51
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52
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Time-of-flight and activation experiments on 147Pm and 171Tm for astrophysics. EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201714601007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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53
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Monte carlo simulations of the n_TOF lead spallation target with the Geant4 toolkit: A benchmark study. EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201714603030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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54
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The 33S(n,α) 30Si cross section measurement at n_TOF-EAR2 (CERN): From 0.01 eV to the resonance region. EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201714608004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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55
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56
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The Nuclear Astrophysics program at n_TOF (CERN). EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201716501014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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57
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High precision measurement of the radiative capture cross section of 238U at the n_TOF CERN facility. EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201714611028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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58
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The measurement programme at the neutron time-of-flight facility n_TOF at CERN. EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201714611002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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59
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7Be(n,α) and 7Be(n,p) cross-section measurement for the cosmological lithium problem at the n_TOF facility at CERN. EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201714601012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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60
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61
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^{7}Be(n,α)^{4}He Reaction and the Cosmological Lithium Problem: Measurement of the Cross Section in a Wide Energy Range at n_TOF at CERN. PHYSICAL REVIEW LETTERS 2016; 117:152701. [PMID: 27768364 DOI: 10.1103/physrevlett.117.152701] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Indexed: 06/06/2023]
Abstract
The energy-dependent cross section of the ^{7}Be(n,α)^{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. The challenges posed by the short half-life of ^{7}Be and by the low reaction cross section have been overcome at n_TOF thanks to an unprecedented combination of the extremely high luminosity and good resolution of the neutron beam in the new experimental area (EAR2) of the n_TOF facility at CERN, the availability of a sufficient amount of chemically pure ^{7}Be, and a specifically designed experimental setup. 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.
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62
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63
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Fission Fragment Angular Distribution measurements of235U and238U at CERN n_TOF facility. EPJ WEB OF CONFERENCES 2016. [DOI: 10.1051/epjconf/201611110002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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64
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Experimental neutron capture data of 58Ni from the CERN n_TOF facility. EPJ WEB OF CONFERENCES 2015. [DOI: 10.1051/epjconf/20159302009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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65
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66
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Novel method to study neutron capture of 235U and 238U simultaneously at keV energies. PHYSICAL REVIEW LETTERS 2014; 112:192501. [PMID: 24877933 DOI: 10.1103/physrevlett.112.192501] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Indexed: 06/03/2023]
Abstract
The neutron capture cross sections of the main uranium isotopes, (235)U and (238)U, were measured simultaneously for keV energies, for the first time by combining activation technique and atom counting of the reaction products using accelerator mass spectrometry. New data, with a precision of 3%-5%, were obtained from mg-sized natural uranium samples for neutron energies with an equivalent Maxwell-Boltzmann distribution of kT ∼ 25 keV and for a broad energy distribution peaking at 426 keV. The cross-section ratio of (235)U(n,γ)/(238)U(n,γ) can be deduced in accelerator mass spectrometry directly from the atom ratio of the reaction products (236)U/(239)U, independent of any fluence normalization. Our results confirm the values at the lower band of existing data. They serve as important anchor points to resolve present discrepancies in nuclear data libraries as well as for the normalization of cross-section data used in the nuclear astrophysics community for s-process studies.
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67
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Measurements of neutron cross sections for advanced nuclear energy systems at n_TOF (CERN). EPJ WEB OF CONFERENCES 2014. [DOI: 10.1051/epjconf/20146610001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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68
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69
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238U(n,γ) reaction cross section measurement with C6D6detectors at the n_TOF CERN facility. EPJ WEB OF CONFERENCES 2014. [DOI: 10.1051/epjconf/20146603061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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70
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Neutron cross-sections for advanced nuclear systems: the n_TOF project at CERN. EPJ WEB OF CONFERENCES 2014. [DOI: 10.1051/epjconf/20137901003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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71
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Neutron capture cross section of unstable 63Ni: implications for stellar nucleosynthesis. PHYSICAL REVIEW LETTERS 2013; 110:022501. [PMID: 23383895 DOI: 10.1103/physrevlett.110.022501] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Indexed: 06/01/2023]
Abstract
The 63Ni(n,γ) cross section has been measured for the first time at the neutron time-of-flight facility n_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged cross sections were calculated for thermal energies from kT=5-100 keV with uncertainties around 20%. Stellar model calculations for a 25M⊙ star show that the new data have a significant effect on the s-process production of 63Cu, 64Ni, and 64Zn in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova.
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72
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73
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74
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75
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76
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Stellar neutron capture rates and the sprocess. EPJ WEB OF CONFERENCES 2012. [DOI: 10.1051/epjconf/20122103006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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77
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78
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79
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Measurement of the 60Fe(n, gamma)61Fe Cross Section at Stellar Temperatures. PHYSICAL REVIEW LETTERS 2009; 102:151101. [PMID: 19518614 DOI: 10.1103/physrevlett.102.151101] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Indexed: 05/27/2023]
Abstract
Observations of galactic gamma-ray activity have challenged the current understanding of nucleosynthesis in massive stars. Recent measurements of (60)Fe abundances relative to ;{26}Al;{g} have underscored the need for accurate nuclear information concerning the stellar production of (60)Fe. In light of this motivation, a first measurement of the stellar (60)Fe(n, gamma)(61)Fe cross section, the predominant destruction mechanism of (60)Fe, has been performed by activation at the Karlsruhe Van de Graaff accelerator. Results show a Maxwellian averaged cross section at kT = 25 keV of 9.9 +/-_{1.4(stat)};{2.8(syst)}mbarn, a significant reduction in uncertainty with respect to existing theoretical discrepancies. This result will serve to significantly constrain models of (60)Fe nucleosynthesis in massive stars.
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80
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Stellar (n,gamma) cross section of 62Ni. PHYSICAL REVIEW LETTERS 2005; 94:092504. [PMID: 15783960 DOI: 10.1103/physrevlett.94.092504] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Revised: 12/15/2004] [Indexed: 05/24/2023]
Abstract
The 62Ni(n,gamma)63Ni(t(1/2)=100+/-2 yr) reaction plays an important role in the control of the flow path of the slow neutron-capture (s) nucleosynthesis process. We have measured for the first time the total cross section of this reaction for a quasi-Maxwellian (kT=25 keV) neutron flux. The measurement was performed by fast-neutron activation, combined with accelerator mass spectrometry to detect directly the 63Ni product nuclei. The experimental value of 28.4+/-2.8 mb, fairly consistent with a recent calculation, affects the calculated net yield of 62Ni itself and the whole distribution of nuclei with 62<A<90 produced by the weak s process in massive stars.
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81
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Neutron Reactions in Astrophysics: The Role of New Facilities and Improved Laboratory Approaches. JOURNAL OF NEUTRON RESEARCH 2005. [DOI: 10.1080/10238160412331299546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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82
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Neutron capture cross section measurement of 151Sm at the CERN neutron time of flight facility (n_TOF). PHYSICAL REVIEW LETTERS 2004; 93:161103. [PMID: 15524972 DOI: 10.1103/physrevlett.93.161103] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Indexed: 05/24/2023]
Abstract
The151Sm(n,gamma)152Sm cross section has been measured at the spallation neutron facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The new facility combines excellent resolution in neutron time-of-flight, low repetition rates, and an unsurpassed instantaneous luminosity, resulting in rather favorable signal/background ratios. The 151Sm cross section is of importance for characterizing neutron capture nucleosynthesis in asymptotic giant branch stars. At a thermal energy of kT=30 keV the Maxwellian averaged cross section of this unstable isotope (t(1/2)=93 yr) was determined to be 3100+/-160 mb, significantly larger than theoretical predictions.
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83
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Evidence for M1 scissors resonances built on the levels in the quasicontinuum of 163Dy. PHYSICAL REVIEW LETTERS 2004; 92:172501. [PMID: 15169140 DOI: 10.1103/physrevlett.92.172501] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2003] [Indexed: 05/24/2023]
Abstract
Spectra of two-step gamma cascades following the thermal 162Dy(n,gamma)163Dy reaction have been measured. Distinct peaklike structures observed at the midpoints of these spectra are interpreted as a manifestation of the low-energy isovector M1 vibrational mode of excited 163Dy nuclei.
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84
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Erratum to “Radiological safety of medical devices sterilized with X-rays, at 7.5 MeV” [Radiation Physics and Chemistry 67 (2003) 149–167]. Radiat Phys Chem Oxf Engl 1993 2003. [DOI: 10.1016/j.radphyschem.2003.10.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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85
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Neutron Capture at keV Energies - Probing the Stellar Interior. J NUCL SCI TECHNOL 2002. [DOI: 10.1080/00223131.2002.10875154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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86
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Elastic alpha-12C scattering and the 12C(alpha,gamma)16O E2 S factor. PHYSICAL REVIEW LETTERS 2002; 88:072501. [PMID: 11863889 DOI: 10.1103/physrevlett.88.072501] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2001] [Indexed: 05/23/2023]
Abstract
Angular distributions of 12C(alpha,alpha)12C have been measured for E(alpha) = 2.6-8.2 MeV, at angles from 24 to 166, yielding 12 864 data points. R-matrix analysis of the ratios of elastic scattering yields a reduced width amplitude of gamma12 = 0.47 +/- 0.06 MeV(1/2) for the Ex = 6.917 MeV (2+) state in 16O(a = 5.5 fm). The dependence of the chi2 surface on the interaction radius a has been investigated and a deep minimum is found at a = 5.42(+0.16)(-0.27) fm. Using this value of gamma12, radiative alpha capture and 16N beta-delayed alpha-decay data, the S factor is calculated at E(c.m.) = 300 keV to be S(E2)(300) = 53(+13)(-18) keV b for destructive interference between the subthreshold resonance tail and the ground state E2 direct capture.
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87
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Neutron capture on (180)Ta(m): clue for an s-process origin of nature's rarest isotope. PHYSICAL REVIEW LETTERS 2001; 87:251102. [PMID: 11736554 DOI: 10.1103/physrevlett.87.251102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2001] [Indexed: 05/23/2023]
Abstract
The neutron capture cross section of (180)Ta(m) has been measured in the keV range, yielding a stellar average of 1465+/-100 mb at kT = 30 keV. Though the sample contained only 6.7 mg (180)Ta(m) (at an enrichment of 5.5%), the few capture events could be separated from much larger backgrounds by a unique combination of high efficiency, good energy resolution, and high granularity of the Karlsruhe 4 pi BaF(2) detector. A detailed s-process analysis based on this first experimental value indicates that (180)Ta(m) is predominantly of s-process origin.
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88
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Neutron capture resonances in 116Sn, 118Sn, and 120Sn. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1996; 54:2732-2739. [PMID: 9971626 DOI: 10.1103/physrevc.54.2732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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89
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Stellar neutron capture cross sections of the tin isotopes. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1996; 54:1451-1462. [PMID: 9971483 DOI: 10.1103/physrevc.54.1451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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90
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Moxon-Rae setup for the measurement of stellar (n, gamma ) rates and the example of 87Rb. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1996; 53:2474-2485. [PMID: 9971228 DOI: 10.1103/physrevc.53.2474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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91
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Neutron capture cross sections of the cerium isotopes for s- and p-process studies. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1996; 53:1397-1408. [PMID: 9971078 DOI: 10.1103/physrevc.53.1397] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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92
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Neutron capture cross section of 15N at stellar energies. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1996; 53:977-981. [PMID: 9971017 DOI: 10.1103/physrevc.53.977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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93
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Neutron capture cross section of 18O and its astrophysical implications. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1996; 53:459-468. [PMID: 9970957 DOI: 10.1103/physrevc.53.459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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94
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Stellar neutron capture cross sections of the Gd isotopes. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1995; 52:2762-2779. [PMID: 9970807 DOI: 10.1103/physrevc.52.2762] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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95
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Resonance neutron capture in 136Ba. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1995; 52:1102-1105. [PMID: 9970598 DOI: 10.1103/physrevc.52.1102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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96
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Stellar (n, gamma ) cross section of the unstable isotope 155Eu. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1995; 51:3465-3471. [PMID: 9970451 DOI: 10.1103/physrevc.51.3465] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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97
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Stellar neutron capture cross sections of Nd, Pm, and Sm isotopes. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1995; 51:1540-1550. [PMID: 9970207 DOI: 10.1103/physrevc.51.1540] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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98
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Stellar cross sections for 33S(n, alpha )30Si, 36Cl(n,p)36S, and 36Cl(n, alpha )33P and the origin of 36S. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1995; 51:379-391. [PMID: 9970073 DOI: 10.1103/physrevc.51.379] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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99
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Stellar neutron capture cross sections of the Ba isotopes. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1994; 50:2582-2601. [PMID: 9969948 DOI: 10.1103/physrevc.50.2582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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100
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Measurement of the resonance at ER=1422 keV in 36Ar(p, gamma )37K. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1993; 48:R1479-R1483. [PMID: 9969065 DOI: 10.1103/physrevc.48.r1479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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