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論文

Status and perspectives of the neutron time-of-flight facility n_TOF at CERN

Chiaveri, E.*; Aberle, O.*; Alcayne, V.*; 木村 敦; 他124名*

EPJ Web of Conferences, 239, p.17001_1 - 17001_8, 2020/09

 被引用回数:3 パーセンタイル:95.51

Since the start of its operation in 2001, the neutron time of-flight facility of CERN, n_TOF, has become one of the most forefront neutron facilities in the world for wide-energy spectrum neutron cross section measurements. Thanks to the combination of excellent neutron energy resolution and high instantaneous neutron flux available in the two experimental areas, the second of which has been constructed in 2014, n_TOF is providing a wealth of new data on neutron-induced reactions of interest for nuclear astrophysics, advanced nuclear technologies and medical applications. In this document the main characteristics of the n_TOF facility and their relevance for neutron studies in the different areas of research will be outlined. In addition, the future perspectives of the facility will be described including the upgrade of the spallation target, the setup of an imaging installation and the construction of a new irradiation area.

論文

Monte Carlo simulations and n-p differential scattering data measured with Proton Recoil Telescopes

Terranova, N.*; Aberle, O.*; Alcayne, V.*; 木村 敦; 他125名*

EPJ Web of Conferences, 239, p.01024_1 - 01024_5, 2020/09

 被引用回数:3 パーセンタイル:95.51

The $$^{235}$$U(n,f) cross section from 20 MeV up to about 1 GeV has been measured relative to the $$^1$$H(n,n)$$^1$$H reaction. The neutron flux impinging on the $$^{235}$$U sample has been obtained by detecting recoil protons originating from n-p scattering in a C$$_2$$H$$_4$$ sample. Two Proton Recoil Telescopes (PRT), consisting of several layers of solid-state detectors and fast plastic scintillators, have been set at proton scattering angles of 25.07$$^{circ}$$ and 20.32$$^{circ}$$. Extensive Monte Carlo simulations were performed to characterize proton transport through the PRTs. In this work we compare measured data collected with the PRTs with a full Monte Carlo simulation based on the Geant-4 toolkit.

論文

Setup for the measurement of the $$^{235}$$U(n, f) cross section relative to n-p scattering up to 1 GeV

Manna, A.*; Aberle, O.*; Alcayne, V.*; 木村 敦; 他125名*

EPJ Web of Conferences, 239, p.01008_1 - 01008_5, 2020/09

 被引用回数:3 パーセンタイル:95.51

The neutron induced fission of $$^{235}$$U is extensively used as a reference for neutron fluence measurements in various applications. However, no data exist on neutron induced fission of $$^{235}$$U above 200 MeV. The neutron facility n_TOF offers the possibility to improve the situation. The measurement of $$^{235}$$U(n,f) relative to the differential n-p scattering cross-section, was carried out with the aim of providing accurate and precise cross section data in the energy range from 10 MeV up to 1 GeV. In this measurements, recoil proton telescopes are used to measure the neutron flux while the fission events are detected and counted with dedicated detectors. In this paper the measurement campaign and the experimental set-up are illustrated.

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:24 パーセンタイル:92.79(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

The Measurement programme at the neutron time-of-flight facility n_TOF at CERN

Gunsing, F.*; Aberle, O.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他147名*

EPJ Web of Conferences, 146, p.11002_1 - 11002_6, 2017/09

 被引用回数:3 パーセンタイル:90.94

CERNのn_TOF中性子飛行時間測定施設は、2001年の事業開始以来、数多くの実験データ取得に利用されてきた。長期に渡り利用された中性子飛行距離185mの第1実験室に加え、2014年からは中性子飛行距離20mの第2実験室が利用可能となり、施設の測定能力が大幅に向上した。n_TOF施設における核データ測定研究活動について総括的に報告する。

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, 146, p.01012_1 - 01012_4, 2017/09

 被引用回数:1 パーセンタイル:61.28

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.

論文

The n_TOF facility; Neutron beams for challenging future measurements at CERN

Chiaveri, E.*; Aberle, O.*; Andrzejewski, J.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他111名*

EPJ Web of Conferences, 146, p.03001_1 - 03001_4, 2017/09

 被引用回数:1 パーセンタイル:61.28

The CERN n_TOF neutron beam facility is characterized by a very high instantaneous neutron flux, excellent TOF resolution at the 185m long flight path (EAR-1), low intrinsic background and coverage of a wide range of neutron energies, from thermal to a few GeV. The overall efficiency of the experimental program and the range of possible measurements has been expanded with the construction of a second experimental area (EAR-2), located 20m on the vertical of the n_TOF spallation target. This upgrade, which benefits from a neutron flux 30 times higher than in EAR-1, provides a substantial extension in measurement capabilities, opening the possibility to collect data on neutron cross-section of isotopes with short half-lives or available in very small amounts. We will discuss the innovative features of the EAR-2 neutron beam that make possible to perform very challenging measurements on short-lived radioisotopes or sub-mg samples, out of reach up to now at other neutron facilities around the world. Finally, the future perspectives of the facility will be presented.

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