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論文

Enhancing the strength and ductility of a medium entropy alloy through non-basal slip activation

Chen, Z.*; Gong, W.; Harjo, S.; 川崎 卓郎; Chen, G.*; 他14名*

Nature Communications (Internet), 16, p.6480_1 - 6480_13, 2025/07

https://doi.org/10.1038/s41467-025-61494-7

Developing alloys with both ultrahigh strength and ductility remains a for- midable scientific challenge, primarily due to the inherent strength-ductility tradeoff. Here, we present an approach to enhance the ductility and strength of a medium-entropy alloy (MEA) featuring a fully recrystallized face-centered cubic/hexagonal close-packed dual-phase ultrafine-grained architecture. This is achieved by activating unusual non-basal slips in the ordered hexagonal close-packed superlattice nanoprecipitates, resulting in this MEA that exhibits remarkable uniform elongation ($$varepsilon$$$$_{u}$$) and ultrahigh yield strength ($$sigma$$$$_{y}$$) across a wide temperature range, particularly at cryogenic temperatures ($$sigma$$$$_{y}$$ $$sim$$ 2100 MPa, $$varepsilon$$$$_{u}$$ $$sim$$ 15%). The non-basal slips in the secondary phase are activated at ultrahigh stress levels, which are compatible with the increased yield strength of the MEA attained through multiple strengthening mechanisms, including grain boundaries, lattice friction, and second-phase nanoprecipitates provided by the multi-principal elements of the entropy alloy. The deformation mechanism elucidated in this work not only leverages the significant strengthening and strain hardening effects of brittle nanoprecipitates but also enables the ductilization of the alloy through sequential non-basal slip during ongoing deformation.

論文

Surface structure of the 3$$times$$3-Si phase on Al(111), studied by the multiple usages of positron diffraction and core-level photoemission spectroscopy

佐藤 祐輔*; 深谷 有喜; 他14名*

Physical Review Materials (Internet), 9(1), p.014002_1 - 014002_11, 2025/01

https://doi.org/10.1103/PhysRevMaterials.9.014002
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

本研究では、陽電子回折と内殻光電子分光の複合利用により、Al(111)3$$times$$3-Si表面の構造を明らかにした。ロッキング曲線の解析では、3$$times$$3-Si相が平坦なハニカム構造から構成されること、また、第一原理計算に基づくSi内殻スペクトルの解析では、単位胞内のSi原子の一つがAl原子と置換されていることがわかった。すなわち、3$$times$$3-Si相の表面超構造はAl原子を内包したSi二次元層である。

論文

次世代原子炉が拓く新しい市場(第3章, 第4章, 第5章, 第7章)

上出 英樹; 川崎 信史; 早船 浩樹; 久保 重信; 近澤 佳隆; 前田 誠一郎; 佐賀山 豊; 西原 哲夫; 角田 淳弥; 柴田 大受; et al.

次世代原子炉が拓く新しい市場; NSAコメンタリーシリーズ, No.28, p.14 - 36, 2023/10

高速炉、高温ガス炉を始めとする次世代原子炉の開発が進み、日本を含む世界の電力あるいは熱利用など産業利用の市場への貢献が目前となっている。ここでは、世界の動向を含め日本の開発状況についてまとめ、特に第4世代原子力システム国際フォーラム(GIF)の活動ならびに日本の高速炉、高温ガス炉、世界のSMRについて開発の現状を解説した。

論文

A New multi-reflection time-of-flight mass spectrograph for the SLOWRI facility

Rosenbusch, M.*; 伊藤 由太; 他14名*

Nuclear Instruments and Methods in Physics Research B, 463, p.184 - 188, 2020/01

https://doi.org/10.1016/j.nimb.2019.05.058
 被引用回数：12 パーセンタイル：73.86(Instruments & Instrumentation)

A new multi-reflection time-of-flight mass spectrograph for nuclear mass measurements with high precision has been constructed at the SLOWRI facility at RIKEN-RIBF. We aim to couple this new device to a cryogenic gas cell operated at the BigRIPS facility of RIBF. It is part of the SLOWRI project for slowing down and stopping intense radioactive ion beams provided downstream of RIKEN's superconducting ring cyclotron accelerator. In particular, this device is dedicated to be located at the end of the BigRIPS beam line to access ions that are presently guided to beam dumps during in-beam experiments. In this article the apparatus is described in detail.

論文

Characterization of the Hamamatsu VUV4 MPPCs for nEXO

Gallina, G.*; 伊藤 由太; 他149名*

Nuclear Instruments and Methods in Physics Research A, 940, p.371 - 379, 2019/10

https://doi.org/10.1016/j.nima.2019.05.096
 被引用回数：40 パーセンタイル：97.04(Instruments & Instrumentation)

In this paper we report on the characterization of the Hamamatsu VUV4 (S/N: S13370-6152) Vacuum Ultra-Violet (VUV) sensitive Multi-Pixel Photon Counters (MPPC)s as part of the development of a solution for the detection of liquid xenon scintillation light for the nEXO experiment. Various MPPC features, such as: dark noise, gain, correlated avalanches, direct crosstalk and Photon Detection Efficiency (PDE) were measured in a dedicated setup at TRIUMF. At an over voltage of 3.1 V and at T = 163 K we report a number of Correlated Avalanches (CAs) per pulse in the interval following the trigger pulse of. At the same settings the Dark-Noise (DN) rate is. Both the number of CAs and the DN rate are within nEXO specifications. The PDE of the Hamamatsu VUV4 was measured for two different devices at for a mean wavelength of 189 nm. At 3.6 V and 3.5 V of over voltage we report a PDE of 13.4 $$%$$ and 11 $$%$$, corresponding to a saturation PDE of 14.8 $$%$$ and 12.2 $$%$$, respectively. Both values are well below the 24 $$%$$ saturation PDE advertised by Hamamatsu. More generally, the second device tested at 3.5 V of over voltage is below the nEXO PDE requirement. The first one instead yields a PDE that is marginally close to meeting the nEXO specifications. This suggests that with modest improvements the Hamamatsu VUV4 MPPCs could be considered as an alternative to the FBK-LF Silicon Photo-Multipliers for the final design of the nEXO detector.

論文

Li(Cd,Mn)P; A New cadmium based diluted ferromagnetic semiconductor with independent spin & charge doping

Han, W.*; Chen, B. J.*; Gu, B.*; 前川 禎通*; 他14名*

Scientific Reports (Internet), 9, p.7490_1 - 7490_6, 2019/05

https://doi.org/10.1038/s41598-019-43754-x
 被引用回数：13 パーセンタイル：48.73(Multidisciplinary Sciences)

We report a new diluted ferromagnetic semiconductor Li$$_{1+y}$$(Cd,Mn)P, wherein carrier is doped via excess Li while spin is doped by isovalence substitution of Mn$$^{2+}$$ into Cd$$^{2+}$$. The extended Cd 4$$d$$-orbitals lead to more itinerant characters of Li$$_{1+y}$$(Cd,Mn)P than that of analogous Li$$_{1+y}$$(Zn,Mn)P. A higher Curie temperature of 45 K than that for Li$$_{1+y}$$(Zn, Mn)P is obtained in Li$$_{1+y}$$(Cd,Mn)P polycrystalline samples by Arrott plot technique. The p-type carriers are determined by Hall effect measurements. The first principle calculations and X-ray diffraction measurements indicate that occupation of excess Li is at Cd sites rather than the interstitial site. Consequently holes are doped by excess Li substitution. More interestingly Li$$_{1+y}$$(Cd,Mn)P shows a very low coercive field ($$<$$100 Oe) and giant negative magnetoresistance (similar to 80%) in ferromagnetic state that will benefit potential spintronics applications.

論文

Measurement of the decays $$Btoetaellnu_ell$$ and $$Btoeta^primeellnu_ell$$ in fully reconstructed events at Belle

Bele$~n$o, C.*; 谷田 聖; Belle Collaboration*; 他144名*

Physical Review D, 96(9), p.091102_1 - 091102_8, 2017/11

AA2018-0506.pdf:0.47MB

https://doi.org/10.1103/PhysRevD.96.091102
 被引用回数：4 パーセンタイル：21.13(Astronomy & Astrophysics)

We report branching fraction measurements of the decays $$B^+toetaell^+nu_ell$$ and $$B^+toeta^primeell^+nu_ell$$ based on 711~fb$$^{-1}$$ of data collected near the $$Upsilon(4S)$$ resonance with the Belle experiment at the KEKB asymmetric-energy $$e^+e^-$$ collider. This data sample contains 772 million $$Bbar B$$~events. One of the two $$B$$~mesons is fully reconstructed in a hadronic decay mode. Among the remaining ("signal-$$B$$") daughters, we search for the $$eta$$~meson in two decay channels, $$etatogammagamma$$ and $$etatopi^+pi^-pi^0$$, and reconstruct the $$eta^{prime}$$~meson in $$eta^primetoetapi^+pi^-$$ with subsequent decay of the $$eta$$ into $$gammagamma$$. Combining the two $$eta$$ modes and using an extended maximum likelihood, the $$B^+toetaell^+nu_ell$$ branching fraction is measured to be $$(4.2pm 1.1 (rm stat.)pm 0.3 (rm syst.))times 10^{-5}$$. For $$B^+toeta^primeell^+nu_ell$$, we observe no significant signal and set an upper limit of $$0.72times 10^{-4}$$ at 90% confidence level.

論文

The Measurement programme at the neutron time-of-flight facility n_TOF at CERN

Gunsing, F.*; Aberle, O.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他147名*

EPJ Web of Conferences, 146, p.11002_1 - 11002_6, 2017/09

https://doi.org/10.1051/epjconf/201714611002
 被引用回数：6 パーセンタイル：93.13(Nuclear Science & Technology)

CERNのn_TOF中性子飛行時間測定施設は、2001年の事業開始以来、数多くの実験データ取得に利用されてきた。長期に渡り利用された中性子飛行距離185mの第1実験室に加え、2014年からは中性子飛行距離20mの第2実験室が利用可能となり、施設の測定能力が大幅に向上した。n_TOF施設における核データ測定研究活動について総括的に報告する。

論文

Monte Carlo simulations of the n_TOF lead spallation target with the Geant4 toolkit; A Benchmark study

Lerendegui-Marco, J.*; Cort$'e$s-Giraldo, M. A.*; Guerrero, C.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他114名*

EPJ Web of Conferences, 146, p.03030_1 - 03030_4, 2017/09

https://doi.org/10.1051/epjconf/201714603030
 被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)

Monte Carlo (MC) simulations are an essential tool to determine fundamental features of a neutron beam, such as the neutron flux or the $$gamma$$ ray background, that sometimes can not be measured or at least not in every position or energy range. Until recently, the most widely used MC codes in this field had been MCNPX and FLUKA. However, the Geant4 toolkit has also become a competitive code for the transport of neutrons after the development of the native Geant4 format for neutron data libraries, G4NDL. In this context, we present the Geant4 simulations of the neutron spallation target of the n TOF facility at CERN, done with version 10.1.1 of the toolkit. The first goal was the validation of the intra-nuclear cascade models implemented in the code using, as benchmark, the characteristics of the neutron beam measured at the first experimental area (EAR1), especially the neutron flux and energy distribution, and the time distribution of neutrons of equal kinetic energy, the so-called Resolution Function. The second goal was the development of a Monte Carlo tool aimed to provide useful calculations for both the analysis and planning of the upcoming measurements at the new experimental area (EAR2) of the facility.

論文

Nuclear data activities at the n_TOF facility at CERN

Gunsing, F.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他141名*

European Physical Journal Plus (Internet), 131(10), p.371_1 - 371_13, 2016/10

https://doi.org/10.1140/epjp/i2016-16371-4
 被引用回数：33 パーセンタイル：57.33(Physics, Multidisciplinary)

Nuclear data in general, and neutron-induced reaction cross sections in particular, are important for a wide variety of research fields. They play a key role in the safety and criticality assessment of nuclear technology, not only for existing power reactors but also for radiation dosimetry, medical applications, the transmutation of nuclear waste, accelerator-driven systems, fuel cycle investigations and future reactor systems as in Generation IV. Applications of nuclear data are also related to research fields as the study of nuclear level densities and stellar nucleosynthesis. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. CERN's neutron time-of-flight facility, n_TOF, has produced a considerable amount of experimental data since it has become fully operational with the start of the scientific measurement program in 2001. While for a long period a single measurement station (EAR1) located at 185 m from the neutron production target was available, the construction of a second beam line at 20 m (EAR2) in 2014 has substantially increased the measurement capabilities of the facility. An outline of the experimental nuclear data activities at n_TOF will be presented.

論文

Measurement of $$e^+e^- to pi^+pi^-psi(2S)$$ via initial state radiation at Belle

Wang, X. L.*; 谷田 聖; Belle Collaboration*; 他144名*

Physical Review D, 91(11), p.112007_1 - 112007_15, 2015/06

AA2015-0519.pdf:0.8MB

https://doi.org/10.1103/PhysRevD.91.112007
 被引用回数：128 パーセンタイル：97.49(Astronomy & Astrophysics)

We report measurement of the cross section of $$e^+e^- to pi^+pi^- psi(2S)$$ between 4.0 and 5.5 GeV, based on an analysis of initial state radiation events in a 980 $${rm fb^{-1}}$$ data sample recorded with the Belle detector. The properties of the $$Y(4360)$$ and $$Y(4660)$$ states are determined. Fitting the mass spectrum of $$pi^+pi^- psi(2S)$$ with two coherent Breit-Wigner functions, we find two solutions with identical mass and width but different couplings to electron-positron pairs: $$M_{Y(4360)}=(4347 pm 6 pm 3)$$ $${rm MeV}/c^2$$, $$Gamma_{Y(4360)} = (103 pm 9 pm 5)$$ MeV, $$M_{Y(4660)}=(4652 pm 10 pm 8)$$ $${rm MeV}/c^2$$, $$Gamma_{Y(4660)} = (68 pm 11 pm 1)$$ MeV, and $${cal B}[Y(4360) to pi^+pi^- psi(2S)]cdot Gamma^{e^+e^-}_{Y(4360)} = (10.9 pm 0.6 pm 0.7)$$ eV and $${cal B}[Y(4660)to pi^+pi^- psi(2S)]cdotGamma^{e^+e^-}_{Y(4660)}=(8.1 pm 1.1 pm 0.5)$$ eV for one solution; or $${cal B}[Y(4360) to pi^+pi^- psi(2S)]cdot Gamma^{e^+e^-}_{Y(4360)} = (9.2 pm 0.6 pm 0.6)$$ eV and $${cal B}[Y(4660)to pi^+pi^- psi(2S)]cdotGamma^{e^+e^-}_{Y(4660)}=(2.0 pm 0.3 pm 0.2)$$ eV for the other. Here, the first errors are statistical and the second systematic. Evidence for a charged charmoniumlike structure at 4.05 $${rm MeV}/c^2$$ is observed is observed in the $$pi^{pm}psi(2S)$$ intermediate state in the $$Y(4360)$$ decays.

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