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論文

Cross section measurements of $$^{155,157}$$Gd(n,$$gamma$$) induced by thermal and epithermal neutrons

Mastromarco, M.*; Manna, A.*; Aberle, O.*; Andrzejewski, J.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他116名*

European Physical Journal A, 55(1), p.9_1 - 9_20, 2019/01

 被引用回数:14 パーセンタイル:93.24(Physics, Nuclear)

Neutron capture cross section measurements on $$^{155}$$Gd and $$^{157}$$Gd were performed using the time-of-flight technique at the n_TOF facility at CERN on isotopically enriched samples. The measurements were carried out in the n TOF experimental area EAR1, at 185m from the neutron source, with an array of 4 C$$_6$$D$$_6$$ liquid scintillation detectors. At a neutron kinetic energy of 0.0253eV, capture cross sections of 62.2(2.2) and 239.8(8.4) kilobarn have been derived for $$^{155}$$Gd and $$^{157}$$Gd, respectively, with up to 6% deviation relative to values presently reported in nuclear data libraries, but consistent with those values within 1.6 standard deviations. A resonance shape analysis has been performed in the resolved resonance region up to 181eV and 307eV, respectively for $$^{155}$$Gd and $$^{157}$$Gd, where on average, resonance parameters have been found in good agreement with evaluations. Above these energies and up to 1keV, the observed resonance-like structure of the cross section has been analysed and characterised. From a statistical analysis of the observed neutron resonances we deduced: neutron strength function of 2.01(28) $$times$$ 10$$^{-4}$$ and 2.17(41) $$times$$ 10$$^{-4}$$; average total radiative width of 106.8(14)meV and 101.1(20)meV and s-wave resonance spacing 1.6(2)eV and 4.8(5)eV for n + $$^{155}$$Gd and n + $$^{157}$$Gd systems, respectively.

論文

Radiative neutron capture on $$^{242}$$Pu in the resonance region at the CERN n_TOF-EAR1 facility

Lerendegui-Marco, J.*; Guerrero, C.*; Mendoza, E.*; Quesada, J. M.*; Eberhardt, K.*; Junghans, A. R.*; 木村 敦; n_TOF Collaboration*; 他126名*

Physical Review C, 97(2), p.024605_1 - 024605_21, 2018/02

 被引用回数:13 パーセンタイル:85.61(Physics, Nuclear)

This paper presents a new time-of-flight capture measurement on $$^{242}$$Pu carried out at n_TOF-EAR1(CERN), focusing on the analysis and statistical properties of the resonance region, below 4 keV. The $$^{242}$$Pu(n,$$gamma$$)reaction on a sample containing 95(4) mg enriched to 99.959% was measured with an array of four C$$_6$$D$$_6$$ detectors and applying the total energy detection technique. The high neutron energy resolution of n_TOF-EAR1 and the good statistics accumulated have allowed us to extend the resonance analysis up to 4 keV, obtaining new individual and average resonance parameters from a capture cross section featuring a systematic uncertainty of 5%, fulfilling the request of the NEA.

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

 被引用回数:0 パーセンタイル:0.08

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.

口頭

Toward modeling of stomatal conductance under elevated ozone in forest trees

星加 康智*; 渡辺 誠*; 堅田 元喜; De Marco, A.*; 出牛 真*; Carriero, G.*; 小池 孝良*; Paoletti, E.*

no journal, , 

対流圏オゾンは、気孔を通じて樹木に吸収され植物葉の被害を引き起こす。この影響を評価するためには気孔コンダクタンスのモデル化が必要である。本研究では、オゾン上昇下での気孔コンダクタンスモデリングに関する我々の最近の研究を報告する。まず、我々は世界中の森林樹木種へのJarvis型のモデルのパラメータをレビューし、夜明け前水ポテンシャルに対する気孔コンダクタンスの応答と最適温度が生長条件によって変化することを示した。次に、オゾン影響を含めた気孔コンダクタンスの最適モデルを、ブナを対象にしたオゾンFACE実験の結果を用いて試験し、モデルが夏季のオゾンによる気孔閉鎖を説明できることを示した。しかしながら、夏から秋にかけての気孔コンダクタンスへのオゾン影響は説明できず、オゾンに対する気孔閉鎖の鈍化プロセスの影響が示唆された。そこで、最終的にこの鈍化プロセスによる植物の炭素獲得と蒸散への影響を、北半球の温帯落葉樹林での詳細な多層地表面モデルと全球大気化学モデルを組み合わせたシミュレーションによって調べた。その結果、オゾンの鈍化は炭素獲得と蒸散に著しい影響をおよぼすことが示された。

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