Jiaqi Zhang ^a, Akifumi Iwamoto ^a,b, Keisuke Shigemori ^a , Masanori Hara ^c , Kohei Yamanoi ^a

a Institute of Laser Engineering, Osaka University, Osaka 5650871, Japan
b National Institute for Fusion Science, National Institutes of Natural Sciences, Gifu 509-5202, Japan
c Academic Assembly, University of Toyama, Toyama 9308555, Japan

Abstract
A typical inertial confinement fusion target comprises a central deuterium-tritium (D-T) gas surrounded by a solid D-T layer inside an outer ablator shell. However, because of the isotope effect, fractionation of the hydrogen isotopologues can occur during the solidification process. This inhomogeneity in the solid D-T layer may lead to a deterioration in the fusion reaction. Thus, effective methods are required to characterize isotopologue distribution and homogeneity in solid D-T layers. The distribution of isotopologues in a solid hydrogen mixture can be simulated numerically using computational fluid dynamics. In this study, thermofluid simulations of the mixture’s solidification process were performed to investigate the mechanism behind component distribution and to analyze the factors affecting the homogeneity. A numerical simulation was conducted to model inhomogeneity formation during the solidification of hydrogen isotopologue mixtures in a 3D wedge-shaped cavity. The simulations revealed inhomogeneities in H₂-D₂, D₂-T₂, and D₂-DT-T₂ mixtures during solidification. For an H₂-D₂ mixture, the simulation showed good agreement with experimental results, validating the computational model. These simulation methods will be used for homogeneity analysis of the solid D-T layer in fuel pellets.

https://doi.org/10.1016/j.fusengdes.2025.114827
Accepted: 23 January 2025

Satoshi Akamaru, Kyosuke Miyake

Abstract
This study investigated the giant magnetoresistance (GMR) effect of a Fe/V(001) multilayer under different hydrogen concentrations in a hydrogen–nitrogen gas mixture to elucidate the effect of hydrogen absorption in the V layer on the exchange interactions between each Fe layer. The resistance against hydrogen concentration in the gas mixture revealed a phase boundary that was dependent on the V thickness in Fe/V, between hydrogen dissolved in the V metal and V hydride phases. The magnetoresistance in Fe/V with a V thickness of 1.7–2.0 nm demonstrated a GMR effect, which was reduced under low hydrogen concentration in the gas mixture, corresponding to the hydrogen dissolved phase in the V layer. However, Fe/V samples with V thicknesses within the range of 2.2–2.7 nm exhibited the GMR effect during the formation of the V hydride phase, although these samples did not display any GMR behavior under nitrogen gas. These behaviors were reversible to hydrogen concentration in the gas mixture. The dependence of the exchange coupling coefficient on the V layer thickness was estimated from the GMR behavior, revealing that the exchange coupling coefficient was governed by the change in the crystalline phase from the V metal to the hydride and not by the thickness of the V layer. In the V hydride phase, the GMR effect was gradually reduced following hydrogen absorption, suggesting that the induced structural disorder and/or stress in the V layer due to excess hydrogen absorption inhibited the exchange interactions between each Fe layer.

https://doi.org/10.1063/5.0250577
Published Online: 10 February 2025

Jiaqi Zhang ^a, Akifumi Iwamoto ^a,b, Keisuke Shigemori ^a , Masanori Hara ^c , Kohei Yamanoi ^a

a Institute of Laser Engineering, Osaka University, Osaka 5650871, Japan
b National Institute for Fusion Science, National Institutes of Natural Sciences, Gifu 509-5202, Japan
c Academic Assembly, University of Toyama, Toyama 9308555, Japan

Abstract
A typical inertial confinement fusion target comprises a central deuterium-tritium (D-T) gas surrounded by a solid D-T layer inside an outer ablator shell. However, because of the isotope effect, fractionation of the hydrogen isotopologues can occur during the solidification process. This inhomogeneity in the solid D-T layer may lead to a deterioration in the fusion reaction. Thus, effective methods are required to characterize isotopologue distribution and homogeneity in solid D-T layers. The distribution of isotopologues in a solid hydrogen mixture can be simulated numerically using computational fluid dynamics. In this study, thermofluid simulations of the mixture’s solidification process were performed to investigate the mechanism behind component distribution and to analyze the factors affecting the homogeneity. A numerical simulation was conducted to model inhomogeneity formation during the solidification of hydrogen isotopologue mixtures in a 3D wedge-shaped cavity. The simulations revealed inhomogeneities in H₂-D₂, D₂-T₂, and D₂-DT-T₂ mixtures during solidification. For an H₂-D₂ mixture, the simulation showed good agreement with experimental results, validating the computational model. These simulation methods will be used for homogeneity analysis of the solid D-T layer in fuel pellets.

https://doi.org/10.1016/j.fusengdes.2025.114827
Accepted:23 January 2025

Hidehisa Hagiwara,* Katsuaki Hayakawa, Kazuki Ishitsuka, Keisuke Awaya, Kazuto Hatakeyama,and Shintaro Ida

Abstract
To make full use of sunlight for water splitting reactions for hydrogen production, a visible-light-driven photocatalyst was developed by modifying TiO₂ nanosheets with Co(OH)₂. By adding an aqueous Co(NO₃)₂·6H₂O solution to a TiO₂ nanosheet suspension, the TiO₂ nanosheets aggregated and Co(OH)₂ was formed. In the ultraviolet−visible (UV−vis) diffuse reflectance spectrum of the photocatalyst, new absorption bands attributable to Co(OH)₂ and the interfacial charge transfer between Co(OH)₂ and the TiO₂ nanosheets appeared at around 600 and 400 nm, respectively. The photocatalytic activity of Co(OH)₂/TiO₂ nanosheets was evaluated in terms of the O₂ evolution reaction in an aqueous AgNO₃ solution, finding that the reaction proceeds under visible light. Furthermore, the investigation of the wavelength dependence of the photocatalytic activity revealed that the photocatalytic reaction on Co(OH)₂/TiO₂ nanosheets proceeds via Co(OH)₂ photocatalysis and interfacial charge transfer between Co(OH)₂ and the TiO₂ nanosheets under visible light irradiation.

https://doi.org/10.1021/acsomega.4c10161
Accepted:January 8, 2025