Person: Vedia Fernández, María Victoria
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 10 of 40
PublicationSummation Calculations for Reactor Antineutrino Spectra, Decay Heat and Delayed Neutron Fractions Involving New TAGS Data and Evaluated Databases(E D P Sciences, 2019) Fraile Prieto, Luis Mario; Vedia Fernández, María Victoria; otros, ...Three observables of interest for present and future reactors depend on the beta decay properties of the fission products: antineutrinos from reactors, the reactor decay heat and delayed neutron emission. In these proceedings, we present new results from summation calculations of the first two quantities quoted above, performed with evolved independent yields coupled with fission product decay data, from various nuclear data bases or models. New TAGS results from the latest experiment of the TAGS collaboration at the JYFL facility of Jyvaskyla will be displayed as well as their impact on the antineutrino spectra and the decay heat associated to fission pulses of the main actinides. PublicationTotal absorption gamma-ray spectroscopy study of the beta-decay of Hg-186(Elsevier Science BV, 2021-08-10) Algora, A.; Ganioglu, E.; Sarriguren, P.; Guadilla, V.; Fraile Prieto, Luis Mario; Nácher, E.; Rubio, B.; Tain, J. L.; Agramunt, J.; Gelletly, W.; Briz, J. A.; Cakirli, R.B.; Fallot, M.; Jordan, D.; Halász, Z.; Kuti, I.; Montaner, A.; Onillón, A.; Origo, S.E.A.; Pérez Cerdán, A.; Rice, S.; Vedia Fernández, María Victoria; Valencia, E.The Gamow-Teller strength distribution of the decay of Hg-186 into Au-186 has been determined for the first time using the total absorption gamma spectroscopy technique and has been compared with theoretical QRPA calculations using the SLy4 Skyrme force. The measured Gamow-Teller strength distribution and the half-life are described by mixing oblate and prolate configurations independently in the parent and daughter nuclei. In this theoretical framework the best description of the experimental beta strength is obtained with dominantly prolate components for both parent Hg-186 and daughter Au-186. The approach also allowed us to determine an upper limit of the oblate component in the parent state. The complexity of the analysis required the development of a new approach in the analysis of the X-ray gated total absorption spectrum. (C) 2021 The Authors. Published by Elsevier B.V. PublicationDecay studies of the long-lived states in Tl-186(Amer Physical Soc, 2020-08-18) Fraile Prieto, Luis Mario; Vedia Fernández, María Victoria; otros, ...Decay spectroscopy of the long-lived states in Tl-186 has been performed at the ISOLDE Decay Station at ISOLDE, CERN. The a decay from the low-spin (2(-)) state in Tl-186 was observed for the first time and a half-life of 3.4(-0.)(4)(+0.5) s was determined. Based on the alpha-decay energy, the relative positions of the long-lived states were fixed, with the (2(-)) state as the ground state, the 7((+)) state at 77(56) keV, and the 10((-)) state at 451(56) keV. The level scheme of the internal decay of the Tl-186(10((-))) state [T-1/2 = 3.40(9) s], which was known to decay solely through emission of 374-keV gamma-ray transition, was extended and a lower limit for the beta-decay branching b(beta) > 5.9(3)% was determined. The extracted retardation factors for the gamma decay of the 10((-) )state were compared to the available data in neighboring odd-odd thallium isotopes indicating the importance of the pi d(3/2) shell in the isomeric decay and significant structure differences between Tl-184 and Tl-186. PublicationFast-timing Measurements in 100Zr Using LaBr3(Ce) Detectors Coupled with Gammasphere(Jagiellonian Univ Press, 2018-03) Vedia Fernández, María Victoria; otros, ...In order to investigate the evolution of nuclear deformation in the region of the chart of nuclides around mass numbers A similar or equal to 110 and A similar or equal to 150, an experiment was performed at the Argonne National Laboratory where the gamma-decay radiation emitted from the fission fragments of Cf-252 was measured using 51 Gammasphere detectors coupled with 25 LaBr3 (Ce) detectors. In this work, a short description of the experimental setup is presented together with some preliminary results from the fast-timing analysis of the 4(+) state of the nucleus Zr-100. A lifetime value of tau = 50(28) ps was obtained using the Generalized Centroid Shift Method. This result agrees with the literature value of tau = 53(4) ps within one standard deviation. PublicationReaction Channel selection techniques and gamma - gamma fast-timing spectroscopy using the v-Ball Spectrometer(Iop Publishing Ltd, 2020) Benito García, Jaime; Fraile Prieto, Luis Mario; Vedia Fernández, María Victoria; otros, ...The reaction of a pulsed O-18 beam on a self-supporting and gold-backed isotopically-enriched Dy-164 target of thickness 6.3 mg/cm(2) at separate primary beam energies of 71, 76 and 80 MeV was studied at the accelerator at the ALTO facility of the IPN Orsay. The gamma rays produced were detected using the newly-constructed v-Ball spectrometer which comprised of HPGe and LaBr3(Ce) detectors. This conference paper describes the methodology and effectiveness of multiplicity/sum-energy gating, for channel selection between fusion evaporation events and lower multiplicity/energy events from inelastic nuclear scattering and Coulomb excitation of the target, and from two-neutron transfer reactions to Dy-166. PublicationFast-timing investigation with LaBr₃(Ce) arrays: detector optimization and measurements in ¹³⁶Te(Universidad Complutense de Madrid, 2019-04-30) Vedia Fernández, María Victoria; Fraile Prieto, Luis MarioNuclei with few valence particles outside of a doubly-magic core provide valuable information about single-particle energies, nucleon-nucleon e_ective interactions and may give insight into the onset of collectivity. The region around 132Sn draws particular attention because of the unexpected modi_cations of the shell structure and the sudden collective behaviour that arises. The 136Te nucleus, with two protons and two neutrons coupled to the doubly-magic 132Sn (Z=50 and N=82) constitutes an excellent testing ground for the study of these phenomena, and so it is studied in this PhD thesis. One of the best means to study exotic nuclei is through lifetime measurements of excited states since they allow direct and model independent access to electromagnetic transition probabilities, which are key quantities for the study of single-particle configurations, nuclear collectivity, and make it possible to test theoretical models. Thus this PhD thesis investigates the 136Te nucleus through the lifetime measurements of its excited states... PublicationFirst lifetime investigations of N > 82 iodine isotopes: The quest for collectivity(Amer Physical Soc, 2021-07-19) Benito García, Jaime; Fraile Prieto, Luis Mario; Sánchez Tembleque, Víctor; Vedia Fernández, María Victoria; otros, ...We report on spectroscopic information and lifetime measurements in the neutron-rich I-135,I-137,I-139 isotopes. This is the first lifetime data on iodine isotopes beyond N = 82. Excited states were populated in fast neutron-induced fission of U-238 at the ALTO facility of IJCLab with the LICORNE neutron source and detected using the hybrid nu-ball spectrometer. The level schemes of the I-135,I-137,I-139 isotopes are revised in terms of excited states with up to maximum spin-parity of (33/2(+)), populated for the first time in fast neutron-induced fission. We provide first results on the lifetimes of the (9/2(1)(+)) and (13/2(1)(+)) states in I-137 and I-139, and the (17/2(1)(+)) state in 137I. In addition, we give upper lifetime limits for the (11/2(1)(+)) states in I135-139, the (15/2(1)(+)) state in I-137, the (17/2(1)(+)) state in I-139, and reexamine the (29/2(1)(+)) state in I-137. The isomeric data in I-13(5) are reinvestigated, such as the previously known (15/2(1)(+)) and (23/21) isomers with T-1/2 of 1.64(14) and 4.6(7) ns, respectively, as obtained in this work. The new spectroscopic information is compared to that from spontaneous or thermal-neutron induced fission and discussed in the context of large scale shell-model (LSSM) calculations for the region beyond Sn-132, indicating the behavior of collectivity for the three valence-proton iodine chain with N = 82, 84, 86. PublicationCharacterization and performance of the DTAS detector(Elsevier Science BV, 2018-12-01) Fraile Prieto, Luis Mario; Vedia Fernández, María Victoria; otros, ...DTAS is a segmented total absorption y-ray spectrometer developed for the DESPEC experiment at FAIR. It is composed of up to eighteen NaI(Tl) crystals. In this work we study the performance of this detector with laboratory sources and also under real experimental conditions. We present a procedure to reconstruct offline the sum of the energy deposited in all the crystals of the spectrometer, which is complicated by the effect of NaI(Tl) light-yield non-proportionality. The use of a system to correct for time variations of the gain in individual detector modules, based on a light pulse generator, is demonstrated. We describe also an event-based method to evaluate the summing-pileup electronic distortion in segmented spectrometers. All of this allows a careful characterization of the detector with Monte Carlo simulations that is needed to calculate the response function for the analysis of total absorption gamma-ray spectroscopy data. Special attention was paid to the interaction of neutrons with the spectrometer, since they are a source of contamination in studies of beta-delayed neutron emitting nuclei. PublicationInvestigation of Low-lying States in 133Sn Populated in the β Decay of 133In Using Isomer-selective Laser Ionization(Jagiellonian Univ Press, 2018-03) Fraile Prieto, Luis Mario; Benito García, Jaime; Carmona Gallardo, Mariano; Martínez Pérez, Cristina; Sánchez-Tembleque Verbo, Victor; Udías Moinelo, José Manuel; Vedia Fernández, María Victoria; Villa Abaunza, Amaia; otros, ...Excited states in the neutron-rich isotope Sn-133 were studied via the beta decay of In-133. Isomer selective ionization using the ISOLDE RILIS enabled the beta decays of In-133(gs) (I-pi = 9/2(+)) and In-133m (I-pi = 1/2(-)) to be studied independently for the first time. A description of the experimental setup at the ISOLDE Decay Station is presented together with preliminary results from the experiment. Publicationbeta decay of In-133: gamma emission from neutron-unbound states in Sn-133(American Physical Society, 2019-02-05) Fraile Prieto, Luis Mario; Benito García, Jaime; Carmona, M.; Martínez Pérez, María Cristina; Sánchez-Tembleque Verbo, Victor; Udías Moinelo, José Manuel; Vedia Fernández, María Victoria; Villa Abaunza, Amaia; otros, ...Excited states in Sn-133 were investigated through the beta decay of In-133 at the ISOLDE facility. The ISOLDE Resonance Ionization Laser Ion Source (RILIS) provided isomer-selective ionization for In-133, allowing us to study separately, and in detail, the beta-decay branch of In-133 J(pi)= (9/2(+)) ground state and its J(pi) = (1/2(-)) isomer.Thanks to the large spin difference of the two beta-decaying states of In-133, it is possible to investigate separately the lower and higher spin states in the daughter, Sn-133, and thus to probe independently different single-particle and single-hole levels. We report here new gamma transitions observed in the decay of In-133, including those assigned to the deexcitation of the neutron-unbound states.