567 research outputs found

    First results from the CAST experiment

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    The CAST Experiment commenced its first phase of solar axion-searching in 2003, and ran successfully for two years. In the transverse field of a decommissioned Large Hadron Collider (LHC) test magnet (9.26m, 9T), the CERN Axion Solar Telescope intends to transform axions -that would be produced in the sun- into X-rays with energies of a few keV. The first results from the analysis of the data taken in 2003 show no signature of axions, implying an upper limit to the axion-photon coupling gaő≥ ‚©Ĺ 1.16 √ó 10‚ĀĽ¬Ļ‚Āį GeV‚ĀĽ¬Ļ at 95% C.L. for ma < 0.02 eV, already a factor 100 better than previous searches. In Phase I the twin bores of the magnet were kept in vacuum. In Phase II (due to start in November 2005) the bores of the magnet will be filled with a buffer gas, which will allow CAST to explore the region of higher axion masses

    Measurement of the neutron-induced fission cross-section of Am at the time-of-flight facility n TOF

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    Abstract. The neutron-induced fission cross-section of 241 Am has been measured relative to the standard fission cross-section of 235 U between 0.5 and 20 MeV. The experiment was performed at the CERN n TOF facility. Fission fragments were detected by a fast ionization chamber by discriminating against the őĪ-particles from the high radioactivity of the samples. The high instantaneous neutron flux and the low background of the n TOF facility enabled us to obtain uncertainties of ‚Čą 5%. With the present results it was possible to resolve discrepancies between previous data sets and to confirm current evaluations, thus providing important information for design studies of future reactors with improved fuel burn-up

    Measurement of the 241Am neutron capture cross section at the n-TOF facility at CERN

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    New neutron cross section measurements of minor actinides have been performed recently in order to reduce the uncertainties in the evaluated data, which is important for the design of advanced nuclear reactors and, in particular, for determining their performance in the transmutation of nuclear waste. We have measured the 241Am(n,ő≥) cross section at the n_TOF facility between 0.2‚ÄČeV and 10‚ÄČkeV with a BaF2 Total Absorption Calorimeter, and the analysis of the measurement has been recently concluded. Our results are in reasonable agreement below 20‚ÄČeV with the ones published by C. Lampoudis et al. in 2013, who reported a 22% larger capture cross section up to 110‚ÄČeV compared to experimental and evaluated data published before. Our results also indicate that the 241Am(n,ő≥) cross section is underestimated in the present evaluated libraries between 20‚ÄČeV and 2‚ÄČkeV by 25%, on average, and up to 35% for certain evaluations and energy ranges.This work was supported in part by the Spanish national company for radioactive waste management ENRESA, through the CIEMAT-ENRESA agreements on ‚ÄúTransmutacion de residuos' radiactivos de alta actividad‚ÄĚ the Spanish Plan Nacional de I+D+i de F¬īńĪsica de Part¬īńĪculas (project FPA2014-53290-C2-1) and the European Commission with the FP7 projects ANDES (FP7-249671) and CHANDA (FP7-605203)

    Measurement and analysis of the Am-241 neutron capture cross section at the n_TOF facility at CERN

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    The Am-241(n, gamma) cross section has been measured at the n_TOF facility at CERN with the n_TOF BaF2 Total Absorption Calorimeter in the energy range between 0.2 eV and 10 keV. Our results are analyzed as resolved resonances up to 700 eV, allowing a more detailed description of the cross section than in the current evaluations, which contain resolved resonances only up to 150-160 eV. The cross section in the unresolved resonance region is perfectly consistent with the predictions based on the average resonance parameters deduced from the resolved resonances, thus obtaining a consistent description of the cross section in the full neutron energy range under study. Below 20 eV, our results are in reasonable agreement with JEFF-3.2 as well as with the most recent direct measurements of the resonance integral, and differ up to 20-30% with other experimental data. Between 20 eV and 1 keV, the disagreement with other experimental data and evaluations gradually decreases, in general, with the neutron energy. Above 1 keV, we find compatible results with previously existing values

    Measurement and analysis of the 241 Am neutron capture cross section at the n_TOF facility at CERN

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    The 241 Am ( n , ő≥ ) cross section has been measured at the n_TOF facility at CERN with the n_TOF BaF 2 Total Absorption Calorimeter in the energy range between 0.2 eV and 10 keV. Our results are analyzed as resolved resonances up to 700 eV, allowing a more detailed description of the cross section than in the current evaluations, which contain resolved resonances only up to 150‚Äď160 eV. The cross section in the unresolved resonance region is perfectly consistent with the predictions based on the average resonance parameters deduced from the resolved resonances, thus obtaining a consistent description of the cross section in the full neutron energy range under study. Below 20 eV, our results are in reasonable agreement with JEFF-3.2 as well as with the most recent direct measurements of the resonance integral, and differ up to 20‚Äď30% with other experimental data. Between 20 eV and 1 keV, the disagreement with other experimental data and evaluations gradually decreases, in general, with the neutron energy. Above 1 keV, we find compatible results with previously existing values.Plan Nacional de I+D+i de F√≠sica de Part√≠culas de Espa√Īa. FPA2016-76765-P y FPA2014-53290-C2-1-PSeventh Framework Programme de la Comunidad Europea. ANDES FP7-249671 y CHANDA FP7- 60520

    Measurement of the 241Am neutron capture cross section at the n-TOF facility at CERN

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    New neutron cross section measurements of minor actinides have been performed recently in order to reduce the uncertainties in the evaluated data, which is important for the design of advanced nuclear reactors and, in particular, for determining their performance in the transmutation of nuclear waste. We have measured the 241 Am(n,ő≥) cross section at the n TOF facility between 0.2 eV and 10 keV with a BaF2 Total Absorption Calorimeter, and the analysis of the measurement has been recently concluded. Our results are in reasonable agreement below 20 eV with the ones published by C. Lampoudis et al. in 2013, who reported a 22% larger capture cross section up to 110 eV compared to experimental and evaluated data published before. Our results also indicate that the 241 Am(n,ő≥) cross section is underestimated in the present evaluated libraries between 20 eV and 2 keV by 25%, on average, and up to 35% for certain evaluations and energy ranges.Plan Nacional I+D+I FPA2014-53290-C2-1Comisi√≥n Europea, ANDES FP7- 249671Comisi√≥n Europea, CHANDA FP7-60520

    Measurement of the 241^{241}Am neutron capture cross section at the n_TOF facility at CERN

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    High-accuracy determination of the neutron flux in the new experimental area n_TOF-EAR2 at CERN

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    A new high flux experimental area has recently become operational at the n_TOF facility at CERN. This new measuring station, n_TOF-EAR2, is placed at the end of a vertical beam line at a distance of approximately 20m from the spallation target. The characterization of the neutron beam, in terms of flux, spatial profile and resolution function, is of crucial importance for the feasibility study and data analysis of all measurements to be performed in the new area. In this paper, the measurement of the neutron flux, performed with different solid-state and gaseous detection systems, and using three neutron-converting reactions considered standard in different energy regions is reported. The results of the various measurements have been combined, yielding an evaluated neutron energy distribution in a wide energy range, from 2meV to 100MeV, with an accuracy ranging from 2%, at low energy, to 6% in the high-energy region. In addition, an absolute normalization of the n_TOF-EAR2 neutron flux has been obtained by means of an activation measurement performed with 197Au foils in the beam.Peer reviewe
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