| Records |
| Author |
n_TOF Collaboration (Moreno-Soto, J. et al); Babiano-Suarez, V.; Caballero-Ontanaya, L.; Domingo-Pardo, C.; Ladarescu, I.; Tain, J.L. |
| Title |
Constraints on the dipole photon strength for the odd uranium isotopes |
Type |
Journal Article |
| Year |
2022 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
| Volume |
105 |
Issue |
2 |
Pages  |
024618 - 14pp |
| Keywords |
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| Abstract |
Background: The photon strength functions (PSFs) and nuclear level density (NLD) are key ingredients for calculation of the photon interaction with nuclei, in particular the reaction cross sections. These cross sections are important especially in nuclear astrophysics and in the development of advanced nuclear technologies. Purpose: The role of the scissors mode in the M1 PSF of (well-deformed) actinides was investigated by several experimental techniques. The analyses of different experiments result in significant differences, especially on the strength of the mode. The shape of the low-energy tail of the giant electric dipole resonance is uncertain as well. In particular, some works proposed a presence of the E1 pygmy resonance just above 7 MeV. Because of these inconsistencies additional information on PSFs in this region is of great interest. Methods: The gamma-ray spectra from neutron-capture reactions on the U-234, U-236, and U-238 nuclei have been measured with the total absorption calorimeter of the n_TOF facility at CERN. The background-corrected sum-energy and multi-step-cascade spectra were extracted for several isolated s-wave resonances up to about 140 eV. Results: The experimental spectra were compared to statistical model predictions coming from a large selection of models of photon strength functions and nuclear level density. No combination of PSF and NLD models from literature is able to globally describe our spectra. After extensive search we were able to find model combinations with modified generalized Lorentzian (MGLO) E1 PSF, which match the experimental spectra as well as the total radiative widths. Conclusions: The constant temperature energy dependence is favored for a NLD. The tail of giant electric dipole resonance is well described by the MGLO model of the E1 PSF with no hint of pygmy resonance. The M1 PSF must contain a very strong, relatively wide, and likely double-resonance scissors mode. The mode is responsible for about a half of the total radiative width of neutron resonances and significantly affects the radiative cross section. |
| Address |
[Moreno-Soto, J.; Berthoumieux, E.; Dupont, E.; Gunsing, F.; Bacak, M.] Univ Paris Saclay, CEA Irfu, F-91191 Gif Sur Yvette, France, Email: jmoreno53@us.es; |
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Thesis |
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| Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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| Language |
English |
Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
2469-9985 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000810791100001 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
5278 |
| Permanent link to this record |
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| Author |
n_TOF Collaboration (Tagliente, G. et al); Domingo-Pardo, C.; Giubrone, G.; Tain, J.L.; Tarifeño-Saldivia, A. |
| Title |
Zr-92(n, gamma) and (n,tot) measurements at the GELINA and n_TOF facilities |
Type |
Journal Article |
| Year |
2022 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
| Volume |
105 |
Issue |
2 |
Pages |
025805 - 14pp |
| Keywords |
|
| Abstract |
Background: Stellar nucleosynthesis of elements heavier than iron is driven by neutron capture processes. Zr-92 is positioned at a strategic point along the slow nucleosynthesis path, given its proximity to the neutron magic number N = 50 and its position at the matching region between the weak and main slow processes. Purpose: In parallel with recent improved astronomical data, the extraction of accurate Maxwellian averaged cross sections (MACSs) derived from a more complete and accurate set of resonance parameters should allow for a better understanding of the stellar conditions at which nucleosynthesis takes place. Methods: Transmission and capture cross section measurements using enriched Zr-92 metallic samples were performed at the time-of flight facilities GELINA of JRC-Geel (BE) and nTOF of CERN (CH). The neutron beam passing through the samples was investigated in transmission measurements at GELINA using a Li-glass scintillator. The gamma rays emitted during the neutron capture reactions were detected by C6D6 detectors at both GELINA and nTOF. Results: Resonance parameters of individual resonances up to 81 keV were extracted from a combined resonance shape analysis of experimental transmissions and capture yields. For the majority of the resonances the parity was determined from an analysis of the transmission data obtained with different sample thicknesses. Average resonance parameters were calculated. Conclusions: Maxwellian averaged cross sections were extracted from resonances observed up to 81 keV. The MACS for kT = 30 keV is fully consistent with experimental data reported in the literature. The MACSs for kT less than or similar to 15 keV are in good agreement with those derived from the ENDF/B-VIII.0 library and recommended in the KADoNTS database. For kT higher than 30 keV differences are observed. A comparison with MACSs obtained with the cross sections recommended in the JEFF-3.3 and JENDL-4.0 libraries shows discrepancies even for kT less than or similar to 15 keV. |
| Address |
[Tagliente, G.; Barbagallo, M.; Colonna, N.; Mastromarco, M.; Variale, V.] Ist Nazl Fis Nucl, Sez Bari, Bari, Italy, Email: giuseppe.tagliente@ba.infn.it |
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Thesis |
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| Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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| Language |
English |
Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
2469-9985 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000766732800002 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
5163 |
| Permanent link to this record |
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| Author |
n_TOF Collaboration (Lederer, C. et al.); Giubrone, G.; Tain, J.L. |
| Title |
Ni-62(n,gamma) and Ni-63(n,gamma) cross sections measured at the n_TOF facility at CERN |
Type |
Journal Article |
| Year |
2014 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
| Volume |
89 |
Issue |
2 |
Pages |
025810 - 11pp |
| Keywords |
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| Abstract |
The cross section of the Ni-62(n,gamma) reaction was measured with the time-of-flight technique at the neutron time-of-flight facility nTOF at CERN. Capture kernels of 42 resonances were analyzed up to 200 keV neutron energy and Maxwellian averaged cross sections (MACS) from kT = 5-100 keV were calculated. With a total uncertainty of 4.5%, the stellar cross section is in excellent agreement with the the KADoNiS compilation at kT = 30 keV, while being systematically lower up to a factor of 1.6 at higher stellar temperatures. The cross section of the Ni-63(n,gamma) reaction was measured for the first time at nTOF. We determined unresolved cross sections from 10 to 270 keV with a systematic uncertainty of 17%. These results provide fundamental constraints on s-process production of heavier species, especially the production of Cu in massive stars, which serve as the dominant source of Cu in the solar system. |
| Address |
[Lederer, C.; Wallner, A.; Pavlik, A.] Univ Vienna, Fac Phys, A-1010 Vienna, Austria, Email: claudia.lederer@ph.ed.uk |
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Thesis |
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| Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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| Language |
English |
Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
0556-2813 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000332175500012 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
1717 |
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| Author |
Yokoyama, R. et al; Tain, J.L.; Algora, A.; Agramunt, J.; Domingo-Pardo, C.; Morales, A.I.; Rubio, B.; Tolosa-Delgado, A. |
| Title |
Strong one-neutron emission from two-neutron unbound states in beta decays of the r-process nuclei Ga-86,Ga-87 |
Type |
Journal Article |
| Year |
2019 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
| Volume |
100 |
Issue |
3 |
Pages |
031302 - 6pp |
| Keywords |
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| Abstract |
beta-delayed one-neutron and two-neutron branching ratios (P-1n and P-2n) have been measured in the decay of A = 84 to 87 Ga isotopes at the Radioactive-Isotope Beam Factory (RIBF) at the RIKEN Nishina Center using a high-efficiency array of He-3 neutron counters (BRIKEN). Two-neutron emission was observed in the decay of Ga-84,Ga-85,Ga-87 for the first time and the branching ratios were measured to be P-2n = 1.6(2)%, 1.3(2)%, and 10.2(28)(stat)(5)(sys)%, respectively. One-neutron branching ratio of Ga-87 (P-1n = 81(9)(stat)(8)(sys)%) and half-life of 29(4) ms were measured for the first time. The branching ratios of Ga-86 were also measured to be P-1n = 74(2)(stat)(8)(sys)% and 16.2(9)(stat)(6)(sys)% with better precision than a previous study. The observation that P-1n > P-2n for both Ga-86,Ga-87 was unexpected and is interpreted as a signature of dominating one-neutron emission from the two-neutron unbound excited states in Ge-86,Ge-87. In order to interpret the experimental results, shell-model and Hauser-Feshbach statistical model calculations of delayed particle and gamma-ray emission probabilities were performed. This model framework reproduces the experimental results. The shell model alone predicts P-2n significantly larger than P-1n for the Ga-87 decay, and it is necessary to invoke a statistical description to successfully explain the observation that P-1n > P-2n. Our new results demonstrate the relevance and importance of a statistical description of neutron emission for the prediction of the decay properties of multineutron emitters and that it must be included in the r-process modeling. |
| Address |
[Yokoyama, R.; Grzywacz, R.; Rasco, B. C.; Brewer, N.; Heideman, J.; King, T. T.; Madurga, M.; Singh, M.] Univ Tennessee, Dept Phys & Astron, Knoxville, TN 37996 USA, Email: ryokoyam@utk.edu |
| Corporate Author |
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Thesis |
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| Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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| Language |
English |
Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
2469-9985 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000486641000001 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
4145 |
| Permanent link to this record |
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| Author |
n_TOF Collaboration (Lederer-Woods, C. et al.); Domingo-Pardo, C.; Tain, J.L. |
| Title |
Destruction of the cosmic gamma-ray emitter Al-26 in massive stars: Study of the key Al-26(n, alpha) reaction |
Type |
Journal Article |
| Year |
2021 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
| Volume |
104 |
Issue |
3 |
Pages |
L032803 - 6pp |
| Keywords |
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| Abstract |
Neutron destruction reactions of the cosmic gamma-ray emitter Al-26 are of importance to determine the amount of Al-26 ejected into our galaxy by supernova explosions and for Al-26 production in asymptotic giant branch stars. We performed a new measurement of the Al-26(n, alpha) reaction up to 160-keV neutron energy at the neutron time-of-flight facilities n_TOF at CERN and GELINA at EC-JRC. We provide strengths for ten resonances, six of them for the first time. We use our data to calculate astrophysical reactivities for stellar temperatures up to 0.7 GK. Our results resolve a discrepancy between the two previous direct measurements of this reaction, and indicate higher stellar destruction rates than the most recently recommended reactivity. |
| Address |
[Lederer-Woods, C.; Woods, P. J.; Davinson, T.; Estrade, A.; Kahl, D.; Lonsdale, S. J.] Univ Edinburgh, Sch Phys & Astron, Peter Guthrie Tait Rd, Edinburgh EH9 3FD, Midlothian, Scotland, Email: claudia.lederer-woods@ed.ac.uk |
| Corporate Author |
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Thesis |
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| Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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| Language |
English |
Summary Language |
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Original Title |
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| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
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Series Issue |
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Edition |
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| ISSN |
2469-9985 |
ISBN |
|
Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000704560300002 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
4988 |
| Permanent link to this record |
