Yamada, Hiroki*; Kobayashi, Keita; Shimizu, Masahiro*; Miura, Kiyotaka*

NPG Asia Materials, 18, p.15_1 - 15_16, 2026/04

https://doi.org/10.1038/s41427-026-00649-4

Silica glass exhibits diverse structural configurations accompanied with densification under varying temperature and pressure conditions; these factors significantly influence its optical properties, such as the refractive index. However, the fundamental structural mechanisms underlying the optical properties change induced by high pressure treatment and femtosecond laser direct writing remain poorly understood. Herein, we report the similarities and differences in the optical responses of densified silica glass induced by these two methods. The most significant difference is that the laser-irradiated region evolves toward a glass structure characteristic of a high fictive temperature by incorporating non-bridging oxygen defects associated with edge-sharing SiO tetrahedra, which induces distinctly different photoluminescence behaviors compared to high pressure treatment.

Aerial monitoring around TEPCO's Fukushima Daiichi Nuclear Power Station and development of radiation monitoring technology for unmanned vehicle in fiscal year 2024 (Contract research)

Futemma, Akira; Ochi, Kotaro; Sasaki, Miyuki; Nakama, Shigeo; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Yamada, Tsutomu*; et al.

JAEA-Technology 2025-016, 253 Pages, 2026/03

JAEA-Technology-2025-016.pdf:20.16MB

Aerial Radiation Monitoring (ARM) has been used to quickly and widely measure radiation distribution caused by the TEPCO's Fukushima Daiichi Nuclear Power Station (FDNPS) accident resulted from the tsunami accompanying the Pacific coast of Tohoku Earthquake on March 11, 2011. Since the accident, As a commissioned project of the Nuclear Regulation Authority, the Japan Atomic Energy Agency (JAEA) has continuously conducted ARM around FDNPS. This report summarizes the results of the 2024 monitoring activities, evaluates temporal changes in ambient dose rates, and identifies factors contributing to these changes. A terrain-corrected analysis was applied to improve dose rates conversion accuracy, and results with and without this correction were compared. A radon-progeny discrimination method was also used to assess its impact on manned-helicopter measurements. Furthermore, development of unmanned airplane monitoring technologies was advanced to enhance the efficiency of wide-area surveys.

A Strategy for selecting additional observation points when estimating radiation source distribution using LASSO regression

Yamada, Susumu; Machida, Masahiko

Nihon Oyo Suri Gakkai Rombunshi, 36(1), p.14 - 32, 2026/03

https://doi.org/10.11540/jsiamt.36.1_14

Estimating the distribution of radiation sources is crucial for the safe decommissioning of reactor buildings. LASSO regression has been applied to estimate radiation sources inside reactor buildings based on radiation measurements. However, LASSO regression requires air dose rates measured at appropriate points to produce accurate estimates. Although a strategy for adding observation points has been proposed, its effectiveness is limited depending on the model size. Therefore, we propose a new strategy that takes into account the estimated source distribution and demonstrate its effectiveness.

Development for temperature measurement of the stripper foil in J-PARC RCS

Yoshimoto, Masahiro; Yamada, Ippei; Nakanoya, Takamitsu; Saha, P. K.; Hatakeyama, Shuichiro; Saeki, Riuji*; Kuramochi, Masaya*; Otsu, Satoru*

Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.274 - 279, 2026/03

https://www.pasj.jp/web_publish/pasj2025/proceedings/PDF/WEP0/WEP033.pdf

To achieve a high-intensity proton beam, the J-PARC 3-GeV rapid cycling synchrotron accelerator (RCS) adopts the multi-turn charge-exchange beam injection scheme, in which the carbon stripper foils remove the electron from the injected H beam to convert the H beam. Up to now, we have demonstrated that the foils have a sufficient lifetime for continuous beam operation at the design power of 1 MW. On the other hand, we are investigating the possibility of increasing the beam power at the J-PARC further; we hope to achieve a maximum output of 2 MW at the RCS. In general, the key issue for the stripper foil at higher power beam irradiation is the shortened lifetime due to the rising foil temperature. As it reaches the sublimation temperature, it is of concern that the foil's thickness is rapidly decreasing. In this presentation, we will report the simulation result of the rising foil temperature according to the RCS beam power upgrade plan and the recent status of the study for the versatile foil temperature measurement.

A Scheme to efficiently select air-dose-rate measurement positions in estimating radiation source distribution

Machida, Masahiko; Yamada, Susumu; Yoshida, Toru*; Hasegawa, Yukihiro*; Yanagi, Hideaki*; Furutachi, Naoya*

Proceedings of Waste Management Symposia 2026 (WM2026) (Internet), 15 Pages, 2026/03

Introduction of classification considered as waste package for dismantling waste in JRTF

Nakajima, Ryota; Sakai, Tatsuya; Tani, Riku; Handa, Yuichi; Sunaoshi, Mizuho*; Inoue, Hidetaka*; Yamada, Satoshi; Shimizu, Osamu

JAEA-Technology 2025-012, 39 Pages, 2026/01

JAEA-Technology-2025-012.pdf:2.31MB

JAERI's Reprocessing Test Facility (JRTF) has transition to decommissioning since 1996 and inside the facility dismantled equipment and instrument. In the dismantling and removal work of glove boxes and other equipment, starting in October 2022, we prepared a "Manual for Separation of Dismantled Materials of JRTF" and carried out sorting and separation of the generated dismantled waste with the aim of producing waste package that meets the technical standards required for disposal to a landfill facility. This report describes the results and findings of sorting and separating the dismantled waste generated during the dismantling and removal work of glove boxes and other equipment in accordance with the "Manual for Separation of Dismantled Materials of JRTF".

Improvement in legal compliance activities of nuclear security in JAEA

Hirata, Tomohiro; Hanawa, Kazutaka; Shibata, Ryodai; Yamada, Hiroyuki; Yamazaki, Katsuyuki

Dai-46-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 4 Pages, 2025/12

no abstracts in English

Freeze-crosslinked biomass-based chitosan sponge hydrogels with metal-induced mechanical enhancement for high-performance Cu and Pb adsorption

Nankawa, Takuya; Sugita, Asako; Fukakusa, Chihoko*; Yamada, Teppei*; Sekine, Yurina

Separation and Purification Technology, 378(3), p.134780_1 - 134780_9, 2025/12

https://doi.org/10.1016/j.seppur.2025.134780

We report a sustainable and chemical free strategy to fabricate sponge like chitosan hydrogels via freeze induced physical crosslinking using mild alkaline solutions, without toxic crosslinkers or synthetic additives. The resulting freeze crosslinked biomass-based chitosan sponge hydrogels exhibited interconnected macropores, high water permeability, excellent compressibility, and mechanical recoverability. These features enabled outstanding adsorption of hazardous heavy metals, achieving far better maximum capacities for Cu and Pb markedly surpassing conventional hydrogels. Notably, Cu adsorption induced visible color changes and enhanced mechanical strength, attributed to metal induced secondary crosslinking between amino and hydroxyl groups and adsorbed ions. Cu adsorption also led to a measurable increase in the Youngs modulus of the hydrogels, likely due to coordination with chitosan functional groups.