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論文

Probing deformation behavior of a refractory high-entropy alloy using ${it in situ}$ neutron diffraction

Zhou, Y.*; Song, W.*; Zhang, F.*; Wu, Y.*; Lei, Z.*; Jiao, M.*; Zhang, X.*; Dong, J.*; Zhang, Y.*; Yang, M.*; et al.

Journal of Alloys and Compounds, 971, p.172635_1 - 172635_7, 2024/01

 被引用回数:0 パーセンタイル:0(Chemistry, Physical)

The grain orientation-dependent lattice strain evolution of a (TiZrHfNb)$$_{98}$$$$N_2$$ refractory high-entropy alloy (HEA) during tensile loading has been investigated using ${it in situ}$ neutron diffraction. The equivalent strain-hardening rate of each of the primary $$<hkl>$$-oriented grain families was found to be relatively low, manifesting the macroscopically weak work-hardening ability of such a body-centered cubic (BCC)-structured HEA. This finding is indicative of a dislocation planar slip mode that is confined in a few single-slip planes and leads to in-plane softening by high pile-up stresses.

論文

Key role of temperature on delamination in solid-state additive manufacturing via supersonic impact

Wang, Q.*; Ma, N.*; Huang, W.*; Shi, J.*; Luo, X.-T.*; 冨高 宙*; 諸岡 聡; 渡邊 誠*

Materials Research Letters (Internet), 11(9), p.742 - 748, 2023/09

Cold spray (CS) has emerged as a representative of solid-state additive manufacturing (AM) via supersonic impact. It enables a high deposition rate of solid-state microparticles. Delamination, however, tends to occur when depositing too thick; this remains to be conquered. Here, a CS-like process, warm spray (WS), was presented. Interestingly, it was found that the appropriate increase in particle temperature can effectively reduce the residual stress amplitude, relieving the concentrated tensile stress and safeguarding the additively manufactured components from interfacial delamination even when depositing too thick. The key role of temperature on delamination was identified in solid-state AM via supersonic impact.

論文

First observation of $$^{28}$$O

近藤 洋介*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; 馬場 秀忠*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.

Nature, 620(7976), p.965 - 970, 2023/08

 被引用回数:5 パーセンタイル:92.64(Multidisciplinary Sciences)

非常に中性子が過剰な原子核$$^{28}$$Oは、陽子、中性子ともに魔法数であることから古くからその性質に興味が持たれていたが、酸素の最後の束縛核$$^{24}$$Oよりも中性子が4個も多いため、これまで観測されてこなかった。この論文では、理化学研究所RIBFにて$$^{29}$$Fからの1陽子ノックアウト反応によって$$^{28}$$Oを生成し、そこから放出される中性子を測定することによって初めてその観測に成功した。核構造の観点からは、$$^{28}$$Oでは二重閉殻が保たれているか興味が持たれていたが、実験で得られた分光学的因子が殻模型計算で予言されて程度の大きいことから、閉殻構造をもたない可能性が高いことがわかった。

論文

Intruder configurations in $$^{29}$$Ne at the transition into the island of inversion; Detailed structure study of $$^{28}$$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

 被引用回数:2 パーセンタイル:68.16(Astronomy & Astrophysics)

$$^{29}$$Neからの1中性子除去反応を用いて、$$^{28}$$Neの詳細な$$gamma$$線分光を行った。平行運動量分布の解析に基づき、$$^{28}$$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。

論文

Extreme phonon anharmonicity underpins superionic diffusion and ultralow thermal conductivity in argyrodite Ag$$_{8}$$SnSe$$_{6}$$

Ren, Q.*; Gupta, M. K.*; Jin, M.*; Ding, J.*; Wu, J.*; Chen, Z.*; Lin, S.*; Fabelo, O.*; Rodriguez-Velamazan, J. A.*; 古府 麻衣子; et al.

Nature Materials, 22, p.999 - 1006, 2023/05

 被引用回数:21 パーセンタイル:99.22(Chemistry, Physical)

Ultralow thermal conductivity and fast ionic diffusion endow superionic materials with excellent performance both as thermoelectric converters and as solid-state electrolytes. Yet the correlation and interdependence between these two features remain unclear owing to a limited understanding of their complex atomic dynamics. Here we investigate ionic diffusion and lattice dynamics in argyrodite Ag$$_{8}$$SnSe$$_{6}$$ using synchrotron X-ray and neutron scattering techniques along with machine-learned molecular dynamics. We identify a critical interplay of the vibrational dynamics of mobile Ag and a host framework that controls the overdamping of low-energy Ag-dominated phonons into a quasi-elastic response, enabling superionicity. Concomitantly, the persistence of long-wavelength transverse acoustic phonons across the superionic transition challenges a proposed 'liquid-like thermal conduction' picture. Rather, a striking thermal broadening of low-energy phonons, starting even below 50 K, reveals extreme phonon anharmonicity and weak bonding as underlying features of the potential energy surface responsible for the ultralow thermal conductivity ($$<$$ 0.5 Wm$$^{-1}$$K$$^{-1}$$) and fast diffusion. Our results provide fundamental insights into the complex atomic dynamics in superionic materials for energy conversion and storage.

論文

Hybridized propagation of spin waves and surface acoustic waves in a multiferroic-ferromagnetic heterostructure

Chen, J.*; 山本 慧; Zhang, J.*; Ma, J.*; Wang, H.*; Sun, Y.*; Chen, M.*; Ma, J.*; Liu, S.*; Gao, P.*; et al.

Physical Review Applied (Internet), 19(2), p.024046_1 - 024046_9, 2023/02

 被引用回数:4 パーセンタイル:90.23(Physics, Applied)

Coherent coupling in magnon based hybrid system has many potential applications in quantum information processing. Magnons can propagate in magnetically ordered materials without any motion of electrons, offering a unique method to build low-power-consumption devices and information channels free of heat dissipation. In this article, we demonstrate the coherent propagation of hybridized modes between spin waves and Love surface acoustic waves in a multiferroic BiFeO$$_{3}$$ and ferromagnetic La$$_{0.67}$$Sr$$_{0.33}$$MnO$$_{3}$$ based heterostructure. The magneto-elastic coupling enables a giant enhancement of strength of the hybridized mode by a factor of 26 compared to that of the pure spin waves. A short wavelength down to 250 nm is demonstrated for the hybridized mode, which is desirable for nanoscale acousto-magnonic applications. Our combined experimental and theoretical analyses represent an important step towards the coherent control in hybrid magnonics, which may inspire the study of magnon-phonon hybrid systems for coherent information processing and manipulation.

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

 被引用回数:17 パーセンタイル:93.62(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

Micro- to nano-scale areal heterogeneity in pore structure and mineral compositions of a sub-decimeter-sized Eagle Ford Shale

Wang, Q.*; Hu, Q.*; Zhao, C.*; Yang, X.*; Zhang, T.*; Ilavsky, J.*; Kuzmenko, I.*; Ma, B.*; 舘 幸男

International Journal of Coal Geology, 261, p.104093_1 - 104093_15, 2022/09

 被引用回数:5 パーセンタイル:69.58(Energy & Fuels)

To understanding the spatial heterogeneity of mineral and pore structure variations in fine-grained shale, microscale X-ray fluorescence (micro-XRF) mapping, (ultra-) small-angle X-ray scattering [(U)SAXS] and wide-angle X-ray scattering were applied for two samples from a piece of Eagle Ford Shale in South Texas. Thin section petrography and field emission-scanning electron microscopy, X-ray diffraction (XRD), total organic carbon, and pyrolysis were also utilized to investigate the potential spatial heterogeneity of pore types, mineral and organic matter compositions for both samples. Overall, the siliceous-carbonate mineral contents in these carbonate-rich Eagle Ford Shale vary between laminations at mm scales. By analyzing six selected sub-samples on each of two samples with X-ray scattering and XRD techniques, nm-sized pores are mainly interparticle ones in the higher calcite regions, where the porosity is also relatively lower, while the lower calcite regions consist of both interparticle and intraparticle pore types with higher porosity. Finally, the micro-XRF and (U)SAXS are combined to generate porosity distribution maps to provide more insights about its heterogeneity related to the laminations and fractures at our observational scales.

論文

Fine structure in the $$alpha$$ decay of the 8$$^{+}$$ isomer in $$^{216,218}$$U

Zhang, M. M.*; Tian, Y. L.*; Wang, Y. S.*; Zhang, Z. Y.*; Gan, Z. G.*; Yang, H. B.*; Huang, M. H.*; Ma, L.*; Yang, C. L.*; Wang, J. G.*; et al.

Physical Review C, 106(2), p.024305_1 - 024305_6, 2022/08

 被引用回数:2 パーセンタイル:52.69(Physics, Nuclear)

The extremely neutron-deficient even-even uranium isotopes $$^{216,218}$$U were produced in the complete-fusion reactions induced by impinging $$^{40}$$Ar and $$^{40}$$Ca ions on $$^{180,182,184}$$W targets. Fusion evaporation residues were separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and subsequently identified using the recoil-$$alpha$$-correlation method. In this paper, we report on new $$alpha$$-decay activities with $$E_{alpha} = 10163(27)$$ keV for $$^{216}$$U and $$E_{alpha} = 10073(16)$$ keV for $$^{218}$$U, which decay from the 8$$^{+}$$ isomeric states of $$^{216,218}$$U into the 2$$^{+}$$ states of their daughter nuclei $$^{212,214}$$Th, respectively. The new results extend the systematics of the $$alpha$$-decay fine structure for the $$N$$ = 124 and 126 even-even isotones.

論文

Transport model comparison studies of intermediate-energy heavy-ion collisions

Walter, H.*; Colonna, M.*; Cozma, D.*; Danielewicz, P.*; Ko, C. M.*; Kumar, R.*; 小野 章*; Tsang, M. Y. B*; Xu, J.*; Zhang, Y.-X.*; et al.

Progress in Particle and Nuclear Physics, 125, p.103962_1 - 103962_90, 2022/07

 被引用回数:48 パーセンタイル:96.94(Physics, Nuclear)

原子核-原子核衝突や原子核の状態方程式の研究において、反応計算モデルは重要なツールとなり、世界中で開発が進んでいる。本論文は、原子力機構のJQMD-2.0を含め、現在開発中の複数のコード開発者の協力により、これらコードを同じ条件で比較することで共通点や差異を明らかにしたプロジェクトTransport Model Evaluation Project (TMEP)を総括したものである。参加したコードはBoltzmann-Uehling-Uhlenbeck(BUU)法に基づく13のコードと、Quantum Molecular Dynamics (QMD)法に基づく12のコードであった。プロジェクトでは、Au原子核同士を衝突させてその終状態を観測する現実的な計算や、一辺が640nmの箱に核子を詰めて時間発展させる仮想的な計算を行った。その結果、BUU法コードとQMD法コードは計算原理が異なるため、計算の設定に関係なく系統的な差異が生じることが明らかになった。その一方で、同じ方法を採用するコード間の比較では、時間発展を細かく計算することでコード間の差は埋まっていき、一定の収束値を持つことが示された。この結果は今後開発される同分野のコードのベンチマークデータとして有用なものであるだけでなく、原子核基礎物理学の実験や理論研究の標準的な指針としても役に立つことが期待される。

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

 被引用回数:45 パーセンタイル:99.49(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

Metalloid substitution elevates simultaneously the strength and ductility of face-centered-cubic high-entropy alloys

Wei, D.*; Wang, L.*; Zhang, Y.*; Gong, W.; 都留 智仁; Lobzenko, I.; Jiang, J.*; Harjo, S.; 川崎 卓郎; Bae, J. W.*; et al.

Acta Materialia, 225, p.117571_1 - 117571_16, 2022/02

 被引用回数:59 パーセンタイル:99.75(Materials Science, Multidisciplinary)

Recently-developed high-entropy alloys (HEAs) containing multiple principal metallic elements have ex-tended the compositional space of solid solutions and the range of their mechanical properties. Here we show that the realm of possibilities can be further expanded through substituting the constituent metals with metalloids, which are desirable for tailoring strength/ductility because they have chemical interactions and atomic sizes distinctly different from the host metallic elements. Specifically, the metalloid substitution increases local lattice distortion and short-range chemical inhomogeneities to elevate strength, and in the meantime reduces the stacking fault energy to discourage dynamic recovery and encourage defect accumulation via partial-dislocation-mediated activities. These impart potent dislocation storage to improve the strain hardening capability, which is essential for sustaining large tensile elongation. As such, metalloid substitution into HEAs evades the normally expected strength-ductility trade-off, enabling an unusual synergy of high tensile strength and extraordinary ductility for these single-phase solid solutions.

論文

Neutron spectroscopy evidence on the dual nature of magnetic excitations in a van der Waals metallic ferromagnet Fe$$_{2.75}$$GeTe$$_{2}$$

Bao, S.*; Wang, W.*; Shangguan, Y.*; Cai, Z.*; Dong, Z.-Y.*; Huang, Z.*; Si, W.*; Ma, Z.*; 梶本 亮一; 池内 和彦*; et al.

Physical Review X, 12(1), p.011022_1 - 011022_15, 2022/02

 被引用回数:11 パーセンタイル:78.27(Physics, Multidisciplinary)

In the local or itinerant extreme, magnetic excitations can be described by the Heisenberg model which treats electron spins as localized moments, or by the itinerant-electron model where the exchange interaction between electrons leads to unequal numbers of electrons with up and down spins. However, the nature of the magnetic excitations has been elusive when both local moments and itinerant electrons are present in the intermediate range. Using inelastic neutron scattering, we provide direct spectroscopic evidence on the coexistence of and interplay between local moments and itinerant electrons in a van der Waals metallic ferromagnet Fe$$_{2.72}$$GeTe$$_{2}$$, which can sustain tunable room-temperature ferromagnetism down to the monolayer limit. We find that there exist ferromagnetic spin-wave excitations dispersing from the zone center at low energies resulting from local moments and a columnlike broad continuum at the zone boundary at high energies up to over 100 meV resulting from itinerant electrons. Unlike the two-dimensional crystal structure, the low-energy mode exhibits a three-dimensional nature, and the high-energy mode also has an out-of-plane dependence. Both modes persist well above the Curie temperature of 160 K. Our neutron spectroscopic data reveal that the low-energy spin waves at 100 K are more coherent than those at 4 K, which is evidence of the weakening of the Kondo screening at high temperatures. These results unambiguously demonstrate the coexistence of local moments and itinerant electrons and the Kondo effect between these two components in Fe$$_{2.72}$$GeTe$$_{2}$$. Such behaviors are generally expected in heavy-fermion systems with heavy $$f$$ electrons but are rarely clearly observed in materials with light $$d$$ electrons. These findings shed light on the understanding of magnetism in transition-metal compounds.

論文

Long decay length of magnon-polarons in BiFeO$$_{3}$$/La$$_{0.67}$$Sr$$_{0.33}$$MnO$$_{3}$$ heterostructures

Zhang, J.*; Chen, M.*; Chen, J.*; 山本 慧; Wang, H.*; Hamdi, M.*; Sun, Y.*; Wagner, K.*; He, W.*; Zhang, Y.*; et al.

Nature Communications (Internet), 12, p.7258_1 - 7258_8, 2021/12

 被引用回数:14 パーセンタイル:77.64(Multidisciplinary Sciences)

Magnons can transfer information in metals and insulators without Joule heating, and therefore are promising for low-power computation. The on-chip magnonics however suffers from high losses due to limited magnon decay length. In metallic thin films, it is typically on the tens of micrometre length scale. Here, we demonstrate an ultra-long magnon decay length of up to one millimetre in multiferroic/ferromagnetic BiFeO$$_{3}$$(BFO)/La$$_{0.67}$$Sr$$_{0.33}$$MnO$$_{3}$$ (LSMO) heterostructures at room temperature. This decay length is attributed to a magnon-phonon hybridization and is more than two orders of magnitude longer than that of bare metallic LSMO. The long-distance modes have high group velocities of 2.5 km$$^{-1}$$ as detected by time-resolved Brillouin light scattering. Numerical simulations suggest that magnetoelastic coupling via the BFO/LSMO interface hybridizes phonons in BFO with magnons in LSMO. Our results provide a solution to the long-standing issue on magnon decay lengths in metallic magnets and advance the bourgeoning field of hybrid magnonics.

論文

Evidence for strong correlations at finite temperatures in the dimerized magnet Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$

Shangguan, Y.*; Bao, S.*; Dong, Z.-Y.*; Cai, Z.*; Wang, W.*; Huang, Z.*; Ma, Z.*; Liao, J.*; Zhao, X.*; 梶本 亮一; et al.

Physical Review B, 104(22), p.224430_1 - 224430_8, 2021/12

 被引用回数:1 パーセンタイル:7.92(Materials Science, Multidisciplinary)

Dimerized magnets forming alternating Heisenberg chains exhibit quantum coherence and entanglement and thus can find potential applications in quantum information and computation. However, magnetic systems typically undergo thermal decoherence at finite temperatures. Here, we show inelastic neutron scattering results on an alternating antiferromagnetic-ferromagnetic chain compound Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$ that the excited quasiparticles can counter thermal decoherence and maintain strong correlations at elevated temperatures. At low temperatures, we observe clear dispersive singlet-triplet excitations arising from the dimers formed along the crystalline $$b$$-axis. The excitation gap is of $$sim$$18 meV and the bandwidth is about half of the gap. The band top energy has a weak modulation along the [100] direction, indicative of a small interchain coupling. The gap increases while the bandwidth decreases with increasing temperature, leading to a strong reduction in the available phase space for the triplons. As a result, the Lorentzian-type energy broadening becomes highly asymmetric as the temperature is raised. These results are associated with a strongly correlated state resulting from hard-core constraint and quasiparticle interactions. We consider these results to be not only evidence for strong correlations at finite temperatures in Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$, but also for the universality of the strongly correlated state in a broad range of quantum magnetic systems.

論文

The $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross section from the surrogate ratio method and its effect on the $$^{60}$$Fe nucleosynthesis

Yan, S. Q.*; Li, X. Y.*; 西尾 勝久; Lugaro, M.*; Li, Z. H.*; 牧井 宏之; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; 廣瀬 健太郎; et al.

Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10

 被引用回数:1 パーセンタイル:8.87(Astronomy & Astrophysics)

The long-lived $$^{60}$$Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe on $$^{59}$$Fe (half-life=44.5 days) is the key reaction for the production of $$^{60}$$Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 $$gamma$$-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5$$pm$$3.5 mb at $$kT$$ = 30 keV and 13.4$$pm$$1.7 mb at $$kT$$ = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of $$^{60}$$Fe from the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe rate are at most 25$$%$$. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of $$^{60}$$Fe.

論文

Dynamical response of transition-edge sensor microcalorimeters to a pulsed charged-particle beam

奥村 拓馬*; 東 俊行*; Bennet, D. A.*; Caradonna, P.*; Chiu, I.-H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; 橋本 直; et al.

IEEE Transactions on Applied Superconductivity, 31(5), p.2101704_1 - 2101704_4, 2021/08

 被引用回数:1 パーセンタイル:11.15(Engineering, Electrical & Electronic)

超伝導転移端センサー(TES)マイクロ熱量計は、優れたエネルギー分解能と高い効率を持った、加速器施設での実験に理想的なX線検出器である。高強度パルス荷電粒子ビームを用いたTES検出器の性能を研究するために、日本の陽子加速器研究施設(J-PARC)でパルスミュオンビームを用いてX線スペクトルを測定した。X線エネルギーの実質的な時間的シフトがパルスミュオンビームの到着時間と相関していることを発見した。これは、最初のパルスビームからのエネルギー粒子の入射によるパルスパイルアップによって合理的に説明された。

論文

Deexcitation dynamics of muonic atoms revealed by high-precision spectroscopy of electronic $$K$$ X rays

奥村 拓馬*; 東 俊行*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; 橋本 直; et al.

Physical Review Letters, 127(5), p.053001_1 - 053001_7, 2021/07

 被引用回数:13 パーセンタイル:79.44(Physics, Multidisciplinary)

超伝導遷移エッジ型センサーマイクロカロリメーターを用いて、鉄のミュー原子から放出される電子$$K$$X線を観測した。FWHMでの5.2eVのエネルギー分解能により、電子特性$$K$$$$alpha$$および$$K$$$$beta$$X線の非対称の広いプロファイルを約6keVの超衛星線$$K$$$$alpha$$線とともに観察することができた。このスペクトルは、電子のサイドフィードを伴う、負ミュオンと$$L$$殻電子による核電荷の時間依存スクリーニングを反映している。シミュレーションによると、このデータは電子$$K$$殻および$$L$$殻の正孔生成と、ミュオンカスケードプロセス中のそれらの時間発展を明確に示している。

論文

Mesoporous alumina-titania composites with enhanced molybdenum adsorption towards medical radioisotope production

Benu, D. P.*; Earnshaw, J.*; Ashok, A.*; 土谷 邦彦; Saptiama, I.*; Yuliarto, B.*; Suendo, V.*; Mukti, R. R.*; 福光 延吉*; 有賀 克彦*; et al.

Bulletin of the Chemical Society of Japan, 94(2), p.502 - 507, 2021/02

 被引用回数:11 パーセンタイル:66.97(Chemistry, Multidisciplinary)

本研究は、TiO$$_{2}$$含有量を変化させたメソポーラスAl$$_{2}$$O$$_{3}$$-TiO$$_{2}$$複合材料の製造開発及び医療用放射性同位元素の製造のためのMo吸着剤の性能向上のために行った。TiO$$_{2}$$の含有量の増加は、元の形態を変えることなく、Al$$_{2}$$O$$_{3}$$表面へのより多くのTiO$$_{2}$$ナノ粒子の形成を促進する。開発したAl$$_{2}$$O$$_{3}$$-2.5%Ti及びAl$$_{2}$$O$$_{3}$$-5%Tiのアルミナ試料はアモルファスであったが、Al$$_{2}$$O$$_{3}$$-10%Tiでは、TiO$$_{2}$$がAl$$_{2}$$O$$_{3}$$表面に被覆されていた。一方、TiO$$_{2}$$の添加により、比表面積はAl$$_{2}$$O$$_{3}$$の177m$$^{2}$$/gからAl$$_{2}$$O$$_{3}$$-5%Ti試料では982m$$^{2}$$/gまで大幅に増加した。これにより、Mo吸着量は、Al$$_{2}$$O$$_{3}$$で37.1mg/g、Al$$_{2}$$O$$_{3}$$-2.5%Tiで39.0mg/g、Al$$_{2}$$O$$_{3}$$-10%Tiで40.5mg/gであったが、Al$$_{2}$$O$$_{3}$$-5%Tiはよりも高い44.5mg/gを示した。これにより、従来のAl$$_{2}$$O$$_{3}$$の吸着能力と比較して、Al$$_{2}$$O$$_{3}$$-TiO$$_{2}$$複合材料の吸着能力の向上に見通しを得た。

論文

Evidence for magnon-phonon coupling in the topological magnet Cu$$_{3}$$TeO$$_{6}$$

Bao, S.*; Cai, Z.*; Si, W.*; Wang, W.*; Wang, X.*; Shangguan, Y.*; Ma, Z.*; Dong, Z.-Y.*; 梶本 亮一; 池内 和彦*; et al.

Physical Review B, 101(21), p.214419_1 - 214419_8, 2020/06

 被引用回数:17 パーセンタイル:74.78(Materials Science, Multidisciplinary)

We perform thermodynamic and inelastic neutron scattering (INS) measurements to study the lattice dynamics (phonons) of a cubic collinear antiferromagnet Cu$$_{3}$$TeO$$_{6}$$ which hosts topological spin excitations (magnons). While the specific heat and thermal conductivity results show that the thermal transport is dominated by phonons, the deviation of the thermal conductivity from a pure phononic model indicates that there is a strong coupling between magnons and phonons. In the INS measurements, we find a mode in the excitation spectra at 4.5 K, which exhibits a slight downward dispersion around the Brillouin zone center. This mode disappears above the N$'{e}$el temperature and thus cannot be a phonon. Furthermore, the dispersion is distinct from that of a magnon. Instead, it can be explained by the magnon-polaron mode, collective excitations resulting from the hybridization between magnons and phonons. We consider the suppression of the thermal conductivity and emergence of the magnon-polaron mode to be evidence for magnon-phonon coupling in Cu$$_{3}$$TeO$$_{6}$$.

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