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1 to 50 of 291 results
  • Experimental neutron capture data of 58Ni from the CERN n_TOF facility

     Zugec, P.; Barbagallo, M.; Colonna, Nicola; Bosnar, D.; Altstadt, S.; Andrzejewski, J.; Audouin, L.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez-Hornillos, MB.; Riego Pérez, Albert
    Physical review C
    Date of publication: 2014-01-09
    Journal article

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    The 58Ni(n,gamma) cross section has been measured at the neutron time of flight facility n_TOF at CERN, in the energy range from 27 meV up to 400 keV. In total, 51 resonances have been analyzed up to 122 keV. Maxwellian averaged cross sections (MACS) have been calculated for stellar temperatures of kT = 5¿100 keV with uncertainties of less than 6%, showing fair agreement with recent experimental and evaluated data up to kT = 50 keV. The MACS extracted in the present work at 30 keV is 34.2 ± 0.6stat ± 1.8sys mb, in agreement with latest results and evaluations, but 12% lower relative to the recent KADoNIS compilation of astrophysical cross sections.When included in models of the s-process nucleosynthesis in massive stars, this change results in a 60% increase of the abundance of 58Ni, with a negligible propagation on heavier isotopes. The reason is that, using both the old or the new MACS, 58Ni is efficiently depleted by neutron captures

  • Measurement of the angular distribution of fission fragments using a PPAC assembly at CERN n_TOF

     Tarrío, D.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Riego Pérez, Albert
    Nuclear instruments and methods in physics research. Section A, accelerators SP
    Date of publication: 2014-01-08
    Journal article

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    A fission reaction chamber based on Parallel Plate Avalanche Counters (PPACs) was built for measuring angular distributions of fragments emitted in neutron-induced fission of actinides at the neutron beam available at the Neutron Time-Of-Flight (n_TOF) facility at CERN. The detectors and the samples were tilted 45° with respect to the neutron beam direction to cover all the possible values of the emission angle of the fission fragments. The main features of this setup are discussed and results on the fission fragment angular distribution are provided for the 232Th(n,f) reaction around the fission threshold. The results are compared with the available data in the literature, demonstrating the good capabilities of this setup

  • Design of a 4 p neutron detector for ß-delay neutron detection experiments.

     Gorlychev, Vitaly
    Defense's date: 2014-02-05
    Universitat Politècnica de Catalunya
    Theses

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    La probabilitat d¿emissió de neutrons retardats per emissió beta és una de les propietats més importants dels nuclis rics en neutrons que es troben lluny de la vall de l¿estabilitat. El coneixement d¿aquest paràmetre ens dona l¿oportunitat de millorar el coneixement de: l¿estructura dels nuclis atòmics i la seva dependència amb la relació N/Z; els processos de captura ràpida de neutrons (procés-r), i amb això l¿estudi de la formació de nuclis en explosions de supernoves; noves dades per aplicacions en la tecnologia de reactors nuclears, donat que es tracta d¿una de les principals característiques per a l¿operació segura de les centrals nuclears actuals.L¿objectiu de la tesi consisteix en dissenyar i provar el prototipus d¿un detector de neutrons amb geometria 4p per experiments de DESPEC, relacionats amb la mesura de la probabilitat d¿emissió de neutrons retardats per desintegració beta. Donat que les probabilitats d¿emissió de neutrons són molt baixes i les seves energies són poc conegudes, es necessari dissenyar un detector amb una elevada eficiència de detecció de neutrons i amb una baixa dependència amb l¿energia d¿aquests, per a un ampli rang d¿energies. El prototipus dissenyat té una eficiència mitja de detecció de neutrons del 27,1% per neutrons amb energies compreses entre 0,01 MeV i 6 MeV. El detector que s¿ha dissenyat està format per 20 comptadors proporcionals de 3He a 20 atm, inserits en una matriu de polietilè. Els comptadors estan distribuïts en dos anells concèntrics, envoltant el forat pel que circularà el feix d¿ions que està situat a l¿eix central de la matriu.La tesi es divideix en tres parts principals: 1) l¿anàlisi de les diverses configuracions i propietats del detector; 2) la selecció de la configuració definitiva del prototipus, incloent l¿electrònica i el sistema d¿adquisició de dades (DAQ); 3) el test del prototipus i la seva calibració amb fonts de neutronsL¿anàlisi de la configuració del detector s¿ha realitzat mitjançant simulacions Monte Carlo (MC) utilitzant el codi MCNPX. Aquestes simulacions MC han sigut útils trobar: la pressió òptima dels comptadors de 3He; el millor nombre de comptadors, tenint en compte el cost i la màxima eficiència de detecció que es pot obtenir; el nombre de comptadors en cada anell concèntric i la distància d¿aquests anells al centre de la matriu de polietilè; la longitud òptima dels comptadors; o el gruix del blindatge per a la reducció de la radiació de fons. Tots aquests estudis han sigut bàsics per obtenir la configuració òptima. El disseny del detector també ha implicat la selecció del sistema d¿adquisició de dades i equips electrònics més adequats. Aquesta activitat s¿ha realitzat amb col¿laboració amb l¿Institut de Física Corpuscular (IFIC-València)¿.Aquesta tesi doctoral també inclou la descripció dels diferents tests realitzats per comprovar les simulacions MC i el sistema DAQ. L¿experiment definitiu es va realitzar a IGISOL (Jyväskilä University ¿ Finland) per tal de comprovar el disseny del detector i el seu funcionament. L¿experiment va permetre obtenir l¿eficiència experimental del detector mesurant l¿emissió retardada de neutrons per desintegració beta de dos nuclis coneguts: 85Rb i 88Br. Els resultats obtinguts mostren un gran acord entre els valors experimentals i les simulacions realitzades.

  • Measurement of the neutron-induced fission cross-section of Am-241 at the time-of-flight facility n_TOF

     Belloni, Fabio; Calviani, Marco; Colonna, Nicola; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Pretel Sanchez, M. del Carmen; Poch Mateu, Antoni
    European physical journal A
    Date of publication: 2013-01
    Journal article

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  • Máster en Ingeniería Nuclear por la UPC (Máster UPC-ENDESA). Confluencia de objetivos de la universidad, la empresa y la sociedad

     Batet Miracle, Lluis; Duch Guillen, Maria Amor; Calviño Tavares, Francisco; Dies Llovera, Javier; del Val, Luis; Fernández-Olano, Pablo
    Reunión Anual de la Sociedad Nuclear Española
    Presentation's date: 2013-09-24
    Presentation of work at congresses

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    El Máster en Ingeniería Nuclear por la UPC pretende formar ingenieros nucleares con un nivel alto de competencias que les permitan optar a puestos de responsabilidad en empresas del sector. El Máster cuenta con el patrocinio de ENDESA y la colaboración de entidades y empresas del sector. El Máster está impartido completamente en inglés y está imbricado en EMINE, European Master in Innovation in Nuclear Energy (KIC-InnoEnergy).

  • Master in Nuclear Engineering in Barcelona: aligning university, utility and society objectives

     Batet Miracle, Lluis; Calviño Tavares, Francisco; Dies Llovera, Javier; Duch Guillen, Maria Amor; del Val, Luis; Fernández-Olano, Pablo
    Nuclear Education and Training
    Presentation's date: 2013-11-19
    Presentation of work at congresses

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  • Neutron capture cross section of unstable 63-Ni: implications for stellar nucleosynthesis

     Lederer, C.; Massimi, C.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; [et, al]
    Physical review letters
    Date of publication: 2013-01-09
    Journal article

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    The 63Ni(n,γ) cross section has been measured for the first time at the neutron time-of-flight facility n_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged cross sections were calculated for thermal energies from   kT=5–100  keV with uncertainties around 20%. Stellar model calculations for a 25M⊙ star show that the new data have a significant effect on the s-process production of 63Cu, 64Ni, and 64Zn in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova.

  • The 93-Zr(n,gamma) reaction up to 8 keV neutron energy

     Tagliente, G.; Milazzo, P.M.; Fujiii, K.; Abbondanno, U.; Aerts, G.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2013-01-31
    Journal article

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    The (n,¿) reaction of the radioactive isotope 93Zr has been measured at the n_TOF high-resolution time-of-flight facility at CERN. Resonance parameters have been extracted in the neutron energy range up to 8 keV, yielding capture widths smaller (14%) than reported in an earlier experiment. These results are important for detailed nucleosynthesis calculations and for refined studies of waste transmutation concepts.

    he (n,gamma) reaction of the radioactive isotope 93Zr has been measured at the n_TOF high-resolution time-of-flight facility at CERN. Resonance parameters have been extracted in the neutron energy range up to 8 keV,yielding capture widths smaller (14%) than reported in an earlier experiment. These results are important for detailed nucleosynthesis calculations and for refined studies of waste transmutation concepts.

  • A new CVD diamond mosaic-detector for (n, a) cross-section measurements at the n_TOF experiment at CERN

     Weiß, C.; Griesmayer, E.; Guerrero, C.; Altstadt, S.; Andrzejewski, J.; Audouin, L.; Badurek, G.; Barbagallo, M.; Bécares, V.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez-Hornillos, MB.; Hernandez Prieto, Alvaro; Riego Pérez, Albert
    Nuclear instruments and methods in physics research. Section A, accelerators SP
    Date of publication: 2013-08-02
    Journal article

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    At the n_TOF experiment at CERN a dedicated single-crystal chemical vapor deposition (sCVD) Diamond Mosaic-Detector has been developed for (n,a) cross-section measurements. The detector, characterized by an excellent time and energy resolution, consists of an array of 9 sCVD diamond diodes. The detector has been characterized and a cross-section measurement has been performed for the 59Ni(n,a)56Fe reaction in 2012. The characteristics of the detector, its performance and the promising preliminary results of the experiment are presented

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    Performance of the neutron time-of-flight facility n TOF at CERN  Open access

     Guerrero, C.; Tsinganis, A; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Hernandez Prieto, Alvaro; Riego Pérez, Albert
    European physical journal A
    Date of publication: 2013-02-25
    Journal article

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    The neutron time-of-flight facility n TOF features a white neutron source produced by spallation through 20 GeV/c protons impinging on a lead target. The facility, aiming primarily at the measurement of neutron-induced reaction cross sections, was operating at CERN between 2001 and 2004, and then underwent a major upgrade in 2008. This paper presents in detail all the characteristics of the new neutron beam in the currently available configurations, which correspond to two different collimation systems and two choices of neutron moderator. The characteristics discussed include the intensity and energy dependence of the neutron flux, the spatial profile of the beam, the in-beam background components and the energy resolution/broadening. The discussion of these features is based on dedicated measurements and Monte Carlo simulations, and includes estimations of the systematic uncertainties of the mentioned quantities.

  • High-accuracy determination of the neutron flux at n TOF

     Barbagallo, M.; Guerrero, C.; Tsinganis, A.; Tarrío, D.; Altstadt, S.; Andriamonje, S.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Becvar, F.; Belloni, Fabio; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez-Hornillos, MB.; Hernandez Prieto, Alvaro; Riego Pérez, Albert
    European physical journal A
    Date of publication: 2013-12-18
    Journal article

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    The neutron flux of the n TOF facility at CERN was measured, after installation of the new spallation target, with four different systems based on three neutron-converting reactions, which represent accepted cross sections standards in different energy regions. A careful comparison and combination of the different measurements allowed us to reach an unprecedented accuracy on the energy dependence of the neutron flux in the very wide range (thermal to 1 GeV) that characterizes the n TOF neutron beam. This is a pre-requisite for the high accuracy of cross section measurements at n TOF. An unexpected anomaly in the neutron-induced fission cross section of U-235 is observed in the energy region between 10 and 30 keV, hinting at a possible overestimation of this important cross section, well above currently assigned uncertainties.

  • SOLVING CHALLENGES IN NUCLEAR DATA

     Cortes Rossell, Guillem Pere; Pretel Sanchez, M. del Carmen; Calviño Tavares, Francisco
    Participation in a competitive project

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    Máster en Ingeniería Nuclear por la UPC (Máster UPC-ENDESA). Balance de la primera edición  Open access

     Batet Miracle, Lluis; Duch Guillen, Maria Amor; Calviño Tavares, Francisco; del Val, Luis; Fernández-Olano, Pablo
    Reunión Anual de la Sociedad Nuclear Española
    Presentation's date: 2012-10-18
    Presentation of work at congresses

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    El Máster en Ingeniería Nuclear por la UPC, está orientado a la formación de ingenieros nucleares con un nivel alto de competencias que les permitan optar a puestos de responsabilidad en empresas del sector. El máster, que ha iniciado su andadura durante el curso 2011-2012, cuenta con el patrocinio de ENDESA y la colaboración de entidades y empresas del sector. En esta ponencia se realiza un balance de los dos primeros semestres del máster y se describen los puntos fuertes y las oportunidades de mejora detectados. En el análisis se ha tenido en cuenta el rendimiento académico de los estudiantes, sus impresiones y el grado de satisfacción. La información se ha recogido a través de encuestas, entrevistas personales y reuniones con todo el grupo de estudiantes. Los 90 créditos ECTS del Máster se reparten en asignaturas obligatorias (46,5) y optativas (13,5) y prácticas externas y Proyecto Final. La participación de expertos externos a la universidad ha sido muy alta (casi un 50 % de la docencia), especialmente en las materias de Gestión de Plantas y Normativa y Seguridad. Todas las materias incluyen actividades basadas en aprendizaje activo y trabajo en equipo: se consigue así que el sistema de evaluación sea una parte integral e inseparable del proceso de aprendizaje. En cada uno de los dos semestres lectivos, los estudiantes desarrollan un proyecto transversal en grupos de tres o cuatro miembros. En general el grado de satisfacción del alumnado es muy bueno, pero se han detectado algunos aspectos referentes a la distribución de la carga de trabajo y a los mecanismos de evaluación que han sido mejorados sobre la marcha. Estas mejoras se incorporarán en la edición de 2012-2013. Creemos que el Máster satisface las expectativas del sector y de la sociedad a la vez que presenta un gran atractivo para los estudiantes.

  • Measurement of resolved resonances of Th-232(n, gamma) at the n_TOF facility at CERN

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen; [et, al]
    Physical review C
    Date of publication: 2012-06-01
    Journal article

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  • Simultaneous measurement of neutron-induced capture and fission reactions at CERN

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; [et, al]
    European physical journal A
    Date of publication: 2012
    Journal article

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  • Measurement and resonance analysis of the 237Np neutron capture cross section

     Cortes Rossell, Guillem Pere; Calviño Tavares, Francisco; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen; [et, al]
    Physical review C
    Date of publication: 2012-04-20
    Journal article

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  • Collimation and Beam Loss Studies in High-Intensity Synchrotrons

     Barranco García, Javier
    Defense's date: 2012-01-20
    Department of Physics and Nuclear Engineering, Universitat Politècnica de Catalunya
    Theses

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  • Datos nucleares para física nuclear e ingeniería nuclear

     Gómez Hornillos, María Belén; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Riego Pérez, Albert; Pretel Sanchez, M. del Carmen; Caballero Folch, Roger; Calviño Tavares, Francisco
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  • Resonance neutron-capture cross sections of stable magnesium isotopes and their astrophysical implications

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2012-04-20
    Journal article

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  • Neutron-induced fission cross section measurement of 233U, 241Am and 243Am in the energy range 0.5MeVE n20MeV at n-TOF at CERN

     Belloni, Fabio; Milazzo, P.M.; Calviani, M.; Colonna, N.; Mastinu, P.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Álvarez-Velarde, F.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physica scripta
    Date of publication: 2012-10
    Journal article

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  • Neutron-induced fission cross section of 245-Cm: New results from data taken at the time-of-flight facility n_TOF

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2012-03-29
    Journal article

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    The neutron-induced fission cross section of 245Cm was measured at n_TOF in a wide energy range and with high resolution. The energy dependence, measured in a single measurement from 30 meV to 1 MeV neutron energy, has been determined with 5% accuracy relative to the 235U(n,f) cross section. In order to reduce the uncertainty on the absolute value, the data have been normalized at thermal energy to recent measurements performed at ILL and BR1. In the energy range of overlap, the results are in fair agreement with some previous measurements and confirm, on average, the evaluated cross section in the ENDF/B-VII.0 database, although sizable differences are observed for some important resonances below 20 eV. A similar behavior is observed relative to JENDL/AC-2008, a reactor-oriented database for actinides. The new results contribute to the overall improvement of the databases needed for the design of advanced reactor systems and may lead to refinements of fission models for the actinides.

  • New Master in Nuclear Engineering in Barcelona: a sinergetic effort of University and utility

     Batet Miracle, Lluis; Calviño Tavares, Francisco; Duch Guillen, Maria Amor; Consul Porras, M. Nieves; Oriol, Carlos; del Val, Luis; Fernández-Olano, Pablo
    Nuclear Education and Training
    Presentation's date: 2011-05-17
    Presentation of work at congresses

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  • Máster en Ingeniería Nuclear por la UPC (Máster UPC-ENDESA)

     Batet Miracle, Lluis; Duch Guillen, Maria Amor; Calviño Tavares, Francisco; del Val, Luis; Fernández-Olano, Pablo
    Sociedad Nuclear Española. Reunión
    Presentation's date: 2011
    Presentation of work at congresses

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    Present status and future programs of the n-TOF experiment  Open access

     Chiaveri, E.; Calviani, M.; Andriamonje, S.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Riego Pérez, Albert; Gómez Hornillos, María Belén; Vlachoudis, V.; Massimi, C.
    International Workshop on Compound Nuclear Reactions and Related Topics
    Presentation's date: 2011-09
    Presentation of work at congresses

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    The neutron time-of-flight facility n_TOF at CERN, Switzerland, operational since 2001, delivers neutrons using the Proton Synchrotron (PS) 20 GeV/c proton beam impinging on a lead spallation target. The facility combines a very high instantaneous neutron flux, an excellent time of flight resolution due to the distance between the experimental area and the production target (185 meters), a low intrinsic background and a wide range of neutron energies, from thermal to GeV neutrons. These characteristics provide a unique possibility to perform neutron-induced capture and fission cross-section measurements for applications in nuclear astrophysics and in nuclear reactor technology. The most relevant measurements performed up to now and foreseen for the future will be presented in this contribution. The overall efficiency of the experimental program and the range of possible measurements achievable with the construction of a second experimental area (EAR-2), vertically located 20 m on top of the n_TOF spallation target, might offer a substantial improvement in measurement sensitivities. A feasibility study of the possible realisation of the installation extension will be also presented.

  • Monte Carlo Simulations for the Study of a Moderated Neutron Detector

     Gómez Hornillos, María Belén; Gorlychev, V.; Caballero Folch, Roger; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen; Calviño Tavares, Francisco; Tain Enriquez, José Luis; Algora, Alejandro; Agramunt Ros, Jorge; Cano-Ott, D.; Martínez, T.; Mendoza Cembranos, Emilio; Rissanen, J.; Äystö, J.; Jokinen, Ari; Eronen, T.; Moore, I.; Penttila, H.
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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  • Neutron measurements for advanced nuclear systems: The n_TOF project at CERN

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén
    Nuclear instruments and methods in physics research. Section B, beam interaction
    Date of publication: 2011-04-21
    Journal article

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    A few years ago, the neutron time-of-flight facility n_TOF was built at CERN to address some of the urgent needs of high-accuracy nuclear data for Accelerator Driven Systems and other advanced nuclear energy systems, as well as for nuclear astrophysics and fundamental nuclear physics. Thanks to the characteristics of the neutron beam, and to state-of-the-art detection and acquisition systems, high quality neutron cross-section data have been obtained for a variety of isotopes, many of which radioactive. Following an important upgrade of the spallation target and of the experimental area, a new measurement campaign has started last year. After a brief review of the most important results obtained so far at n_TOF, the new features of the facility are presented, together with the first results on the commissioning of the neutron beam. The plans for future measurements, in particular related to nuclear technology are finally discussed.

  • High-energy neutron-induced fission cross sections of natural lead and bismuth-209

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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    The CERN Neutron Time-Of-Flight (n TOF) facility is well suited to measure small neutron- induced ssion cross sections, as those of subactinides. The cross section ratios of natPb and 209Bi relative to 235U and 238U were measured using PPAC detectors. The fragment coincidence method allows to unambiguously identify the ssion events. The present experiment provides the rst results for neutron-induced ssion up to 1 GeV for natPb and 209Bi. A good agreement with previous experimental data below 200 MeV is shown. The comparison with proton-induced ssion indicates that the limiting regime where neutron-induced and proton-induced ssion reach equal cross section is close to 1 GeV.

  • 237-Np(n,f) cross section: new data and present status

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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    In this document, we present the nal result obtained at the n TOF experiment for the neutron- induced ssion cross section of the 237Np, from the ssion threshold up to 1 GeV. The method applied to get this result is brie y discussed. n TOF data are compared to the last experimental measurements using other TOF facilities or the surrogate method, reported experiments performed with monoenergetic sources and the FISCAL systematic, including a discussion about the existing discrepancies.

  • Fission cross-section measurements of 233-U, 245-Cm and 241,243-Am at CERN n_TOF facility

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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    Neutron-induced ssion cross-sections of minor actinides have been measured using the n TOF white neutron source at CERN, Geneva, as part of a large experimental program aiming at collecting new data relevant for nuclear astrophysics and for the design of advanced reactor systems. The measurements at n TOF take advantage of the innovative features of the n TOF facility, namely the wide energy range, high instantaneous neutron ux and good energy resolution. Final results on the ssion cross-section of 233U, 245Cm and 243Am from thermal to 20 MeV are here reported, together with preliminary results for 241Am. The measurement have been performed with a dedicated Fast Ionization Chamber (FIC), a ssion fragment detector with a very high e ciency, relative to the very well known cross-section of 235U, measured simultaneously with the same detector.

  • The Role of Fe and Ni for S-process Nucleosynthesis and Innovative Nuclear Technologies

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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  • Study of Photon Strength Function of Actinides: the Case of 235-U, 238-Np and 241-Pu

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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  • Characterization of the New n_TOF Neutron Beam: Fluence, Prole and Resolution

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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  • Measurement of the neutron-induced fission cross-section of 243Am relative to 235U from 0.5 to 20 MeV

     Belloni, Fabio; Calviani, M.; Colonna, N.; Mastinu, P.; Milazzo, P.M.; Abbondanno, U.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen; [et, al]
    European physical journal A
    Date of publication: 2011-12
    Journal article

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    The ratio of the neutron-induced fission cross-sections of 243Am and 235U was measured in the energy range from 0.5 to 20 MeV with uncertainties of ≈4%. The experiment was performed at the CERN n TOF facility using a fast ionization chamber. With the good counting statistics that could be achieved thanks to the high instantaneous flux and the low backgrounds, the present results are useful for resolving discrepancies in previous data sets and are important for future reactors with improved fuel burn-up.

  • Improved neutron capture cross section measurements with the n_TOF total absorption Cclorimeter

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; [et, al]
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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    The n TOF collaboration operates a Total Absorption Calorimeter (TAC) [1] for measuring neu- tron capture cross-sections of low-mass and/or radioactive samples. The results obtained with the TAC have led to a substantial improvement of the capture cross sections of 237Np and 240Pu [2]. The experience acquired during the rst measurements has allowed us to optimize the performance of the TAC and to improve the capture signal to background ratio, thus opening the way to more complex and demanding measurements on rare radioactive materials. The new design has been reached by a series of detailed Monte Carlo simulations of complete experiments and dedicated test measurements. The new capture setup will be presented and the main achievements highlighted.

  • Neutron Capture Measuremetns on Minor Actinides at the n_TOF Facility at CERN: Past, Present and Future

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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  • Past, present and future of the n_TOF facility at CERN

     Calviño Tavares, Francisco; Gómez Hornillos, María Belén; Cortes Rossell, Guillem Pere
    Journal of the Korean Physical Society
    Date of publication: 2011-08-12
    Journal article

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  • Measurement of the 236U(n, f ) cross section from 170 meV to 2 MeV at the CERN n TOF facility

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2011-10-31
    Journal article

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    The neutron-induced fission cross section of 236U was measured at the neutron Time-of-Flight (n TOF) facility at CERN relative to the standard 235U(n,f ) cross section for neutron energies ranging from above thermal to several MeV. The measurement, covering the full range simultaneously, was performed with a fast ionization chamber, taking advantage of the high resolution of the n TOF spectrometer. The n TOF results confirm that the first resonance at 5.45 eV is largely overestimated in some nuclear data libraries. The resonance triplet around 1.2 keV was measured with high resolution and resonance parameters were determined with good accuracy. Resonances at high energy have also been observed and characterized and different values for the cross section are provided for the region between 10 keV and the fission threshold. The present work indicates various shortcomings of the current nuclear data libraries in the subthreshold region and provides the basis for an accurate re-evaluation of the 236U(n,f ) cross section, which is of great relevance for the development of emerging or innovative nuclear reactor technologies.

  • 197-Au(n,gamma ) cross section in the unresolved resonance region

     Lederer, C.; Colonna, N.; Domingo Pardo, César; Gunsing, F.; Käppeler, F.; Massimi, C.; Mengoni, A.; Wallner, A.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Álvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P A.; Audouin, L.; Badurek, G.; Barbagallo, M.; Baumann, P.; Becvár, F.; Belloni, Fabio; Berthoumieux, E.; Calviani, M.; Calviño Tavares, Francisco; Cano-Ott, D.; Capote, R.; Carrapiço, C.; Carrillo de Albornoz, A.; Cennini, P.; Chepel, V.; Chiaveri, E.; Cortes Rossell, Guillem Pere; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillmann, I.; Dolfini, R.; Dridi, W.; Duran, I.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fujiii, K.; Furman, W.; Goncalves, I.; Gonzalez-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Isaev, S.; Jericha, E.; Kadi, Y; Karadimos, D.; Karamanis, D.; Kerveno, M.; Ketlerov, V.; Koehler, P.; Konovalov, V.; Kossionides, E.; Krticka, M.; Lampoudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Losito, R.; Lukic, S.; Marganiec, J.; Márques, L.; Marrone, S.; Martínez, T.; Mastinu, P.; Mendoza, E.; Milazzo, P.M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Pigni, M.T.; Plag, R.; Plompen, A.; Plukis, A.; Poch Pares, Agusti; Praena, J.; Pretel Sanchez, M. del Carmen; Quesada, J.; Rauscher, T.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Santos, C.; Sarchiapone, L.; Sarmento, R.; Savvidis, I.; Stephan, C.; Tagliente, G.; Tain Enriquez, José Luis; Tarrío, D.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wendler, H.; Wiescher, M.; Wisshak, K.; Lozano, Manuel
    Physical review C
    Date of publication: 2011-03-17
    Journal article

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    The cross section of the reaction 197Au(n,γ ) was measured with the time-of-flight technique at the n TOF (neutron time-of-flight) facility in the unresolved resonance region between 5 and 400 keV using a pair of C6D6 (where D denotes 2H) liquid scintillators for the detection of prompt capture γ rays. The results with a total uncertainty of 3.9%–6.7% for a resolution of 20 bins per energy decade show fair agreement with the Evaluated Nuclear Data File Version B-VII.0 (ENDF/B-VII.0), which contains the standard evaluation. The Maxwellianaveraged cross section (MACS) at 30 keV is in excellent agreement with the one according to the ENDF/B-VII.0 evaluation and 4.7% higher than the MACS measured independently by activation technique. Structures in the cross section, which had also been reported earlier, have been interpreted as being due to clusters of resonances.

  • 96Zr(n,gamma ) measurement at the n TOF facility at CERN

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Pretel Sanchez, M. del Carmen; Poch Pares, Agusti
    Physical review C
    Date of publication: 2011-03-17
    Journal article

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    The (n,γ ) cross section of 96Zr has been investigated at the CERN n TOF spallation neutron source. Highresolution time-of-flight measurements using an enriched ZrO2 sample allowed us to analyze 15 resonances below 40 keV with improved accuracy. On average, the capture widths were found to be 25% smaller than reported in earlier experiments. If complemented with the contribution by direct radiative capture, the derived Maxwellian averaged cross sections are consistent with activation data at kT = 25 keV. The present results confirm the astrophysical implications for the s-process branching at 95Zr.

  • Neutron-induced fission cross section of nat-Pb and 209-Bi from threshold to 1 GeV: An improved parametrization

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2011-04-28
    Journal article

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  • Neutron capture on Zr94: Resonance parameters and Maxwellian-averaged cross sections

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2011-07-11
    Journal article

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  • Neutron-induced fission cross-section of U-233 in the energy range 0.5 < E-n < 20 MeV

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    European physical journal A
    Date of publication: 2011-01
    Journal article

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    The neutron-induced fission cross-section of 233U has been measured at the CERN n TOF facility relative to the standard fission cross-section of 235U between 0.5 and 20MeV. The experiment was performed with a fast ionization chamber for the detection of the fission fragments and to discriminate against α-particles from the natural radioactivity of the samples. The high instantaneous flux and the low background of the n TOF facility result in data with uncertainties of ≈ 3%, which were found in good agreement with previous experiments. The high quality of the present results allows to improve the evaluation of the 233U(n,f) cross-section and, consequently, the design of energy systems based on the Th/U cycle.

  • Access to the full text
    Commissionning of the n_TOF-Ph2 facility  Open access

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén
    PHYSOR 2010 ¿ Advances in Reactor Physics to Power the Nuclear Renaissance
    Presentation's date: 2010
    Presentation of work at congresses

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    The white spectrum neutron time-of-flight facility n_TOF is operating at CERN since 2001. The neutron beam has a very high instantaneous flux and high resolution in energy and it is delivered in the experimental area located 187 m downstream from the spallation target. The intense neutron fluence per proton burst results in a much enhanced signal to background ratio for neutron capture and fission reactions on radioactive isotopes, thus making the facility well suited for accurate measurement of neutron-induced reaction cross-sections. This is especially true to highly radioactive targets which are of major importance in new nuclear energy system such as Gen-IV reactors, especially those with fast spectrum. Combined with state-of-the-art detectors and with advanced data acquisition systems, the innovative characteristics of the n_TOF neutron beam allow collecting data on a variety of stable and radioactive isotopes of interest for nuclear astrophysics and for applications to advanced reactor technologies.

  • Measurements of high-energy neutron-induced fission of nat-Pb and 209-Bi

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    EFNUDAT ¿ Measurements and Models of Nuclear Reactions
    Presentation's date: 2010
    Presentation of work at congresses

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  • Neutron cross-sections for next generation reactors3A New data from n_TOF

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Applied radiation and isotopes
    Date of publication: 2010-03
    Journal article

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  • Au-197(n,gamma) cross section in the resonance region

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2010-04
    Journal article

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  • The Zr-92(n,gamma) reaction and its implications for stellar nucleosynthesis

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2010-05
    Journal article

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  • Contribución española a los gastos mantenimiento y operación del experimento N_TOF(CERN)para el año 2010

     Calviño Tavares, Francisco; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen; Gómez Hornillos, María Belén; Cortes Rossell, Guillem Pere
    Participation in a competitive project

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  • Neutron-induced fission cross section of U-234 and Np-237 measured at the CERN Neutron Time-of-Flight (n_TOF) facility

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2010-09-08
    Journal article

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  • Access to the full text
    Neutron physics of the Re/Os clock. III. Resonance analyses and stellar (n,gamma) cross sections of 186,187,188-Os  Open access

     Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch Pares, Agusti; Pretel Sanchez, M. del Carmen
    Physical review C
    Date of publication: 2010-07-15
    Journal article

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    Neutron resonance analyses have been performed for the capture cross sections of 186Os, 187Os, and 188Os measured at the n TOF facility at CERN. Resonance parameters have been extracted up to 5, 3, and 8 keV, respectively, using the SAMMY code for a full R-matrix fit of the capture yields. From these results average resonance parameters were derived by a statistical analysis to provide a comprehensive experimental basis for modeling of the stellar neutron capture rates of these isotopes in terms of the Hauser-Feshbach statistical model. Consistent calculations for the capture and inelastic reaction channels are crucial for the evaluation of stellar enhancement factors to correct the Maxwellian averaged cross sections obtained from experimental data for the effect of thermally populated excited states. These factors have been calculated for the full temperature range of current scenarios of s-process nucleosynthesis using the combined information of the experimental data in the region of resolved resonances and in the continuum. The consequences of this analysis for the s-process component of the 187Os abundance and the related impact on the evaluation of the time duration of galactic nucleosynthesis via the Re/Os cosmochronometer are discussed.