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351. Measurement of neutron induced fission of 235U, 233U and 245Cm with the FIC detector at the CERN n_TOF facility

Author: Marco Calviani, Dimitrios Karadimos, U. Abbondanno, G. Aerts, H. Álvarez, F. Álvarez-Velarde, S. Andriamonje, J. Andrzejewski, P. Assimakopoulos, L. Audouin, G. Badurek, P. Baumann, F. Bečvář, E. Berthoumieux, F. Calviño, D. Cano-Ott, R. Capote, C. Carrapiço, P. Cennini, V. Chepel, E. Chiaveri, N. Colonna, G. Cortes, A. Couture, J. Cox, M. Dahlfors, S. David, I. Dillmann, C. Domingo-Pardo, W. Dridi, I. Duran, C. Eleftheriadis, M. Embid-Segura, L. Ferrant, A. Ferrari, R. Ferreira-Marques, K. Fujii, W. Furman, I. Goncalves, E. González-Romero, F. Gramegna, C. Guerrero, F. Gunsing, B. Haas, R. Haight, M. Heil, A. Herrera-Martinez, M. Igashira, E. Jericha, F. Käppeler, Y. Kadi, D. Karamanis, M. Kerveno, P. Koehler, E. Kossionides, M. Krtička, C. Lampoudis, H. Leeb, A. Lindote, I. Lopes, M. Lozano, S. Lukic, J. Marganiec, S. Marrone, T. Martínez, C. Massimi, P. Mastinu, A. Mengoni, P. M. Milazzo, C. Moreau, M. Mosconi, F. Neves, H. Oberhummer, S. O'Brien, J. Pancin, C. Papachristodoulou, C. Papadopoulos, C. Paradela, N. Patronis, A. Pavlik, P. Pavlopoulos, L. Perrot, M. T. Pigni, R. Plag, A. Plompen, A. Plukis, A. Poch, J. Praena, C. Pretel, J. Quesada, T. Rauscher, R. Reifarth, C. Rubbia, G. Rudolf, P. Rullhusen, J. Salgado, C. Santos, L. Sarchiapone, I. Savvidis, C. Stephan, G. Tagliente, J. L. Tain, L. Tassan-Got, L. Tavora, R. Terlizzi, G. Vannini, P. Vaz, A. Ventura, D. Villamarin, M. C. Vincente, V. Vlachoudis, R. Vlastou, F. Voss, S. Walter, M. Wiescher, K. Wisshak, Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, and Universitat Politècnica de Catalunya. GREENER - Grup de recerca d'estudis energètics i de les radiacions
Subjects: Physics, Física [Àrees temàtiques de la UPC], Physics::Instrumentation and Detectors, Fission, Nuclear Theory, Nuclear data, Nuclear energy, Neutron radiation, Residus radioactius, Nuclear physics, Nuclear wastes, Neutron flux, Ionization chamber, Neutron cross section, Energia nuclear, Neutron, Spallation, Nuclear Experiment
Abstract: A series of measurements of neutron induced fission cross section of various TRU isotopes have been performed at the CERN n TOF spallation neutron facility, in the energy range from thermal to nearly 250 MeV. The experimental apparatus consists in a fast ionization chamber (FIC), used as a fission fragment detector with a high efficiency. Good discrimination between alphas and fission fragments can be obtained with a simple amplitude threshold. In order to allow the monitoring of the neutron beam and to extract the n TOF neutron flux, the well known cross section of the 235U(n,f) reaction, considered as a fission standard, has been used. Preliminary results for the cross section are shown for some selected isotopes such as 235U, 233U and 245Cm in the energy range from 0.050 eV to about 2MeV.
Published: 2007
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352. New stellar (n,γ) cross sections and the 'Karlsruhe Astrophysical Database of Nucleosynthesis in Stars'

Author: Matthias Heil, Ralf Plag, Thomas Rauscher, C. Domingo-Pardo, Friedrich-Karl Thielemann, F. Käppeler, and I. Dillmann
Subjects: Nuclear physics, Physics, Stars, Isotopes of selenium, Database, Isotopes of palladium, Nucleosynthesis, Neutron cross section, Nuclear data, computer.software_genre, s-process, computer, p-process
Abstract: Since April 2005 a regularly updated stellar neutron cross section compilation is available online at http://nuclear-astrophysics.fzk.de/kadonis. This online-database is called the ``Karlsruhe Astrophysical Database of Nucleosynthesis in Stars`` project and is based on the previous Bao et al. compilation from the year 2000. The present version KADoNIS v0.2 (January 2007) includes recommended cross sections for 280 isotopes between H-1 and (210)po and 75 semi-empirical estimates for isotopes without experimental information. Concerning stellar (n,gamma) cross sections of the 32 stable, proton-rich isotopes produced by the p process experimental information is only available for 20 isotopes, but 9 of them have rather large uncertainties of
Published: 2007
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353. Measurement of the 209Bi(n,γ)210Big cross section and updated s-process analysis of the Pb/Bi region

Author: Anton Wallner, C. Domingo-Pardo, R. Gallino, F. Käppeler, Christof Vockenhuber, Sara Bisterzo, and M. Heil
Subjects: Nuclear physics, Chemistry, law, Metallicity, Neutron cross section, Van de Graaff generator, Nuclear data, Neutron, Ground state, s-process, law.invention, Accelerator mass spectrometry
Abstract: The neutron capture cross section of 209 Bi(n,γ) 210 Bi has been measured using the 3.7MV Van de Graaff accelerator at Forschungszentrum Karlsruhe. The measurement was carried out by activation of a high purity Bi sample in a quasi-stellar neutron spectrum with kT = 25keV by employing the 7 Li(p,n) 7 Be reaction at Ep = 1912keV. We performed four activations: two to count the α-activity of 210 Po and two more for Accelerator Mass Spectrometry (AMS) analysis at the VERA facility in Vienna. The aim of our study is to measure the partial cross sections to the ground and the isomeric state with improved accuracy, which is necessary to understand the recycling via α-decay of 210,211 Po and the corresponding accumulation of the s-process abundances at the end of the s-path. The Maxwellian averaged cross section for populating the ground state of 210 Bi at a thermal energy of kT = 30keV was determined to be � σv� /vT = 2.16 ± 0.07mb. For the isomeric state the measurements are in progress. Based on the present results and on the new data for the stable Pb isotopes measured at n TOF, we performed a theoretical analysis using stellar models of Asymptotic Giant Branch (AGB) stars. The effect of the new cross section values in the Pb/Bi region was studied by averaging the results of stellar models for M = 1. 5a nd 3Mand a half-solar metallicity for the main component, and at (Fe/H)= −1.3 for the strong component. At this lower metallicity the AGB stars have been shown to produce the maximum amount of s-process lead, thus providing a good approximation of the strong component. A study of these aspect is in preparation.
Published: 2007
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354. Inelastic neutron scattering cross section of 187Os at 30 keV

Author: R. Plag, Martin Heil, M. Mosconi, Alberto Mengoni, and F. Käppeler
Subjects: Nuclear reaction, Nuclear physics, Cross section (physics), Chemistry, Scattering, Astrophysics::High Energy Astrophysical Phenomena, Neutron cross section, Neutron, Neutron radiation, Atomic physics, Inelastic scattering, Inelastic neutron scattering
Abstract: The Re/Os cosmochronometer requires a precise determination of the neutron capture cross section of 187 Os at the stellar conditions of s-process nucleosynthesis, i.e., the effective stellar values for thermal energies between 8 and 25 keV. This implies a correction to the cross section measured in the laboratory, because at these temperatures most of the 187 Os nuclei are in the first exited state at 9.75 keV. In order to support the necessary Hauser- Feshbach calculations of the capture cross section for the excited states, it is important to consider the competition by the inelastic channels, including the so-called super-elastic scattering, where the neutron gains in energy. In this context, the inelastic scattering cross section of 187 Os has been measured using a pulsed neutron beam with an energy of 30 ± 9 keV (FWHM) and a repetition rate of 1 MHz. Neutrons were produced directly at the threshold of the 7 Li(p,n) 7 Be reaction in order to take advantage of the sharp collimation from reaction kinematics. To compensate for the low neutron yield close to threshold, scattered neutrons were recorded with three efficient 6 Li-glass scintillators 11 cm in diameter, located at 90 and 120 deg with respect to the neutron beam. Data have been taken with isotopically enriched 187 Os and 188 Os, the latter for measuring the elastic component separately. The analysis of the data was performed by a complete Monte Carlo simulation of the experiment. The results for the inelastic cross section are compared to previous data and are discussed with respect to the stellar (n,γ) rates, which are instrumental for an evaluation of the Re/Os cosmochronometer.
Published: 2007
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355. Neutron resonance spectroscopy at n TOF at CERN

Author: F. Gunsing, U. Abbondanno, G. Aerts, H. Álvarez, F. Álvarez-Velarde, S. Andriamonje, J. Andrzejewski, P. Assimakopoulos, L. Audouin, G. Badurek, P. Baumann, F. Bečvář, E. Berthoumieux, F. Calviño, M. Calviani, D. Cano-Ott, R. Capote, C. Carrapiço, P. Cennini, V. Chepel, E. Chiaveri, N. Colonna, G. Cortes, A. Couture, J. Cox, M. Dahlfors, S. David, I. Dillmann, C. Domingo-Pardo, W. Dridi, I. Duran, C. Eleftheriadis, M. Embid-Segura, L. Ferrant, A. Ferrari, R. Ferreira-Marques, K. Fujii, W. Furman, I. Goncalves, E. González-Romero, F. Gramegna, C. Guerrero, B. Haas, R. Haight, M. Heil, A. Herrera-Martinez, M. Igashira, E. Jericha, F. Käppeler, Y. Kadi, D. Karadimos, D. Karamanis, M. Kerveno, P. Koehler, E. Kossionides, M. Krtička, C. Lampoudis, H. Leeb, A. Lindote, I. Lopes, M. Lozano, S. Lukic, J. Marganiec, S. Marrone, T. Martínez, C. Massimi, P. Mastinu, A. Mengoni, P. M. Milazzo, C. Moreau, M. Mosconi, F. Neves, H. Oberhummer, S. O'Brien, J. Pancin, C. Papachristodoulou, C. Papadopoulos, C. Paradela, N. Patronis, A. Pavlik, P. Pavlopoulos, L. Perrot, M. T. Pigni, R. Plag, A. Plompen, A. Plukis, A. Poch, J. Praena, C. Pretel, J. Quesada, T. Rauscher, R. Reifarth, C. Rubbia, G. Rudolf, P. Rullhusen, J. Salgado, C. Santos, L. Sarchiapone, I. Savvidis, C. Stephan, G. Tagliente, J. L. Tain, L. Tassan-Got, L. Tavora, R. Terlizzi, G. Vannini, P. Vaz, A. Ventura, D. Villamarin, M. C. Vincente, V. Vlachoudis, R. Vlastou, F. Voss, S. Walter, M. Wiescher, K. Wisshak, Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, and Universitat Politècnica de Catalunya. GREENER - Grup de recerca d'estudis energètics i de les radiacions
Subjects: Physics, Large Hadron Collider, Astrophysics::High Energy Astrophysical Phenomena, Neutron stimulated emission computed tomography, Nuclear Theory, Nuclear structure, Nuclear data, Neutron scattering, Neutrons -- Seccions, Nuclear physics, Física::Astronomia i astrofísica [Àrees temàtiques de la UPC], Physics::Accelerator Physics, Neutron, Neutron resonance, Atomic physics, Spectroscopy, Nuclear Experiment, Excitation
Abstract: Neutron resonance spectroscopy plays an important role in the investigation of neutron induced reaction cross sections and nuclear structure in the MeV excitation range. Neutron time-of-flight facilities are the most used installations to explore neutron resonances. In this paper we describe the basic features of neutron resonance spectroscopy together with recent results from the time-of-flight facility n TOF at CERN.
Published: 2007

356. Half-life ofHf183

Author: F. Käppeler, Walter Kutschera, Christof Vockenhuber, I. Dillmann, Max Bichler, and Anton Wallner
Subjects: Nuclear physics, Physics, Nuclear and High Energy Physics, Double beta decay, Radiative capture, Analytical chemistry, Half-life, Decay curve, Radioactive decay
Abstract: Significant amounts of the neutron-rich isotope $^{183}\mathrm{Hf}$ have been produced by $(n,\ensuremath{\gamma})$ reaction on the long-lived $^{182}\mathrm{Hf}$ (${t}_{1/2}=8.9\ifmmode\times\else\texttimes\fi{}{10}^{6}$ y) during an irradiation with thermal neutrons. The half-life of $^{183}\mathrm{Hf}$ has been remeasured with high precision using the decay curve of its most abundant \ensuremath{\gamma} rays. The new half-life value is $1.018\ifmmode\pm\else\textpm\fi{}0.002$ h, which is 4.6% shorter and eight times more accurate than the previous recommended value.
Published: 2006
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357. Resonance capture cross section ofPb207

Author: M. Embid-Segura, E. Griesmayer, M. Kerveno, Manuel Lozano, Sara Bisterzo, P. Cennini, A. Herrera-Martinez, N. Patronis, S. Walter, P. M. Milazzo, G. Cortes, A. Pavlik, E. Jericha, B. Haas, G. Aerts, R. C. Haight, M. Mosconi, Alberto Mengoni, R. Gallino, C. Domingo-Pardo, S. David, G. Tagliente, C. Stephan, S. O'Brien, A. Goverdovski, F. Alvarez-Velarde, I. Goncalves, Michael Heil, M. Igashira, L. Audouin, R. Vlastou, Gerald Badurek, Roberto Capote, M. Oshima, P.A. Assimakopoulos, R. Terlizzi, Thomas Rauscher, I. Savvidis, R. Dolfini, J. Andrzejewski, F. Neves, Alfredo Ferrari, R. Ferreira-Marques, Rene Reifarth, C. Pretel, L. Tavora, Carlo Rubbia, G. Vannini, D. Karadimos, V. Vlachoudis, L. Perrot, J. Salgado, Michael Wiescher, E. Kossionides, H. Frais-Koelbl, P. Pavlopoulos, J. M. Quesada, A. Poch, P. Rullhusen, D. Villamarin, V. Konovalov, F. Käppeler, C. Lamboudis, J. L. Tain, V. Chepel, J. Pancin, V. Ketlerov, E. Gonzalez-Romero, C. Papachristodoulou, L. Sarchiapone, C. T. Papadopoulos, A. J. M. Plompen, K. Fujii, E. Berthoumieux, I. Duran, P. Baumann, E. Chiaveri, I. Dillman, D. Cano-Ott, W. Dridi, G. Rudolf, I. Lopes, M. C. Vincente, M. Rosetti, S. Marrone, C. Eleftheriadis, A. Plukis, Yacine Kadi, S. Isaev, U. Abbondanno, C. Moreau, P. E. Koehler, M. Dahlfors, P. Vaz, M. Krtička, Alberto Ventura, Aaron Couture, J. Marganiec, S. Andriamonje, P. F. Mastinu, L. Ferrant, L. Fitzpatrick, C. Carrapiço, J. Cox, Laurent Tassan-Got, D. Karamanis, F. Gramegna, W.I. Furman, A. Lindote, Carlos Guerrero, Heinz Oberhummer, Ralf Plag, F. Gunsing, F. Voss, F. Becvar, Nicola Colonna, K. Wisshak, H. Alvarez-Pol, H. Wendler, C. Paradela, F. Calviño, H. Leeb, and S. Lukic
Subjects: Physics, Nuclear and High Energy Physics, Astrophysics::High Energy Astrophysical Phenomena, 01 natural sciences, 7. Clean energy, Neutron temperature, Nuclear physics, Neutron capture, 13. Climate action, 0103 physical sciences, Neutron cross section, Radiative transfer, r-process, Neutron, Atomic physics, 010306 general physics, s-process, 010303 astronomy & astrophysics, Energy (signal processing)
Abstract: The radiative neutron capture cross section of {sup 207}Pb has been measured at the CERN neutron time of flight installation n{sub T}OF using the pulse height weighting technique in the resolved energy region. The measurement has been performed with an optimized setup of two C{sub 6}D{sub 6} scintillation detectors, which allowed us to reduce scattered neutron backgrounds down to a negligible level. Resonance parameters and radiative kernels have been determined for 16 resonances by means of an R-matrix analysis in the neutron energy range from 3 keV to 320 keV. Good agreement with previous measurements was found at low neutron energies, whereas substantial discrepancies appear beyond 45 keV. With the present results, we obtain an s-process contribution of 77{+-}8% to the solar abundance of {sup 207}Pb. This corresponds to an r-process component of 23{+-}8%, which is important for deriving the U/Th ages of metal poor halo stars.
Published: 2006
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358. The Weak sr(p)–Process in Massive Stars

Author: Alexander Heger, S. E. Woosley, F. Käppeler, R. Gallino, and Marco Pignatari
Subjects: Physics, Stars, Astrophysics, Neutron density, p-process
Published: 2006
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359. New measurement of neutron capture resonances inBi209

Author: S. David, A. Pavlik, G. Tagliente, C. Domingo-Pardo, M. Oshima, W.I. Furman, J. Andrzejewski, M. Rosetti, E. Gonzalez-Romero, Carlo Rubbia, A. Lindote, A. Plukis, A. J. M. Plompen, V. Vlachoudis, P. E. Koehler, V. Chepel, M. Dahlfors, P. Baumann, L. Perrot, D. Karamanis, G. Vannini, E. Kossionides, M. Krtička, M. C. Vincente, V. Konovalov, P. Vaz, L. Ferrant, F. Calviño, G. Rudolf, I. Lopes, A. Goverdovski, Alberto Ventura, Aaron Couture, L. Sarchiapone, P. Cennini, J. Salgado, F. Käppeler, L. Fitzpatrick, M. Embid-Segura, A. Poch, V. Ketlerov, Ralf Plag, C. Moreau, E. Jericha, G. Aerts, F. Gramegna, C. Papachristodoulou, Alfredo Ferrari, R. Ferreira-Marques, I. Duran, A. Herrera-Martinez, N. Patronis, R. Vlastou, J. Marganiec, Manuel Lozano, S. Andriamonje, F. Alvarez-Velarde, M. Mosconi, J. Pancin, E. Chiaveri, G. Cortes, H. Leeb, C. T. Papadopoulos, Carlos Guerrero, D. Cano-Ott, H. Frais-Koelbl, Heinz Oberhummer, R. C. Haight, S. Isaev, I. Goncalves, Alberto Mengoni, Thomas Rauscher, I. Dillman, P. F. Mastinu, C. Stephan, S. O'Brien, Roberto Capote, W. Dridi, P.A. Assimakopoulos, Gerald Badurek, R. Dolfini, U. Abbondanno, P. M. Milazzo, F. Gunsing, F. Neves, D. Karadimos, E. Griesmayer, M. Igashira, R. Terlizzi, C. Pretel, S. Marrone, L. Audouin, R. Gallino, L. Tavora, C. Paradela, J. Cox, Michael Heil, C. Lamboudis, J. L. Tain, E. Berthoumieux, K. Fujii, P. Rullhusen, Michael Wiescher, Laurent Tassan-Got, M. Kerveno, L. Marques, A. Carrillo de Albornoz, I. Savvidis, S. Lukic, S. Walter, C. Eleftheriadis, Yacine Kadi, D. Villamarin, K. Wisshak, H. Wendler, F. Voss, Nicola Colonna, H. Alvarez-Pol, Rene Reifarth, P. Pavlopoulos, J. M. Quesada, B. Haas, and F. Bečvář
Subjects: Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, 7. Clean energy, 01 natural sciences, Nuclear physics, Neutron capture, 13. Climate action, Nucleosynthesis, 0103 physical sciences, Neutron cross section, r-process, Spallation, Neutron, Alpha decay, Nuclear Experiment, s-process, 010303 astronomy & astrophysics
Abstract: The neutron capture cross section of Bi-209 has been measured at the CERN n_TOF facility by employing the pulse-height-weighting technique. Improvements over previous measurements are mainly because of an optimized detection system, which led to a practically negligible neutron sensitivity. Additional experimental sources of systematic error, such as the electronic threshold in the detectors, summing of gamma-rays, internal electron conversion, and the isomeric state in bismuth, have been taken into account. gamma-Ray absorption effects inside the sample have been corrected by employing a nonpolynomial weighting function. Because Bi-209 is the last stable isotope in the reaction path of the stellar s-process, the Maxwellian averaged capture cross section is important for the recycling of the reaction flow by alpha decays. In the relevant stellar range of thermal energies between kT=5 and 8 keV our new capture rate is about 16 presently accepted value used for nucleosynthesis calculations. At this low temperature an important part of the heavy Pb-Bi isotopes are supposed to be synthesized by the s-process in the He shells of low mass, thermally pulsing asymptotic giant branch stars. With the improved set of cross sections we obtain an s-process fraction of 19 +/- 3 residual of 81 +/- 3 is also of relevance for the design of accelerator driven systems based on a liquid metal Pb/Bi spallation target.
Published: 2006
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360. Neutron capture cross section ofTh232measured at the n_TOF facility at CERN in the unresolved resonance region up to 1 MeV

Author: Roberto Capote, P.A. Assimakopoulos, R. Vlastou, E. Berthoumieux, J. Marganiec, S. Andriamonje, E. Chiaveri, P. F. Mastinu, F. Gramegna, L. Tavora, L. Sarchiapone, M. Oshima, J. Andrzejewski, P. Pavlopoulos, A. J. M. Plompen, G. Aerts, C. T. Papadopoulos, V. Chepel, M. C. Vincente, Christoph A. Stephan, Carlo Rubbia, M. Embid-Segura, V. Vlachoudis, G. Rudolf, I. Lopes, E. Kossionides, S. David, Manuel Lozano, P. Baumann, G. Vannini, A. Herrera-Martinez, N. Patronis, D. Villamarin, F. Käppeler, C. Pretel, S. Isaev, P. Rullhusen, Marco T. Pigni, J. Pancin, G. Taliente, James L. Cox, A. Carrillo de Albornoz, Alberto Mengoni, L. Ferrant, L. Fitzpatrick, E. Gonzalez-Romero, I. Duran, Corrie S. Moreau, S. Walter, A. Plukis, K. Wisshak, H. Frais-Koelbl, I. Savvidis, J. Salgado, I. Dillman, E. Jericha, P. Cennini, L. Marques, A. Poch, Masayuki Igashira, Michael Heil, M. Krtička, K. Fujii, M. Mosconi, V. Ketlerov, H. Wendler, P. E. Koehler, L. Perrot, S. O'Brien, Ralf Plag, F. Neves, P. M. Milazzo, F. Gunsing, R. Ferreira-Marques, Alfredo Ferrari, R. Terlizzi, Yacine Kadi, E. Griesmayer, A. Lindote, R. C. Haight, D. Karamanis, A. Goverdovski, F. Alvarez-Velarde, F. Calviño, H. Leeb, Gerald Badurek, R. Dolfini, M. Rosetti, L. Audouin, W.I. Furman, C. Eleftheriadis, D. Cano-Ott, Thomas Rauscher, D. Karadimos, C. A. Papachristodoulou, Michael Wiescher, Carlos Guerrero, U. Abbondanno, Heinz Oberhummer, V. Konovalov, C. Paradela, S. Lukic, F. Voss, F. Becvar, Nicola Colonna, Rene Reifarth, J. M. Quesada, L. Tassan-Got, B. Haas, W. Dridi, M. Dahlfors, P. Vaz, Isabel S. Gonçalves, Alberto Ventura, Aaron Couture, A. Pavlik, S. Marrone, C. Domingo-Pardo, M. Kerveno, H. Álvarez, C. Lamboudis, J. L. Tain, and G. Cortes
Subjects: Physics, Nuclear and High Energy Physics, Range (particle radiation), Large Hadron Collider, 010308 nuclear & particles physics, 7. Clean energy, 01 natural sciences, Resonance (particle physics), Nuclear physics, Cross section (physics), Neutron capture, 0103 physical sciences, Neutron cross section, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Isotopes of thorium
Abstract: We have measured the neutron capture reaction yield of Th-232 at the neutron time-of-flight facility n_TOF 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 data. The average cross section has been expressed in terms of average resonance parameters using the partial waves l=0,1, and 2.
Published: 2006
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361. Low-lyingE1,M1, andE2strength distributions inXe124,126,128,129,130,131,132,134,136: Systematic photon scattering experiments in the mass region of a nuclear shape or phase transition

Author: G. Friessner, Gencho Rusev, C. Scholl, Christoph Kohstall, Norbert Pietralla, Marcus Scheck, D. Mücher, K. Wisshak, U. Kneissl, P. von Brentano, Ronald Schwengner, H. H. Pitz, N. Hollmann, F. Stedile, J. Jolie, F. Käppeler, K. D. Schilling, H. von Garrel, V. Werner, L. Käubler, A. Linnemann, L. K. Kostov, Stephen D. Walter, and C. Fransen
Subjects: Physics, Nuclear and High Energy Physics, Phase transition, Resonance fluorescence, Critical point (thermodynamics), Branching fraction, Bremsstrahlung, Isotopes of xenon, Nuclear resonance fluorescence, Atomic physics, Radioactive decay
Abstract: Systematic nuclear resonance fluorescence (NRF) experiments on all nine stable (seven even-even and two odd-mass) Xe isotopes have been performed at the bremsstrahlung facility of the 4.3-MV Stuttgart Dynamitron accelerator. For the first time thin-walled, high-pressure gas targets (about 70 bar) with highly enriched target material were used in NRF experiments. Precise excitation energies, transition strengths, spins, and decay branching ratios were obtained for numerous states, most of them previously unknown. The systematics of the observed $E1$ two-phonon excitations (${2}^{+}\ensuremath{\bigotimes}{3}^{\ensuremath{-}}$) and $M1$ excitations to ${1}^{+}$ mixed-symmetry states in the even-even isotopes are discussed with respect to the new critical point symmetry E(5). The fragmentation of these fundamental dipole excitation modes in the odd-mass isotopes $^{129,131}\mathrm{Xe}$ is shown and discussed. In the even-even nuclei several low-lying $E2$ excitations were observed.
Published: 2006
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362. Fast neutron capture on the Hf isotopes: Cross sections, isomer production, and stellar aspects

Author: K. Wisshak, M. Krtička, F. Bečvář, Marco Pignatari, R. Gallino, L. Kazakov, F. Voss, and F. Käppeler
Subjects: Physics, Nuclear and High Energy Physics, education.field_of_study, Branching fraction, Isotopes of lithium, Population, Neutron, Production (computer science), Atomic physics, education, s-process, Energy (signal processing), Neutron temperature
Abstract: The ($n,\ensuremath{\gamma}$) cross sections of $^{176}\mathrm{Hf}$, $^{177}\mathrm{Hf}$, $^{178}\mathrm{Hf}$, $^{179}\mathrm{Hf}$, and $^{180}\mathrm{Hf}$ have been measured in the energy range from 3 to 225 keV relative to the gold standard. Neutrons were produced via the $^{7}\mathrm{Li}$($p,n$)$^{7}\mathrm{Be}$ reaction and capture events were registered with the Karlsruhe 4\ensuremath{\pi} barium fluoride detector. The overall uncertainties are between 0.9 and 2.6%, about 5 times smaller than in previous experiments. Partial cross sections to ground and isomeric states could be experimentally identified for neutron capture on $^{176,177,178,179}\mathrm{Hf}$, indicating a strong population of yet-unknown isomeric states in $^{177}\mathrm{Hf}$ and $^{180}\mathrm{Hf}$. This feature was confirmed by extensive GEANT simulations based on calculated capture cascades. The deduced Maxwellian-averaged ($n,\ensuremath{\gamma}$) cross sections for thermal energies between $\mathit{kT}=8$ and 100 keV contribute to the analysis of the s-process branchings at $A=176$ and $A=179/180$ and have significant consequences for the separation of the solar s- and r-process components.
Published: 2006
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363. Measurement of theSm151(n,γ) cross section from 0.6 eV to 1 MeV via the neutron time-of-flight technique at the CERN n_TOF facility

Author: J.C. Soares, J. Andrzejewski, L. Ferrant, Carlo Rubbia, A. Herrera-Martinez, V. Vlachoudis, P. E. Koehler, S. Isaev, J. Salgado, A. Poch, U. Abbondanno, B. Haas, P. Cennini, I. Goncalves, V. Chepel, E. Gonzalez-Romero, Alberto Mengoni, A. Molina-Coballes, V. Konovalov, Thomas Rauscher, M. Kritĉka, Yacine Kadi, J. Cox, Laurent Tassan-Got, M. Embid-Segura, A. Plukis, I. Duran-Escribano, E. Griesmayer, M. Kerveno, P. Baumann, R. C. Haight, M. Mosconi, D. Karadimos, F. Voss, D. Cortina, Manuel Lozano, Rene Reifarth, José M. Martínez-Val, G. Vannini, A.J.P.L. Policarpo, F. Bečvář, S. David, C. Stephan, S. O'Brien, P. Pavlopoulos, J. M. Quesada, P. M. Milazzo, G. Tagliente, W. Rapp, A. Pavlik, José Manuel Perlado, G. Aerts, Heinz Oberhummer, Michael Wiescher, R. Terlizzi, A. J. M. Plompen, G. Rudolf, V. Ketlerov, Nicola Colonna, L. Perrot, Saed Dababneh, J. Marganiec, C. Domingo-Pardo, E. Berthomieux, W.I. Furman, H. Alvarez-Pol, Subramanian Raman, A. Goverdovski, F. Alvarez-Velarde, S. Andriamonje, G. Cortes, L. Tavora, C. Pretel, Marco T. Pigni, Gerald Badurek, P. F. Mastinu, R. Dolfini, S. Marrone, A. Lindote, R. Gallino, P. Rullhusen, Marco Pignatari, M. Vincente-Vincente, Michael Heil, M. Rosetti, Roberto Capote, C. Lamboudis, J. L. Tain, Ralf Plag, J. Benlliure, K. Fujii, C. Moreau, E. Jericha, F. Neves, F. Calviño, H. Leeb, H. Frais-Koelbl, T. Papaevangelou, J. Pancin, D. Villamarin-Fernandez, E. Chiaveri, C. Paradela, S. Lukic, K. Wisshak, D. Cano-Ott, H. Wendler, F. Gunsing, M. Dahlfors, P. Vaz, Alberto Ventura, Aaron Couture, Alfredo Ferrari, R. Ferreira-Marques, F. Gramegna, F. Käppeler, and M.I. Lopes
Subjects: Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, Scintillator, 01 natural sciences, 7. Clean energy, Nuclear physics, 13. Climate action, Neutron flux, Nucleosynthesis, 0103 physical sciences, Neutron cross section, Nuclear astrophysics, Neutron, Spallation, Atomic physics, 010306 general physics, s-process
Abstract: The Sm151(n,γ) 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_TOF facility at CERN; the γ rays from capture events were detected with organic C6D6 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 D0 =1.49±0.07 eV, and a neutron strength function of S0 =(3.87±0.33) ×10-4. 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. © 2006 The American Physical Society.
Published: 2006
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364. Stellar neutron capture cross sections of the Lu isotopes

Author: F. Voss, L. Kazakov, K. Wisshak, and F. Käppeler
Subjects: Physics, Nuclear and High Energy Physics, Proton, Branching fraction, chemistry.chemical_element, Lutetium, law.invention, Nuclear physics, Neutron capture, chemistry, law, Van de Graaff generator, Neutron, Nuclear Experiment, s-process, Energy (signal processing)
Abstract: The neutron capture cross sections of $^{175}\mathrm{Lu}$ and $^{176}\mathrm{Lu}$ have been measured in the energy range 3--225 keV at the Karlsruhe 3.7 MV Van de Graaff accelerator. Neutrons were produced via the $^{7}\mathrm{Li}$($p,n$)$^{7}\mathrm{Be}$ reaction by bombarding metallic Li targets with a pulsed proton beam, and capture events were registered with the Karlsruhe 4\ensuremath{\pi} barium fluoride detector. The cross sections were determined relative to the gold standard using isotopically enriched as well as natural lutetium oxide samples. Overall uncertainties of \ensuremath{\sim}1% could be achieved in the final cross section ratios to the gold standard, about a factor of 5 smaller than in previous works. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT = 8 and 100 keV. These values are systematically larger by \ensuremath{\sim}7% than those reported in recent evaluations. These results are of crucial importance for the assessment of the s-process branchings at A = 175/176.
Published: 2006
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365. Stellar neutron capture cross section of the unstables-process branching pointSm151

Author: Alberto Mengoni, M. Krtička, Roberto Gallino, F. Voss, Subramanian Raman, F. Käppeler, and K. Wisshak
Subjects: Physics, Nuclear and High Energy Physics, Branching fraction, Barium fluoride, chemistry.chemical_element, Nuclear physics, Samarium, Neutron capture, chemistry.chemical_compound, chemistry, Excited state, Neutron cross section, Neutron, Atomic physics, s-process
Abstract: The neutron capture cross sections of the radioactive isotope $^{151}\mathrm{Sm}$ and of natural samarium have been measured in the energy range from 3 keV to 225 keV at the Karlsruhe 3.7 MV Van de Graaff accelerator. Neutrons were produced via the $^{7}\mathrm{Li}$($p,n$)$^{7}\mathrm{Be}$ reaction by bombarding metallic Li targets with a pulsed proton beam and capture events were registered with the Karlsruhe 4\ensuremath{\pi} Barium Fluoride Detector. The cross sections were determined relative to the gold standard using a 206 mg sample of samarium oxide with 90% enrichment in $^{151}\mathrm{Sm}$. Over most of the measured energy range uncertainties of ~2--3% could be achieved for the $^{151}\mathrm{Sm}$/$^{197}\mathrm{Au}$ ratio. Maxwellian averaged neutron capture cross sections of $^{151}\mathrm{Sm}$ were calculated for thermal energies between kT = 8 keV and 100 keV with due consideration of the stellar enhancement factor and were found to be systematically larger than all previous theoretical predictions used in the analysis of the s-process branching at $^{151}\mathrm{Sm}$. In the context of the branching analysis, an experimental determination of the stellar enhancement factor due to captures in thermally excited states is proposed, and the tentative determination of the p-process residual of $^{152}\mathrm{Gd}$ and a few other cases is discussed.
Published: 2006
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366. Experimental (n,γ) cross sections of thep-process nucleiSe74andSr84

Author: Matthias Heil, F. Käppeler, Friedrich-Karl Thielemann, Thomas Rauscher, and I. Dillmann
Subjects: Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, Stable isotope ratio, Gamma process, 7. Clean energy, 01 natural sciences, p-process, Nuclear physics, Nucleosynthesis, Photodisintegration, 0103 physical sciences, r-process, Neutron, Atomic physics, p-Nuclei, 010306 general physics
Abstract: The nucleosynthesis of elements beyond iron is dominated by the s and r processes. However, a small amount of stable isotopes on the proton-rich side cannot be made by neutron capture and are thought to be produced by photodisintegration reactions on existing seed nuclei in the so-called ``p process.'' So far most of the p-process reactions are not yet accessible by experimental techniques and have to be inferred from statistical Hauser-Feshbach model calculations. The parametrization of these models has to be constrained by measurements on stable proton-rich nuclei. A series of (n,\ensuremath{\gamma}) activation measurements, related by detailed balance to the respective photodisintegrations, were carried out at the Karlsruhe Van de Graaff accelerator using the $^{7}\mathrm{Li}$(p,n)$^{7}\mathrm{Be}$ source for simulating a Maxwellian neutron distribution of kT = 25 keV. First results for the experimental (n,\ensuremath{\gamma}) cross sections of the light p nuclei $^{74}\mathrm{Se}$ and $^{84}\mathrm{Sr}$ are reported. These experimental values were used for an extrapolation to the Maxwellian averaged cross section at 30 keV, $\ensuremath{\langle}\ensuremath{\sigma}\ensuremath{\rangle}{}_{30}$, yielding 271 \ifmmode\pm\else\textpm\fi{} 15 mb for $^{74}\mathrm{Se}$, and 300 \ifmmode\pm\else\textpm\fi{} 17 mb for the total capture cross section of $^{84}\mathrm{Sr}$. The partial cross section to the isomer in $^{85}\mathrm{Sr}$ was found to be 190 \ifmmode\pm\else\textpm\fi{} 10 mb.
Published: 2006
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367. Implications of $^{151}$Sm(n,$\gamma$) Cross Section at n_TOF

Author: S. Lukic, N. Colonna, C. T. Papadopoulos, K. Wisshak, C. Rubbia, Corrie S. Moreau, M. Embid-Segura, G. Aerts, Manuel Lozano, A. Plukis, M. Oshima, J. Andrzejewski, A. Carrillo de Albornoz, A. Ventura, Isabel S. Gonçalves, A. Pavlik, F. Voss, H. Wendler, C. Domingo-Pardo, J. Salgado, S. Marrone, A. Poch, P. Cennini, L. Sarchiapone, J. Marganiec, E. Kossionides, S. Andriamonje, I. Savvidis, M. Kerveno, S. Walter, M. Rosetti, C. Eleftheriadis, E. Chiaveri, Ralf Plag, B. Haas, P. F. Mastinu, V. Chepell, Vasilis Vlachoudis, E. Griesmayer, F. Gramegna, K. Fujii, A. Herrera-Martinez, M. Mosconi, V. Konovalov, F. Calviño, H. Leeb, Arnaud Ferrari, M. C. Vincente, A. Mengoni, S. O'Brien, F. Neves, Matthias Heil, J. Pancin, P. M. Milazzo, Leila Soares Marques, C. Stephan, F. Gunsing, R. Gallino, Carlos Guerrero, A. J. M. Plompen, M. Dahlfors, U. Abbondanno, V. Ketlerov, Heinz Oberhummer, Y. Kadi, R. Terlizzi, M. Krtička, W. Dridi, P. Vaz, F. Käppeler, S. David, P. Pavlopoulos, G. Tagliente, H. Frais‐Koelb, L. Tavora, S. Isaev, R. Ferreira-Marques, W.I. Furman, H. Álvarez, James L. Cox, Rene Reifarth, I. Duran, Aaron Couture, A. Goverdovski, F. Alvarez-Velarde, P. Rullhusen, C. Lamboudis, J. L. Tain, C. A. Papachristodoulou, C. Pretel, D. Cano-Ott, E. Jericha, Thomas Rauscher, Gerald Badurek, L. Ferrant, F. Bečvář, R. C. Haight, R. Dolfini, D. Karadimos, J. M. Quesada, L. Tassan-Got, R. Vlastou, C. Paradela, E. Berthoumieux, L. Fitzpatrick, L. Audouin, E. González-Romero, Michael Wiescher, D. Villamarin, A. Lindote, Masayuki Igashira, D. Karamanis, I. Dillmann, P. E. Koehler, N. Patronis, Isabel Lopes, L. Perrot, G. Rudolf, P. Baumann, G. Vannini, G. Cortes, Roberto Capote, P.A. Assimakopoulos, S.V. Harissopulos, P. Demetriou, E. Julin, Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Département Recherches Subatomiques (DRS-IPHC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), European Organization for Nuclear Research (CERN), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and nTOF
Subjects: Physics, Mass number, 020206 networking & telecommunications, 02 engineering and technology, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 25.40.Lw, 27.70.+q, 29.30.-h, Nuclear physics, astronomy, Cross section (physics), Neutron capture, Nucleosynthesis, 0202 electrical engineering, electronic engineering, information engineering, Neutron cross section, nuclei with mass number 150 to 189, 020201 artificial intelligence & image processing, Neutron, samarium, Spectroscopy, s-process, time of flight spectroscopy, neutron radiative capture
Abstract: International audience; The accurate knowledge of the $^{151}$Sm(n,$\gamma$) cross section has important implications for the nuclear technologies as well as for fundamental studies. Due to its radioactivity, the only experimental data available on $^{151}$Sm were derived from a transmission measurement. Nowadays thanks to the innovative features of neutron time-of-flight facility (n_TOF), it was possible to measure $^{151}$Sm(n,$\gamma$) cross section in a wide energy range and with good accuracy. We present, here, the main experimental results together with the implications concerning the nuclear astrophysical part.
Published: 2006
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368. Measurement of the resonance capture cross section of 204,206Pb and termination of the s-process

Author: M. Rosetti, M. Embid-Segura, R. Vlastou, A. Pavlik, R. Gallino, E. Berthoumieux, E. Griesmayer, C. Domingo-Pardo, G. Vannini, Manuel Lozano, L. Tavora, F. Käppeler, D. Karamanis, I. Dillmann, N. Patronis, H. Álvarez, M. Oshima, D. Cano-Ott, J. Andrzejewski, C. Lamboudis, J. L. Tain, I. Savvidis, A. Goverdovski, Thomas Rauscher, Carlos Guerrero, U. Abbondanno, K. Fujii, M. Dahlfors, E. Jericha, F. Gramegna, F. Alvarez-Velarde, V. Chepel, G. Rudolf, Matthias Heil, C. Eleftheriadis, P. Vaz, J. Pancin, Heinz Oberhummer, I. Duran, N. Colonna, P. Baumann, D. Karadimos, P. Rullhusen, F. Bečvář, Aaron Couture, Isabel Lopes, P. Pavlopoulos, S. David, G. Tagliente, M. C. Vincente, E. González-Romero, Corrie S. Moreau, M. Kerveno, S. Walter, A. Herrera-Martinez, Gerald Badurek, R. C. Haight, V. Konovalov, Arnaud Ferrari, J. Marganiec, R. Dolfini, H. Leeb, C. Paradela, L. Audouin, V. Ketlerov, Ralf Plag, L. Perrot, E. Kossionides, G. Aerts, A. Ventura, Y. Kadi, G. Cortes, A. J. M. Plompen, Michael Wiescher, P. E. Koehler, J. Salgado, A. Poch, A. Carrillo de Albornoz, L. Ferrant, H. Frais-Koelbl, S. Isaev, A. Plukis, P. Cennini, Masayuki Igashira, L. Fitzpatrick, K. Wisshak, W.I. Furman, James L. Cox, Alberto Mengoni, Rene Reifarth, D. Villamarin, C. Pretel, C. T. Papadopoulos, H. Wendler, F. Voss, M. Krtička, F. Calviño, Roberto Capote, M. Mosconi, C. Stephan, F. Gunsing, F. Neves, P.A. Assimakopoulos, P. M. Milazzo, J. M. Quesada, L. Marques, C. Rubbia, L. Sarchiapone, S. O'Brien, C. A. Papachristodoulou, L. Tassan-Got, Isabel S. Gonçalves, R. Ferreira-Marques, S. Marrone, R. Terlizzi, Vasilis Vlachoudis, B. Haas, S. Andriamonje, A. Lindote, E. Chiaveri, P. F. Mastinu, S. Lukic, and W. Dridi
Subjects: Nuclear physics, Physics, Neutron capture, Time of flight, Cross section (physics), Stellar nucleosynthesis, Nucleosynthesis, Nuclear cross section, Neutron, s-process
Abstract: The neutron capture cross sections of 204Pb and 206Pb have been measured at the CERN n_TOF installation using the time of flight method with the pulse height weighting technique. In a preliminary analysis of 204Pb we have determined by first time the capture cross sections for two strong s‐wave resonances below 2.5 keV, which seem to enhance the Maxwellian Averaged Cross Section at kT = 5 keV by about a factor of two with respect to the value assumed so far. In 206Pb we have determined capture cross sections for a large number (97) of resonances, which were not reported in the two previous capture measurements. We discuss preliminary implications of the new cross sections in the stellar nucleosynthesis of the Pb isotopes.
Published: 2006
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369. Neutron cross section measurements at n_TOF for ADS related estudies

Author: S. Walter, L. Ferrant, M Embid Segura, L itzpatrick, E. Jericha, A. J. M. Plompen, Ralf Plag, I. Duran, G. Rudolf, I. Lopes, D. Villamarin, W.I. Furman, James L. Cox, M. C. Vincente, Masayuki Igashira, A. Ventura, V. Chepel, C. A. Papachristodoulou, J. Salgado, S. Lukic, A. Poch, F. Neves, P. M. Milazzo, Christoph A. Stephan, A. Herrera-Martinez, N. Patronis, Arnaud Ferrari, R. C. Haight, V. Ketlerov, Alberto Mengoni, G. Vannini, C. Paradela, M Krti ka, Carlos Guerrero, B. Haas, L. Tavora, Heinz Oberhummer, S. Isaev, F. Voss, L. Audouin, M. Oshima, A. Carrillo de Albornoz, J. Andrzejewski, F. Gunsing, U. Abbondanno, Manuel Lozano, Nicola Colonna, Corrie S. Moreau, F Be vá, H. Álvarez, Cristian Massimi, Vasilis Vlachoudis, C. Pretel, M. Dahlfors, P. Pavlopoulos, C. Lamboudis, J. L. Tain, F. Gramegna, I. Savvidis, P. Vaz, H Frais-Kölbl, W. Dridi, N. Bustreo, G. Cortes, E. Griesmayer, P. Rullhusen, Rene Reifarth, L. Perrot, D. Cano-Ott, Aaron Couture, K. Wisshak, M Wiescherand, S. O`Brien, V. Konovalov, P. E. Koehler, Thomas Rauscher, P aumann, S. David, J. M. Quesada, C. T. Papadopoulos, L. Tassan-Got, J. Pancin, Roberto Capote, P.A. Assimakopoulos, C. Rubbia, D. Karadimos, G. Tagliente, Isabel S. Gonçalves, S. Marrone, A. Lindote, R. Vlastou, E. Berthoumieux, M. Kerveno, A. Pavlik, C. Domingo-Pardo, E. González-Romero, H. Wendler, A. Goverdovski, F. Alvarez-Velarde, Gerald Badurek, R. Dolfini, P. Cennini, K. Fujii, M. Rosetti, H. Leeb, M. Mosconi, R. Terlizzi, L. Marques, L. Sarchiapone, Matthias Heil, Y. Kadi, F. Käppeler, E. Kossionides, G. Aerts, R. Gallino, J. Marganiec, S. Andriamonje, E. Chiaveri, P. F. Mastinu, D. Karamanis, I. Dillmann, A. Plukis, F. Calviño, R. Ferreira-Marques, C. Eleftheriadis, Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, and Universitat Politècnica de Catalunya. GREENER - Grup de recerca d'estudis energètics i de les radiacions
Subjects: History, Astrofísica nuclear, Neutron cross sections, Nuclear transmutation, Nuclear engineering, Nuclear Theory, Nuclear physics, Neutrons -- Seccions, Education, Radiació ionitzant -- Mesures de seguretat, Radioactive wastes, Neutron cross section, Nuclear astrophysics, Neutron, Nuclear Experiment, Physics, Large Hadron Collider, Física [Àrees temàtiques de la UPC], Time-of-flight mass spectrometry, Radioactive waste, Neutron radiation, Waste disposal, Residus radioactius, Computer Science Applications, Shielding (Radiation), Physics::Accelerator Physics, Física nuclear, Nucleon
Abstract: A neutron Time-of-Flight facility (n_TOF) is available at CERN since 2001. The innovative features of the neutron beam, in particular the high instantaneous flux, the wide energy range, the high resolution and the low background, make this facility unique for measurements of neutron induced reactions relevant to the field of Emerging Nuclear Technologies, as well as to Nuclear Astrophysics and Fundamental Nuclear Physics. The scientific motivations that have led to the construction of this new facility are here presented. The main characteristics of the n_TOF neutron beam are described, together with the features of the experimental apparata used for cross-section measurements. The main results of the first measurement campaigns are presented. Preliminary results of capture cross-section measurements of minor actinides, important to ADS project for nuclear waste transmutation, are finally discussed.
Published: 2006

370. Measurement of 139La(n,γ) Cross Section

Author: C. T. Papadopoulos, Matthias Heil, A. Goverdovski, J. Pancin, D. Karamanis, I. Dillmann, J. Salgado, F. Alvarez-Velarde, V. Chepel, G. Rudolf, C. Rubbia, Isabel S. Gonçalves, S. Marrone, M. C. Vincente, M. Kerveno, A. Herrera-Martinez, N. Patronis, A. Poch, F. Calviño, H. Leeb, Rene Reifarth, Gerald Badurek, R. Dolfini, G. Cortes, H. Álvarez, C. Lamboudis, J. L. Tain, Arnaud Ferrari, Y. Kadi, M. Embid-Segura, P. Pavlopoulos, C. Stephan, F. Gunsing, P. Baumann, H. Frais-Koelbl, P. Cennini, M. Dahlfors, L. Marques, J. M. Quesada, P. Vaz, S. Isaev, L. Tassan-Got, R. Gallino, Manuel Lozano, J. Marganiec, Roberto Capote, P.A. Assimakopoulos, Corrie S. Moreau, I. Duran, Aaron Couture, M. Krtička, K. Wisshak, S. David, M. Mosconi, A. Lindote, M. Rosetti, I. Savvidis, L. Ferrant, G. Tagliente, E. Kossionides, C. Eleftheriadis, G. Vannini, F. Käppeler, B. Haas, H. Wendler, A. Pavlik, L. Fitzpatrick, S. O'Brien, M. Oshima, A. J. M. Plompen, R. Ferreira-Marques, C. Domingo-Pardo, L. Sarchiapone, R. Vlastou, E. Berthoumieux, R. C. Haight, D. Villamarin, J. Andrzejewski, R. Terlizzi, Isabel Lopes, C. Paradela, James L. Cox, S. Andriamonje, L. Perrot, L. Audouin, A. Mengoni, E. Chiaveri, P. E. Koehler, P. F. Mastinu, G. Aerts, Michael Wiescher, V. Ketlerov, C. Pretel, L. Tavora, N. Colonna, E. Griesmayer, A. Plukis, P. Rullhusen, Thomas Rauscher, F. Voss, Masayuki Igashira, K. Fujii, D. Cano-Ott, V. Konovalov, D. Karadimos, E. González-Romero, W. Dridi, Vasilis Vlachoudis, A. Ventura, F. Bečvář, S. Lukic, F. Gramegna, A. Carrillo de Albornoz, E. Jericha, W.I. Furman, F. Neves, P. M. Milazzo, C. A. Papachristodoulou, Carlos Guerrero, U. Abbondanno, Heinz Oberhummer, S. Walter, and Ralf Plag
Subjects: Physics, Nuclear physics, Neutron capture, Large Hadron Collider, Neutron cross section, Resonance, Neutron, Average level, s-process, R-matrix
Abstract: We measured the neutron capture cross section of 139La relative to 197Au in the energy range of 0.6 eV to 9 keV at n_TOF, the neutron time‐of‐flight facility at CERN. After a description of the experimental apparatus, we discuss data analysis procedures. The data were fitted using R‐matrix formalism to extract resonance parameters which, in turn, were used to calculate average level spacings D0 = 268 ± 22 eV and D1 < 250 eV, and neutron strength functions S0 = (0.79 ± 0.03)×10−4 and S1 = (0.73 ± 0.05)×10−4 for s‐ and p‐wave resonances. The data also were used to determine Maxwellian‐averaged neutron capture cross sections which, in turn, were used to calculate the 139La abundance synthesized in a stellar model of the main component of the s process.
Published: 2006
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371. Method for (n,γ) cross section measurements on unstable isotopes

Author: S. Walter, Ralf Plag, Michael Heil, Rene Reifarth, and F. Käppeler
Subjects: Nuclear physics, Physics, Nuclear reaction, Time of flight, Neutron flux, Neutron source, Neutron, s-process, Stellar evolution, Calorimeter
Abstract: Branching points in the s process provide information of the stellar interior and are considered as stringent tests of stellar models. Current measurements with the time of flight (TOF) technique are limited by the available neutron fluxes which require — even under ideal circumstances — sample masses of at least several milligram. For short lived nuclei, this would imply severe backgrounds due to the activity of the sample. We propose to increase the sensitivity of the TOF method such that target masses in the microgram region can be used. This is achieved by shortening the flight path down to a few centimeters, setting up the neutron production target inside a 4π BaF2 calorimeter. Some first results of background test measurements as well as of computer simulations with GEANT are shown.
Published: 2006
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372. Determination of the stellar (n,$\gamma$) cross section of $^{54}Fe$ with accelerator mass spectrometry

Author: L. Coquard, Klaus Knie, F. Käppeler, Anton Wallner, I. Dillmann, and W. Kutschera
Subjects: Nuclear physics, Physics, Cross section (physics), Astrophysics and Astronomy, Accelerator mass spectrometry
Published: 2006

373. Neutron capture in massive stars — the challenge of the weak s process

Author: F. Käppeler and Matthias Heil
Subjects: Physics, Astronomy, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Abundance of the chemical elements, Neutron capture, Stars, Neutron star, Nucleosynthesis, Astrophysics::Solar and Stellar Astrophysics, r-process, Halo, s-process, Astrophysics::Galaxy Astrophysics
Abstract: Neutron capture nucleosynthesis in massive stars has regained considerable interest for the analysis of abundance patterns in very early, metal‐poor halo stars as well as for a quantitative picture of galactic chemical evolution. This so‐called weak component, which is responsible for the s abundances between Fe and Y, turned out to be very sensitive to the stellar neutron capture cross sections of the isotopes in this mass region. However, these data are incomplete and exhibit large discrepancies between different experiments. New facilities and experimental techniques have to be invoked to meet these challenges.
Published: 2006
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374. Anomalous neutron radiative capture in 197Au revisited

Author: F. Voss, M. Krtička, I. Tomandl, Matthias Heil, Rene Reifarth, K. Wisshak, F. Käppeler, and F. Bečvář
Subjects: Nuclear physics, Physics, Neutron capture, Neutron cross section, Neutron source, r-process, Neutron, Nuclear drip line, Neutron scattering, Neutron temperature
Abstract: This work is focused on understanding the behavior of the photon strength function of 198Au using a novel approach based on studying γ cascades following the neutron capture in 197Au.
Published: 2006
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375. An independent measurement of the 12C(α, γ)16O cross section with the Karlsruhe 4π BaF2 detector

Author: F. Käppeler, K. Wisshak, R. Plag, and M. Heil
Subjects: Physics, Nuclear physics, Cross section (physics), Scintillation counter, Detector, Measuring instrument, Gamma ray, Beam (structure), Particle detector, Semiconductor detector
Abstract: Many measurements of the 12C(α, γ)16O cross section have been performed up to now but only a few could measure at energies as low as 1 MeV. All of these measurements at low energy have been carried out using Germanium detectors. The low gamma‐ray efficiency of these detectors was compensated by very intense beam currents, which may cause considerable uncertainties due to severe target degradation. A verification of these data with a completely different approach, which could reveal systematic uncertainties, was still missing.The realization of such an independent measurement was performed with the Karlsruhe 4π BaF2 array. Due to its high gamma‐ray efficiency the beam current could be substantially reduced thus minimizing the thermal load of the target and avoiding sputtering effects.
Published: 2006
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376. Present status of the KADoNiS database

Author: M. Heil, Thomas Rauscher, I. Dillmann, F. Käppeler, and Ralf Plag
Subjects: Physics, Astrophysics and Astronomy, Database, 010308 nuclear & particles physics, Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics, computer.software_genre, 01 natural sciences, Alpha (programming language), Nucleosynthesis, 0103 physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment, 010303 astronomy & astrophysics, computer
Abstract: The "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars" (KADoNiS) project is an online database for experimental cross sections relevant to the $s$ process and $p$ process. It is available under \http://nuclear-astrophysics.fzk.de/kadonis and consists of two parts. Part 1 is an updated sequel to the well-known Bao et al. compilations from 1987 and 2000, which is online since April 2005. An extension of this $s$-process database to $(n,p)$ and $(n,\alpha)$ cross sections at $kT$= 30 keV, as in the first version of the Bao compilation, is planned. The second part of KADoNiS is a $p$-process library, which includes all available experimental data from $(p,\gamma)$, $(p,n)$, $(\alpha,\gamma)$, $(\alpha,n)$, $(\alpha,\alpha)$, $(n,\alpha)$ and $(\gamma,n)$ reactions in or close to the respective Gamow window. Despite the great number of reactions required for a $p$-process reaction network, experimental data is still scarce and up to now restricted to stable targets. Given here is a short overview about the present status of the KADoNiS database., Comment: Proceedings "Nuclei in the Cosmos" NIC-IX, June 25-30 2006, CERN, Geneva/ Switzerland, published in "Proceedings of Science", PoS(NIC-IX)090
Published: 2006

377. Neutron Capture Cross Section Measurements at n_TOF of 237Np, 240Pu and 243Am for the Transmutation of Nuclear Waste

Author: D. Karamanis, N. Patronis, M. Krtička, F. Calviño, V. Ketlerov, G. Cortes, C. Eleftheriadis, Matthias Heil, J. Pancin, R. Ferreira-Marques, T. Martinez, R. Gallino, A. J. M. Plompen, G. Aerts, Rene Reifarth, P. Cennini, E. Kossionides, Masayuki Igashira, Y. Kadi, J. Salgado, A. Pavlik, N. Colonna, A. Poch, C. Domingo-Pardo, H. Frais-Koelbl, J. M. Quesada, L. Tassan-Got, Roberto Capote, P.A. Assimakopoulos, M. Mosconi, V. Chepel, G. Rudolf, H. Leeb, M. Rosetti, James L. Cox, M. Oshima, P. Pavlopoulos, B. Haas, S. O'Brien, R. C. Haight, J. Andrzejewski, A. Plukis, P. Baumann, C. Paradela, L. Audouin, R. Terlizzi, L. Sarchiapone, D. Cano-Ott, H. Álvarez, K. Wisshak, Isabel Lopes, G. Vannini, S. Andriamonje, L. Tavora, I. Duran, C. Lamboudis, J. L. Tain, Michael Wiescher, I. Dillman, Thomas Rauscher, W. Dridi, K. Fujii, V. Konovalov, L. Ferrant, S. David, A. Lindote, G. Tagliente, D. Karadimos, E. Chiaveri, P. F. Mastinu, M. Dahlfors, P. Rullhusen, P. Vaz, Carlos Guerrero, L. Fitzpatrick, L. Marques, U. Abbondanno, H. Wendler, E. González-Romero, M. Kerveno, Aaron Couture, J. Marganiec, C. Stephan, F. Gunsing, Heinz Oberhummer, D. Villamarin, Corrie S. Moreau, F. Käppeler, P. E. Koehler, L. Perrot, F. Bečvář, C. Pretel, Alberto Mengoni, C. T. Papadopoulos, W.I. Furman, A. Carrillo de Albornoz, M. Embid-Segura, C. Rubbia, Isabel S. Gonçalves, S. Marrone, A. Goverdovski, F. Alvarez-Velarde, C. A. Papachristodoulou, E. Griesmayer, Gerald Badurek, Manuel Lozano, S. Walter, E. Jericha, R. Dolfini, Ralf Plag, F. Neves, P. M. Milazzo, R. Vlastou, E. Berthoumieux, F. Gramegna, I. Savvidis, F. Voss, M. C. Vincente, Vasilis Vlachoudis, S. Lukic, A. Ventura, A. Herrera-Martinez, Arnaud Ferrari, S. Isaev, Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, and Universitat Politècnica de Catalunya. GREENER - Grup de recerca d'estudis energètics i de les radiacions
Subjects: Neutron capture, Nuclear transmutation, Chemistry, Nuclear engineering, Radioactive waste, Residus radioactius, Neutrons -- Seccions, Calorimeter, Nuclear wastes, Plutonium-240, Neutron flux, Física::Astronomia i astrofísica [Àrees temàtiques de la UPC], Neutron cross section, Física nuclear, Neutron
Abstract: Accurate and reliable neutron capture cross section data for actinides are necessary for the proper design, safety regulation and precise performance assessment of transmutation devices such as Fast Critical Reactors or Accelerator Driven Systems. In particular, the neutron capture cross sections of 237Np, 240Pu and 243Am play a key role in the design and optimization of strategies for the Transmutation of Nuclear Waste. The listed cross sections have been measured in 2004 at n_TOF [1] with a high accuracy due to a combination of features unique in the world: high instantaneous neutron fluence and excellent energy resolution of the n_TOF facility, innovative Data Acquisition System based on flash ADCs and the use of a high performance BaF2 Total Absorption Calorimeter as a detection device.
Published: 2006
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378. Activation Measurement of the $^{19}F(n,\gamma)^{20}F$ cross section

Author: Ethan Uberseder, Joachim Görres, F. Käppeler, Wiescher Michael, and Michael Heil
Subjects: Physics, Nuclear physics, Cross section (physics), Astrophysics and Astronomy
Published: 2006

379. Independent evidence for M1 scissors resonances built on the levels in the quasicontinuum of 163Dy

Author: F. Voss, Rene Reifarth, Matthias Heil, K. Wisshak, I. Tomandl, F. Käppeler, M. Krtička, and F. Bečvář
Subjects: Physics, Nuclear physics, Neutron capture, Astrophysics::High Energy Astrophysical Phenomena, Radiative capture, Thermal, Resonance, Multiplicity (mathematics), Neutron, Atomic physics, Neutron temperature, Spectral line
Abstract: The spectra of γ‐rays following the capture of neutrons in 162Dy at neutron energy region of 90–100 keV, where p‐wave neutron resonances dominate, were measured for individual γ multiplicities. These data support independently the main assessment from our previous study of the two‐step γ cascades, following the thermal s‐wave neutron capture in 162Dy, that the M1 scissors‐mode resonances are built on all levels of 163Dy, including the levels in the quasicontinuum.
Published: 2006
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380. Experimental studies of thermal effects during s-process nucleosynthesis

Author: F. Käppeler
Subjects: Physics, Nuclear physics, Nucleosynthesis, Excited state, Beta particle, Atomic physics, Ground state, s-process, Spectroscopy, Excitation, Radioactive decay
Abstract: Two recent experimental studies are reported which contribute to our understanding of the temperature during the s-process as well as to possible thermal effects on beta decay life-times. (i) The determination of the temperature characteristic for the weak s-process component depends critically on the beta decay half-life of the isomeric state in 79 Se. A first measurement of this half-life is presented and the implications for the s-process are discussed. (ii) In a second experiment we investigate the mechanism by which the ground state and the isomeric state in 176Lu might be thermally equilibrated. This problem is the key to a possible interpretation of 176Lu as a cosmic clock. As direct transitions between the long-lived ground state (t1/2= 3.6 1010 y) and the 3.7h isomer are strongly forbidden, equilibration may occur through thermally populated states at higher excitation. Branchings in the decay of these excited states to the ground state and to the isomer as well are searched for by high resolution gammaray spectroscopy at the ILL high flux reactor in Grenoble.
Published: 2005
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381. Measurements of neutron capture cross-sections at n_TOF

Author: H. Leeb, A. J. M. Plompen, A. Pavlik, C. Domingo-Pardo, K. Wisshak, F. Gunsing, H. Wendler, M. Embid-Segura, Cristian Massimi, D. Villamarin, G. Rudolf, I. Lopes, A. Goverdovski, P. Cennini, G. Vannini, F. Alvarez-Velarde, J. Marganiec, V. Ketlerov, W.I. Furman, D. Cortina, Manuel Lozano, S. Andriamonje, J. Salgado, A. Poch, Gerald Badurek, E. Berthoumieux, I. Duran, A. Lindote, R. Dolfini, M. Mosconi, F. Voss, P. F. Mastinu, G. Aerts, P. M. Milazzo, M. Dahlfors, Marco Pignatari, C. Stephan, S. O'Brien, F. Bečvář, P. Vaz, J. Cox, Rene Reifarth, R. Terlizzi, T. Papaevangelou, Alberto Ventura, Laurent Tassan-Got, C. Pretel, E. Griesmayer, Aaron Couture, M. Krtička, F. Calviño, L. Tavora, José M. Martínez-Val, H. Frais-Koelbl, Nicola Colonna, C. Lamboudis, J. L. Tain, S. David, Saed Dababneh, P. Pavlopoulos, H. Alvarez-Pol, I. Goncalves, G. Tagliente, L. Perrot, J. M. Quesada, Yacine Kadi, P. Rullhusen, P. E. Koehler, J. Pancin, Thomas Rauscher, M. C. Vincente, A. Herrera-Martinez, José Manuel Perlado, E. Gonzalez-Romero, J. Andrzejewski, R. Gallino, E. Chiaveri, J.C. Soares, Heinz Oberhummer, D. Cano-Ott, D. Karadimos, G. Cortes, F. Gramegna, A. Plukis, R. C. Haight, Carlo Rubbia, A.J.P.L. Policarpo, C. Paradela, E. Jericha, B. Haas, V. Vlachoudis, Alberto Mengoni, S. Lukic, A. Molina-Coballes, Michael Heil, S. Isaev, L. Ferrant, U. Abbondanno, Ralf Plag, J. Benlliure, V. Chepel, V. Konovalov, Roberto Capote, Michael Wiescher, F. Neves, S. Marrone, P. Baumann, M. Kerveno, F. Käppeler, Giuseppe Lorusso, Alfredo Ferrari, R. Ferreira-Marques, C. Moreau, W. Rapp, Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Département Recherches Subatomiques (DRS-IPHC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Pole Universitaire Leonard de Vinci, Pôle Universitaire Léonard de Vinci (PULV), A.J. Kreiner, O. Civitarese, C. Dorso, G. Garcia Bermudez, A.J. Pacheco, N.N. Scoccola, nTOF, and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 28.20.-v, 28.41.Rc, 28.41.Kw, 26.30.+k, neutron flux, Materials science, Large Hadron Collider, Nuclear transmutation, Astrophysics::High Energy Astrophysical Phenomena, nucleosynthesis, 020206 networking & telecommunications, 02 engineering and technology, radioactive waste disposal, radioactive waste processing, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, Nuclear physics, Neutron capture, Time of flight, Stellar nucleosynthesis, Nucleosynthesis, Neutron flux, 0202 electrical engineering, electronic engineering, information engineering, Physics::Accelerator Physics, 020201 artificial intelligence & image processing, Neutron, Nuclear Experiment
Abstract: International audience; Capture cross-sections on isotopes relevant to accelerator driven systems for energy production and nuclear waste transmutation, and to stellar nucleosynthesis have been studied at the innovative neutron time of flight facility n_TOF at CERN. The extremely high instantaneous neutron flux and the low background conditions in the experimental area make this facility unique for accurate measurements on low-mass or radioactive samples. The n_TOF facility is described, together with the features of the experimental apparata used. First results of the experimental campaign 2002-2004 are presented.
Published: 2005
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382. Measurement of $^{139}$La(n,$\gamma$) Cross Section at n_TOF

Author: M. Mosconi, S. O'Brien, F. Käppeler, R. Terlizzi, W.I. Furman, Carlos Guerrero, U. Abbondanno, Heinz Oberhummer, C. A. Papachristodoulou, L. Tavora, A. Herrera-Martinez, S. Walter, V. Chepel, Ralf Plag, M. Krtička, G. Vannini, P. Rullhusen, F. Gramegna, P. Vaz, I. Savvidis, G. Rudolf, Corrie S. Moreau, R. Ferreira-Marques, R. C. Haight, P. Baumann, M. Oshima, K. Fujii, J. Andrzejewski, C. Paradela, S. Andriamonje, L. Audouin, G. Aerts, S. David, E. Chiaveri, G. Tagliente, P. F. Mastinu, Michael Wiescher, C. Stephan, G. Cortes, Masayuki Igashira, E. Jericha, D. Cano-Ott, E. Griesmayer, F. Gunsing, N. Colonna, V. Konovalov, L. Perrot, Matthias Heil, J. Pancin, R. Vlastou, Roberto Capote, A. J. M. Plompen, P.A. Assimakopoulos, S. Lukic, A. Plukis, E. Berthoumieux, J. Salgado, A. Poch, A. Lindote, J. Marganiec, Y. Kadi, D. Karamanis, I. Dillmann, M. C. Vincente, H. Frais-Koelbl, F. Neves, N. Patronis, F. Voss, Isabel Lopes, I. Duran, P. M. Milazzo, James L. Cox, A. Goverdovski, Vasilis Vlachoudis, S. Isaev, L. Sarchiapone, F. Alvarez-Velarde, A. Carrillo de Albornoz, F. Bečvář, R. Gallino, A. Ferrari, M. Dalhfors, Gerald Badurek, K. Wisshak, R. Dolfini, C. Pretel, P. E. Koehler, H. Wendler, F. Calviño, H. Leeb, E. Kossionides, A. Ventura, P. Pavlopoulos, Rene Reifarth, L. Ferrant, H. Álvarez, Aaron Couture, L. Fitzpatrick, C. Lamboudis, J. L. Tain, A. Pavlik, D. Villamarin, C. Domingo-Pardo, J. M. Quesada, M. Embid-Segura, L. Tassan-Got, Manuel Lozano, C. T. Papadopoulos, C. Rubbia, B. Haas, Isabel S. Gonçalves, L. Marques, S. Marrone, M. Kerveno, W. Dridi, A. Mengoni, V. Ketlerov, C. Eleftheriadis, Thomas Rauscher, D. Karadimos, E. González-Romero, M. Rosetti, P. Cennini, Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Département Recherches Subatomiques (DRS-IPHC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), S.V. Harissopulos, P. Demetriou, E. Julin, and nTOF
Subjects: nuclei with mass number 90 to 149, lanthanum, Chemistry, Radiative capture, Analytical chemistry, Resonance, 020206 networking & telecommunications, 02 engineering and technology, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Abundance of the chemical elements, Cross section (physics), Neutron capture, 25.40.Lw, 29.30.-h, 0202 electrical engineering, electronic engineering, information engineering, 020201 artificial intelligence & image processing, Neutron, Spectroscopy, s-process, time of flight spectroscopy, neutron radiative capture
Abstract: International audience; The capture cross section of the 139La has been measured relative to 197Au standard at n_TOF. We provide here a short description of the experimental apparatus and of the data analysis procedures. The extracted resonance parameters allow to calculate the fundamental nuclear quantities such as average spacing $\langleD\rangle$ 1=0 = 268 ± 22 eV, $\langleD\rangle$ 1=1 < 250 eV neutron strength functions S0 = (0.79 ± 0.03)×10-4, and S1 = (0.73 ± 0.05)×10-4 and the Maxwellian-averaged capture cross section (MACS). The MACS is particularly useful for the determination of the abundance synthesized by the main component of the s process
Published: 2005
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383. Quasistellar spectrum for neutron activation measurements atkT=5keV

Author: Michael Heil, Rene Reifarth, Ralf Plag, Saed Dababneh, F. Käppeler, A. Juseviciute, and S. O'Brien
Subjects: Physics, Nuclear physics, Nuclear and High Energy Physics, Neutron capture, Neutron emission, Nucleosynthesis, Astrophysics::High Energy Astrophysical Phenomena, Spectrum (functional analysis), Neutron cross section, Neutron, Atomic physics, s-process, Energy (signal processing)
Abstract: We have measured the neutron energy spectrum of the $^{18}\mathrm{O}$($p,n$)$^{18}\mathrm{F}$ reaction at a proton energy of 2582 keV, 8 keV above the reaction threshold. At this energy the resulting neutron spectrum resembles almost perfectly a Maxwellian distribution at a thermal energy of $\mathrm{kT}=5.1\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$. Since all neutrons are emitted in a forward cone of 140${}^{\ensuremath{\circ}}$ opening angle, this reaction can be used for neutron activation measurements similar to the $^{7}\mathrm{Li}$(p,n)$^{7}\mathrm{Be}$ reaction, which is known for producing a thermal spectrum with $\mathrm{kT}=25\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$. Measured neutron capture cross sections at $\mathrm{kT}=5.1\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ and $\mathrm{kT}=25\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ can be used to interpolate to $\mathrm{kT}=8\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$, which characterizes the dominant neutron exposure during s-process nucleosynthesis in thermally pulsing low-mass AGB stars. In a first application of this new method the Maxwellian-averaged neutron capture cross section of $^{138}\mathrm{Ba}$ was measured to be $〈\ensuremath{\sigma}v〉/{v}_{T}=13.0\ifmmode\pm\else\textpm\fi{}0.5\phantom{\rule{0.3em}{0ex}}\mathrm{mb}$ at $\mathrm{kT}=5.1\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$.
Published: 2005
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384. High-Resolution Study of 237Np Fission Cross Section from 5 eV to 1 MeV

Author: M. Embid-Segura, L. Perrot, V. Ketlerov, G. Vannini, Ralf Plag, J. Benlliure, D. Cortina, Manuel Lozano, A. Goverdovski, F. Alvarez-Velarde, R. Vlastou, E. Jericha, Gerald Badurek, K. Wisshak, R. Gallino, E. Berthoumieux, L. Audouin, F. Voss, Masayuki Igashira, F. Becvar, H. Álvarez, Matthias Heil, R. Dolfini, C. Lamboudis, J. L. Tain, M. Kerveno, J. Pancin, M. Krtička, C. T. Papadopoulos, A. Mengoni, A. Herrera-Martinez, N. Patronis, Rene Reifarth, C. Rubbia, R. Ferreira-Marques, P. Pavlopoulos, Isabel S. Gonçalves, L. Tavora, S. Marrone, G. Aerts, Arnaud Ferrari, Y. Kadi, Vasilis Vlachoudis, G. Cortes, V. Chepel, G. Rudolf, H. Wendler, R. C. Haight, Carlos Guerrero, U. Abbondanno, A. J. M. Plompen, H. Frais-Koelbl, J. M. Quesada, P. E. Koehler, M. C. Vincente, N. Colonna, L. Tassan-Got, C. Paradela, E. Kossionides, P. Rullhusen, S. David, P. Baumann, C. Stephan, Heinz Oberhummer, Michael Wiescher, L. Marques, L. Ferrant, J. Marganiec, Roberto Capote, P. Vaz, P.A. Assimakopoulos, C. Pretel, F. Gunsing, A. Carrillo de Albornoz, L. Fitzpatrick, M. Sedysheva, D. Karamanis, S. Isaev, Isabel Lopes, P. Cennini, L. Sarchiapone, W.I. Furman, James L. Cox, S. Lukic, A. Lindote, G. Tagliente, Aaron Couture, F. Käppeler, A. Plukis, A. Ventura, E. Griesmayer, M. Mosconi, C. A. Papachristodoulou, A. Pavlik, D. Villamarin, D. Kolokolov, S. Andriamonje, M. Oshima, J. Andrzejewski, C. Domingo-Pardo, F. Gramegna, S. O'Brien, B. Haas, Corrie S. Moreau, R. Terlizzi, A. Dorochenko, D. Cano-Ott, E. Chiaveri, P. F. Mastinu, I. Duran, V. Konovalov, J. Salgado, M. Rosetti, A. Poch, W. Dridi, F. Neves, F. Calviño, H. Leeb, P. M. Milazzo, K. Fujii, Thomas Rauscher, D. Karadimos, E. González-Romero, Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches Subatomiques (IReS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), R.C. Haight, M.B. Chadwick, T. Kawano, P. Talou, nTOF, and Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear
Subjects: Physics, Nuclear reaction, Isotopes of uranium, Nuclear transmutation, 010308 nuclear & particles physics, Fission, Nuclear Theory, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 7. Clean energy, Neutron temperature, Nuclear physics, 0103 physical sciences, Uranium-235, Neutron cross section, 25.85.Ec, 27.90.+b, 25.40.Sc, Neutron, Nuclear Experiment, 010306 general physics
Abstract: PACS; International audience; A series of measurements of 237Np fission cross section have been performed at the CERN spallation neutron facility n_TOF which covers a wide energy range from 1 eV up to 250 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with registration efficiency of not less than 97 %. Particular attention was paid to correct the fission cross section with use of 235U standard. Total experimental uncertainties are determined to be at the level of 3%. Analysis of the experimental data in the restricted neutron energy from 5 eV up to 1 MeV showed a systematic deviation from evaluated data (ENDF/B-VI). This discrepancy amounts to up to a factor 3 for resolved resonances in the neutron energy range of 5 eV - 2 KeV, and is in good agreement with some previous experiments. A similar disagreement at the level of 6-7% was found for higher energies around the threshold (En = 300 keV-1 MeV). This energy range is essential for the transmutation of neptunium in ADS or fast reactors. It is concluded that an updated evaluation of nuclear data for 237Np is required
Published: 2005
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385. Stellar Neutron Capture on Neon Isotopes

Author: F. Käppeler, Ralf Plag, Alberto Mengoni, Matthias Heil, R. Gallino, and A. Juseviciute
Subjects: Physics, Red giant, chemistry.chemical_element, Abundance of the chemical elements, Neutron temperature, Nuclear physics, Neon, Neutron capture, chemistry, Isotopes of neon, Astrophysics::Solar and Stellar Astrophysics, Neutron, Astrophysics::Earth and Planetary Astrophysics, s-process, Astrophysics::Galaxy Astrophysics
Abstract: The stellar (n,γ) cross sections of the Ne isotopes are important for a number of astrophysical quests, i.e., for the interpretation of abundance patterns in presolar material or with respect to the s‐process neutron balance in red giant stars. This paper presents resonance studies of experimental data in the keV range, which had not been fully analyzed before. The analyses were carried out with the R‐matrix code SAMMY including the consistent treatment of possible interferences in the resonant part. With these results the resonant part of the neon cross sections could be determined. If the component due to direct radiative capture is normalized at thermal neutron energies, one finds that the stellar rates had been grossly overestimated.
Published: 2005
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386. Measurements at n_TOF of the neutron capture cross section of minor actinides relevant to the nuclear waste transmutation

Author: M. Oshima, J. Andrzejewski, M. Krtička, Alfredo Ferrari, F. Calviño, Carlo Rubbia, G. Aerts, V. Vlachoudis, Corrie S. Moreau, R. Ferreira-Marques, V. Chepel, G. Rudolf, S. Lukic, L. Tavora, K. Wisshak, A. Pavlik, C. Domingo-Pardo, V. Konovalov, J. Salgado, A. Poch, P. Baumann, P. Rullhusen, S. Andriamonje, G. Vannini, F. Voss, H. Wendler, Carlos Guerrero, E. Chiaveri, P. F. Mastinu, Isabel Lopes, A. J. M. Plompen, E. Jericha, A. Herrera-Martinez, N. Patronis, E. Griesmayer, Yacine Kadi, H. Leeb, R. C. Haight, N. Colonna, U. Abbondanno, Heinz Oberhummer, Alberto Mengoni, James L. Cox, R. Gallino, F. Gramegna, L. Perrot, C. Paradela, F. Bečvář, S. David, D. Karamanis, L. Audouin, T. Papaevangelou, G. Cortes, G. Tagliente, Ralf Plag, J. Benlliure, J. Pancin, A. Carillo de Albornoz, Michael Wiescher, Michael Heil, C. Stephan, F. Gunsing, Masayuki Igashira, D. Cano-Ott, F. Neves, P. M. Milazzo, A. Plukis, P. E. Koehler, Roberto Capote, H. Frais-Koelbl, W.I. Furman, P.A. Assimakopoulos, J. Marganiec, R. Vlastou, A. Goverdovski, I. Duran, Georgios Perdikakis, E. Kossionides, E. Berthoumieux, F. Alvarez-Velarde, M. C. Vincente, C. A. Papachristodoulou, L. Sarchiapone, Gerald Badurek, S. Isaev, R. Dolfini, P. Cennini, M. Mosconi, A. Lindote, S. O'Brien, R. Terlizzi, A. Ventura, P. Vaz, Aaron Couture, C. T. Papadopoulos, B. Haas, L. Ferrant, Isabel S. Gonçalves, S. Marrone, L. Fitzpatrick, H. Álvarez, C. Lamboudis, J. L. Tain, M. Embid-Segura, D. Villamarin, M. Kerveno, W. Dridi, D. Cortina, Manuel Lozano, Rene Reifarth, J. M. Quesada, L. Tassan-Got, P. Pavlopoulos, L. Marques, K. Fujii, M. Rosetti, C. Pretel, V. Ketlerov, Thomas Rauscher, D. Karadimos, E. González-Romero, F. Käppeler, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, European Commission 5th Framework Programme, Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches Subatomiques (IReS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and nTOF
Subjects: Materials science, Nuclear transmutation, 010308 nuclear & particles physics, Nuclear engineering, Radioactive waste, chemistry.chemical_element, Americium, 25.40.Lw, 28.20.-v, 28.41.Kw, 27.90.+b, 28.41.Ak, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 7. Clean energy, Calorimeter, Plutonium, chemistry, Neutron flux, 0103 physical sciences, Neutron cross section, Neutron, 010306 general physics
Abstract: Accurate and reliable neutron-capture cross-section data for actinides are necessary for the proper design, safety regulation, and precise performance assessment of transmutation devices such as Fast Critical Reactors or Accelerator Driven Systems. In particular, the neutron-capture cross sections of 237Np, 240Pu, and 243Am play a key role in the design and optimization of a strategy for the Nuclear Waste Transmutation. The listed cross sections have been measured in 2004 at n_TOF with a high accuracy due to a combination of features unique in the world: high instantaneous neutron fluence and excellent energy resolution of the n_TOF facility, innovative Data Acquisition System based on flash ADCs, and the use of a high-performance BaF2 Total Absorption Calorimeter as a detection device. European Commission 5th Framework Programme FIKW-CT-2000-00107
Published: 2005
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387. Neutron capture cross section measurements for nuclear astrophyisics at CERN n_TOF

Author: P. Cennini, W. Rapp, E. Griesmayer, J. Marganiec, G. Cortes, J. Salgado, V. Chepel, A. Poch, R. C. Haight, J. Andrzejewski, M. Mosconi, Carlo Rubbia, F. Gunsing, S. Andriamonje, C. Lamboudis, J. L. Tain, M. C. Vincente, V. Vlachoudis, A. Pavlik, M. Rosetti, C. Domingo-Pardo, I. Duran, C. Stephan, S. O'Brien, P. Baumann, Alfredo Ferrari, R. Ferreira-Marques, J. Cox, P. F. Mastinu, G. Aerts, Laurent Tassan-Got, J.C. Soares, C. Paradela, Michael Wiescher, H Frais-Kölbl, Marco Pignatari, R. Terlizzi, V. Konovalov, R. Gallino, D. Villamarin, I. Goncalves, M. Dahlfors, Roberto Capote, L. Ferrant, L. Tavora, S. Lukic, L. Perrot, P. Vaz, Alberto Ventura, Aaron Couture, Thomas Rauscher, F. Neves, P. Rullhusen, J. Pancin, S. Isaev, E. Chiaveri, D. Cano-Ott, U. Abbondanno, Rene Reifarth, G. Vannini, Michael Heil, M. Krtička, F. Calviño, T. Papaevangelou, D. Karadimos, P. M. Milazzo, C. Moreau, K. Wisshak, S. David, A.J.P.L. Policarpo, G. Tagliente, P. Pavlopoulos, Saed Dababneh, M. Embid-Segura, Yacine Kadi, J. M. Quesada, E. Jericha, A. Herrera-Martinez, P. E. Koehler, D. Cortina, Manuel Lozano, F. Voss, F. Käppeler, F. Becvar, G. Lorusso, E. Berthoumieux, Alberto Mengoni, B. Haas, E. Gonzalez-Romero, Nicola Colonna, C. Pretel, H. Alvarez-Pol, A. Plukis, V. Ketlerov, F. Gramegna, H. Wendler, Ralf Plag, J. Benlliure, A. Molina-Coballes, H. Leeb, A. J. M. Plompen, G. Rudolf, I. Lopes, W.I. Furman, A. Lindote, M. Kerveno, José M. Martínez-Val, José Manuel Perlado, Heinz Oberhummer, S. Marrone, A. Goverdovski, F. Alvarez-Velarde, Gerald Badurek, R. Dolfini, U. Abbondanno, G. Aert, F. Alvarez-Velarde, H. Alvarez-Pol, S. Andriamonje, J. Andrzejewski, G. Badurek, P. Baumann, F. Becvar, J. Benlliure, E. Berthoumieux, F. Calvino, D. Cano-Ott, R. Capote, P. Cennini, V. Chepel, E. Chiaveri, N. Colonna, G. Corte, D. Cortina, A. Couture, J. Cox, S. Dababneh, M. Dahlfor, S. David, R. Dolfini, C. Domingo-Pardo, I. Duran, M. Embid-Segura, L. Ferrant, A. Ferrari, R. Ferreira-Marque, H. Frais-Koelbl, W. Furman, I. Goncalve, R. Gallino, E. Gonzalez-Romero, A. Goverdoski, F. Gramegna, E. Griesmayer, F. Gunsing, B. Haa, R. Haight, M. Heil, A. Herrera-Martinez, S. Isaev, E. Jericha, F. Kaeppeler, Y. Kadi, D. Karadimo, M. Kerveno, V. Ketlerov, P. Koehler, V. Konovalov, M. Krticka, C. Lamboudi, H. Leeb, A. Lindote, I. Lope, G. Lorusso, M. Lozano, S. Lukic, J. Marganiec, S. Marrone, J. Martinez-Val, P. Mastinu, A. Mengoni, P.M. Milazzo, A. Molina-Coballe, C. Moreau, M. Mosconi, F. Neve, H. Oberhummer, S. O'Brien, J. Pancin, T. Papaevangelou, C. Paradela, A. Pavlik, P. Pavlopoulo, J.M. Perlado, L. Perrot, M. Pignatari, R. Plag, A. Plompen, A. Pluki, A. Poch, A. Policarpo, C. Pretel, J. Quesada, W. Rapp, T. Rauscher, R. Reifarth, M. Rosetti, C. Rubbia, G. Rudolf, P. Rullhusen, J. Salgado, J.C. Soare, C. Stephan, G. Tagliente, J.L. Tain, L. Tassan-Got, L. Tavora, R. Terlizzi, G. Vannini, P. Vaz, A. Ventura, D. Villamarin, M. C. Vincente, V. Vlachoudi, F. Vo, H. Wendler, M. Wiescher, K. Wisshak, Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. GREENER - Grup de recerca d'estudis energètics i de les radiacions, Institut de Recherches Subatomiques (IReS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), L. Buchmann, M. Comyn, J. Thomson, and nTOF
Subjects: Nuclear and High Energy Physics, Astrofísica nuclear, Neutron cross sections, Proton, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Neutrons -- Seccions, Nuclear physics, Cross section (physics), Neutron flux, 0103 physical sciences, Neutron cross section, Nuclear astrophysics, Spallation, Neutron, 010306 general physics, Nuclear Experiment, Physics, Neutrons, Large Hadron Collider, Física [Àrees temàtiques de la UPC], 010308 nuclear & particles physics, Radioactivity, Physics::Accelerator Physics, Física nuclear
Abstract: A series of neutron capture cross section measurements of interest to nuclear astrophysics have been recently performed at n_TOF, the neutron spallation source operating at CERN. The low repetition frequency of the proton beam driver, the extremely high instantaneous neutron flux, and the low background conditions in the experimental area are optimal for capture cross section measurements on low-mass or radioactive samples. An overview of the measurements performed during the two experimental campaigns in 2002 and 2003 is presented with special emphasis on the measurement of the capture cross sections of the Os isotopes relevant for the cosmochronology based on the Re/Os clock. http://www.sciencedirect.com/science/article/B6TVB-4GFTP27-40/1/e75becb4002b5a2d671901c2aa851543
Published: 2005
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388. Measurement of the 151Sm n,gamma 152Sm cross section at n_TOF

Author: Roberto Capote, V. Chepel, S. David, P. Baumann, G. Vannini, G. Tagliente, Enrico Chiaveri, M. Rosetti, W. Rapp, M. Krtička, F. Calviño, S. Lukic, Corrie S. Moreau, L. Perrot, P. Pavlopoulos, L. Tavora, José M. Martínez-Val, J. Salgado, A. Poch, Saed Dababneh, F. Gramegna, R. Flag, José Manuel Perlado, P. Rullhusen, G. Aerts, R. Gallino, V. Ketlerov, A. Lindote, Heinz Oberhummer, L. Ferrant, J. Marganiec, S. Andriamonje, C. Pretel, P. Cennini, E. Gonzalez-Romero, A. Goverdovski, Michael Heil, J. Andrzejewski, F. Neves, P. M. Milazzo, J. Benlliure, A. J. M. Plompen, P. F. Mastinu, S. Isaev, M. Embid-Segura, Gerald Badurek, R. C. Haight, R. Dolfini, M. Mosconi, Marco Pignatari, U. Abbondanno, G. Rudolf, I. Lopes, E. Jericha, F. Voss, C. Stephan, S. O'Brien, C. Paradela, W.I. Furman, D. Villamarin, A. Herrera-Martinez, Thomas Rauscher, D. Cortina, Manuel Lozano, F. Alvarez-Velarde, Arnaud Ferrari, Nicola Colonna, R. Terlizzi, James L. Cox, V. Konovalov, Vasilis Vlachoudis, H. Alvarez-Pol, Michael Wiescher, E. Berthoumieux, D. Karadimos, P. E. Koehler, Rene Reifarth, Alberto Mengoni, Daniel Cano-Ott, A.J.P.L. Policarpo, Subramanian Raman, A. Molina-Coballes, A. Plukis, J. M. Quesada, L. Tassan-Got, T. Papaevangelou, B. Haas, J.C. Scares, I. Duran, A. Ventura, Y. Kadi, H. Frais-Koelbl, R. Ferreira-Marques, E. Griesmayer, C. Rubbia, Isabel S. Gonçalves, S. Marrone, M.C. Vincente, C. Lamboudis, J. L. Tain, M. Kerveno, F. Bečvář, M. Dahlfors, P. Vaz, Aaron Couture, A. Pavlik, C. Domingo-Pardo, J. Pancin, F. Käppeler, F. Gunsing, H. Leeb, K. Wisshak, H. Wendler, G. Cortes, Institut de Recherches Subatomiques (IReS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), L. Buchmann, M. Comyn, J. Thomson, Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. GREENER - Grup de recerca d'estudis energètics i de les radiacions, S. Marrone, U. Abbondanno, G. Aert, F. Alvarez-Velarde, H. Alvarez-Pol, S. Andriamonje, J. Andrzejewski, G. Badurek, P. Baumann, F. Becvar, J. Bennliure, E. Berthoumieux, F. Calvino, D. Cano-Ott, R. Capote, P. Cennini, V. Chepel, E. Chiaveri, N. Colonna, G. Corte, D. Cortina, A. Couture, J. Cox, S. Dababneh, M. Dahlfor, S. David, R. Dolfini, C. Domingo-Pardo, I. Duran, M. Embid-Segura, L. Ferrant, A. Ferrari, R. Ferreira-Marque, H. Frais-Koelbl, W. Furman, I. Goncalve, R. Gallino, E. Gonzalez-Romero, A. Goverdoski, F. Gramegna, E. Griesmayer, F. Gunsing, B. Haa, R. Haight, M. Heil, A. Herrera-Martinez, S. Isaev, E. Jericha, F. Kaeppeler, Y. Kadi, D. Karadimo, M. Kerveno, V. Ketlerov, P. Koehler, V. Konovalov, M. Krticka, C. Lamboudi, H. Leeb. A. Lindote, I. Lope, M. Lozano, S. Lukic, J. Marganiec, J. Martinez-Val, P. Mastinu, A. Mengoni, P.M. Milazzo, A. Molina-Coballe, C. Moreau, M. Mosconi, F. Neve, H. Oberhummer, S. O'Brien, J. Pancin, T. Papaevangelou, C. Paradela, A. Pavlik, P. Pavlopoulo, J.M. Perlado, L. Perrot, M. Pignatari, R. Plag, A. Plompen, A. Pluki, A. Poch, A. Policarpo, C. Pretel, J. Quesada, S. Raman, W. Rapp, T. Rauscher, R. Reifarth, M. Rosetti, C. Rubbia, G. Rudolf, P. Rullhusen, J. Salgado, J.C. Soare, C. Stephan, G. Tagliente, J.L. Tain, L. Tassan-Got, L. Tavora, R. Terlizzi, G. Vannini, P. Vaz, A. Ventura, D. Villamarin, M. C. Vincente, V. Vlachoudi, F. Vo, H. Wendler, M. Wiescher, and K. Wisshak
Subjects: Physics, Nuclear reaction, Neutrons, Nuclear and High Energy Physics, Física [Àrees temàtiques de la UPC], Branching fraction, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Giant star, 01 natural sciences, Neutrons--Capture, Nuclear physics, Stars, Nucleosynthesis, 0103 physical sciences, Asymptotic giant branch, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, s-process, Nuclear Experiment, 010303 astronomy & astrophysics, Dimensionless quantity
Abstract: The 151 Sm(n, γ ) 152 Sm cross section, which is important for the interpretation of the 151 Sm branching as an s -process thermometer, was measured from 1 eV up to 1 MeV at the innovative n_TOF facility at CERN. Based on these data, the Maxwellian-averaged cross section at k T = 30 keV is found to be 3100±160 mb. This value can be used to constrain the thermodynamical conditions in Asymptotic Giant Branch (AGB) stars during He-shell burning.
Published: 2005
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389. Measurements of the 90,91,92,94,96 Zr n, gamma cross-sections at n_TOF

Author: G. Cortes, Roberto Capote, P. Cennini, A. J. M. Plompen, G. Rudolf, I. Lopes, C. Pretel, G. Vannini, M. Mosconi, P. Pavlopoulos, A. Pavlik, James L. Cox, C. Stephan, S. O'Brien, C. Domingo-Pardo, S. David, R. Gallino, R. Terlizzi, G. Tagliente, F. Voss, J. Andrzejewski, Michael Heil, F. Käppeler, E. Griesmayer, V. Ketlerov, A. Molina-Coballes, L. Ferrant, L. Tavora, W. Rapp, Rene Reifarth, José M. Martínez-Val, J. Pancin, G. Aerts, J. Salgado, M. C. Vincente, A. Poch, A. Herrera-Martinez, Arnaud Ferrari, Nicola Colonna, P. Rullhusen, Corrie S. Moreau, L. Perrot, Alberto Mengoni, J.C. Soares, I. Duran, José Manuel Perlado, Heinz Oberhummer, Thomas Rauscher, Vasilis Vlachoudis, H. Alvarez-Pol, M. Dahlfors, J. M. Quesada, V. Chepel, L. Tassan-Got, V. Konovalov, Y. Kadi, D. Karadimos, P. Baumann, H. Frais-Koelbl, S. Isaev, U. Abbondanno, D. Cano-Ott, W.I. Furman, A.J.P.L. Policarpo, P. Vaz, Aaron Couture, S. Lukic, G. Lorusso, B. Haas, E. Gonzalez-Romero, E. Berthoumieux, P. E. Koehler, Enrico Chiaveri, M. Rosetti, Ralf Plag, J. Benlliure, F. Gramegna, A. Plukis, C. Lamboudis, J. L. Tain, R. C. Haight, M. Kerveno, C. Paradela, M. Krtička, A. Ventura, Saed Dababneh, Michael Wiescher, J. Marganiec, S. Andriamonje, D. Villamarin, P. F. Mastinu, Marco Pignatari, M. Embid-Segura, D. Cortina, Manuel Lozano, C. Rubbia, Isabel S. Gonçalves, S. Marrone, E. Jericha, K. Wisshak, H. Wendler, F. Gunsing, F. Neves, F. Calviño, H. Leeb, P. M. Milazzo, R. Ferreira-Marques, T. Papaevangelou, F. Bečvář, A. Lindote, A. Goverdovski, F. Alvarez-Velarde, Gerald Badurek, R. Dolfini, L. Buchmann, M. Comyn, J. Thomson, Département Recherches Subatomiques (DRS-IPHC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), nTOF, Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. GREENER - Grup de recerca d'estudis energètics i de les radiacions, G. Tagliente, U. Abbondanno, G. Aert, F. Alvarez-Velarde, H. Alvarez-Pol, S. Andriamonje, J. Andrzejewski, G. Badurek, P. Baumann, F. Becvar, J. Benlliure, E. Berthoumieux, F. Calvino, D. Cano-Ott, R. Capote, P. Cennini, V. Chepel, E. Chiaveri, N. Colonna, G. Corte, D. Cortina, A. Couture, J. Cox, S. Dababneh, M. Dahlfor, S. David, R. Dolfini, C. Domingo-Pardo, I. Duran, M. Embid-Segura, L. Ferrant, A. Ferrari, R. Ferrera-Marque, H. Frais-Koelbl, W. Furman, I. Goncalve, R. Gallino, E. Gonzalez-Romero, A. Goverdoski, F. Gramegna, E. Griesmayer, F. Gunsing, B. Haa, R. Haight, M. Heil, A. Herrera-Martinez, S. Isaev, E. Jericha, F. Kaeppeler, Y. Kadi, D. Karadimo, M. Kerveno, V. Ketlerov, P. Koehler, V. Konovalov, M. Krticka, C. Lamboudi, H. Leeb, A. Lindote, I. Lope, G. Lorusso, M. Lozano, S. Lukic, J. Marganiec, S. Marrone, J. Martinez-Val, P. Mastinu, A. Mengoni, P.M. Milazzo, A. Molina-Coballe, C. Moreau, M. Mosconi, F. Neve, H. Oberhummer, S. O'Brien, J. Pancin, T. Papaevangelou, C. Paradela, A. Pavlik, P. Pavlopoulo, J.M. Perlado, L. Perrot, M. Pignatari, R. Plag, A. Plompen, A. Pluki, A. Poch, A. Policarpo, C. Pretel, J. Quesada, W. Rapp, T. Rauscher, R. Reifarth, M. Rosetti, C. Rubbia, G. Rudolf, P. Rullhusen, J. Salgado, I.C. Soare, C. Stephan, J.L. Tain, L. Tassan-Got, L. Tavora, R. Terlizzi, G. Vannini, P. Vaz, A. Ventura, D. Villamarin, M.C. Vincente, V. Vlachoudi, F. Vo, H. Wendler, M. Wiescher, and K. Wisshak
Subjects: Nuclear and High Energy Physics, Neutron cross sections, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, Neutron scattering, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, Neutrons -- Seccions, Neutron time-of-flight scattering, Nuclear physics, 0103 physical sciences, Neutron cross section, Neutrons -- Mesurament, Neutron, 010306 general physics, Nuclear Experiment, Physics, Bonner sphere, 010308 nuclear & particles physics, Neutrons--Measurement, Neutron stimulated emission computed tomography, Neutron temperature, Neutron capture, Física::Astronomia i astrofísica [Àrees temàtiques de la UPC], Physics::Accelerator Physics
Abstract: Neutron capture cross sections of the 90,91,92,94,96Zr have been measured over the energy range from 1 eV to 1 MeV at the spallation neutron facility n TOF at CERN in 2003. The innovative features of the neutron beam, in particular the high instantaneous flux, the high energy resolution and low background, together with improvements of the neutron sensitivity of the capture detectors make this facility unique for neutron-induced reaction cross section measurements with much improved accuracy. The preliminary results of the Zr measurements show capture resonance strengths generally smaller than in previous measurements.
Published: 2005
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390. 197Au(n,γ) - towards a new standard for energies relevant to stellar nucleosynthesis

Author: N. Colonna, Ralf Nolte, C. Lederer, Matthias Heil, Ulrich Giesen, Rene Reifarth, Stefan Schmidt, I. Dillmann, Anton Wallner, M. Mosconi, Alberto Mengoni, C. Domingo-Pardo, F. Käppeler, F. Gunsing, Cristian Massimi, C Lederer, N Colonna, I Dillmann, C Domingo-Pardo, U Giesen, F Gunsing, M Heil, F Käppeler, C Massimi, A Mengoni, M Mosconi, R Nolte, R Reifarth, S Schmidt, and A Wallner
Subjects: Physics, 197Au, History, Large Hadron Collider, Resolution (electron density), Neutron spectra, Resonance (particle physics), Neutron cross section standard, Computer Science Applications, Education, Nuclear physics, Cross section (physics), Stellar nucleosynthesis, Neutron source, Neutron, Nuclear Experiment, s process
Abstract: Two experiments were performed to resolve a discrepancy of the 197Au(n, γ) cross section between the IAEA standard evaluation and the reference cross section for astrophysical experiments in the lower keV energy region. We measured the 197Au(n, γ) reaction by means of the time-of-flight technique with n-TOF at CERN and extracted the cross section in the unresolved resonance region between 5-400 keV with an overall uncertainty from 3.9-6.7% for a resolution of 20 bins per energy decade. Additionally, we remeasured the neutron spectrum of the 7Li(p, n) 7Be reaction with E p=1912 keV, which was used as a neutron source for determining the astrophysical reference cross section. The n-TOF data are already fully analyzed and published. The results are in good agreement with the ENDF standard evaluation, but uncertainties don't allow to draw definite conclusions. The analysis of the neutron spectrum of 7Li(p, n) 7Be is underway, preliminary results will be reported here.
Published: 2012
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391. Neutron Capture Cross Section Measurement ofSm151at the CERN Neutron Time of Flight Facility (n_TOF)

Author: I. Goncalves, C. Lamboudis, J. L. Tain, Thomas Rauscher, L. Tavora, M. Embid-Segura, D. Karadimos, Rene Reifarth, D. Cortina, Manuel Lozano, A.J.P.L. Policarpo, José M. Martínez-Val, F. Gramegna, P. Pavlopoulos, P. Rullhusen, J. Andrzejewski, M. Kerveno, F. Käppeler, M. Krtička, T. Papaevangelou, J. M. Quesada, Carlo Rubbia, A. Pavlik, José Manuel Perlado, L. Ferrant, Heinz Oberhummer, G. Cortes, C. Domingo-Pardo, V. Vlachoudis, Saed Dababneh, M. Rosetti, V. Konovalov, F. Voss, W.I. Furman, Alfredo Ferrari, R. Ferreira-Marques, Nicola Colonna, E. Gonzalez-Romero, S. Marrone, H. Alvarez-Pol, A. Plukis, A. Lindote, Subramanian Raman, J. Pancin, R. Gallino, J. Cox, C. Paradela, G. Aerts, V. Ketlerov, J. Marganiec, E. Griesmayer, P. M. Milazzo, E. Chiaveri, Laurent Tassan-Got, S. Lukic, S. Andriamonje, D. Cano-Ott, Michael Heil, P. F. Mastinu, Marco Pignatari, Roberto Capote, Ralf Plag, J. Benlliure, W. Rapp, H. Frais-Koelbl, M. Dahlfors, P. Vaz, Alberto Ventura, Aaron Couture, C. Pretel, F. Neves, E. Jericha, I. Duran, D. Villamarin, P. E. Koehler, E. Berthoumieux, A. Herrera-Martinez, R. C. Haight, Alberto Mengoni, A. Molina-Coballes, G. Vannini, F. Bečvář, L. Perrot, S. David, G. Tagliente, V. Chepel, J. Salgado, A. Poch, P. Baumann, Michael Wiescher, Yacine Kadi, C. Moreau, M. C. Vincente, J.C. Soares, S. Isaev, U. Abbondanno, F. Gunsing, A. J. M. Plompen, G. Rudolf, I. Lopes, P. Cennini, K. Wisshak, A. Goverdovski, F. Alvarez-Velarde, Gerald Badurek, R. Dolfini, M. Mosconi, C. Stephan, S. O'Brien, R. Terlizzi, H. Wendler, F. Calviño, H. Leeb, and B. Haas
Subjects: Physics, Luminosity (scattering theory), 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, General Physics and Astronomy, 01 natural sciences, 7. Clean energy, Nuclear physics, Neutron capture, Time of flight, Nucleosynthesis, 0103 physical sciences, Neutron cross section, Spallation, Neutron, Nuclear Experiment, 010306 general physics, s-process
Abstract: The Sm-151(n,gamma)Sm-152 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 Sm-151 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.
Published: 2004
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392. Stellar (n,gamma) cross section of 62Ni

Author: H, Nassar, M, Paul, I, Ahmad, D, Berkovits, M, Bettan, P, Collon, S, Dababneh, S, Ghelberg, J P, Greene, A, Heger, M, Heil, D J, Henderson, C L, Jiang, F, Käppeler, H, Koivisto, S, O'Brien, R C, Pardo, N, Patronis, T, Pennington, R, Plag, K E, Rehm, R, Reifarth, R, Scott, S, Sinha, X, Tang, and R, Vondrasek
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 62A90 produced by the weak s process in massive stars.
Published: 2004

393. Stellar neutron capture onTam180. II. Defining thes-process contribution to nature’s rarest isotope

Author: Oscar Straniero, Rene Reifarth, S. Masera, F. Voss, K. Wisshak, F. Käppeler, R. Gallino, Matthias Heil, Claudia Travaglio, and C. Arlandini
Subjects: Nuclear physics, Physics, Nuclear and High Energy Physics, Neutron capture, Isotope, Radiative capture, Astrophysics, s-process
Published: 2004
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394. Stellar neutron capture onTam180. I. Cross section measurement between10keVand100keV

Author: Rene Reifarth, F. Käppeler, F. Voss, F. Bečvář, Matthias Heil, M. Krtička, C. Arlandini, and K. Wisshak
Subjects: Physics, Nuclear and High Energy Physics, Cross section (physics), chemistry.chemical_compound, Neutron capture, Proton, chemistry, Barium fluoride, Content (measure theory), Neutron cross section, Neutron, Atomic physics, Energy (signal processing)
Abstract: The neutron capture cross section of $^{180}\mathrm{Ta}^{m}$ has been measured at energies between $10\phantom{\rule{0.3em}{0ex}}\text{keV}$ and $100\phantom{\rule{0.3em}{0ex}}\text{keV}$ in a time-of-flight experiment at the Karlsruhe $3.7\phantom{\rule{0.3em}{0ex}}\text{MV}$ Van de Graaff accelerator. Neutrons were produced via the $^{7}\mathrm{Li}(p,n)^{7}\mathrm{Be}$ reaction by bombarding metallic Li targets with a pulsed proton beam, and gold was used as a cross section standard. Though the world supply of enriched $^{180}\mathrm{Ta}^{m}$ was available for this experiment, the sample consisted of only $150\phantom{\rule{0.3em}{0ex}}\text{mg}$ ${\text{Ta}}_{2}{\mathrm{O}}_{5}$ with a $^{180}\mathrm{Ta}^{m}$ content of only $5.5%$. The difficult separation of the comparably few capture events in $^{180}\mathrm{Ta}^{m}$ from the much larger background due to captures in $^{181}\mathrm{Ta}$ could be achieved by means of the Karlsruhe $4\ensuremath{\pi}$ barium fluoride detector, taking advantage of its combination of high efficiency, good energy resolution, and high granularity. The cross section was determined with an overall uncertainty of better than $10%$ in the energy range from $30\phantom{\rule{0.3em}{0ex}}\text{keV}$ to $100\phantom{\rule{0.3em}{0ex}}\text{keV}$ and could be used for renormalizing statistical model calculations in the entire energy range of astrophysical interest, which had predicted about two times larger values. Based on these first experimental data, Maxwellian averaged neutron capture cross sections were calculated for thermal energies between $kT=8\phantom{\rule{0.3em}{0ex}}\text{keV}$ and $100\phantom{\rule{0.3em}{0ex}}\text{keV}$.
Published: 2004
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395. Neutron capture studies on unstableCs135for nucleosynthesis and transmutation

Author: N. Patronis, P. E. Koehler, Alberto Mengoni, D. Karamanis, Saed Dababneh, R. Gallino, F. Käppeler, P.A. Assimakopoulos, Michael Heil, and Ralf Plag
Subjects: Physics, Nuclear and High Energy Physics, Neutron capture, chemistry, Nuclear transmutation, Nucleosynthesis, Neutron cross section, chemistry.chemical_element, Neutron, Atomic physics, Activation method, Helium, Neutron temperature
Abstract: The neutron capture cross section of the unstable isotope $^{135}\mathrm{Cs}$ was measured relative to that of gold by means of the activation method. The sample was produced by ion implantation in a high resolution mass separator and irradiated with quasimonoenergetic neutrons at $30\phantom{\rule{0.3em}{0ex}}\text{keV}$ and $500\phantom{\rule{0.3em}{0ex}}\text{keV}$, using the $^{7}\mathrm{Li}(p,n)^{7}\mathrm{Be}$ reaction. An additional irradiation with thermal neutrons has been carried out for defining the sample mass and for measuring the half-life of $^{136}\mathrm{Cs}$. The neutron capture cross sections were determined as $164\ifmmode\pm\else\textpm\fi{}10\phantom{\rule{0.3em}{0ex}}\text{mb}$ and $34.8\ifmmode\pm\else\textpm\fi{}3.0\phantom{\rule{0.3em}{0ex}}\text{mb}$ at $30\phantom{\rule{0.3em}{0ex}}\text{keV}$ and $500\phantom{\rule{0.3em}{0ex}}\text{keV}$, respectively, and were used to normalize the theoretically derived cross section shape. Based on these data, refined statistical model calculations were performed to obtain the $(n,\ensuremath{\gamma})$ cross sections of the short-lived isotopes $^{134}\mathrm{Cs}$ and $^{136}\mathrm{Cs}$ as well. Updated Maxwellian-averaged capture cross sections of all unstable Cs isotopes were calculated for a range of thermal energies characteristic of helium burning scenarios for an improved $s$-process analysis of the Xe-Cs-Ba region.
Published: 2004
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396. Measurement of the n-TOF beam profile with a micromegas detector

Author: J. Pancin, U. Abbondanno, G. Aerts, H. Alvarez, S. Andriamonje, A. Angelopoulos, P. Assimakopoulos, C. Bacri, G. Badurek, P. Baumann, F. Bečvář, H. Beer, J. Benlliure, B. Berthier, E. Berthoumieux, S. Boffi, C. Borcea, E. Boscolo-Marchi, N. Bustreo, F. Calvino, D. Cano-ott, R. Capote, P. Carlson, P. Cennini, V. Chepel, E. Chiaveri, N. Colonna, G. Cortes, D. Cortina, A. Couture, J. Cox, S. Dababneh, M. Dahlfors, S. David, A. Delbart, J. Derre, R. Dolfini, C. Domingo, I. Duran-Escribano, C. Eleftheriadis, M. Embid-Segura, L. Ferrant, A. Ferrari, L. Ferreira-Lourenco, R. Ferreiramarques, H. Frais-Koelbl, W. Furman, Y. Giomataris, I. Goncalves, E. Gonzalez-Romero, A. Goverdovski, F. Gramegna, E. Griesmayer, F. Gunsing, R. Haight, M. Heil, A. Herrera-Martinez, K. Ioannides, N. Janeva, F. Jeanneau, E. Jericha, F. Käppeler, Y. Kadi, D. Karamanis, A. Kelic, V. Ketlerov, G. Kitis, P. Koehler, V. Konovalov, E. Kossionides, V. Lacoste, H. Leeb, A. Lindote, I. Lopes, M. Lozano, S. Lukic, S. Markov, S. Marrone, J. Martinez-Val, P. Mastinu, A. Mengoni, P. Milazzo, E. Minguez, A. Molina-Coballes, C. Moreau, F. Neves, H. Oberhummer, S. O'brien, I. Papadopoulos, T. Papavengelou, C. Paradela, A. Pavlik, P. Pavlopoulos, A. Perez-Parra, J. Perlado, V. Peskov, L. Perrot, R. Plag, A. Plompen, A. Plukis, A. Poch, A. Policarpo, C. Pretel, J. Quesada, M. Radici, S. Raman, W. Rapp, R. Reifarth, F. Rejmund, M. Rosetti, C. Rubbia, G. Rudolf, P. Rullhusen, J. Salgado, E. Savvidis, C. Stephan, G. Tagliente, J. Tain, C. Tapia, L. Tassan-Got, L. Tavora, R. Terlizzi, M. Terrani, N. Tsangas, G. Vannini, P. Vaz, A. Ventura, D. Villamarin-Fernandez, M. Vincente-Vincente, V. Vlachoudis, R. Vlastou, F. Voss, H. Wendler, M. Wiescher, K. Wisshak, L. Zanini, J.Pancin, U.Abbondanno, G.Aert, H.Alvarez, S.Adriamonje, A.Angelopoulo, P.Assimakopoulo, C.Bacri, C.Badurek, P.Bauman, F.Becvar, H.Beer, J.Benlliure, B.Berthier, E.Berthoumieux, S.Boffi, C.Borcea, N.Bustreo, F.Calvino, D.Cano-Ott, R.Capote, P.Carlson, P.Cennini, V.Chepel, E.Chiaveri, N.Colonna, G.Corte, D.Cortina, A.Couture, J.Cox, S.Dababneh, M.Dahlfor, S.David, R.Dolfini, C.Domingo, I.Dura-Escribano, C.Eleftheriadi, M.Embid-Segura, L.Ferrant, A.Ferrari, L.Ferreira-Lourenco, R.Ferreira-Marque, H.Frais-Koelbl, W.Furman, Y.Giomatari, I.Goncalve, E.Gonzales-Romero, A.Goverdovski, F.Gramegna, E.Griiesmayer, F.GGunsing, R.Haight, M.Heil, A.Errera-Martinez, K.Ioannide, N.Janeva, E.Jericha, Y.Kadi, F.Kappeler, D.Karamani, A.Kelic, V.Ketlerov, G.Kiti, P.Koehler, V.Konovalov, E.Kossionide, V.Lacoste, H.Leeb, A.Lindote, I.Lope, M.Lozano, S.Lukic, S.Markov, S.Marrone, J.Martinez-Val, P.Mastinu, A.Mengoni, P.Milazzo, E.Minguez, C.Moreau, F.Neve, H.Oberhummer, S.O’Brien, C.Paradela, A.Pavlik, P.Pavlopoulo, A.Perez-Parra, J.Perlado, L.Perrot, V.Peskov, R.Plag, A.Plomplen, A.Pluki, A.Poch, A.policarpo, C.Pretel, J.Quesada, M.Radici, W.Rapp, R.Reifarth, F.Rejmund, M.Rosetti, C.Rubbia, G.Rudolf, P.Rullhusen, J.Salgado, E.Savvidi, C.Stephan, G.Tagliente, J.Tain, C.Tapia, L.Tassan-Got, L.Tavora, M.Terrani, N.Tsanga, G.Vannini, P.Vaz, A.Ventura, D.Villamarin-Fernandez, M.Vincente-Vincente, V.Vlachoudi, R.Vlastou, F.Vo, H.Wendler, M.Wiescher, K.Wisshak, and L.Zanini
Subjects: Elastic scattering, Physics, Nuclear and High Energy Physics, Argon, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, Beam profile, Nuclear Theory, chemistry.chemical_element, MicroMegas detector, NUCLEAR PHYSICS, Neutron radiation, Nuclear physics, Neutron capture, chemistry, NEUTRON BEAMS, Neutron cross section, MICROMEGAS DETECTOR, Neutron detection, Neutron beam profiler, Neutron, Nuclear Experiment, Instrumentation, Micromegas
Abstract: A Micromegas detector was used in the neutron Time-Of-Flight (n_TOF) facility at CERN to evaluate the spatial distribution of the neutron beam as a function of its kinetic energy. This was achieved over a large range of neutron energies by using two complementary processes: at low energy by capture of a neutron via the 6Li(n,[alpha])t reaction, and at high energy by elastic scattering of neutrons on gas nuclei (argon+isobutane or helium+isobutane). Data are compared to Monte Carlo simulations and an analytic function fitting the beam profile has been calculated with a sufficient precision to use in neutron capture experiments at the n_TOF facility. http://www.sciencedirect.com/science/article/B6TJM-4BRSWVV-3/1/01dd54d28c7a57560574f1adfbd8a2f0
Published: 2004

397. Nucleosynthesis at the termination point of the s process

Author: Rene Reifarth, Michael Wiescher, U. Ratzel, Roberto Gallino, Claudia Travaglio, C. Arlandini, F. Käppeler, Alberto Mengoni, and Aaron Couture
Subjects: Physics, Nuclear and High Energy Physics, Nucleosynthesis, Star (game theory), Metallicity, Neutron, Production (computer science), Sensitivity (control systems), Atomic physics, s-process, XX, Abundance of the chemical elements
Abstract: Stellar cross sections of importance with respect to the termination of the $s$-process reaction chain have been determined for the two cases, $^{208}\mathrm{Pb}(\mathit{n},\ensuremath{\gamma})^{209}\mathrm{Pb}$ and $^{209}\mathrm{Bi}(\mathit{n},\ensuremath{\gamma})^{210}\mathrm{Bi}^{g}$, yielding $kT=30\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ values of $⟨\ensuremath{\sigma}v⟩∕{v}_{T}=0.31\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.3em}{0ex}}\mathrm{mb}$ and $2.54\ifmmode\pm\else\textpm\fi{}0.14\phantom{\rule{0.3em}{0ex}}\mathrm{mb}$, respectively. The measurements were carried out by activation of Pb and Bi samples in a quasistellar neutron spectrum using gold as a cross section standard. With this technique the uncertainties reported in previous works could be considerably reduced. The measurements are complemented by a discussion of the recycling at the termination point of the $s$-process neutron capture chain in a $3{M}_{\astrosun{}}$ and $[\mathrm{Fe}∕\mathrm{H}]=\ensuremath{-}1.3$ asymptotic giant branch star. At this metallicity, AGB stars give rise to the maximum production of $s$-process lead. The sensitivity of the isotopic lead abundances is discussed with respect to the remaining cross section uncertainties. The information obtained in this work is also of relevance for an assessment of the $\ensuremath{\alpha}$ activity due to a buildup of $^{210}\mathrm{Po}$ in $\mathrm{Pb}∕\mathrm{Bi}$ cooled fast reactor systems.
Published: 2004

398. Gamma spectroscopy using two Clover detectors in close geometry

Author: S. O'Brien, N. Patronis, Saed Dababneh, Rene Reifarth, Joachim Görres, D. Karamanis, F. Käppeler, P.A. Assimakopoulos, and Michael Heil
Subjects: Physics, Nuclear and High Energy Physics, Spectrometer, summing correction, business.industry, coincidence mode, clover detector, Detector, addback mode, Geometry, Particle detector, Coincidence, background reduction, Semiconductor detector, Optics, Measuring instrument, Gamma spectroscopy, gamma-ray detection, business, Spectroscopy, Instrumentation, direct mode
Abstract: A gamma spectrometer composed of two Clover Ge detectors in close geometry is described. The advantages and drawbacks of the different modes of operation are investigated. The use of offline coincidence analysis for substantial background reduction is presented and an experimental approach for the determination of the summing correction factor is formulated. (C) 2003 Elsevier B.V. All rights reserved. Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment
Published: 2004

399. Neutron capture cross section of139La

Author: Saed Dababneh, R. Gallino, Marco Pignatari, Michael Heil, Rene Reifarth, F. Käppeler, Ralf Plag, and S. O'Brien
Subjects: Physics, Nuclear and High Energy Physics, Neutron capture, Radiative capture, Neutron cross section, Neutron, Nuclear cross section, Atomic physics, Activation method, Proton energy, Spectroscopy
Abstract: The neutron capture cross section of ${}^{139}\mathrm{La}$ has been measured relative to that of ${}^{197}\mathrm{Au}$ by means of the activation method. The sample was irradiated in a quasistellar neutron spectrum for $kT=25\mathrm{keV}$ generated via the ${}^{7}\mathrm{Li}{(p,n)}^{7}\mathrm{Be}$ reaction with the proton energy adjusted 30 keV above the threshold. Maxwellian averaged neutron capture cross sections were calculated for energies $kT=5--100\mathrm{keV}.$ The new value for $kT=30\mathrm{keV}$ is found to be $31.6\ifmmode\pm\else\textpm\fi{}0.8\mathrm{mb},$ 18% lower and considerably less uncertain than the previously recommended value of $38.4\ifmmode\pm\else\textpm\fi{}2.7\mathrm{mb}.$ With these results the s- and r-process components could be more accurately determined, making lanthanum a reliable s- and r-process indicator in stellar spectroscopy.
Published: 2003
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400. Stellar He burning of18O:A measurement of low-energy resonances and their astrophysical implications

Author: Joachim Görres, Rene Reifarth, Michael Heil, H. Leiste, F. Käppeler, Michael Wiescher, and Saed Dababneh
Subjects: Physics, Nuclear and High Energy Physics, Stars, chemistry.chemical_compound, chemistry, Nucleosynthesis, Asymptotic giant branch, Resonance, Neutron, Sensitivity (control systems), Atomic physics, s-process, Bismuth germanate
Abstract: The ${}^{22}\mathrm{Ne}(\ensuremath{\alpha},n)$ reaction is the main neutron source for neutron capture nucleosynthesis $(s$ process) in massive stars and plays also a significant role for the s process in thermally pulsing asymptotic giant branch stars. In these scenarios, ${}^{22}\mathrm{Ne}$ is produced by the reaction sequence ${}^{14}\mathrm{N}(\ensuremath{\alpha},\ensuremath{\gamma}{)}^{18}\mathrm{F}({\ensuremath{\beta}}^{+}{)}^{18}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma}{)}^{22}\mathrm{Ne}.$ While the first reaction is well understood, \ensuremath{\alpha} capture on ${}^{18}\mathrm{O}$ was affected by considerable uncertainties. At the temperatures of stellar He burning, the reaction rate is determined by two resonances at \ensuremath{\alpha} energies of 470 and 566 keV. Since these resonances were not yet successfully measured, the rates had to be based on estimated resonance strengths. In the present work, the first direct measurement of the partial strengths of these extremely weak low-energy resonances is reported. The use of a high-efficiency segmented Ge detector in coincidence with bismuth germanate oxide counters covering a large solid angle led to a significantly improved experimental sensitivity, thus allowing for the clear identification of specific \ensuremath{\gamma} transitions. As a result, resonance strengths of 0.71\ifmmode\pm\else\textpm\fi{}0.17 \ensuremath{\mu}eV and 0.48\ifmmode\pm\else\textpm\fi{}0.16 \ensuremath{\mu}eV could be obtained for the 566- and 470-keV resonances, respectively. When compared to the previously reported upper limits of \ensuremath{\leqslant}1.7 \ensuremath{\mu}eV, these results provide a reliable basis for the determination of the reaction rate during stellar He burning. Accordingly, these data reduce the uncertainties in the s process neutron balance.
Published: 2003
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