14 research outputs found

    Suppression of Coulomb-nuclear interference in the near-barrier elastic scattering of 17 Ne from 208 Pb

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    The proton drip-line nucleus 17Ne is considered a good candidate for a Borromean two-proton halo with a 15O + p+ pstructure. Angular distributions of the elastic scattering and inclusive 15O production for a 136 MeV 17Ne beam incident on a 208Pb target were measured for the first time at the SPIRAL1 facility, GANIL. Use of the GLORIA detector array allowed high-resolution data over a wide angular range from 20◦up to 95◦in the laboratory frame to be obtained. The elastic scattering angular distribution shows similarities with those for both 6He and 20Ne at equivalent collision energies with respect to the corresponding Coulomb barriers, exhibiting the suppression of the Coulomb rainbow peak characteristic of strong coupling. Optical model and coupled channel fits suggest that this is due to a combination of coupling to low-lying quadrupole resonances and Coulomb dipole coupling to the low-lying continuum, although their relative importance depends on the relevant B(E2)values which remain to be firmly determined

    Interaction of 8He with 208Pb at near-barrier energies: 4He and 6He production

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    Angular distributions for the inclusive 4He and 6He production cross sections in the 8He+208Pb system at incident energies of 16 and 22 MeV measured at the SPIRAL facility of the GANIL laboratory are presented. Using a combination of kinematical arguments and distorted wave Born approximation (DWBA) calculations, neutron transfer reactions were inferred to be the dominant contributors to both inclusive cross sections. Model-dependent values for the ratios of two- to one-neutron stripping, s2n/s1n, were derived and compared with previous results for 8He and 6He projectiles incident on other heavy targets. Three- and four-neutron stripping were inferred to be the main processes leading to 4He production, although the exact mechanism remains to be elucidated.The authors would like to thank the staff of the GANIL accelerator facility for providing the high-quality 8He beam. This work was supported in part by Grants No. FPA-2010-22131-CO2-01 (FINURA) and No. FPA2013-47327-C2-1-R from the Spanish Ministry of Economy and Competitiveness, UNAM-PAPIIT IA103218 (Mexico); Grant No. N202 033637 from the Ministry of Science and Higher Education of Poland; the National Science Centre of Poland under Contracts No. 2013/08/M/ST2/00257 (LEA-COPIGAL) and No. 2014/14/M/ST2/00738 (COPIN-INFN Collaboration); and Grant No. EUI2009-04163432 (EUROGENESIS) from the European Science Foundation

    Sub-barrier fusion of 6He with 206Pb

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    Cross-sections for the production of 210Po nuclei in 6He + 206Pb collisions over the incident energy range 14–18MeV were measured by means of the activation technique and a radiochemical analysis. The elastic scattering at 18.0MeV was also measured providing a precise value for the 210Po production cross-section at this energy. The results are at variance with the earlier experimental data and rather in accord with the predictions of a density-dependent barrier penetration model for the fusion process. A proper treatment of beam energy distribution for the evaluation of the activation data is discussed

    Riesgo de subsidencia kárstica en áreas urbanas: el caso de Zaragoza

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    Parte del monográfico "Riesgos geológicos externos".[EN] This paper deals with the problems generated by karst in gypsum around Zaragoza, the development of alluvial sinkholes and the concomitant risks. Sinkhole geometry depends on the mechanical behaviour of the cover overlying the evaporitic bedrock: non-cohesive soils favour the development of basin and funnel shaped dolines, whereas cohesive covers lead to the development of well-shaped collapses. Surface survey in areas prone to develop dolines is based on aerial photographs, in situ features (such as topographic depressions, stepped ground, anomalous man-made fills, wet-ground vegetation), and location of building pathologies in urban areas. In some cases, the structure and geometry of dolines can be studied in section (road cuts, for instance), where the features of natural fills allow to characterize the evolutionary patterns and sedimentation- subsidence interactions. Through dating of such fills the rate of subsidence can be estimated, and linked to possible episodes of climate variations. Doline evolution through time, either by comparison of aerial photographs taken in different years or by instrumental survey, yields the scenario of a dynamic process with subsidence rates up to 12 cm/year, where cycles of steady subsidence periods and sudden collapse are identified. In the Zaragoza area, the consequences of karst subsidence are outstanding. They dramatically increased from the 70’s, when large portions of the territory, formerly of agricultural use, turned into urban, industrial and service uses. Prevention and hazard management of karstic risks on urban and peri-urban areas must include: 1) early detection of the problem, in surface as well as underground (by means of geophysical surveys), and 2) adaptation of land use to the degree of affection by karst and the potential susceptibility. Geology, geotechnics and engineering have specific roles on risk management strategies by diminishing either the exposition to karst hazard or the vulnerability of man made structures.[ES] Este trabajo analiza, desde múltiples puntos de vista, la problemática del karst en yesos en el entorno de Zaragoza, el desarrollo de dolinas aluviales y los riesgos que éstas conllevan. La morfología de las dolinas depende del comportamiento mecánico de la cobertera situada sobre el sustrato yesífero: en coberteras sin cohesión aparecen morfologías en embudo y en cubeta, producidas por subsidencia continuada, mientras en coberteras con cohesión se producen dolinas en ventana provocadas por colapso brusco. El reconocimiento superficial de las dolinas se basa en la observación de fotografías aéreas, en el análisis visual del terreno (depresiones topográficas, escalones, áreas de vegetación o rellenos antrópicos anómalos) y en la observación y análisis de daños en áreas urbanizadas. También pueden estudiarse la geometría y la estructura interna de las dolinas en secciones del terreno donde éstas hayan quedado expuestas. Así, las características de sus rellenos naturales permiten conocer las pautas y tasas de evolución y las interacciones entre la subsidencia kárstica y los procesos sedimentarios. El estudio de la evolución temporal de las dolinas, a partir de la comparación de fotografías aéreas de distintos años o del seguimiento instrumental de las mismas, ha permitido reconocer que se trata de un proceso dinámico que llega a alcanzar velocidades de hundimiento de 12 cm/año. En dicha evolución es frecuente la ocurrencia cíclica de periodos de subsidencia lenta y eventos de hundimiento brusco. La afección causada por la subsidencia kárstica en Zaragoza es muy significativa. Ésta se incrementó a partir de los años 70 del siglo pasado, cuando buena parte del suelo agrícola que circundaba la ciudad fue destinado a uso urbano, industrial y grandes infraestructuras. La prevención y manejo del riesgo kárstico en áreas urbanas y peri-urbanas debe contemplar: (1) la detección precoz de los fenómenos tanto en superficie como en profundidad (a partir de estudios geofísicos), y (2) la adaptación del uso del suelo a su grado de afección por fenómenos kársticos y a su susceptibilidad potencial a los mismos. La geología, la geotecnia y la ingeniería desempeñan, cada una, un papel específico en la estrategia para reducir el riesgo, bien sea evitando la exposición al peligro o disminuyendo la vulnerabilidad de las construcciones.Peer reviewe

    Actualidad y prospectiva de la investigación científica en el Centro Universitario Amecameca de la Universidad Autónoma del Estado de México

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    Con responsabilidad, se organizó un programa cuya finalidad fuera publicitar con transparencia dichos avances, a través de un esfuerzo de rendición de cuentas a la comunidad inmediata, la universitaria, y a la comunidad abierta, la sociedad que la principal referencia para tal efecto. El programa se concretiza a través del presente libro, conformado con una inspiración de investigación multidisciplinaria; sin embargo, para llegar a tal fin, el reto es realizar el proceso de búsqueda y generación de conocimiento transitando hacia la colaboración de los cuerpos académicos, que puedan construir nuevos conocimientos fortalecidos por la convergencia de diferentes campos del saber. En consecuencia, la primera etapa de esta estrategia es la publicidad de los trabajos investigativos ejercidos, para hacer un balance al día, pero también proyectar el futuro de cada campo y área del conocimiento. La organización explicativa está organizada por tres bloques representativos del quehacer en la generación de conocimiento del Centro Universitario, un primer bloque centra el interés en las humanidades, educación y sustentabilidad; el segundo bloque lo integra la reflexión científica sobre la construcción democrática, derechos humanos y equidad de género; en el tercer segmento se destina a la seguridad alimentaria, salud pública y sistemas agropecuarios. La actualidad de la investigación eleva la producción lograda y lo que en el momento se encuentra en construcción y los alcances que produce para la docencia, la investigación misma, y para la sociedad en general. La prospectiva es un área que todos los capítulos desarrollan con el propósito de delinear los alcances innovadores por andar en teoría, metodología e incluso en los saberes mismo

    A dosimetric model for determining the effectiveness of soil covers for phosphogypsum waste piles

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    Phosphogypsum (PG) is a by-product of the phosphoric acid production process that contains high concentrations of U-series radionuclides. PG piles formed during the last 30 years cover about 1,200 hectares and are located close to the town of Huelva (Spain) on a salt-marsh. The regional government of Andalusia restored the area beginning in 1990 by covering it with a 25-cm-thick layer of natural soil. With this restoration, the external gamma-dose rate in the zone has decreased drastically, approaching near environmental background values. This conclusion is based on results obtained through in-situ monitoring measurements and through a dosimetric model developed for that particular radiation source. As the model uses average parameters of the studied site, its output does not show a correlation point by point with the in-situ monitoring measurements. However, a good agreement is observed in average values over the covered piles. The model gives an average dose rate of 0.41 mGy y21 and the in situ monitoring 0.40 mGy y21 . Based on this model, it is possible to calculate the necessary thickness of soil to reduce the dosimetric contribution from a similar extension of PG until the desired level is reached. In our conditions, in a 25-cm-thick soil, about 0.19 mGy y21 is the increase produced by the PG layer in relation to an infinitum soil layer. Consequently, no radiological concern exists in the restored zones with respect to the external gamma radiatio

    A simple method for efficiency calibration of HPGe detectors in gamma-spectrometric measurements

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    In this paper a simple, rapid and general method for g-ray efficiency calibration of Ge detectors for environmental samples is presented. This method is based on the use of an active natural solid sample with several g-emissions (in our case, 226Ra) as the calibrating matrix for determining the full energy peak efficiency (FEPE) ec vs g-emission energy Eg and the sample height h in a counting cylindrical geometry. The 226Ra activity concentration is determined by a-particle spectrometry, a method that has previously been validate

    An innovative Superconducting Recoil Separator for HIE-ISOLDE

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    The ISOLDE Scientific Infrastructure at CERN offers a unique range of post-accelerated radioactive beams. The scientific program can be improved with the “Isolde Superconducting Recoil Separator” (ISRS), an innovative spectrometer able to deliver unprecedented (A, Z) resolution. In this paper we present an overview of the physics and ongoing technical developments.Work partially funded by the Grant PID2021-127711NB-I00 (Spanish Ministry of Science and Innovation, Spain), the Recovery and Resilience Facility (Spain), and the European Union – Next Generation EU funds.Departamento de Física Aplicad
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