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論文

Probing the quantum phase transition in Mott insulator BaCoS$$_{2}$$ tuned by pressure and Ni substitution

Guguchia, Z.*; Frandsen, B. A.*; Santos-Cottin, D.*; 社本 真一; Gauzzi, A.*; 植村 泰朋*; 他12名*

Physical Review Materials (Internet), 3(4), p.045001_1 - 045001_9, 2019/04

$$mu$$SRを用いて、BaCoS$$_{2}$$を圧力とNi置換でモット転移を調整し、量子相転移の様子を調べた。その結果、ゼロ温度で両方の量子相転移が一次転移であることがわかった。

論文

Measurement of $$^{73}$$Ge(n,$$gamma$$) cross sections and implications for stellar nucleosynthesis

Lederer-Woods, C.*; Battino, U.*; Ferreira, P.*; Gawlik, A.*; 木村 敦; n_TOF Collaboration*; 他128名*

Physics Letters B, 790, p.458 - 465, 2019/03

$$^{73}Ge(n,gamma)$$ cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at $$kT$$ =30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of $$^{73}$$Ge produced in stars, which would explain the low isotopic abundance of $$^{73}$$Ge in the solar system.

論文

Experimental setup and procedure for the measurement of the $$^7$$Be(n,p)$$^7$$Li reaction at n_TOF

Barbagallo, M.*; Andrzejewski, J.*; Mastromarco, M.*; Perkowski, J.*; Damone, L. A.*; Gawlik, A.*; 木村 敦; n_TOF Collaboration*; 他122名*

Nuclear Instruments and Methods in Physics Research A, 887, p.27 - 33, 2018/04

Following the completion of the second neutron beam line and the related experimental area (EAR2) at the n_TOF spallation neutron source at CERN, several experiments were planned and performed. The high instantaneous neutron flux available in EAR2 allows to investigate neutron induced reactions with charged particles in the exit channel even employing targets made out of small amounts of short-lived radioactive isotopes. After the successful measurement of the $$^7$$Be(n,$$alpha$$)cross section, the $$^7$$Be(n,p)$$^7$$Li reaction was studied in order to provide still missing cross section data of relevance for Big Bang Nucleosynthesis (BBN), in an attempt to find a solution to the cosmological Lithium abundance problem. This paper describes the experimental setup employed in such a measurement and its characterization.

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

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

The $$^{33}$$S(n, $$alpha$$)$$^{30}$$Si cross section measurement at n_TOF-EAR2 (CERN); From 0.01 eV to the resonance region

Sabat$'e$-Gilarte, M.*; Praena, J.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他126名*

EPJ Web of Conferences (Internet), 146, p.08004_1 - 08004_4, 2017/09

 パーセンタイル:100

CERNのn_TOF第2実験室において、$$^{10}$$B(n,$$alpha$$)を標準断面積として用い、$$^{33}$$S(n, $$alpha$$)$$^{30}$$Si反応断面積を測定した。本実験室では初めてとなる0.01eVから100keVまでの実験データを取得し、本データより0.01eVから10keVまでの中性子断面積を導出した。本反応は、$$^{10}$$B(n, $$alpha$$)反応とともに放射線療法への利用が期待されているが、従来報告された断面積値間には大きな差異がある。本研究により導出した断面積は、信頼性ある断面積評価に反映されることが期待される。

論文

Measurement of the $$^{240}$$Pu(n,f) cross-section at the CERN n_TOF facility; First results from experimental area II (EAR-2)

Stamatopoulos, A.*; Tsinganis, A.*; Colonna, N.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他126名*

EPJ Web of Conferences (Internet), 146, p.04030_1 - 04030_4, 2017/09

 被引用回数:2 パーセンタイル:4.05

The accurate knowledge of the neutron-induced fission cross-sections of actinides and other isotopes involved in the nuclear fuel cycle is essential for the design of advanced nuclear systems, such as Generation-IV nuclear reactors. Such experimental data can also provide the necessary feedback for the adjustment of nuclear model parameters used in the evaluation process, resulting in the further development of nuclear fission models. In the present work, the $$^{240}$$Pu(n,f) cross-section was measured at CERN n_TOF facility relative to the well-known $$^{235}$$U(n,f) cross section, over a wide range of neutron energies, from meV to almost MeV, using the time-of-flight technique and a set-up based on Micromegas detectors. This measurement was the first experiment to be performed at n_TOF new experimental area (EAR-2), which offers a significantly higher neutron flux compared to the already existing experimental area (EAR-1).Preliminary results as well as the experimental procedure, including a description of the facility and the data handling and analysis, are presented.

論文

$$^7$$Be(n,$$alpha$$) and $$^7$$Be(n,p) cross-section measurement for the cosmological lithium problem at the n_TOF facility at CERN

Barbagallo, M.*; Colonna, N.*; Aberle, O.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他125名*

EPJ Web of Conferences (Internet), 146, p.01012_1 - 01012_4, 2017/09

 パーセンタイル:100

The Cosmological Lithium Problem refers to the large discrepancy between the abundance of primordial $$^7$$Li predicted by the standard theory of Big Bang Nucleosynthesis and the value inferred from the so-called "Spite plateau" in halo stars. A possible explanation for this longstanding puzzle in Nuclear Astrophysics is related to the incorrect estimation of the destruction rate of $$^7$$Be, which is responsible for the production of 95% of primordial Lithium. While charged-particle induced reactions have mostly been ruled out, data on the $$^7$$Be(n,$$alpha$$) and $$^7$$Be(n,p) reactions are scarce or completely missing, so that a large uncertainty still affects the abundance of $$^7$$Li predicted by the standard theory of Big Bang Nucleosynthesis. Both reactions have been measured at the n_TOF facility at CERN, providing for the first time data in a wide neutron energy range._1

論文

$$^{7}$$Be($$n, alpha)^{4}$$He reaction and the cosmological lithium problem; Measurement of the cross section in a wide energy range at n_TOF at CERN

Barbagallo, M.*; Musumarra, A.*; Cosentino, L.*; Maugeri, E.*; Heinitz, S.*; Mengoni, A.*; Dressler, R.*; Schumann, D.*; K$"a$ppeler, F.*; 原田 秀郎; et al.

Physical Review Letters, 117(15), p.152701_1 - 152701_7, 2016/10

 被引用回数:31 パーセンタイル:6.11(Physics, Multidisciplinary)

The energy-dependent cross section of the $$^{7}$$Be($$n, alpha)^{4}$$He reaction, of interest for the so-called cosmological lithium problem in big bang nucleosynthesis, has been measured for the first time from 10 meV to 10 keV neutron energy. Coincidences between the two alpha particles have been recorded in two Si-$$^{7}$$Be-Si arrays placed directly in the neutron beam. The present results are consistent, at thermal neutron energy, with the only previous measurement performed in the 1960s at a nuclear reactor. The energy dependence reported here clearly indicates the inadequacy of the cross section estimates currently used in BBN calculations. Although new measurements at higher neutron energy may still be needed, the n_TOF results hint at a minor role of this reaction in BBN, leaving the long-standing cosmological lithium problem unsolved.

論文

Experimental setup and procedure for the measurement of the $$^{7}$$Be(n, $$alpha$$)$$alpha$$ reaction at n_TOF

Cosentino, L.*; Musumarra, A.*; Barbagallo, M.*; Pappalardo, A.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他126名*

Nuclear Instruments and Methods in Physics Research A, 830, p.197 - 205, 2016/09

 被引用回数:8 パーセンタイル:10.94(Instruments & Instrumentation)

The newly built second experimental area EAR2 of the n_TOF spallation neutron source at CERN allows to perform (n, charged particles) experiments on short-lived highly radioactive targets. This paper describes a detection apparatus and the experimental procedure for the determination of the cross-section of the $$^{7}$$ Be(n, $$alpha$$) reaction, which represents one of the focal points toward the solution of the cosmological Lithium abundance problem, and whose only measurement, at thermal energy, dates back to 1963. This newly developed setup could likely be useful also to study other challenging reactions requiring the detectors to be installed directly in the neutron beam.

論文

The New vertical neutron beam line at the CERN n_TOF facility design and outlook on the performance

Wei${ss}$, C.*; Chiaveri, E.*; Girod, S.*; Vlachoudis, V.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他126名*

Nuclear Instruments and Methods in Physics Research A, 799, p.90 - 98, 2015/11

 被引用回数:36 パーセンタイル:0.65(Instruments & Instrumentation)

At the neutron time-of-flight facility n_TOF at CERN a new vertical beam line was constructed in 2014, in order to extend the experimental possibilities at this facility to an even wider range of challenging cross-section measurements of interest in astrophysics, nuclear technology and medical physics. The design of the beamline and the experimental hall was based on FLUKA Monte Carlo simulations, aiming at maximizing the neutron flux, reducing the beam halo and minimizing the background from neutrons interacting with the collimator or back-scattered in the beam dump. The present paper gives an overview on the design of the beam line and the relevant elements and provides an outlook on the expected performance regarding the neutron beam intensity, shape and energy resolution, as well as the neutron and photon backgrounds.

論文

Development of single-sided silicon detectors in the emulsion-hybrid system at J-PARC

Lee, J. Y.*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 佐甲 博之; 佐藤 進; 杉村 仁志; 谷田 聖; et al.

JPS Conference Proceedings (Internet), 8, p.021008_1 - 021008_6, 2015/09

A new single-sided silicon micro-strip detector (SSD) is being developed at the J-PARC K1.8 beam line for an emulsion-counter hybrid experiment (J-PARC E07). The SSD will be mainly used for vertex measurements in emulsion plates. Two prototypes of SSD have been fabricated to check the performance of the circuit board and silicon sensors. The first prototype consists of only one layer of a silicon sensor whereas the second prototype consists of two layers of silicon sensors. The final product will be a stack of 4 layers of silicon sensors in the order of $$X$$-$$Y$$-$$X$$-$$Y$$. The first and second prototypes of SSD have been tested and the final product will be fabricated based on the test result.

報告書

再処理施設周辺環境放射線監視年報 1988年(1月$$sim$$12月)

石田 順一郎; 片桐 裕実*; 林 直美*; 成田 脩; 他12名*

PNC-TN8440 89-004, 163 Pages, 1989/02

PNC-TN8440-89-004.pdf:5.69MB

東海事業所では,「動力炉・核燃料開発事業団東海事業所再処理施設保安規定,第6編環境監視」に従い,再処理施設の周辺地域において環境放射線(能)モニタリングを実施している。本報告書は1988年1月から12月までの間に実施した環境監視の結果をまとめたものであり,放出記録に基づく周辺公衆の被ばく線量の算定結果についても合わせて収録した。 また,付録として,環境監視計画の概要,・測定方法の概要,測定結果及びその経時変化,気象統計結果,放射性廃棄物の放出状況,被ばく線量算定結果の詳細等を収録した。

12 件中 1件目~12件目を表示
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