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論文

Partial photoneutron cross sections for $$^{207,208}$$Pb

近藤 壮雄*; 宇都宮 弘章*; Goriely, S.*; 岩本 ちひろ*; 秋宗 秀俊*; 山形 民穂*; 豊川 弘之*; 原田 秀郎; 北谷 文人; Lui, Y.-W.*; et al.

Nuclear Data Sheets, 119, p.310 - 313, 2014/05

https://doi.org/10.1016/j.nds.2014.08.085
 被引用回数：1 パーセンタイル：87.37(Physics, Nuclear)

Using linearly-polarized laser-Compton scattering $$gamma$$-rays, partial E1 and M1 photoneutron cross sections along with total cross sections were determined for $$^{207,208}$$Pb at four energies near threshold by measuring anisotropies in photoneutron emission. Separately, total photoneutron cross sections were measured for $$^{207,208}$$Pb with a high-efficiency 4$$pi$$ neutron detector. The partial cross section measurement provides direct evidence for the presence of pygmy dipole resonance (PDR) in $$^{207,208}$$Pb near the neutron threshold. The strength of PDR amounts to 0.32% - 0.42% of the Thomas-Reiche-Kuhn sum rule. Several $$mu$$$$^{2}$$$$_{N}$$ units of B(M1)$$uparrow$$ strength were observed in $$^{207,208}$$Pb just above neutron threshold, which correspond to M1 cross sections less than 10% of the total photoneutron cross sections.

論文

Photoneutron cross sections for Mo isotopes; A Step toward a unified understanding of($$gamma$$,n) and (n,$$gamma$$)reactions

宇都宮 弘章*; Goriely, S.*; 近藤 壮雄*; 岩本 ちひろ*; 秋宗 秀俊*; 山県 民穂*; 豊川 弘之*; 原田 秀郎; 北谷 文人; Lui, Y.-W.*; et al.

Physical Review C, 88(1), p.015805_1 - 015805_6, 2013/07

https://doi.org/10.1103/PhysRevC.88.015805
 被引用回数：58 パーセンタイル：3.56(Physics, Nuclear)

Photoneutron cross sections were measured for $$^{94}$$Mo,$$^{95}$$Mo,$$^{96}$$Mo, $$^{97}$$Mo,$$^{98}$$Mo, and $$^{100}$$Mo near the neutron threshold with quasi-monochromatic laser-Compton scattering $$gamma$$-rays. The photoneutron data were analyzed with the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially-symmetric-deformed Gogny HFB plus QRPA model of E1 $$gamma$$-ray strength. Combining the $$gamma$$-ray strength function constrained by the present photoneutron data with either the nuclear resonance fluorescence data or the updated Oslo data to supplement the data below the neutron threshold, a thorough analysis of the reverse (n,$$gamma$$) cross sections is made whenever measurements are available. The Oslo data and the corresponding uncertainties are updated based on the latest results of the s-wave neutron spacing and the average radiative width determined in particular for $$^{96}$$Mo.

論文

$$gamma$$-ray strength function method; A Way from photoneutron emission to radiative neutron capture

宇都宮 弘章*; 秋宗 秀俊*; 山県 民穂*; 岩本 ちひろ*; Goriely, S.*; Daoutidis, I.*; 豊川 弘之*; 原田 秀郎; 北谷 文人; 岩本 信之; et al.

Proceedings of 14th International Symposium on Capture $$gamma$$-Ray Spectroscopy and Related Topics, p.505 - 514, 2013/05

Radiative neutron capture cross section are of direct relevance for the synthesis of heavy elements referred to as the s-process and the r-process in nuclear astrophysics and constitute basic data in the field of nuclear engineering. The surrogate reaction technique is in active use to indirectly determine radiative neutron capture cross sections for unstable nuclei. We have devised an indirect method alternative to the surrogate reaction technique on the basis of the $$gamma$$-ray strength function ($$gamma$$-SF), a nuclear statistical quantity that interconnects photoneutron emission and radiative neutron capture in Hauser-Feshbach model calculation. The primary strength of the $$gamma$$-SF is low-energy E1 strength in the tail of GDR. We outline the $$gamma$$-SF method and show application of the method to Zr, Pd and Sn isotopes. In the application of the $$gamma$$-SF method, it is important to use $$gamma$$-SF, which incorporates extra strengths of PDR and/or M1 resonance emerging around neutron threshold.

論文

Total and partial photoneutron cross sections for Pb isotopes

近藤 壮雄*; 宇都宮 弘章*; Goriely, S.*; Daoutidis, I.*; 岩本 ちひろ*; 秋宗 秀俊*; 岡本 明之*; 山県 民穂*; 鎌田 正輝*; 伊藤 修*; et al.

Physical Review C, 86(1), p.014316_1 - 014316_7, 2012/07

https://doi.org/10.1103/PhysRevC.86.014316
 被引用回数：32 パーセンタイル：12.78(Physics, Nuclear)

レーザ逆コンプトン$$gamma$$線と高検出効率4$$pi$$型中性子検出器を用いて、$$^{206,207,208}$$Pbの中性子閾値近傍における全光核反応断面積を測定した。また、直線偏光させた$$gamma$$線と中性子放出角の非等方性を測定することにより、$$^{207,208}$$Pbに対する$$E$$1及び$$M$$1励起による部分光核反応断面積を導出した。この結果、中性子閾値近傍においては$$E$$1励起が支配的であることなど$$gamma$$線強度関数に関する実験的知見を得た。

論文

Photoneutron cross sections for $$^{118-124}$$Sn and the $$gamma$$-ray strength function method

宇都宮 弘章*; Goriely, S.*; 鎌田 正輝*; 秋宗 秀俊*; 近藤 壮雄*; 伊藤 修*; 岩本 ちひろ*; 山県 民穂*; 豊川 弘之*; Lui, Y.-W.*; et al.

Physical Review C, 84(5), p.055805_1 - 055805_6, 2011/11

https://doi.org/10.1103/PhysRevC.84.055805
 被引用回数：37 パーセンタイル：10.14(Physics, Nuclear)

$$^{118}$$Sn, $$^{119}$$Sn, $$^{120}$$Sn, $$^{122}$$Sn、及び$$^{124}$$Snに対し、中性子閾値近傍の光核反応断面積を準単色レーザ逆コンプトン光を用いて測定した。得られた測定データと既存の中性子捕獲データを、ピグミー共鳴を電磁双極子励起モードに組み込んだ計算コードにより系統的に解析した。本手法、いわゆる、$$gamma$$線強度関数法を適用することにより、放射性核種$$^{121}$$Sn及び$$^{123}$$Snの中性子捕獲断面積を導出した。

論文

The $$gamma$$SF method

宇都宮 弘章*; Goriely, S.*; 秋宗 秀俊*; 山形 民穂*; 近藤 壮雄*; 岩本 ちひろ*; 岡本 明之*; 原田 秀郎; 北谷 文人; 後神 進史*; et al.

AIP Conference Proceedings 1377, p.255 - 259, 2011/10

https://doi.org/10.1063/1.3628388
 被引用回数：0 パーセンタイル：100

The $$gamma$$-ray strength function ($$gamma$$SF) interconnects radiative neutron capture and photoneutron emission as a common ingredient in the statistical model. Outlined here is an indirect method of determining radiative neutron-capture cross sections for unstable nuclei based on the $$gamma$$-ray strength function. Application examples of the $$gamma$$SF method are demonstrated.

論文

Application of the $$gamma$$SF method to palladium

宇都宮 弘章*; Goriely, S.*; Arteaga, D. P.*; Daoutidis, I.*; 秋宗 秀俊*; 山県 民穂*; 近藤 壮雄*; 岩本 ちひろ*; 鎌田 正輝*; 伊藤 修*; et al.

AIP Conference Proceedings 1377, p.450 - 452, 2011/10

https://doi.org/10.1063/1.3628442
 被引用回数：0 パーセンタイル：100

Photoneutron cross sections were measured for $$^{108}$$Pd, $$^{106}$$Pd, and $$^{105}$$Pd with laser-Compton scattering $$gamma$$-ray beams in an application of the $$gamma$$SF method to a radioactive nucleus $$^{107}$$Pd. We present radiative neutron cross sections for $$^{107}$$Pd [6.5$$times$$10$$^{6}$$ y] obtained with the $$gamma$$SF method.

論文

Striking behavior of photoneutron cross sections for $$^{90}$$Zr near threshold

宇都宮 弘章*; Goriely, S.*; 秋宗 秀俊*; 山形 民穂*; 近藤 壮雄*; 岩本 ちひろ*; 伊藤 修*; 鎌田 正輝*; 井尾 雅則*; 楠瀬 幸一*; et al.

AIP Conference Proceedings 1377, p.447 - 449, 2010/10

https://doi.org/10.1063/1.3628441
 被引用回数：0 パーセンタイル：100

Photoneutron cross sections for $$^{90}$$Zr near neutron threshold were examined with a photon difference technique using laser Compton scattering $$gamma$$-ray beams. The cross section decreasing in the vicinity of neutron threshold exhibited a steep rise within 150 keV above the threshold. We draw attention to a possible relation of this striking behavior to the 3P valence neutron resonance known in neutron capture in the mass region A $$approx$$ 90.

口頭

Energy resolution evaluation of decoupled neutron moderator for stress measurements via neutron diffraction with compact neutron source

角田 龍之介*; 高村 正人*; 徐 平光; 岩本 ちひろ*; 高梨 宇宙*; 大竹 淑恵*; 栗原 諒*; 高橋 進*; 鈴木 裕士

no journal, , 

During the production of high-strength steel structural parts, the residual stress is necessary to be well controlled for the better dimensional accuracy and the longer service life. The neutron diffraction measurement is a good candidate to monitor the microscopic lattice strain of polycrystalline materials in bulk average. RANS (Riken Accelerator-driven Compact Neutron Source) has been developed and upgraded aiming at in-house, on-site and on-demand measurements to meet with industrial needs. Recently, the phase volume fractions and the bulk textures of steel materials have been measured successfully at RANS. In order to measure the lattice strain at RANS, it is required to improve the energy resolution to observe slight peak shift, and the decoupled moderator is thought as a good solution method for that. In this study, a new decoupled moderator consisting of polyethylene with 20 cmm thickness and B$$_{4}$$C rubber was designed and fabricated, and its neutron beam characteristic was investigated in order to improve the time energy resolution to realize in-house neutron stress measurement at RANS. Here, the preliminary results of the resolutions comparing between the new decoupled moderator and the traditional coupled moderators with 20 and 40 mm thickness polyethylene will be reported together with the scattering angle dependent instrumental resolution of the linear neutron position-sensitive detector.

口頭

鉄鋼材料の集合組織測定研究に関する大型中性子施設とRIKEN小型中性子源の連携

徐 平光; 高村 正人*; 池田 義雅*; 角田 龍之介*; 高橋 進*; 箱山 智之*; 岩本 ちひろ*; 大竹 淑恵*; 鈴木 裕士

no journal, , 

自動車の軽量化のために使用されている高張力薄鋼板は、プレス成形による加工性が低いことから、生産不良が多い。そのため、プレス成形性を向上させる手段の一つとして、鋼材の集合組織制御に期待が寄せられている。実用に供される金属材料の微視組織は不均一な集合組織を有している。圧延板の加工性など金属材料のマクロな特性を議論する際には、金属材料のバルク平均の集合組織を考慮することが適切だと考えられる。中性子線を用いた集合組織測定は、高い透過性と大きなゲージ体積という特徴を生かして、加工性に直結する金属材料のバルク平均情報を容易に測定することができる。しかしながら、日本国内に限らず、世界中には、集合組織が測定できる中性子回折装置が極めて少ない。そこで、我々は研究用原子炉施設(JRR-3)の定常中性子源と大強度陽子加速器施設(J-PARC)のパルス中性子源を用いた集合組織測定技術を確立し、世界トップレベルの測定精度を有する集合組織測定装置を開発した。近年、中性子評価技術をより広く普及するため、理化学研究所が"いつでも、どこでも、手軽に利用できる"をキャッチフレーズとした小型中性子源(RANS)の開発を進めており、我々がこれまでに培ってきたノウハウを最大限に生かして、RANSを用いた粉末回折技術や集合組織測定技術の開発に挑戦してきた。本発表では、JRR-3, J-PARCおよびRANSで開発した鉄鋼材料の集合組織測定技術を簡単に紹介するとともに、中性子回折による集合組織測定研究に関して大型中性子施設と小型中性子源との連携案について議論する。

口頭

Neutron diffraction with RANS for industrial "on-site" applications

高村 正人*; 岩本 ちひろ*; 徐 平光; 角田 龍之介*; 栗原 諒*; 箱山 智之*; 池田 義雅*; 鈴木 裕士; 大竹 淑恵*

no journal, , 

High strength steels are becoming more and more important in automotive body structures for good weight reduction, providing further requirement in the balance between strength and formability. Numerical models in forming simulations taking into account the texture evolution may accurately analyze macroscopic plastic behavior, through referring to local surface texture measurement using Electron backscatter diffraction or X-ray diffraction. In contrast, neutron diffraction may measure the microstructure factors including bulk-averaged texture, enable to more deeply understand the mechanisms of deformation behavior. Such neutron diffraction studies usually require large-scale experimental facilities like a reactor and a large accelerator, so meet certain difficulty in the instrumental accessibility. To solve these problems, Riken Accelerator-driven Compact Neutron Source (RANS) has been developed. On-site evaluation of microstructural factors enables us to analyze metal deformation processes more efficiently. Authors have recently succeeded in accurately measuring the texture evolution of an IF steel and also in determining the retained austenite volume fraction of multi-phase steels, by optimizing the beam condition and layout of collimators, samples, detectors, etc. These results show the possibility of practical use of an in-house compact neutron source in laboratories of universities, research institutes and industrial firms.

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