|
|
Babiano-Suarez, V. et al, Lerendegui-Marco, J., Balibrea-Correa, J., Caballero, L., Calvo, D., Ladarescu, I., et al. (2021). Imaging neutron capture cross sections: i-TED proof-of-concept and future prospects based on Machine-Learning techniques. Eur. Phys. J. A, 57(6), 197–17pp.
Abstract: i-TED is an innovative detection system which exploits Compton imaging techniques to achieve a superior signal-to-background ratio in (n, gamma) cross-section measurements using time-of-flight technique. This work presents the first experimental validation of the i-TED apparatus for high-resolution time-of-flight experiments and demonstrates for the first time the concept proposed for background rejection. To this aim, the Au-197(n, gamma) and Fe-56(n, gamma) reactions were studied at CERN n_TOF using an i-TED demonstrator based on three position-sensitive detectors. Two C6D6 detectors were also used to benchmark the performance of i-TED. The i-TED prototype built for this study shows a factor of similar to 3 higher detection sensitivity than state-of-the-art C6D6 detectors in the 10 keV neutron-energy region of astrophysical interest. This paper explores also the perspectives of further enhancement in performance attainable with the final i-TED array consisting of twenty position-sensitive detectors and newanalysis methodologies based on Machine-Learning techniques.
|
|
|
|
n_TOF Collaboration(Amaducci, S. et al), Babiano-Suarez, V., Caballero-Ontanaya, L., Domingo-Pardo, C., Ladarescu, I., & Tain, J. L. (2021). First Results of the Ce-140(n,gamma)Ce-141 Cross-Section Measurement at n_TOF. Universe, 7(6), 200–11pp.
Abstract: An accurate measurement of the Ce-140(n,gamma) energy-dependent cross-section was performed at the n_TOF facility at CERN. This cross-section is of great importance because it represents a bottleneck for the s-process nucleosynthesis and determines to a large extent the cerium abundance in stars. The measurement was motivated by the significant difference between the cerium abundance measured in globular clusters and the value predicted by theoretical stellar models. This discrepancy can be ascribed to an overestimation of the Ce-140 capture cross-section due to a lack of accurate nuclear data. For this measurement, we used a sample of cerium oxide enriched in Ce-140 to 99.4%. The experimental apparatus consisted of four deuterated benzene liquid scintillator detectors, which allowed us to overcome the difficulties present in the previous measurements, thanks to their very low neutron sensitivity. The accurate analysis of the p-wave resonances and the calculation of their average parameters are fundamental to improve the evaluation of the Ce-140 Maxwellian-averaged cross-section.
|
|
|
|
Agramunt, J. et al, Algora, A., Domingo-Pardo, C., Jordan, D., Rubio, B., Tain, J. L., et al. (2014). New Beta-delayed Neutron Measurements in the Light-mass Fission Group. Nucl. Data Sheets, 120, 74–77.
Abstract: A new accurate determination of beta-delayed neutron emission probabilities from nuclei in the low mass region of the light fission group has been performed. The measurements were carried out using the BELEN 4 pi neutron counter at the IGISOL-JYFL mass separator in combination with a Penning trap. The new results significantly improve the uncertainties of neutron emission probabilities for Br-91, As-86, As-85, and Ge-85 nuclei.
|
|
|
|
Martinez, T. et al, Agramunt, J., Algora, A., Domingo-Pardo, C., Jordan, M. D., Rubio, B., et al. (2014). MONSTER: a TOF Spectrometer for beta-delayed Neutron Spectroscopy. Nucl. Data Sheets, 120, 78–80.
Abstract: beta-delayed neutron (DN) data, including emission probabilities, P-n, and energy spectrum, play an important role in our understanding of nuclear structure, nuclear astrophysics and nuclear technologies. A MOdular Neutron time-of-flight SpectromeTER (MONSTER) is being built for the measurement of the neutron energy spectra and branching ratios. The TOF spectrometer will consist of one hundred liquid scintillator cells covering a significant solid angle. The MONSTER design has been optimized by using Monte Carlo (MC) techniques. The response function of the MONSTER cell has been characterized with mono-energetic neutron beams and compared to dedicated MC simulations.
|
|
|
|
Caballero-Folch, R. et al, Domingo-Pardo, C., Tain, J. L., Agramunt, J., Algora, A., & Rubio, B. (2014). beta-decay and beta-delayed Neutron Emission Measurements at GSI-FRS Beyond N=126, for r-process Nucleosynthesis. Nucl. Data Sheets, 120, 81–83.
Abstract: New measurements of very exotic nuclei in the neutron-rich region beyond N=126 have been performed at the GSI facility with the fragment separator (FRS). The aim of the experiment is to determine half-lives and beta-delayed neutron emission branching ratios of isotopes of Hg, Tl and Pb in this region. This contribution summarizes final counting statistics for identification and for implantation, as well as the present status of the data analysis of the half-lives. In summary, isotopes of Pt, Au, Hg, Ti, Pb, Bi, Po, At, Rn and Fr were clearly identified and several of them (Hg208-211, Tl211-215, Pb214-218) were implanted with enough statistics to determine their half-lives. About half of them are expected to be neutron emitters, in such cases it will become possible to obtain the neutron emission probabilities, P-n.
|
|
|
|
n_TOF Collaboration(Lederer, C. et al), Giubrone, G., Domingo-Pardo, C., & Tain, J. L. (2014). Neutron Capture Reactions on Fe and Ni Isotopes for the Astrophysical s-process. Nucl. Data Sheets, 120, 201–204.
Abstract: Neutron capture cross sections in the keV neutron energy region are the key nuclear physics input to study the astrophysical slow neutron capture process. In the past years, a series of neutron capture cross section measurements has been performed at the neutron time-of-flight facility n_TOF at CERN focussing on the Fe/Ni mass region. Recent results and future developments in the neutron time-of-flight technique are discussed.
|
|
|
|
n_TOF Collaboration(Weiss, C. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2014). The (n,alpha) Reaction in the s-process Branching Point Ni-59. Nucl. Data Sheets, 120, 208–210.
Abstract: The (n,alpha) reaction in the radioactive Ni-59 is of relevance in nuclear astrophysics as Ni-59 can be considered as the first branching point in the astrophysical s-process. Its relevance in nuclear technology is especially related to material embrittlement in stainless steel. However, there is a discrepancy between available experimental data and the evaluated nuclear data files for this reaction. At the n_TOF facility at CERN, a dedicated system based on sCVD diamond diodes was set up to measure the Ni-59(n,alpha)Fe-56 cross section. The results of this measurement, with special emphasis on the dominant resonance at 203 eV, are presented here.
|
|
|
|
n_TOF Collaboration(Lederer, C. et al), Domingo-Pardo, C., & Tain, J. L. (2011). Au-197(n,gamma) cross section in the unresolved resonance region. Phys. Rev. C, 83(3), 034608–11pp.
Abstract: The cross section of the reaction Au-197(n,gamma) was measured with the time-of-flight technique at the n_TOF (neutron time-of-flight) facility in the unresolved resonance region between 5 and 400 keV using a pair of C6D6 (where D denotes H-2) liquid scintillators for the detection of prompt capture gamma rays. The results with a total uncertainty of 3.9%-6.7% for a resolution of 20 bins per energy decade show fair agreement with the Evaluated Nuclear Data File Version B-VII.0 (ENDF/B-VII.0), which contains the standard evaluation. The Maxwellian-averaged cross section (MACS) at 30 keV is in excellent agreement with the one according to the ENDF/B-VII.0 evaluation and 4.7% higher than the MACS measured independently by activation technique. Structures in the cross section, which had also been reported earlier, have been interpreted as being due to clusters of resonances.
|
|
|
|
n_TOF Collaboration(Paradela, C. et al), Domingo-Pardo, C., & Tain, J. L. (2010). Neutron-induced fission cross section of U-234 and Np-237 measured at the CERN Neutron Time-of-Flight (n_TOF) facility. Phys. Rev. C, 82(3), 034601–11pp.
Abstract: A high-resolution measurement of the neutron-induced fission cross section of U-234 and Np-237 has been performed at the CERN Neutron Time-of-Flight facility. The cross sections have been determined in a wide energy range from 1 eV to 1 GeV using the evaluated U-235 cross section as reference. In these measurements the energy determination for the U-234 resonances could be improved, whereas previous discrepancies for the Np-237 resonances were confirmed. New cross-section data are provided for high neutron energies that go beyond the limits of prior evaluations, obtaining important differences in the case of Np-237.
|
|
|
|
n_TOF Collaboration(Tarrio D. et al.), Domingo-Pardo, C., & Tain, J. L. (2011). Neutron-induced fission cross section of Pb-nat and Bi-209 from threshold to 1 GeV: An improved parametrization. Phys. Rev. C, 83(4), 044620–9pp.
Abstract: Neutron-induced fission cross sections for Pb-nat and Bi-209 were measured with a white-spectrum neutron source at the CERN Neutron Time-of-Flight (n_TOF) facility. The experiment, using neutrons from threshold up to 1 GeV, provides the first results for these nuclei above 200 MeV. The cross sections were measured relative to U-235 and U-238 in a dedicated fission chamber with parallel plate avalanche counter detectors. Results are compared with previous experimental data. Upgraded parametrizations of the cross sections are presented, from threshold energy up to 1 GeV. The proposed new sets of fitting parameters improve former results along the whole energy range.
|
|
