V. Bécares
A5103007607- Nuclear Physics and Applications
- Nuclear reactor physics and engineering
- Radiation Detection and Scintillator Technologies
- Nuclear physics research studies
- Particle Detector Development and Performance
- Radiation Therapy and Dosimetry
- Atomic and Subatomic Physics Research
- Nuclear Materials and Properties
- Particle physics theoretical and experimental studies
- Particle accelerators and beam dynamics
- Graphite, nuclear technology, radiation studies
- High-Energy Particle Collisions Research
- Superconducting Materials and Applications
- Astro and Planetary Science
- Boron Compounds in Chemistry
- X-ray Spectroscopy and Fluorescence Analysis
- Magnetic confinement fusion research
- Advanced NMR Techniques and Applications
- Quantum Chromodynamics and Particle Interactions
- Fusion materials and technologies
- Astronomical and nuclear sciences
- Field-Flow Fractionation Techniques
- Muon and positron interactions and applications
- Neutrino Physics Research
- Heat transfer and supercritical fluids
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2015-2024
Universidad Complutense de Madrid
2010-2024
Eurostat
2016
Unidades Centrales Científico-Técnicas
2016
University of Vienna
2014
Czech Technical University in Prague
2011
University of Basel
2011
University of Bologna
2011
Istituto Nazionale di Fisica Nucleare
2011
Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering
2011
The neutron time-of-flight facility n_TOF features a white source produced by spallation through 20GeV/c protons impinging on lead target. facility, aiming primarily at the measurement of neutron-induced reaction cross sections, was operating CERN between 2001 and 2004, then underwent major upgrade in 2008. This paper presents detail all characteristics new beam currently available configurations, which correspond to two different collimation systems choices moderator. discussed include...
The energy-dependent cross section of the ^{7}Be(n,α)^{4}He reaction, interest for so-called cosmological lithium problem in big bang nucleosynthesis, has been measured first time from 10 meV to keV neutron energy. challenges posed by short half-life ^{7}Be and low reaction have overcome at n_TOF thanks an unprecedented combination extremely high luminosity good resolution beam new experimental area (EAR2) facility CERN, availability a sufficient amount chemically pure ^{7}Be, specifically...
At the neutron time-of-flight facility n_TOF at CERN a new vertical beam line was constructed in 2014, order to extend experimental possibilities this an even wider range of challenging cross-section measurements interest astrophysics, nuclear technology and medical physics. The design hall based on FLUKA Monte Carlo simulations, aiming maximizing flux, reducing halo minimizing background from neutrons interacting with collimator or back-scattered dump. present paper gives overview relevant...
We report on the measurement of ^{7}Be(n,p)^{7}Li cross section from thermal to approximately 325 keV neutron energy, performed in high-flux experimental area (EAR2) n_TOF facility at CERN. This reaction plays a key role lithium yield big bang nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements this did not cover energy window interest BBN, and they showed large discrepancy between each other. was with Si telescope high-purity sample produced by...
The $^{63}$Ni($n, \gamma$) cross section has been measured for the first time at neutron time-of-flight facility n\_TOF CERN from thermal energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian Averaged Cross Sections calculated kT = 5 keV 100 with uncertainties around 20%. Stellar model calculations a 25 M$_\odot$ star show that new data have significant effect on $s$-process production $^{63}$Cu, $^{64}$Ni, and $^{64}$Zn in massive stars,...
The neutron sensitivity of the C$_6$D$_6$ detector setup used at n_TOF for capture measurements has been studied by means detailed GEANT4 simulations. A realistic software replica entire experimental hall, including beam line, sample, supports and walls area implemented in simulations have analyzed same manner as data, particular applying Pulse Height Weighting Technique. validated against a measurement background performed with $^\mathrm{nat}$C showing an excellent agreement above 1 keV. At...
This work reports on accurate, high-resolution measurements of the $^{25}$Mg($n, \gamma$)$^{26}$Mg and tot$) cross sections in neutron energy range from thermal to about 300 keV, leading a significantly improved parametrization. The relevant resonances for $n+^{25}$Mg were characterized combined R-matrix analysis experimental data. resulted an unambiguous spin/parity assignment corresponding excited states $^{26}$Mg. With this information upper limits reaction rates $^{22}$Ne($\alpha,...
The cross section of the $^{62}$Ni($n,\gamma$) reaction was measured with time-of-flight technique at neutron facility n_TOF CERN. Capture kernels 42 resonances were analyzed up to 200~keV energy and Maxwellian averaged sections (MACS) from $kT=5-100$ keV calculated. With a total uncertainty 4.5%, stellar is in excellent agreement KADoNiS compilation $kT=30$ keV, while being systematically lower factor 1.6 higher temperatures. $^{63}$Ni($n,\gamma$) for first time n_TOF. We determined...
The $^{58}$Ni $(n,\gamma)$ cross section has been measured at the neutron time of flight facility n_TOF CERN, in energy range from 27 meV up to 400 keV. In total, 51 resonances have analyzed 122 Maxwellian averaged sections (MACS) calculated for stellar temperatures kT$=$5-100 keV with uncertainties less than 6%, showing fair agreement recent experimental and evaluated data kT = 50 MACS extracted present work 30 is 34.2$\pm$0.6$_\mathrm{stat}\pm$1.8$_\mathrm{sys}$ mb, latest results...
A fission reaction chamber based on Parallel Plate Avalanche Counters (PPACs) was built for measuring angular distributions of fragments emitted in neutron-induced actinides at the neutron beam available Neutron Time-Of-Flight (n_TOF) facility CERN. The detectors and samples were tilted 45° with respect to direction cover all possible values emission angle fragments. main features this setup are discussed results fragment distribution provided 232Th(n,f) around threshold. compared data...
Nuclear data in general, and neutron-induced reaction cross sections particular, are important for a wide variety of research fields. They play key role the safety criticality assessment nuclear technology, not only existing power reactors but also radiation dosimetry, medical applications, transmutation waste, accelerator-driven systems, fuel cycle investigations future reactor systems as Generation IV. Applications related to fields study level densities stellar nucleosynthesis....
The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with uranium to make mixed oxide (MOX) fuel. In this way the Pu from is used in a new reactor cycle, contributing long-term sustainability energy. However, an extensive use MOX fuels, particular fast reactors, requires more accurate capture and fission cross sections for some isotopes. case $^{242}\mathrm{Pu}$ there are sizable discrepancies among existing cross-section measurements included...
The 241Am(n,γ) cross section has been measured at the n_TOF facility CERN using deuterated benzene liquid scintillators, commonly known as C6D6 detectors, and time-of-flight spectrometry. results in resolved resonance range bring new constraints to evaluations below 150 eV, energy upper limit was extended from 320 eV with a total of 172 resonances not present current evaluations. thermal capture found be σth=678±68 b, which is good agreement most previous measurements. unresolved region...
The $^{238}\mathrm{U}$ to $^{235}\mathrm{U}$ fission cross section ratio has been determined at n_TOF up $\ensuremath{\approx}1$ GeV, with two different detection systems, in geometrical configurations. A total of four datasets collected and compared. They are all consistent each other within the relative systematic uncertainty 3--4%. data have suitably combined yield a unique as function neutron energy. result confirms current evaluations 200 MeV. Good agreement is also observed theoretical...
The newly built second experimental area EAR2 of the n_TOF spallation neutron source at CERN allows to perform (n, charged particles) experiments on short-lived highly radioactive targets. This paper describes a detection apparatus and procedure for determination cross-section 7Be(n,α)α reaction, which represents one focal points toward solution cosmological Lithium abundance problem, whose only measurement, thermal energy, dates back 1963. apparently unsurmountable difficulties stemming...
The neutron capture cross sections of several unstable nuclides acting as branching points in the $s$ process are crucial for stellar nucleosynthesis studies. $^{171}\mathrm{Tm}$ (${t}_{1/2}=1.92\text{ }\text{ }\mathrm{yr}$) is part around mass $A\ensuremath{\sim}170$ but its section a function energy not known to date. In this work, following production first time more than 5 mg at high-flux reactor Institut Laue-Langevin France, sample was produced Paul Scherrer Institute Switzerland. Two...
Within the frame of EU H2020 program SANDA project, sensitivity and uncertainty analyses have been performed for ESFR, ASTRID ALFRED reactor concepts multi-purpose flexible irradiation facility MYRRHA. Relevant parameters, namely effective multiplication factor, delayed neutron fraction, Doppler reactivity coefficient, void worth control rods investigated. SCALE, Serpent 2 MCNP6.2+SUMMON codes together with covariance data JEFF-3.3 nuclear library used this study. A ranking most important...
The measurement of the capture cross-section fissile elements, utmost importance for design innovative nuclear reactors and management waste, faces particular difficulties related to $ \gamma$ -ray background generated in competing fission reactions. At CERN neutron time-of-flight facility n_TOF we have combined Total Absorption Calorimeter (TAC) detector with a set three 235U loaded MicroMegas (MGAS) detectors measuring simultaneously two reactions: fission. results presented here include...
AbstractAbstractThe area ratio method of Sjöstrand is generally considered one the most reliable reactivity determination methods and thus a major candidate for off-line calibration purposes in future accelerator-driven systems high-level waste incineration. In this work, has been evaluated experimentally under thorough conditions strongly heterogeneous subcritical facility YALINA-Booster. Both strengths weaknesses have identified. Most surprisingly, it found that estimates may differ factor...