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
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
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 =30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of Ge produced in stars, which would explain the low isotopic abundance of Ge in the solar system.
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 Be(n,)cross section, the Be(n,p)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.
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 Pu carried out at n_TOF-EAR1(CERN), focusing on the analysis and statistical properties of the resonance region, below 4 keV. The Pu(n,)reaction on a sample containing 95(4) mg enriched to 99.959% was measured with an array of four CD 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.
Sabat-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
CERNのn_TOF第2実験室において、B(n,)を標準断面積として用い、S(n, )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、B(n, )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。
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
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 Pu(n,f) cross-section was measured at CERN n_TOF facility relative to the well-known 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.
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
The Cosmological Lithium Problem refers to the large discrepancy between the abundance of primordial 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 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 Be(n,) and Be(n,p) reactions are scarce or completely missing, so that a large uncertainty still affects the abundance of 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
Barbagallo, M.*; Musumarra, A.*; Cosentino, L.*; Maugeri, E.*; Heinitz, S.*; Mengoni, A.*; Dressler, R.*; Schumann, D.*; Kppeler, F.*; 原田 秀郎; et al.
Physical Review Letters, 117(15), p.152701_1 - 152701_7, 2016/10
The energy-dependent cross section of the Be(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-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.
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
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 Be(n, ) 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.
Wei, 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
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.
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 ---. The first and second prototypes of SSD have been tested and the final product will be fabricated based on the test result.
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