JAEA
  • help
  • PC | SP
  • JP | EN
          
検索対象：     
報告書番号：
※ 半角英数字
 年 ～ 
 年
全てクリア
検索結果：　89 件中 1件目～20件目を表示

発表形式

Initialising ...

選択項目を絞り込む

掲載資料名

Initialising ...

発表会議名

Initialising ...

筆頭著者名

Initialising ...

キーワード

Initialising ...

使用言語

Initialising ...

発行年

Initialising ...

開催年

Initialising ...

選択した検索結果をダウンロード

論文

Martensitic transformation-governed Luders deformation enables large ductility and late-stage strain hardening in ultrafine-grained austenitic stainless steel at low temperatures

Mao, W.*; Gao, S.*; Gong, W.; 川崎 卓郎; 伊東 達矢; Harjo, S.; 辻 伸泰*

Acta Materialia, 278, p.120233_1 - 120233_13, 2024/10

https://doi.org/10.1016/j.actamat.2024.120233
 被引用回数：2 パーセンタイル：59.42(Materials Science, Multidisciplinary)

Using a hybrid method of in situ neutron diffraction and digital image correlation, we found that ultrafine-grained 304 stainless steel exhibits Luders deformation after yielding, in which the deformation behavior changes from a cooperation mechanism involving dislocation slip and martensitic transformation to one primarily governed by martensitic transformation, as the temperature decreases from 295 K to 77 K. Such martensitic transformation-governed Luders deformation delays the activation of plastic deformation in both the austenite parent and martensite product, resulting in delayed strain hardening. This preserves the strain-hardening capability for the later stage of deformation, thereby maintaining a remarkable elongation of 29% while achieving a high tensile strength of 1.87 GPa at 77 K.

論文

France-Japan collaboration on severe accident studies in sodium-cooled fast reactors, 2; Methodologies and calculations of severe accident phases

曽我部 丞司; 石田 真也; 田上 浩孝; 岡野 靖; 神山 健司; 小野田 雄一; 松場 賢一; 山野 秀将; 久保 重信; 久保田 龍三郎*; et al.

Proceedings of International Conference on Nuclear Fuel Cycle (GLOBAL2024) (Internet), 4 Pages, 2024/10

日仏協力の枠組みにおいて、タンク型ナトリウム冷却高速を対象とした過酷事故の評価手法を定義し、解析評価を実施した。

論文

Internal strain measurement by neutron diffraction under transverse compressive stress for Nb$$_{3}$$Sn wires with and without Cu-Nb reinforcement

中本 美緒*; 菅野 未知央*; 荻津 透*; 杉本 昌弘*; 谷口 諒*; 廣瀬 清慈*; 川崎 卓郎; Gong, W.; Harjo, S.; 淡路 智*; et al.

IEEE Transactions on Applied Superconductivity, 34(5), p.8400806_1 - 8400806_6, 2024/08

https://doi.org/10.1109/TASC.2024.3379124
 被引用回数：0 パーセンタイル：0.00(Engineering, Electrical & Electronic)

For an accelerator magnet, a certain mechanical strength is required to sustain against a transverse compression stress due to Lorentz force. A bronze-route Nb$$_{3}$$Sn wire with Cu-Nb reinforcement was developed by Tohoku University and Furukawa Electric to enhance the strength against axial tension. The Cu-Nb reinforcement wire also exhibited some indication of strength improvement against transverse compression; however, the details of a reinforcement mechanism for the transverse compression stress have not been clarified. In this study, the internal strains of Nb$$_{3}$$Sn bronze-route wires with and without the Cu-Nb reinforcement under transverse compression stress were evaluated by neutron diffraction at BL19 (TAKUMI) in J-PARC. The samples were attached to jig with solder only at the ends and compression was applied at the center of the samples with 30-mm anvil with 5-mm wide and 8- to 15-mm high beam. Since a critical current, Ic of a superconducting wire depends on the three-dimensional strain, internal strain of Nb$$_{3}$$Sn along the axial and two orthogonal radial directions were evaluated at room temperature (RT). In the different setup, Ic measurements of the wires under transverse compression stresses were also performed at 4.2 K and 14.5 T. Using 3-mm wide anvil, the transverse compression was applied at 4.2 K or RT. The neutron diffraction results indicated no significant differences in the internal strains of Nb$$_{3}$$Sn under transverse compression between the samples with and without Cu-Nb reinforcement, while the Ic measurements showed potential increase in the irreversible stress ($$sigma$$$$_{irr}$$) for Cu-Nb reinforced wires. The reason for this discrepancy was discussed based on the difference in the experimental setups for each measurement.

論文

Development of an Fe$$^{rm II}$$ complex exhibiting intermolecular proton shifting coupled spin transition

Ji, T.*; Su, S.*; Wu, S.*; 堀 優太*; 重田 育照*; Huang, Y.*; Zheng, W.*; Xu, W.*; Zhang, X.*; 鬼柳 亮嗣; et al.

Angewandte Chemie; International Edition, 63(25), p.e202404843_1 - e202404843_6, 2024/04

https://doi.org/10.1002/anie.202404843
 被引用回数：0 パーセンタイル：0.00(Chemistry, Multidisciplinary)

In this study, we investigated reversible intermolecular proton shifting (IPS) coupled with spin transition (ST) in a novel Fe$$^{rm II}$$ complex. The host Fe$$^{rm II}$$ complex and the guest carboxylic acid anion were connected by intermolecular hydrogen bonds (IHBs). We extended the intramolecular proton transfer coupled ST phenomenon to the intermolecular system. The dynamic phenomenon was confirmed by variable-temperature single-crystal X-ray diffraction, neutron crystallography, and infrared spectroscopy.

論文

${it In situ}$ neutron diffraction revealing the achievement of excellent combination of strength and ductility in metastable austenitic steel by grain refinement

Mao, W.; Gong, W.; Harjo, S.; 諸岡 聡; Gao, S.*; 川崎 卓郎; 辻 伸泰*

Journal of Materials Science & Technology, 176, p.69 - 82, 2024/03

https://doi.org/10.1016/j.jmst.2023.07.036
 被引用回数：5 パーセンタイル：16.17(Materials Science, Multidisciplinary)

Fe-24Ni-0.3C(wt.%)準安定オーステナイト鋼の降伏応力は、平均結晶粒径が35$$mu$$m(粗粒[CG])から0.5$$mu$$m(超微細粒[UFG])に減少すると3.5倍(158$$rightarrow$$551MPa)に増加したが、引張伸びは大きく維持された(0.87$$rightarrow$$0.82)。結晶粒径が力学特性と変形機構に及ぼす影響を定量的に明らかにするため、室温での引張変形中にCGとUFG Fe-24Ni-0.3C鋼のその場中性子回折測定を行った。CGとUFG試料における塑性変形の初期段階は転位すべりによって支配され、変形後期には変形誘起マルテンサイト変態(DIMT)も生じた。結晶粒の微細化により、DIMTの開始応力が大きく増加し、ひずみに関するDIMTの速度が抑制されることがわかった。結果として、(i)結晶粒微細化によりオー ステナイトが安定化し、DIMTに対して最も安定な結晶粒である$$<$$111$$>$$//LD(LD:負荷方向)オーステナイト粒でのDIMTの開始が大幅に遅れた。その結果、UFG試験片の$$<$$111$$>$$//LDオーステナイト粒のほとんどはマルテンサイトに変態しなかった。(ii)結晶粒の微細化は、マルテンサイト変態の自己促進効果も抑制した。それにもかかわらず、UFG試験片の変態速度が低いDIMTは、CG試験片のより応力を増加させるのに効率がよく、変形中に均一な変形を維持するのに適していた。以上の現象は、UFG準安定オーステナイト鋼の優れた強度と延性の両立に相互に寄与している。

論文

Deformation-induced martensitic transformation at tensile and compressive deformations of bainitic steels with different carbon contents

上路 林太郎*; Gong, W.; Harjo, S.; 川崎 卓郎; 柴田 曉伸*; 木村 勇次*; 井上 忠信*; 土田 紀之*

ISIJ International, 64(2), p.459 - 465, 2024/01

https://doi.org/10.2355/isijinternational.ISIJINT-2023-253
 被引用回数：0 パーセンタイル：0.00(Metallurgy & Metallurgical Engineering)

Deformation-induced martensitic transformation (DIMT) during tensile or compressive deformations of the bainitic steels with various carbon content (0.15%C, 0.25%C, 0.62%C) was studied. In all of the bainitic steels, the tensile deformation exhibited larger work hardening than the compression. This difference indicates the suppression of the DIMT at the compression, and actually the measurements of electron back scattering diffraction (EBSD) confirmed the less reduction of retained austenite at the compression of all the bainitic steels. Additionally, the steel with the highest carbon content was examined by in situ neutron diffraction and clarified the difference similar to that obtained by the EBSD measurement. The regression of the relation between the fraction of austenite and applied strain with the conventional empirical equation revealed that the kinetic of DIMT is strongly dependent with the stress polarity, but not significantly changed by the carbon content.

論文

Change in mechanical properties of high-strength martensitic steel by the combination of pre-strain and deformation temperature

土田 紀之*; Kuramoto, Shota*; 上路 林太郎*; Gong, W.; Harjo, S.; 廣井 孝介; 河村 幸彦*

ISIJ International, 64(2), p.354 - 360, 2024/01

https://doi.org/10.2355/isijinternational.ISIJINT-2023-216
 被引用回数：0 パーセンタイル：0.00(Metallurgy & Metallurgical Engineering)

The effects of pre-strain on the mechanical properties of high strength martensitic steels were investigated using either strain tempering (ST) or quenching and tempering (QT) samples. In the tensile tests at deformation temperatures between 296 and 573 K, the ST sample exhibited an increase in both the tensile strength (TS) and uniform elongation (U El) at 473 to 523 K, whereas the QT sample showed an increase in U El with little change in the TS and yield strength (YS). The results of in situ neutron diffraction experiments revealed an increase in the stress partitioning to the bcc phase with an increase in the deformation temperature from 296 to 523 K. The difference in the phase stress between the bcc and cementite phases decreased with an increase in the temperature due to the decrease in the cementite strength. Pre-strain of 0.5% increased the YS at 296 K with a slight work hardening; the initial dislocation density ($$rho$$) decreased at 523 K, but increased significantly after yielding, leading to a better combination of TS and U.El. The combination of pre-strain, tempering, and deformation temperatures caused the change in $$rho$$ before deformation and the increase in $$rho$$ after yielding of the martensitic steel.

論文

Quantitatively evaluating the huge L$"u$ders band deformation in an ultrafine grain stainless steel by combining ${it in situ}$ neutron diffraction and digital image correlation analysis

Mao, W.; Gao, S.*; Gong, W.; Harjo, S.; 川崎 卓郎; 辻 伸泰*

Scripta Materialia, 235, p.115642_1 - 115642_6, 2023/10

https://doi.org/10.1016/j.scriptamat.2023.115642
 被引用回数：10 パーセンタイル：82.42(Nanoscience & Nanotechnology)

本研究では、巨大なリューダースバンド変形を示す超微細粒(UFG)ステンレス鋼の引張その場中性子回折とデジタル画像相関測定を行い、バンド伝播中の歪硬化に対するオーステナイト母相と変形誘起マルテンサイトの個々の寄与を評価した。定量的解析の結果、UFG構造によって流動応力が大幅に増加した場合、オーステナイト母相のひずみ硬化は均一な変形を維持するには不十分であることがわかった。リューダースバンドの伝播に必要なひずみ硬化は、マルテンサイトの形成とその内部の高い内部応力によってもたらされた。

論文

Lattice parameters of austenite and martensite during transformation for Fe-18Ni alloy investigated through ${it in situ}$ neutron diffraction

Gong, W.; Harjo, S.; 友田 陽*; 諸岡 聡; 川崎 卓郎; 柴田 曉伸*; 辻 伸泰*

Acta Materialia, 250, p.118860_1 - 118860_16, 2023/05

https://doi.org/10.1016/j.actamat.2023.118860
 被引用回数：16 パーセンタイル：92.13(Materials Science, Multidisciplinary)

Martensitic transformation is accompanied by the generation of microscale and macroscale internal stresses during cooling below the martensitic transformation start temperature. These internal stresses have been determined through X-ray or neutron diffraction, but the reported results are not consistent, probably because the measured lattice parameter is influenced not only by the internal stress but also by several factors, including solute elements and crystal defects. Therefore, ${it in situ}$ neutron diffraction combined with dilatometry measurements during martensitic transformation and subsequent cyclic tempering were performed for an Fe-18Ni alloy. The phase strains calculated by lattice parameter variations show that a hydrostatic compressive strain in austenite and a tensile strain in martensite arose as the martensitic transformation progressed during continuous cooling or isothermal holding. However, the phase stresses of austenite and martensite estimated from these strains failed to hold stress balance law when dense crystal defects involved in the processes. After these crystal defects were removed by appropriate tempering, the stress balance law held well. Meanwhile, the phase stresses of austenite and martensite were changed to opposite, revealing their true identity. Various crystal defects in austenite and martensite, introduced by plastic accommodation, were suggested to affect their lattice parameters and then their phase stresses.

論文

Compressive deformation behavior of AZ31 alloy at 21K; An ${it In situ}$ neutron diffraction study

Gong, W.; 川崎 卓郎; Zheng, R.*; 眞山 剛*; Sun, B.*; 相澤 一也; Harjo, S.; 辻 伸泰*

Scripta Materialia, 225, p.115161_1 - 115161_5, 2023/03

https://doi.org/10.1016/j.scriptamat.2022.115161
 被引用回数：7 パーセンタイル：54.52(Nanoscience & Nanotechnology)

Deformation behavior during uniaxial compression at 21 K and 298 K in a commercial AZ31 magnesium alloy was studied by ${it in situ}$ neutron diffraction. Decreasing the deformation temperature resulted in a slight increase in yield stress (115 MPa $$rightarrow$$ 139 MPa), but a remarkable enhancement in both the fracture stress (365 MPa $$rightarrow$$ 551 MPa) and fracture strain (12.8% $$rightarrow$$ 16.5%). The low temperature sensitivity of the {10$$overline{1}$$2} extension twinning which governed the macroscopic yielding led to the slight increase in yield stress. At 21K, basal slip was suppressed, while the extension twinning was promoted resulted in higher twin volume fraction. In the late stage of deformation, the {10$$overline{1}$$1}-{10$$overline{1}$$2} double twinning was suppressed, which is considered to be the reason to delay the fracture at 21 K.

論文

Stress partitioning between bcc and cementite phases discussed from phase stress and dislocation density in martensite steels

土田 紀之*; 上路 林太郎*; Gong, W.; 川崎 卓郎; Harjo, S.

Scripta Materialia, 222, p.115002_1 - 115002_6, 2023/01

https://doi.org/10.1016/j.scriptamat.2022.115002
 被引用回数：9 パーセンタイル：64.03(Nanoscience & Nanotechnology)

The present study investigated the tensile deformation behavior of quenched and tempered martensite steels at various austenitization and tempering temperatures using in situ neutron diffraction experiments. Phase lattice strains in the bcc and cementite ($$theta$$) phases and dislocation structures in the bcc phase were analyzed. The phase lattice strain in bcc became almost stagnant after yielding as the tempering temperature increased. The phase lattice strain in $$theta$$ increased linearly with an increase in the flow stress, independent of the austenitization and tempering temperatures. The stress partitioning between bcc and $$theta$$ was confirmed after the yielding of bcc, which contributed to the work hardening. The phase stresses of bcc and $$theta$$ and their stress partitioning improve the mechanical properties of martensite steels, which can be summarized by the systematic changes in phase lattice strain and dislocation properties due to the austenitization and tempering temperatures.

論文

${it In situ}$ observation of twinning and detwinning in AZ31 alloy

Gong, W.; Zheng, R.*; Harjo, S.; 川崎 卓郎; 相澤 一也; 辻 伸泰*

Journal of Magnesium and Alloys (Internet), 10(12), p.3418 - 3432, 2022/12

https://doi.org/10.1016/j.jma.2022.02.002
 被引用回数：31 パーセンタイル：94.20(Metallurgy & Metallurgical Engineering)

Twinning and detwinning behavior of a commercial AZ31 magnesium alloy during cyclic compression-tension deformation with a total strain amplitude of 4% ($$pm$$2%) was evaluated using the complementary techniques of ${it in situ}$ neutron diffraction, identical area electron backscatter diffraction, and transmission electron microscopy. In-situ neutron diffraction demonstrates that the compressive deformation was dominated by twin nucleation, twin growth, and basal slip, while detwinning dominated the unloading of compressive stresses and subsequent tension stage. A large number of $$<c>$$-component dislocations observed in twins and the detwinned regions were attributed to the dislocation transmutation during the twinning and detwinning. The accumulation of barriers including twin boundaries and various types of dislocations enhanced the interactions of migrating twin boundary with these barriers during twinning and detwinning, which is considered to be the origin for increasing the work hardening rate in cyclic deformation of the AZ31 alloy.

論文

Rediscovery of Hall-Petch strengthening in bulk ultrafine grained pure Mg at cryogenic temperature; A Combined ${it in situ}$ neutron diffraction and electron microscopy study

Zheng, R.*; Gong, W.; Du, J.-P.*; Gao, S.*; Liu, M.*; Li, G.*; 川崎 卓郎; Harjo, S.; Ma, C.*; 尾方 成信*; et al.

Acta Materialia, 238, p.118243_1 - 118243_15, 2022/10

https://doi.org/10.1016/j.actamat.2022.118243
 被引用回数：37 パーセンタイル：96.34(Materials Science, Multidisciplinary)

Grain refinement can lead to the strengthening of metallic materials according to the Hall-Petch relationship. However, our recent results suggested that grain boundary sliding is the dominant deformation mode in bulk ultrafine grained (UFG) pure Mg at room temperature, leading to softening. Here, for the first time, we report that the Hall-Petch strengthening can be regained in bulk UFG pure Mg at cryogenic temperature. At 77K, the UFG pure Mg with a mean grain size of 0.6 $$mu$$m exhibited ultrahigh tensile yield strength and ultimate tensile strength of 309 MPa and 380 MPa, respectively. Combined ${it in situ}$ neutron diffraction and electron microscopy investigation indicated that residual dislocation structures and deformation twins hardly formed in the UFG specimen during tensile test at 298K. In contrast, fast accumulation of lattice defects and remarkable reorientation were evident at 77K, suggesting that the grain-boundary-mediated process was suppressed and the plastic deformation was dominated by dislocation slip and deformation twinning. In addition, all the pure Mg specimens exhibited pronounced strain hardening at 77 K, which was mainly attributed to the suppressed grain boundary sliding and dynamic recovery. The mean dislocation density and relative fractions of dislocations with various Burgers vectors of the UFG specimen deformed at 77K were determined quantitatively from neutron diffraction data.

論文

Achieving excellent mechanical properties in type 316 stainless steel by tailoring grain size in homogeneously recovered or recrystallized nanostructures

Liu, M.*; Gong, W.; Zheng, R.*; Li, J.*; Zhang, Z.*; Gao, S.*; Ma, C.*; 辻 伸泰*

Acta Materialia, 226, p.117629_1 - 117629_13, 2022/03

https://doi.org/10.1016/j.actamat.2022.117629
 被引用回数：74 パーセンタイル：99.38(Materials Science, Multidisciplinary)

One hopeful path to realize good comprehensive mechanical properties in metallic materials is to accomplish homogeneous nanocrystalline (NC) or ultrafine grained (UFG) structure with low dislocation density. In this work, high pressure torsion deformation followed by appropriate annealing was performed on 316 stainless steel (SS). For the first time, we successfully obtained NC/UFG 316 SS having uniform microstructures with various average grain sizes ranging from 46 nm to 2.54 $$mu$$m and low dislocation densities. Among the series, an un-precedentedly high yield strength (2.34 GPa) was achieved at the smallest grain size of 46 nm, in which dislocation scarcity induced hardening accounting for 57% of the strength. On the other hand, exceptional strength-ductility synergy with high yield strength (900 MPa) and large uniform elongation (27%) was obtained in the fully recrystallized specimen having the grain size of 0.38 $$mu$$m. The high yield stress and scarcity of dislocation sources in recrystallized UFGs activated stacking faults and deformation twins nucleating from grain boundaries during straining, and their interaction with dislocations allowed for sustainable strain hardening, which also agreed with the plaston concept recently proposed. The multiple deformation modes activated, together with the effective strengthening mechanisms, were responsible for the outstanding comprehensive mechanical performance of the material.

論文

Joint environmental radiation survey by JAEA and KAERI around the Fukushima Daiichi Nuclear Power Plant; Performance of mobile gamma-ray spectrometry using backpack and carborne survey platforms

Ji, Y.-Y.*; 越智 康太郎; Hong, S. B.*; 中間 茂雄; 眞田 幸尚; 三上 智

Health Physics, 121(6), p.613 - 620, 2021/12

https://doi.org/10.1097/HP.0000000000001471
 被引用回数：1 パーセンタイル：11.05(Environmental Sciences)

原子力機構(JAEA)と韓国原子力研究所(KAERI)との間に締結された放射線防護や環境放射線測定に関する共同研究に基づき、福島第一原子力発電所周辺の放射性セシウム沈着量を評価するための合同測定が実施された。まず初めに、バックパック測定プラットフォームを用いた可搬型$$gamma$$線スペクトロメトリーが3つの地点で実施された。車両測定は、各バックパック測定地点間を移動する際に、車内に$$gamma$$線スペクトロメーターを搭載することで実施した。車体による放射線の遮蔽の影響を加味した上で、評価手法の妥当性が検証された。

論文

Catalog of gamma-ray glows during four winter seasons in Japan

和田 有希*; 松本 崇弘*; 榎戸 輝揚*; 中澤 知洋*; 湯浅 孝行*; 古田 禄大*; 米徳 大輔*; 澤野 達哉*; 岡田 豪*; 南戸 秀仁*; et al.

Physical Review Research (Internet), 3(4), p.043117_1 - 043117_31, 2021/12

https://doi.org/10.1103/PhysRevResearch.3.043117

In 2015 the Gamma-Ray Observation of Winter Thunderstorms (GROWTH) collaboration launched a mapping observation campaign for high-energy atmospheric phenomena related to thunderstorms and lightning discharges. This campaign has developed a detection network of gamma rays with up to 10 radiation monitors installed in Kanazawa and Komatsu cities, Ishikawa Prefecture, Japan, where low-charge-center winter thunderstorms frequently occur. During four winter seasons from October 2016 to April 2020, in total 70 gamma-ray glows, minute-lasting bursts of gamma rays originating from thunderclouds, were detected. Their average duration is 58.9 sec. Among the detected events, 77% were observed in nighttime. The gamma-ray glows can be classified into temporally-symmetric, temporally-asymmetric, and lightning-terminated types based on their count-rate histories. An averaged energy spectrum of the gamma-ray glows is well fitted with a power-law function with an exponential cutoff, whose photon index, cutoff energy, and flux are 0.613 $$pm$$ 0.009, 4.68 $$pm$$ 0.04 MeV, and (1.013 $$pm$$ 0.003) $$times$$ 10$$^{-5}$$ erg cm$$^{-2}$$s$$^{-1}$$ (0.2-20.0 MeV), respectively. The present paper provides the first catalog of gamma-ray glows and their statistical analysis detected during winter thunderstorms in the Kanazawa and Komatsu areas.

論文

High-temperature antiferromagnetism in Yb based heavy fermion systems proximate to a Kondo insulator

鈴木 慎太郎*; 田久保 耕*; 久我 健太郎*; 髭本 亘; 伊藤 孝; 冨田 崇弘*; 志村 恭通*; 松本 洋介*; Bareille, C.*; 和達 大樹*; et al.

Physical Review Research (Internet), 3(2), p.023140_1 - 023140_12, 2021/05

https://doi.org/10.1103/PhysRevResearch.3.023140

本論文では常圧において転移温度が20Kに達するYb化合物の発見について報告している。価数揺動物質$$alpha$$-YbAlB$$_4$$のAlサイトをMnに置換することで、反強磁性転移温度が極めて高くなるだけでなく、重い電子状態から近藤半導体に近い抵抗の大きな金属状態へと変わることが見出された。

論文

Performance of in situ gamma-ray spectrometry in the assessment of radioactive cesium deposition around the Fukushima Daiichi Nuclear Power Plant

Ji, Y.-Y.*; 越智 康太郎; Hong, S. B.*; 中間 茂雄; 眞田 幸尚; 三上 智

Radiation Physics and Chemistry, 179, p.109205_1 - 109205_11, 2021/02

https://doi.org/10.1016/j.radphyschem.2020.109205
 被引用回数：8 パーセンタイル：69.95(Chemistry, Physical)

福島第一原子力発電所周辺の異なる線量レベルのエリアで、様々なサーベイプラットフォームを用いin-situ $$gamma$$線スペクトロメトリーを実施した。地表における放射性セシウム沈着量を、高純度Ge半導体検出器とLaBr$$_{3}$$(Ce)検出器を用いて評価するために、福島第一原子力発電所周辺の6か所のサイト(うち2つは帰還困難区域)が選択された。2018年10月に行ったin-situ測定の結果、$$^{137}$$Csの沈着量は6つのサイトで30-3000kBq m$$^{-2}$$の範囲にあった。また、広範囲の代表的な深度分布を直接的に計算するin-situ測定手法を導入し、その結果が同じサイトで採取された土壌サンプルの結果をよく表現していることが分かった。

論文

Production of $$^{266}$$Bh in the $$^{248}$$Cm($$^{23}$$Na,5$$n$$)$$^{266}$$Bh reaction and its decay properties

羽場 宏光*; Fan, F.*; 加治 大哉*; 笠松 良崇*; 菊永 英寿*; 小森 有希子*; 近藤 成美*; 工藤 久昭*; 森本 幸司*; 森田 浩介*; et al.

Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08

https://doi.org/10.1103/PhysRevC.102.024625
 被引用回数：6 パーセンタイル：51.86(Physics, Nuclear)

The nuclide $$^{266}$$Bh was produced in the $$^{248}$$Cm($$^{23}$$Na,5n)$$^{266}$$Bh reaction at beam energies of 125.9, 130.6, and 135.3 MeV. Decay properties of $$^{266}$$Bh were investigated with a rotating wheel apparatus for $$alpha$$ and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. The half-life of $$^{266}$$Bh was measured to be $$T_{rm 1/2}$$ = 10.0$$^{+2.6}_{-1.7}$$ s. The $$alpha$$-particle energies of $$^{266}$$Bh disperse widely in the range of 8.62 - 9.40 MeV. The maximum production cross section for the $$^{248}$$Cm($$^{23}$$Na,5n)$$^{266}$$Bh reaction was determined to be $$sigma$$ = 57 $$pm$$ 14 pb at 130.6 MeV.

論文

Nature of the Dirac gap modulation and surface magnetic interaction in axion antiferromagnetic topological insulator MnBi$$_{2}$$Te$$_{4}$$

Shikin, A. M.*; Estyunin, D. A.*; Klimovskikh, I. I.*; Filnov, S. O.*; Kumar, S.*; Schwier, E. F.*; 宮本 幸治*; 奥田 太一*; 木村 昭夫*; 黒田 健太*; et al.

Scientific Reports (Internet), 10, p.13226_1 - 13226_13, 2020/08

https://doi.org/10.1038/s41598-020-70089-9
 被引用回数：70 パーセンタイル：95.80(Multidisciplinary Sciences)

Modification of the gap at the Dirac point (DP) in axion antiferromagnetic topological insulator MnBi$$_{2}$$Te$$_{4}$$ and its electronic and spin structure have been studied by angle- and spin-resolved photoemission spectroscopy (ARPES) under laser excitation at various temperatures, light polarizations and photon energies. We have distinguished both large and reduced gaps at the DP in the ARPES dispersions, which remain open above the N$'{e}$el temperature of $$T_textrm{N}$$ = 24.5 K. We propose that the gap above $$T_textrm{N}$$ remains open due to a short-range magnetic field generated by chiral spin fluctuations. Spin-resolved ARPES, XMCD and circular dichroism ARPES measurements show a surface ferromagnetic ordering for the large gap sample and apparently significantly reduced effective magnetic moment for the reduced gap sample.

89 件中 1件目～20件目を表示