Calviño Tavares, Francisco
Total activity: 316
Expertise
Active Teaching and Learning Methodologies, Experimental Nuclear Physics, University Management
Professional category
University lecturer
Doctoral courses
Doctor en Ciencias Físicas
Research group
GREENER - Research group on studies in energy and radiation.
Department
Department of Physics and Nuclear Engineering
Institute
Institute of Energy Technology
School
Barcelona School of Industrial Engineering (ETSEIB)
E-mail
francisco.calvinoupc.edu
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Links of interest
CERN Open in new window
Richard Felder. Resources in Science and Engineering Education Open in new window

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1 to 50 of 316 results
  • Experimental neutron capture data of 58Ni from the CERN n_TOF facility

     ¿ugec, Petar; Barbagallo, Massimo; Colonna, Nicola; Bosnar, Damir; Altstadt, Sebastian; Andrzejewski, Józef; Audouin, Ludmila; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; 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

    The 58Ni(n,γ ) 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

  • GEANT4 simulation of the neutron background of the C6D6 set-up for capture studies at n_TOF

     ¿ugec, Petar; Colonna, Nicola; Bosnar, Damir; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Riego Pérez, Albert
    Nuclear instruments and methods in physics research. Section A, accelerators SP
    Date of publication: 2014-05-20
    Journal article

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    The neutron sensitivity of the C6D6 detector setup used at n_TOF facility for capture measurements has been studied by means of detailed GEANT4 simulations. A realistic software replica of the entire n_TOF experimental hall, including the neutron beam line, sample, detector supports and the walls of the experimental area has been implemented in the simulations. The simulations have been analyzed in the same manner as experimental data, in particular by applying the Pulse Height Weighting Technique. The simulations have been validated against a measurement of the neutron background performed with a nat-C sample, showing an excellent agreement above 1 keV. At lower energies, an additional component in the measured nat-C yield has been discovered, which prevents the use of nat-C data for neutron background estimates at neutron energies below a few hundred eV. The origin and time structure of the neutron background have been derived from the simulations. Examples of the neutron background for two different samples are demonstrating the important role of accurate simulations of the neutron background in capture cross-section measurements

    The neutron sensitivity of the C6D6 detector setup used at n_TOF facility for capture measurements has been studied by means of detailed GEANT4 simulations. A realistic software replica of the entire n_TOF experimental hall, including the neutron beam line, sample, detector supports and the walls of the experimental area has been implemented in the simulations. The simulations have been analyzed in the same manner as experimental data, in particular by applying the Pulse Height Weighting Technique. The simulations have been validated against a measurement of the neutron background performed with a nat-C sample, showing an excellent agreement above 1 keV. At lower energies, an additional component in the measured nat-C yield has been discovered, which prevents the use of nat-C data for neutron background estimates at neutron energies below a few hundred eV. The origin and time structure of the neutron background have been derived from the simulations. Examples of the neutron background for two different samples are demonstrating the important role of accurate simulations of the neutron background in capture cross-section measurements

  • 62Ni(n,gamma) and 63Ni(n,gamma) cross sections measured at the n_TOF facility at CERN

     Lederer, Claudia; Massimi, Cristian; Berthoumieux, Eric; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Riego Pérez, Albert
    Physical review C
    Date of publication: 2014-02-28
    Journal article

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    The cross section of the Ni62(n,gamma) reaction was measured with the time-of-flight technique at the neutron time-of-flight facility n_TOF at CERN. Capture kernels of 42 resonances were analyzed up to 200 keV neutron energy and Maxwellian averaged cross sections (MACS) from kT= 5¿100 keV were calculated. With a total uncertainty of 4.5%, the stellar cross section is in excellent agreement with the the KADoNiS compilation at kT=30 keV, while being systematically lower up to a factor of 1.6 at higher stellar temperatures. The cross section of the Ni63(n,¿) reaction was measured for the first time at n_TOF. We determined unresolved cross sections from 10 to 270 keV with a systematic uncertainty of 17%. These results provide fundamental constraints on s-process production of heavier species, especially the production of Cu in massive stars, which serve as the dominant source of Cu in the solar system.

    The cross section of the Ni62(n,gamma) reaction was measured with the time-of-flight technique at the neutron time-of-flight facility n_TOF at CERN. Capture kernels of 42 resonances were analyzed up to 200 keV neutron energy and Maxwellian averaged cross sections (MACS) from kT= 5–100 keV were calculated. With a total uncertainty of 4.5%, the stellar cross section is in excellent agreement with the the KADoNiS compilation at kT=30 keV, while being systematically lower up to a factor of 1.6 at higher stellar temperatures. The cross section of the Ni63(n,¿) reaction was measured for the first time at n_TOF. We determined unresolved cross sections from 10 to 270 keV with a systematic uncertainty of 17%. These results provide fundamental constraints on s-process production of heavier species, especially the production of Cu in massive stars, which serve as the dominant source of Cu in the solar system.

  • Measurement and analysis of the Am 241 (n, gamma) cross section with liquid scintillator detectors using time-of-flight spectroscopy at the n-TOF facility at CERN

     Fraval, Kevin; Gunsing, Frank; Altstadt, Sebastian; Andrzejewski, Józef; Audouin, Ludmila; Barbagallo, Massimo; Bécares, Vicente; Belloni, Fabio; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Hernandez Prieto, Alvaro; Riego Pérez, Albert
    Physical review C
    Date of publication: 2014-04-23
    Journal article

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    The Am241(n,¿) cross section has been measured at the n-TOF facility at CERN using deuterated benzene liquid scintillators, commonly known as C6D6 detectors, and time-of-flight spectrometry. The results in the resolved resonance range bring new constraints to evaluations below 150 eV, and the energy upper limit was extended from 150 to 320 eV with a total of 172 new resonances not present in current evaluations. The thermal capture cross section was found to be sth=678±68 b, which is in good agreement with evaluations and most previous measurements. The capture cross section in the unresolved resonance region was extracted in the remaining energy range up to 150 keV, and found to be larger than current evaluations and previous measurements. © 2014 American Physical Society.

    The Am241(n,¿) cross section has been measured at the n-TOF facility at CERN using deuterated benzene liquid scintillators, commonly known as C6D6 detectors, and time-of-flight spectrometry. The results in the resolved resonance range bring new constraints to evaluations below 150 eV, and the energy upper limit was extended from 150 to 320 eV with a total of 172 new resonances not present in current evaluations. The thermal capture cross section was found to be sth=678±68 b, which is in good agreement with evaluations and most previous measurements. The capture cross section in the unresolved resonance region was extracted in the remaining energy range up to 150 keV, and found to be larger than current evaluations and previous measurements. © 2014 American Physical Society.

  • Ni-62(n,gamma) and Ni-63(n,gamma) cross sections measured at the n_TOF facility at CERN

     Lederer, Claudia; Massimi, Cristian; Berthoumieux, Eric; Colonna, Nicola; Dressler, Rugard; Guerrero, Carlos; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Riego Pérez, Albert; [et, al]
    Physical review C
    Date of publication: 2014-02-28
    Journal article

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    The cross section of the Ni-62(n,gamma) reaction was measured with the time-of-flight technique at the neutron time-of-flight facility n_TOF at CERN. Capture kernels of 42 resonances were analyzed up to 200 keV neutron energy and Maxwellian averaged cross sections (MACS) from kT = 5-100 keV were calculated. With a total uncertainty of 4.5%, the stellar cross section is in excellent agreement with the the KADoNiS compilation at kT = 30 keV, while being systematically lower up to a factor of 1.6 at higher stellar temperatures. The cross section of the Ni-63(n,gamma) reaction was measured for the first time at n_TOF. We determined unresolved cross sections from 10 to 270 keV with a systematic uncertainty of 17%. These results provide fundamental constraints on s-process production of heavier species, especially the production of Cu in massive stars, which serve as the dominant source of Cu in the solar system.

    The cross section of the Ni-62(n,gamma) reaction was measured with the time-of-flight technique at the neutron time-of-flight facility n_TOF at CERN. Capture kernels of 42 resonances were analyzed up to 200 keV neutron energy and Maxwellian averaged cross sections (MACS) from kT = 5-100 keV were calculated. With a total uncertainty of 4.5%, the stellar cross section is in excellent agreement with the the KADoNiS compilation at kT = 30 keV, while being systematically lower up to a factor of 1.6 at higher stellar temperatures. The cross section of the Ni-63(n,gamma) reaction was measured for the first time at n_TOF. We determined unresolved cross sections from 10 to 270 keV with a systematic uncertainty of 17%. These results provide fundamental constraints on s-process production of heavier species, especially the production of Cu in massive stars, which serve as the dominant source of Cu in the solar system.

  • 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).

    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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    Measurements of neutron cross sections for advanced nuclear energy systems at n-TOF (CERN)  Open access

     Barbagallo, Massimo; Colonna, Nicola; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Riego Pérez, Albert
    International Nuclear Physics Conference
    Presentation's date: 2013-06
    Presentation of work at congresses

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    The n-TOF facility operates at CERN with the aim of addressing the request of high accuracy nuclear data for advanced nuclear energy systems as well as for nuclear astrophysics. Thanks to the features of the neutron beam, important results have been obtained on neutron induced fission and capture cross sections of U, Pu and minor actinides. Recently the construction of another beam line has started; the new line will be complementary to the first one, allowing to further extend the experimental program foreseen for next measurement campaigns.

    The n-TOF facility operates at CERN with the aim of addressing the request of high accuracy nuclear data for advanced nuclear energy systems as well as for nuclear astrophysics. Thanks to the features of the neutron beam, important results have been obtained on neutron induced fission and capture cross sections of U, Pu and minor actinides. Recently the construction of another beam line has started; the new line will be complementary to the first one, allowing to further extend the experimental program foreseen for next measurement campaigns.

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    The nucleosynthesis of heavy elements in Stars: The key isotope 25Mg  Open access

     Massimi, Cristian; Koehler, Paul E.; Kopecky, Stefan; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere
    International Nuclear Physics Conference
    Presentation's date: 2013-06-02
    Presentation of work at congresses

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    We have measured the radiative neutron-capture cross section and the total neutron-induced cross section of one of the most important isotopes for the s process, the 25Mg. The measurements have been carried out at the neutron time-of-flight facilities n-TOF at CERN (Switzerland) and GELINA installed at the EC-JRC-IRMM (Belgium). The cross sections as a function of neutron energy have been measured up to approximately 300 keV, covering the energy region of interest to the s process. The data analysis is ongoing and preliminary results show the potential relevance for the s process. © Owned by the authors, published by EDP Sciences, 2014.

    We have measured the radiative neutron-capture cross section and the total neutron-induced cross section of one of the most important isotopes for the s process, the 25Mg. The measurements have been carried out at the neutron time-of-flight facilities n-TOF at CERN (Switzerland) and GELINA installed at the EC-JRC-IRMM (Belgium). The cross sections as a function of neutron energy have been measured up to approximately 300 keV, covering the energy region of interest to the s process. The data analysis is ongoing and preliminary results show the potential relevance for the s process. © Owned by the authors, published by EDP Sciences, 2014.

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    238U(n, gamma) reaction cross section measurement with C6D6 detectors at the n_TOF CERN facility.  Open access

     Mingrone, Federica; Massimi, Cristian; Vannini, Gianni; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Hernandez Prieto, Alvaro; Riego Pérez, Albert
    International Nuclear Physics Conference
    Presentation's date: 2013-06-02
    Presentation of work at congresses

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    The radiative capture cross section of 238U is very important for the developing of new reactor technologies and the safety of existing ones. Here the preliminary results of the 238U(n,¿) cross section measurement performed at n-TOF with C6D6 scintillation detectors are presented, paying particular attention to data reduction and background subtraction. © Owned by the authors, published by EDP Sciences, 2014.

    The radiative capture cross section of 238U is very important for the developing of new reactor technologies and the safety of existing ones. Here the preliminary results of the 238U(n,¿) cross section measurement performed at n-TOF with C6D6 scintillation detectors are presented, paying particular attention to data reduction and background subtraction. © Owned by the authors, published by EDP Sciences, 2014.

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

     Barbagallo, Massimo; Guerrero, Carlos; Tsinganis, A.; Tarrío, D.; Altstadt, Sebastian; Andriamonje, S.; Andrzejewski, Józef; Audouin, Ludmila; Bécares, Vicente; Becvar, F.; Belloni, Fabio; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Hernandez Prieto, Alvaro; Riego Pérez, Albert
    European physical journal A
    Date of publication: 2013-12-18
    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.

    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 235U 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.

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

     Weiß, C.; Griesmayer, E.; Guerrero, Carlos; Altstadt, Sebastian; Andrzejewski, Józef; Audouin, Ludmila; Badurek, G.; Barbagallo, Massimo; Bécares, Vicente; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; 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

    At then_TOFexperimentatCERNadedicatedsingle-crystalchemicalvapordeposition(sCVD)Diamond Mosaic-Detectorhasbeendevelopedfor(n,α) cross-sectionmeasurements.Thedetector,characterized by anexcellenttimeandenergyresolution,consistsofanarrayof9sCVDdiamonddiodes.Thedetector has beencharacterizedandacross-sectionmeasurementhasbeenperformedforthe 59Ni(n,α)56Fe reaction in2012.Thecharacteristicsofthedetector,itsperformanceandthepromisingpreliminary results oftheexperimentarepresented.

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

     Lederer, Claudia; Massimi, Cristian; 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.

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

     Guerrero, Carlos; Tsinganis, A; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Hernandez Prieto, Alvaro; Riego Pérez, Albert; [et, al]
    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.

  • 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, Nicola; 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.

  • 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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    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.

  • ß-delayed neutron emission measurements around the third r-process abundance peak

     Caballero Folch, Roger; Domingo Pardo, César; Taín, J.L.; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Calviño Tavares, Francisco; Riego Pérez, Albert
    La Rábida, International Scientific Meeting on Nuclear Physics
    Presentation's date: 2012-09-09
    Presentation of work at congresses

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    This contribution summarizes an experiment performed at GSI (Germany) in the neutron-rich region beyond N=126. The aim of this measurement is to provide the nuclear physics input of relevance for r-process model calculations, aiming at a better understanding of the third r-process abundance peak. Many exotic nuclei were measured around 211Hg and 215Tl. Final ion identification diagrams are given in this contribution. For most of them, we expect to derive halflives and and ß -delayed neutron emission probabilities. The detectors used in this experiment were the Silicon IMplantation and Beta Absorber (SIMBA) detector, based on an array of highly segmentedsilicon detectors, and the BEta deLayEd Neutron (BELEN) detector, which consisted of 30 3He counters embedded in a polyethylene matrix.

  • ß-delayed neutron emission measurements around the third r-process abundance peak

     Caballero Folch, Roger; Domingo Pardo, César; Cortes Rossell, Guillem Pere; Calviño Tavares, Francisco; Riego Pérez, Albert
    International Symposium on Nuclei in the Cosmos
    Presentation's date: 2012-08-06
    Presentation of work at congresses

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    The elements heavier than iron are produced in the Universe mainly by means of the slow (s) and rapid (r) neutron capture processes (for a recent review see e.g. [1]). The latter nucleosynthesis mechanism occurs between the valley of stability and the neutron drip line, passing along the neutron shell closures where exceptionally long half-lives and small neutron capture cross sections yield the three characteristic abundance maxima at A ~ 80, 130 and 195.

  • Nuclear Astrophysics at n-TOF, CERN

     Tagliente, G.; Abbondanno, U.; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Poch, A.; Pretel Sanchez, M. del Carmen
    International Conference on Nuclear Reaction Mechanisms
    Presentation's date: 2012-06
    Presentation of work at congresses

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    The neutron time of flight (n-TOF) facility at CERN is a spallation neutron source with white neutron energy spectrum (from thermal to several GeV), covering the full energy range of interest for nuclear astrophysics, in particular for measurements of the neutron capture cross section required in s-process nucleosynthesis. This contribution presents an overview on the astrophysical program carried on at the n-TOF facility, the main results and their implications.

  • Measurement of the fission fragment angular distribution for Th-232(n,f) at the CERN n-TOF facility

     Tarrío, D.; Tassan Got, Laurence; Calviño Tavares, Francisco; Cortes Rossell, Guillem Pere; Gómez Hornillos, María Belén; Riego Pérez, Albert
    International Conference on Nuclear Reaction Mechanisms
    Presentation's date: 2012-06
    Presentation of work at congresses

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    A fission reaction chamber was designed to measure the angular distribution of the fragments emitted in neutron-induced fission reactions at n-TOF. Up to ten Parallel Plate Avalanche Counters can be included and kept at controlled low-pressure gas. Counters are tilted 45° with respect to the neutron beam direction and up to nine targets can be interleaved in between. A first measurement of the 232Th(n,f) was recently done and preliminary experimental results demonstrating the suitability of the setup are presented here.

  • 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
    Participation in a competitive project

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  • FPA2011-28770-C03-03 Datos nucleares para física nuclear e ingeniería nuclear

     Batet Miracle, Lluis; Calviño Tavares, Francisco; Pretel Sanchez, M. del Carmen; Cortes Rossell, Guillem Pere; Caballero Folch, Roger
    Participation in a competitive project

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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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  • 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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  • 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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  • 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.

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

     Lederer, Claudia; Domingo Pardo, César; Gunsing, Frank; Käppeler, F.; Massimi, Cristian; Mengoni, A.; Wallner, A.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Álvarez-Velarde, F.; Andriamonje, S.; Assimakopoulos, P A.; Badurek, G.; Barbagallo, Massimo; Baumann, P.; Becvár, F.; Belloni, Fabio; Berthoumieux, Eric; 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.; 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, Paul E.; 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, Gianni; Vaz, P.; Ventura, A.; Villamarin, D.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wendler, H.; Wiescher, M.; Wisshak, K.; Lozano, Manuel; Colonna, Nicola; Guerrero, Carlos; Andrzejewski, Józef; Audouin, Ludmila
    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.

  • 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.

  • 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.

  • 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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  • 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.

  • Access to the full text
    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, Cristian
    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.