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Title: Measurement of the {sup 151}Sm(n,{gamma}) cross section from 0.6 eV to 1 MeV via the neutron time-of-flight technique at the CERN n{sub T}OF facility

Abstract

The {sup 151}Sm(n,{gamma}) cross section was measured with the time-of-flight technique from 0.6 eV up to 1 MeV relative to the Au standard with an overall uncertainty of typically 6%. Neutrons were produced by spallation at the innovative n{sub T}OF facility at CERN; the {gamma} rays from capture events were detected with organic C{sub 6}D{sub 6} scintillators. Experimental setup and data analysis procedures are described with emphasis on the corrections for detection efficiency, background subtraction, and neutron flux determination. At low energies, resonances could be resolved up to about 1 keV, yielding a resonance integral of 3575{+-}210 b, an average s-wave resonance spacing of <D{sub 0}>=1.49{+-}0.07 eV, and a neutron strength function of <S{sub 0}>=(3.87{+-}0.33)x10{sup -4}. Maxwellian-averaged capture cross sections are reported for thermal energies between 5 and 100 keV. These results are of relevance for nuclear structure studies, nuclear astrophysics, and nuclear technology. The new value of the Maxwellian-averaged cross section at kT=30 keV is 3.08{+-}0.15 b, considerably larger than previous theoretical estimates, and provides better constraints for the thermodynamic conditions during the occurrence of the slow neutron capture process in low-mass stars during their asymptotic giant branch phase.

Authors:
; ; ;  [1]; ; ; ;  [2]; ; ; ; ; ; ;  [3]; ; ; ; ;  [4]
  1. Dipartimento di Fisica and INFN Bari (Italy)
  2. Instituto Nazionale di Fisica Nucleare Sezione di Trieste (Italy)
  3. CEA/Saclay-DSM/DAPNIA/SPhN, Gif-sur-Yvette (France)
  4. Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, Madrid (Spain) (and others)
Publication Date:
OSTI Identifier:
20771351
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 73; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevC.73.034604; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CAPTURE; CERN; CORRECTIONS; CROSS SECTIONS; EFFICIENCY; EV RANGE; GAMMA RADIATION; KEV RANGE; MEV RANGE; NEUTRON FLUX; NEUTRON REACTIONS; NUCLEAR STRUCTURE; RESONANCE; S WAVES; SAMARIUM 151; SLOW NEUTRONS; SPALLATION; STRENGTH FUNCTIONS; TIME-OF-FLIGHT METHOD

Citation Formats

Marrone, S., Colonna, N., Tagliente, G., Terlizzi, R., Abbondanno, U., Fujii, K., Milazzo, P. M., Moreau, C., Aerts, G., Andriamonje, S., Berthomieux, E., Gunsing, F., Pancin, J., Perrot, L., Plukis, A., Alvarez-Velarde, F., Cano-Ott, D., Embid-Segura, M., Gonzalez-Romero, E., and Villamarin-Fernandez, D. Measurement of the {sup 151}Sm(n,{gamma}) cross section from 0.6 eV to 1 MeV via the neutron time-of-flight technique at the CERN n{sub T}OF facility. United States: N. p., 2006. Web. doi:10.1103/PhysRevC.73.034604.
Marrone, S., Colonna, N., Tagliente, G., Terlizzi, R., Abbondanno, U., Fujii, K., Milazzo, P. M., Moreau, C., Aerts, G., Andriamonje, S., Berthomieux, E., Gunsing, F., Pancin, J., Perrot, L., Plukis, A., Alvarez-Velarde, F., Cano-Ott, D., Embid-Segura, M., Gonzalez-Romero, E., & Villamarin-Fernandez, D. Measurement of the {sup 151}Sm(n,{gamma}) cross section from 0.6 eV to 1 MeV via the neutron time-of-flight technique at the CERN n{sub T}OF facility. United States. doi:10.1103/PhysRevC.73.034604.
Marrone, S., Colonna, N., Tagliente, G., Terlizzi, R., Abbondanno, U., Fujii, K., Milazzo, P. M., Moreau, C., Aerts, G., Andriamonje, S., Berthomieux, E., Gunsing, F., Pancin, J., Perrot, L., Plukis, A., Alvarez-Velarde, F., Cano-Ott, D., Embid-Segura, M., Gonzalez-Romero, E., and Villamarin-Fernandez, D. Wed . "Measurement of the {sup 151}Sm(n,{gamma}) cross section from 0.6 eV to 1 MeV via the neutron time-of-flight technique at the CERN n{sub T}OF facility". United States. doi:10.1103/PhysRevC.73.034604.
@article{osti_20771351,
title = {Measurement of the {sup 151}Sm(n,{gamma}) cross section from 0.6 eV to 1 MeV via the neutron time-of-flight technique at the CERN n{sub T}OF facility},
author = {Marrone, S. and Colonna, N. and Tagliente, G. and Terlizzi, R. and Abbondanno, U. and Fujii, K. and Milazzo, P. M. and Moreau, C. and Aerts, G. and Andriamonje, S. and Berthomieux, E. and Gunsing, F. and Pancin, J. and Perrot, L. and Plukis, A. and Alvarez-Velarde, F. and Cano-Ott, D. and Embid-Segura, M. and Gonzalez-Romero, E. and Villamarin-Fernandez, D.},
abstractNote = {The {sup 151}Sm(n,{gamma}) cross section was measured with the time-of-flight technique from 0.6 eV up to 1 MeV relative to the Au standard with an overall uncertainty of typically 6%. Neutrons were produced by spallation at the innovative n{sub T}OF facility at CERN; the {gamma} rays from capture events were detected with organic C{sub 6}D{sub 6} scintillators. Experimental setup and data analysis procedures are described with emphasis on the corrections for detection efficiency, background subtraction, and neutron flux determination. At low energies, resonances could be resolved up to about 1 keV, yielding a resonance integral of 3575{+-}210 b, an average s-wave resonance spacing of <D{sub 0}>=1.49{+-}0.07 eV, and a neutron strength function of <S{sub 0}>=(3.87{+-}0.33)x10{sup -4}. Maxwellian-averaged capture cross sections are reported for thermal energies between 5 and 100 keV. These results are of relevance for nuclear structure studies, nuclear astrophysics, and nuclear technology. The new value of the Maxwellian-averaged cross section at kT=30 keV is 3.08{+-}0.15 b, considerably larger than previous theoretical estimates, and provides better constraints for the thermodynamic conditions during the occurrence of the slow neutron capture process in low-mass stars during their asymptotic giant branch phase.},
doi = {10.1103/PhysRevC.73.034604},
journal = {Physical Review. C, Nuclear Physics},
number = 3,
volume = 73,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • The151Sm(n,?)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 (t1/2=93??yr) was determined to be 3100{+-}160??mb, significantly larger than theoretical predictions.
  • A high-resolution measurement of the neutron-induced fission cross section of {sup 234}U and {sup 237}Np 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 {sup 235}U cross section as reference. In these measurements the energy determination for the {sup 234}U resonances could be improved, whereas previous discrepancies for the {sup 237}Np 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 {sup 237}Np.
  • We have measured the neutron capture reaction yield of {sup 232}Th at the neutron time-of-flight facility n{sub T}OF at CERN in the energy range from 1 eV to 1 MeV. The average capture cross section has been extracted in the energy range from 4 keV up to 1 MeV with an overall accuracy better than 4%. An independent IAEA evaluation shows good agreement with the data. The average cross section has been expressed in terms of average resonance parameters using the partial waves l=0,1, and 2.
  • The {sup 233}U(n,f) cross section has been measured at the white neutron source n{sub T}OF in a wide energy range with a dedicated fission ionization chamber. We report here the results from {approx}30 meV to 1 MeV neutron energy. The {sup 233}U(n,f) cross section has been determined relative to a reference sample of {sup 235}U(n,f) measured simultaneously with the same detector. The very high instantaneous neutron flux and the intrinsically low background of the n{sub T}OF installation result in an accuracy around 3% in the whole energy range, while the energy resolution of the neutron beam allows for an accuratemore » description of the fission cross section by means of R-matrix analysis over a wide energy range. The results are, in general, in good agreement with the most recent high-accuracy measurement of this fission cross section, over the more limited range of the previous measurements, and indicated that even the latest evaluations underestimate the cross section in the epithermal region. The present high-quality data provide the basis for a more precise evaluation of the {sup 233}U fission cross section and for improving the reliability of databases needed for the design of new energy systems based on the Th/U cycle.« less
  • The precise determination of the neutron capture cross sections of {sup 186}Os and {sup 187}Os is important to define the s-process abundance of {sup 187}Os at the formation of the solar system. This quantity can be used to evaluate the radiogenic component of the abundance of {sup 187}Os due to the decay of the unstable {sup 187}Re (t{sub 1/2}=41.2 Gyr) and from this to infer the time duration of the nucleosynthesis in our galaxy (Re/Os cosmochronometer). The neutron capture cross sections of {sup 186}Os, {sup 187}Os, and {sup 188}Os have been measured at the CERN n{sub T}OF facility from 1more » eV to 1 MeV, covering the entire energy range of astrophysical interest. The measurement has been performed by time-of-flight technique using isotopically enriched samples and two C{sub 6}D{sub 6} scintillation detectors for recording the prompt gamma rays emitted in the capture events. Maxwellian averaged capture cross sections have been determined for thermal energies between kT=5 and 100 keV corresponding to all possible s-process scenarios. The estimated uncertainties for the values at 30 keV are 4.1, 3.3, and 4.7% for {sup 186}Os, {sup 187}Os, and {sup 188}Os, respectively.« less