Interaction of solute manganese and nickel atoms with dislocation loops in iron-based alloys irradiated with 2.8 MeV Fe ions at 400 C

Nguyen, B. V. C.*; 村上 健太*; Chena, L.*; Phongsakorn, P. T.*; Chen, X.*; 橋本 貴司; Hwang, T.*; 古澤 彰憲; 鈴木 達也*

Nuclear Materials and Energy (Internet), 39, p.101639_1 - 101639_9, 2024/06

https://doi.org/10.1016/j.nme.2024.101639

In reactor pressure vessel materials, the formation of Mn- and Ni-rich nanoclusters is a major cause of neutron irradiation embrittlement. The segregation of these solute atoms into dislocation loops has attracted attention as a mechanism to accelerate solute clustering. In this study, the behaviors of solute Mn and Ni atoms in Fe-0.6wt.%Ni, Fe-1.4wt.%Mn, and Fe-1.4wt.%Mn-0.6wt.%Ni alloys irradiated at 400 C up to 3 dpa were analyzed using three-dimensional atom probe tomography. Solute atom clusters were observed in all materials, and their shapes were spherical, flat, and torus in FeNi, FeMn, and FeMnNi, respectively. In ternary alloy FeMnNi, Mn and Ni atoms were concentrated in the sample in the form of arcs, and the orientation of the plane containing the arcs was estimated by comparing field desorption images. The size, number density, and orientation of this structure were found to be in good agreement with those of both types of dislocation loops, namely, b = 1/2 111 and b = 100, identified in a previous study using the same material. The positions of Ni and Mn enrichment did not fully overlap. Ni atoms tended to be concentrated more in the inner part of the loop than the Mn atoms. Mn atoms were enriched only in the vicinity of the dislocation loops, whereas Ni atoms showed a higher concentration inside the dislocation loops than in the bulk.

Acoustically driven magnon-phonon coupling in a layered antiferromagnet

Lyons, T. P.*; Puebla, J.*; 山本 慧; Deacon, R. S.*; Hwang, Y.*; 石橋 幸治*; 前川 禎通*; 大谷 義近*

Physical Review Letters, 131(19), p.196701_1 - 196701_6, 2023/11

https://doi.org/10.1103/PhysRevLett.131.196701

Harnessing the causal relationships between mechanical and magnetic properties of van der Waals materials presents a wealth of untapped opportunity for scientific and technological advancement, from precision sensing to novel memories. This can, however, only be exploited if the means exist to efficiently interface with the magnetoelastic interaction. Here, we demonstrate acoustically-driven spin-wave resonance in a crystalline antiferromagnet, chromium trichloride, via surface acoustic wave irradiation. The resulting magnon-phonon coupling is found to depend strongly on sample temperature and external magnetic field orientation, and displays a high sensitivity to extremely weak magnetic anisotropy fields in the few mT range. Our work demonstrates a natural pairing between power-efficient strain-wave technology and the excellent mechanical properties of van der Waals materials, representing a foothold towards widespread future adoption of dynamic magneto-acoustics.

Intruder configurations in Ne at the transition into the island of inversion; Detailed structure study of Ne

Wang, H.*; 安田 昌弘*; 近藤 洋介*; 中村 隆司*; Tostevin, J. A.*; 緒方 一介*; 大塚 孝治*; Poves, A.*; 清水 則孝*; 吉田 数貴; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

https://doi.org/10.1016/j.physletb.2023.138038

Neからの1中性子除去反応を用いて、Neの詳細な線分光を行った。平行運動量分布の解析に基づき、Neの準位構造とスピンパリティを決定し、初めて負のパリティ状態を同定した。測定された断面積と運動量分布から、N=20とN=28のシェルギャップの消失の証拠となる有意なintruder p-wave強度が明らかになった。束縛状態については、弱いf-waveの可能性のある強度が観測された。いくつかの有効相互作用を用いた大規模殻模型計算では、実験的に観測された大きなp-wave強度と小さなf-wave強度は再現されず、Ne同位体に沿った反転の島への遷移の完全な理論的記述への挑戦が続いていることを示している。

Assessment of doses in contaminated urban areas; Modelling exercise based on Fukushima data

高原 省五; Charnock, T. W.*; Silva, K.*; Hwang, W. T.*; Lee, J.*; Yu, C.*; Kamboj, S.*; Yankovich, T.*; Thiessen, K. M.*

Journal of Radiological Protection, 42(2), p.020517_1 - 020517_13, 2022/06

https://doi.org/10.1088/1361-6498/ac7088

5つの最新の線量評価モデルを利用して、福島第一原子力発電所事故により汚染された都市部の住民の線量を評価・比較した。モデル間での評価結果の比較に加え、モデルによる評価結果と実際の測定値との比較も実施した。また、評価方法として、確率論的方法と決定論的方法の双方を採用し、方法の違いによる評価結果の違いについても比較した。確率論的方法による屋内外の作業員の線量分布の予測は、実際の測定値とよく一致した。また、国際放射線防護委員会が提案した概念に基づき、代表的な人の線量を評価するためにモデルを適用したところ、決定論的アプローチで得られた代表的な人の線量は、確率論的アプローチで得られた線量よりも常に高いことが明らかとなった。なお、本研究は、国際原子力機関におけるMODARIA I及びIIを通じて行われたものである。

Observation of spin-dependent charge symmetry breaking in interaction; -ray spectroscopy of He

山本 剛史*; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 金原 慎二; 中田 祥之; 佐甲 博之; et al.

Physical Review Letters, 115(22), p.222501_1 - 222501_5, 2015/11

AA2015-0707.pdf:0.5MB

https://doi.org/10.1103/PhysRevLett.115.222501

The energy spacing between the spin-doublet bound state of He was determined to be keV, by measuring rays for the transition with a high efficiency germanium detector array in coincidence with the He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the ground state but is vanishingly small in the excited state, demonstrating that the CSB interaction has spin dependence.

Development of a GEM-TPC for H-dibaryon search experiment at J-PARC

佐甲 博之; Ahn, J. K.*; Baek, K. H.*; Bassalleck, B.*; Fujioka, H.*; Guo, L.*; 長谷川 勝一; Hicks, K.*; Honda, R.*; Hwang, S. H.*; et al.

Journal of Instrumentation (Internet), 9(4), p.C04009_1 - C04009_10, 2014/04

https://doi.org/10.1088/1748-0221/9/04/C04009

(,)反応によるHダイバリオン探索実験(J-PARC E42)のためのTPCの開発を行っている。TPCにおいてHが2個のと2個のに崩壊する事象を測定する。TPCのドリフト体積は50cm直径、55cmドリフト長を持つ8角柱構造をしておりAr-CHガスを使用する。増幅部には3層のGEMを使用する。荷電粒子の運動量測定のためTPCにはドリフト電場と平行に鉛直方向の1Tの双極磁場を超伝導ヘルムホルツ型磁石によりかける。H崩壊のアクセプタンスを最大にするためダイアモンド標的がTPC内部の筒状の穴に設置される。さらに、超高レートのビームをTPCに直接照射するため陽イオンフィードバックを極力抑制必要がある。このためTPCにGEMとgating gridを採用した。

Electronic structure of GaCrN and Si-doping effects studied by photoemission and X-ray absorption spectroscopy

Song, G.*; 小林 正起*; Hwang, J. I.*; 片岡 隆*; 滝沢 優*; 藤森 淳; 大河内 拓雄; 竹田 幸治; 岡根 哲夫; 斎藤 祐児; et al.

Physical Review B, 78(3), p.033304_1 - 033304_4, 2008/07

https://doi.org/10.1103/PhysRevB.78.033304

The electronic structure of the magnetic semiconductor GaCrN, and the effect of Si doping on it have been investigated by photoemission and soft X-ray absorption spectroscopy. We have confirmed that Cr in GaN is predominantly trivalent when substituting for Ga and that Cr 3 states appear within the band gap of GaN just above the N 2-derived valence-band maximum. As a result of Si doping, downward shifts of the core levels (except for Cr 2) and the formation of new states near the Fermi level were observed, which we attribute to the upward chemical-potential shift and the formation of a small amount of Cr species caused by electron doping. Possibility of Cr-rich cluster growth by Si doping are discussed based on the spectroscopic and magnetization data.

Effect of neutron irradiation on rhenium cluster formation in tungsten and tungsten rhenium alloys and Introduction of the research for aging management of JAEA

Hwang, T.; 長谷川 晃*; 戸村 恵子*; 海老澤 直樹*; 外山 健*; 永井 康介*; 福田 誠*; 宮澤 健*; 田中 照也*; 野上 修平*

no journal, , 

To clarify the irradiation hardening behavior of neutron-irradiated tungsten(W), the formation behavior of rhenium(Re)-enriched cluster and W-Re precipitation with displacement damage in fission reactors environment was investigated by the atom probe tomography (APT) technique, and the results obtained by APT and microstructural observation by transmission electron microscopy (TEM) were compared. The samples were irradiated to 0.96 dpa at 538C in a fast experimental reactor Joyo, and irradiated to 0.90 dpa at 500C in a mixed spectrum reactor HFIR. The chemical compositions of the matrix, Re clusters, and precipitates were determined by the AP analysis. The Joyo-irradiated samples contained lower levels of transmuted Re and Os, while the HFIR-irradiated samples contained higher levels of Re and Os. The Re-enriched clusters demonstrated characteristic spatial distribution related to defect cluster distribution in each irradiated specimen.