29 research outputs found

    Neutron capture and total cross-section measurements on 94,95,96Mo at n_TOF and GELINA

    Get PDF
    This work was supported by the EUFRAT open-access project of the JRC Geel and received funding from the Euratom research and training programme 2014-2018 under grant agreement No 847594 (ARIEL).Capture and total cross section measurements for 94'95'96 MO have been performed at the neutron time -of-flight facilities, n_TOF at CERN and GELINA at JRC-Geel. The measurements were performed using isotopically enriched samples with an enrichment above 95% for each of the (94'95'96)M0 isotopes. The capture measurements were performed at n_TOF using C6D6 detectors and a new sTED detector. The transmission measurements were performed at a 10 m station of GELINA using a Li-6 glass neutron detector. Preliminary results of these measurements are presented.EUFRAT open-access project of the JRC GeelEuratom 84759

    Pushing the high count rate limits of scintillation detectors for challenging neutron-capture experiments

    Full text link
    One of the critical aspects for the accurate determination of neutron capture cross sections when combining time-of-flight and total energy detector techniques is the characterization and control of systematic uncertainties associated to the measuring devices. In this work we explore the most conspicuous effects associated to harsh count rate conditions: dead-time and pile-up effects. Both effects, when not properly treated, can lead to large systematic uncertainties and bias in the determination of neutron cross sections. In the majority of neutron capture measurements carried out at the CERN n\_TOF facility, the detectors of choice are the C6_{6}D6_{6} liquid-based either in form of large-volume cells or recently commissioned sTED detector array, consisting of much smaller-volume modules. To account for the aforementioned effects, we introduce a Monte Carlo model for these detectors mimicking harsh count rate conditions similar to those happening at the CERN n\_TOF 20~m fligth path vertical measuring station. The model parameters are extracted by comparison with the experimental data taken at the same facility during 2022 experimental campaign. We propose a novel methodology to consider both, dead-time and pile-up effects simultaneously for these fast detectors and check the applicability to experimental data from 197^{197}Au(nn,Îł\gamma), including the saturated 4.9~eV resonance which is an important component of normalization for neutron cross section measurements

    Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF

    Get PDF
    This article presents a few selected developments and future ideas related to the measurement of (n,Îł) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with Îł-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area

    Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF

    Get PDF
    This article presents a few selected developments and future ideas related to the measurement of (n,Îł) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with Îł-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area

    Scientific motivations for a reassessment of the neutron capture cross sections of erbium isotopes in the high-sensitivity thermal energy range for LWR systems

    No full text
    Research conducted in the last twenty years in the field of burnable absorbers showed that erbium isotopes can be considered as an excellent alternative absorber to gadolinium isotopes for their neutronic and nuclear safety improving features. The development of the Erbium Super High Burnup (Er-SHB) concept demonstrated that erbium could be directly mixed in all fuel pins of a fuel assembly (FA) at the Beginning of Life (BOL). This innovative design allows an improvement of nuclear safety, a better control of the operational and accidental transient phase and an extension of the fuel life with respect to the most used burnable absorber (i.e., gadolinium). Furthermore, the extensive use of an Er-SHB fuel design would allow the production of higher enriched nuclear fuel (i.e., >5 wt%) within the existing manufacturing facilities without any modification of the facility itself and with a general improvement of the nuclear safety of the front-end phase of the nuclear fuel cycle. Nevertheless, reported erbium cross-sections are dated and poorly investigated in the high sensitivity thermal energy region for nuclear technology. In addition, some of them (i.e., Er-166) are reported with an uncertainty that is too high for their use in the future design of the erbia-doped LWR assembly by the industry. On the other hand, evaluated uncertainties by the ENDF/B-VIII.0 library in the thermal/epithermal region for the most sensitive isotopes (i.e., Er-167) seem to be too low with respect to both the experimental data and the analysis of the results provided by some erbia-doped critical systems of the International Critical Safety Benchmark Evaluation Project (ICSBEP). Based on the reanalysis of the ICSBEP outcomes, and a sensitivity-uncertainty analysis (S&U) on an Er-SHB LWR assembly, this article shows that recent evaluations appear inadequate to provide accurate criticality calculations for a system all equipped with erbium fuel pins for neutronic design purpose. Moreover, the S&U results have shown the importance of erbium isotopes to correctly evaluate the uncertainty associated with a Light Water Reactor (LWR) critical system. They confirmed the need for a re-evaluation of their neutron capture cross section by means of a new experimental campaign. A proposal aiming at performing a new capture measurement of erbium isotope cross sections has already been submitted to GELINA facility at Geel (Belgium), which is particularly suitable for neutron capture and transmission measurements in the thermal and epithermal energy regions. On August 2021, U.S. Nuclear Energy Agency (NEA) added the revaluation of Er-167(n, Îł) in its High Priority Request List (HPRL) based on the outcomes reported in this work. On January 2022, GELINA Scientific Committee accepted the proposal within the 2021 calls for open access to JRC Research Infrastructures in the research filed of European Research for nuclear reaction, radioactivity, radiation and technology studies in science and application (EUFRAT)

    Measurement and analysis of 155,157Gd(n,Îł) from thermal energy to 1 keV

    Get PDF
    We have measured the capture cross section of the 155Gd and 157Gd isotopes between 0.025 eV and 1 keV. The capture events were recorded by an array of 4 C6D6 detectors, and the capture yield was deduced exploiting the total energy detection system in combination with the Pulse Height Weighting Techniques. Because of the large cross section around thermal neutron energy, 4 metallic samples of different thickness were used to prevent problems related to self-shielding. The samples were isotopically enriched, with a cross contamination of the other isotope of less than 1.14%. The capture yield was analyzed with an R-Matrix code to describe the cross section in terms of resonance parameters. Near thermal energies, the results are significantly different from evaluations and from previous time-of-flight experiments. The data from the present measurement at n_TOF are publicly available in the experimental nuclear reaction database EXFOR

    Measurement and analysis of

    Get PDF
    We have measured the capture cross section of the 155Gd and 157Gd isotopes between 0.025 eV and 1 keV. The capture events were recorded by an array of 4 C6D6 detectors, and the capture yield was deduced exploiting the total energy detection system in combination with the Pulse Height Weighting Techniques. Because of the large cross section around thermal neutron energy, 4 metallic samples of different thickness were used to prevent problems related to self-shielding. The samples were isotopically enriched, with a cross contamination of the other isotope of less than 1.14%. The capture yield was analyzed with an R-Matrix code to describe the cross section in terms of resonance parameters. Near thermal energies, the results are significantly different from evaluations and from previous time-of-flight experiments. The data from the present measurement at n_TOF are publicly available in the experimental nuclear reaction database EXFOR

    Measurement and analysis of 155,157^{155,157}Gd(n,Îł\gamma) from thermal energy to 1 keV

    No full text
    International audienceWe have measured the capture cross section of the 155^{155}Gd and 157^{157}Gd isotopes between 0.025 eV and 1 keV. The capture events were recorded by an array of 4 C6_{6}D6_{6} detectors, and the capture yield was deduced exploiting the total energy detection system in combination with the Pulse Height Weighting Techniques. Because of the large cross section around thermal neutron energy, 4 metallic samples of different thickness were used to prevent problems related to self-shielding. The samples were isotopically enriched, with a cross contamination of the other isotope of less than 1.14%. The capture yield was analyzed with an R-Matrix code to describe the cross section in terms of resonance parameters. Near thermal energies, the results are significantly different from evaluations and from previous time-of-flight experiments. The data from the present measurement at n_TOF are publicly available in the experimental nuclear reaction database EXFOR.</jats:p
    corecore