Evaporation residues produced in spallation of 208Pb by protons at 500A MeV

The production cross sections of fragmentation-evaporation residues in the reaction Pb+p at 500A MeV have been measured using the inverse-kinematics method and the FRS spectrometer (GSI). Fragments were identified in nuclear charge using ionisation chambers. The mass identification was performed event-by-event using the B-rho - TOF - Delta-E technique. Although partially-unresolved ionic charge states induced an ambiguity on the mass of some heavy fragments, production rates could be obtained with a high accuracy by systematically accounting for the polluting ionic charge states. The contribution of multiple reactions in the target was subtracted using a new, partly self-consistent code. The isobaric distributions are found to have a shape very close to the one observed in experiments at higher energy. Kinematic properties of the fragments were also measured. The total and the isotopic cross sections, including charge-pickup cross sections, are in good agreement with previous measurements. The data are discussed in the light of previous spallation measurements, especially on lead at 1 GeV

From the HINDAS Project : Excitation Functions for Residual Nuclide Production by Proton-Induced Reactions

peer reviewe

Spallation reactions. A successful interplay between modeling and applications

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie

Production rates and proton-induced production cross sections of 129I from Te and Ba: An attempt to model the 129I production in stony meteoroids and 129I in a Knyahinya sample

Proton-induced production cross sections of 129I from Te and Ba are presented. Earlier assumptions that Te is the most important target element in meteoroids are confirmed. Based on this data set and the experimental production rates of 129I from thick-target experiments, the production of 129I in stony meteoroids is modeled using a GCR flux density of 4.06 cm^(-2) s^(-1). The results of this modeling must be considered preliminary because the contribution from neutron capture on 128Te needs further investigation. We obtained modeled production rates that agree with experimental results for samples from two medium-sized meteorites (Abee and Knyahinya). However, we find that this model does not describe 41Ca in lunar rocks well and seems to overestimate 129I production in larger bodies, such as Allende. We present elemental production rates from Te and Ba based on our modeling as well as for a model that describes neutron capture products. For 129I analysis of Knyahinya, a novel method to separate Te and analysis using ICP-MS was used, enabling the use of experimental elemental concentrations obtained from the same meteorite to calculate 129I production.The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Proton-induced production cross-sections and production rates of Ca-41 from Ni

Proton-induced production cross-sections of Ca-41 from Ni are presented. Moreover, depth-dependent production rates of Ca-41 from Ni were determined in a meteoroid simulation experiment. Based on these data, modelled production rates of Ca-41 from Ni in iron meteoroids are presented as a function of depth and size. These data are relevant for modelling the production rate ratio of Ca-41/Cl-36 in metal phases of meteoroids and thus for the application of the Ca-41-Cl-36 method to determine terrestrial ages of meteorites

Evaluación de hardware basada en rendimiento-costo, para la adquisición óptima de computadoras personales.

Con la finalidad de disponer de criterios técnicos que orienten a los compradores comunes de computadoras, a la hora de seleccionar equipos informáticos que ofrezcan el mejor desempeño dentro del presupuesto disponible y basados en la relación del rendimiento versus precio, se desarrolla un censo dentro de la población universitaria entre los meses de enero a marzo de 2019; a los que se le aplican dos encuestas como medio de recolección de datos, las cuales presentan un 37.5% de preguntas abiertas y un 62.5% de cerradas, ambas fueron estructuradas y validadas como referentes para la obtención de los resultados. Se desarrolla un modelo de análisis no experimental en donde los resultados obtenidos se contrastan contra un modelo de evaluación basado en la distribución normal. Como aspecto concluyente, bajo el modelo de evaluación propuesto se determinó que, dentro del grupo de referencia, únicamente el 18.81% de las respuestas fueron aciertos, lo que se refleja en un nivel de conocimiento muy bajo en cuanto a la comprensión de las características fundamentales de sus equipos