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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

https://doi.org/10.1038/s41586-023-06352-6
 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

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

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

https://doi.org/10.1103/PhysRevApplied.19.024046
 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

https://doi.org/10.1016/j.actamat.2022.118243
 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

https://doi.org/10.1016/j.coal.2022.104093
 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

Quantum critical spin-liquid-like behavior in the $$S$$ = $$frac{1}{2}$$ quasikagome-lattice compound CeRh$$_{1-x}$$Pd$$_x$$Sn investigated using muon spin relaxation and neutron scattering

Tripathi, R.*; Adroja, D. T.*; Ritter, C.*; Sharma, S.*; Yang, C.*; Hillier, A. D.*; Koza, M. M.*; Demmel, F.*; Sundaresan, A.*; Langridge, S.*; et al.

Physical Review B, 106(6), p.064436_1 - 064436_17, 2022/08

https://doi.org/10.1103/PhysRevB.106.064436
 被引用回数：2 パーセンタイル：34.67(Materials Science, Multidisciplinary)

We present the results of muon spin relaxation ($$mu$$SR) and neutron scattering measurements on the Ce-based quasikagome lattice CeRh$$_{1-x}$$Pd$$_x$$Sn ($$x$$ = 0.1 to 0.75). Our $$mu$$SR results reveal the absence of both static long-range magnetic order and spin freezing down to 0.05 K in the $$x$$ = 0.1 sample, which is consistent with neutron scattering results. The weak temperature-dependent plateaus of the dynamic spin fluctuations below 0.2 K in zero field together with its longitudinal-field (LF) dependence indicate the presence of dynamic spin fluctuations persisting even at 0.05 K without static magnetic order. We argue that such a behavior for $$x$$ = 0.1 can be attributed to a metallic spin-liquid-like ground state near the quantum critical point in the frustrated Kondo lattice. The LF-$$mu$$SR study suggests that the out of kagome plane spin fluctuations are responsible for the spin-liquid behavior.

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

https://doi.org/10.1103/PhysRevC.106.024305
 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

https://doi.org/10.1016/j.ppnp.2022.103962
 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

https://doi.org/10.1016/j.actamat.2022.117629
 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

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

https://doi.org/10.1038/s41467-021-27405-2
 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

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

https://doi.org/10.3847/1538-4357/ac12ce
 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

Half-integer Shapiro steps in strong ferromagnetic Josephson junctions

Yao, Y.*; Cai, R.*; Yang, S.-H.*; Xing, W.*; Ma, Y.*; 森 道康; Ji, Y.*; 前川 禎通; Xie, X.-C.*; Han, W.*

Physical Review B, 104(10), p.104414_1 - 104414_6, 2021/09

https://doi.org/10.1103/PhysRevB.104.104414
 被引用回数：2 パーセンタイル：7.92(Materials Science, Multidisciplinary)

We report the experimental observation of half-integer Shapiro steps in the strong ferromagnetic Josephson junction (Nb-NiFe-Nb) by investigating the current-phase relation under radio-frequency microwave excitation. The half-integer Shapiro steps are robust in a wide temperature range from T = 4 to 7 K. The half-integer Shapiro steps could be attributed to co-existence of 0- and $$pi$$-states in the strong ferromagnetic NiFe Josephson junctions with the spatial variation of the NiFe thickness. This scenario is also supported by the high-resolution transmission electron microscopy characterization of the Nb/NiFe/Nb junction.

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

https://doi.org/10.1109/TASC.2021.3067793
 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

https://doi.org/10.1103/PhysRevLett.127.053001
 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

Non-destructive analysis of samples with a complex geometry by NRTA

Ma, F.; Kopecky, S.*; Alaerts, G.*; 原田 秀郎; Heyse, J.*; 北谷 文人; Noguere, G.*; Paradela, C.*; $v{S}$alamon, L.*; Schillebeeckx, P.*; et al.

Journal of Analytical Atomic Spectrometry, 35(3), p.478 - 488, 2020/03

AA2019-0356.pdf:2.54MB

https://doi.org/10.1039/C9JA00342H
 被引用回数：3 パーセンタイル：22.14(Chemistry, Analytical)

The use of Neutron Resonance Transmission Analysis to characterize homogeneous samples not fulfilling good transmission geometry conditions is discussed. Analytical expressions for such samples have been derived and implemented in the resonance shape analysis code REFIT. They were validated by experiments at the time-of-flight facility GELINA using a set of metallic natural copper samples. The expressions were used to derive sample characteristics by a least squares adjustment to experimental transmission data. In addition, the resonance parameters of Cu for energies below 6 keV, which are reported in the literature and recommended in evaluated data libraries, were verified. This research was implemented under the subsidiary for nuclear security promotion of MEXT.

論文

Shell structure of the neutron-rich isotopes $$^{69,71,73}$$Co

Lokotko, T.*; Leblond, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Poves, A.*; Nowacki, F.*; 緒方 一介*; 吉田 数貴; Authelet, G.*; et al.

Physical Review C, 101(3), p.034314_1 - 034314_7, 2020/03

https://doi.org/10.1103/PhysRevC.101.034314
 被引用回数：10 パーセンタイル：69.78(Physics, Nuclear)

中性子過剰核である$$^{69,71,73}$$Coに対する($$p,2p$$)ノックアウト反応が理化学研究所RIBFで測定された。$$gamma-gamma$$ coincidenceの方法で準位構造が決定され、測定された包括的断面積および排他的断面積から暫定的ではあるがスピン・パリティが決定された。殻模型計算との比較により、$$^{69,71,73}$$Coの低励起状態には球形核と変形核が共存することが示唆された。

論文

IRDFF-II; A New neutron metrology library

Trkov, A.*; Griffin, P. J.*; Simakov, S. P.*; Greenwood, L. R.*; Zolotarev, K. I.*; Capote, R.*; Aldama, D. L.*; Chechev, V.*; Destouches, C.*; Kahler, A. C.*; et al.

Nuclear Data Sheets, 163, p.1 - 108, 2020/01

https://doi.org/10.1016/j.nds.2019.12.001
 被引用回数：91 パーセンタイル：99.77(Physics, Nuclear)

60MeVまでの核分裂炉、核融合炉の中性子計測のための核データであるIRDFF-IIが公開された。このライブラリは、(a)研究炉応用、(b)商業炉の安全性応用、(c)核融合材料開発のための損傷研究、をサポートしている。本論文は、ライブラリの内容、検証プロセスについて述べ、幅広い中性子場でのベンチマークデータを提供している。このライブラリは様々な応用のための中性子計測における国際的な基準データとなることが期待される。

論文

Fine structure in the $$alpha$$ decay of $$^{223}$$U

Sun, M. D.*; Liu, Z.*; Huang, T. H.*; Zhang, W. Q.*; Andreyev, A. N.; Ding, B.*; Wang, J. G.*; Liu, X. Y.*; Lu, H. Y.*; Hou, D. S.*; et al.

Physics Letters B, 800, p.135096_1 - 135096_5, 2020/01

https://doi.org/10.1016/j.physletb.2019.135096
 被引用回数：11 パーセンタイル：79.42(Astronomy & Astrophysics)

Fine structure in the $$alpha$$ decay of $$^{223}$$U was observed in the fusion-evaporation reaction $$^{187}$$Re($$^{40}$$Ar,p3n) by using fast digital pulse processing technique. Two $$alpha$$-decay branches of $$^{223}$$U feeding the ground state and 244 keV excited state of $$^{219}$$Th were identified by establishing the decay chain $$^{223}$$U$$rightarrow$$$$^{219}$$Th$$rightarrow$$$$^{215}$$Ra$$rightarrow$$$$^{211}$$Rn. The $$alpha$$-particle energy for the ground-state to ground-state transition of $$^{223}$$U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62$$^{+14}_{-10} mu$$s. Evolution of nuclear structure for $$N$$=131 even-$$Z$$ isotones from Po to U was discussed in the frameworks of nuclear mass and reduced $$alpha$$-decay width, a weakening octupole deformation in the ground state of $$^{223}$$U relative to its lighter isotones $$^{219}$$Ra and $$^{211}$$Th was suggested.

論文

Comparison of heavy-ion transport simulations; Collision integral with pions and $$Delta$$ resonances in a box

小野 章*; Xu, J.*; Colonna, M.*; Danielewicz, P.*; Ko, C. M.*; Tsang, M. B.*; Wang, Y,-J.*; Wolter, H.*; Zhang, Y.-X.*; Chen, L.-W.*; et al.

Physical Review C, 100(4), p.044617_1 - 044617_35, 2019/10

AA2019-0025.pdf:2.76MB

https://doi.org/10.1103/PhysRevC.100.044617
 被引用回数：58 パーセンタイル：98.56(Physics, Nuclear)

2017年4月に開催された国際会議Transport2017において、重イオン核反応モデルの国際的な比較が議論された。重イオン加速器の安全評価や宇宙飛行士の被ばく評価等で重要な役割を果たすため、世界中で重イオン核反応の様々な理論モデルが開発されている。本研究では、辺の長さが20fmの直方体に320個の中性子と陽子をランダム配置し、それらが70fm/cの間に起こす散乱の回数やエネルギーを計算した。ここでは、特にパイオンやその前駆体であるデルタ共鳴の生成に注目して比較を行った。参加コードは、個々の粒子の時間発展を追うQMD型コードと、粒子の位置や運動量の確率分布を決めておき、散乱や崩壊が発生したときそれらを乱数サンプリングするBUU型コードがあり、発表者が用いたJQMDは前者に属する。本研究により、計算における時間刻みが各コードによる結果の差の主な原因であることが分かった。さらに、今後のJQMDの改良方針の策定に有益な知見を得ることができた。

論文

Sample shape effect on nuclear material quantification with neutron resonance transmission analysis

土屋 晴文; Ma, F.; 北谷 文人; Paradella, C.*; Heyse, J.*; Kopecky, S.*; Schillebeeckx, P.*

Proceedings of 41st ESARDA Annual Meeting (Internet), p.374 - 377, 2019/05

From a viewpoint of nuclear safeguards and nuclear security, non-destructive assay (NDA) techniques are needed to quantify special nuclear materials (SNMs) in nuclear fuels such as spent fuels and fuel debris. Neutron Resonance Transmission Analysis (NRTA) is an NDA technique and it measures the amount of U isotopes in a U$$_{3}$$O$$_{8}$$ sample within 1% accuracy and Pu isotopes in a PuO$$_{2}$$ sample within 5% accuracy. However, NRTA measurements done so far were mainly applied to homogeneous samples with a constant thickness. Spent fuel and especially debris have irregular shapes that affect the NRTA measurements. In order to investigate the influence of irregular-shaped samples, NRTA experiments were done with a copper bar sample with different rotation angles with respect to neutron beams, at a neutron Time-Of-Flight (TOF) facility GELINA (Belgium). Analytical models for irregular shaped samples proposed by Harada et al. (JNST, 2015) were applied to the experimental data. It has been found that the experimental data can be well reproduced by the proposed models. In this presentation, we report how analytical models are applied to a real NRTA experiment with a Cu bar sample and discuss a future prospect of a compact NRTA system for SNM quantification. This research was implemented under the subsidiary for nuclear security promotion of MEXT.

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