Radiolysis of ammonia-containing ices by energetic, heavy and highly charged ions inside dense astrophysical environments

Deeply inside dense molecular clouds and protostellar disks, the interstellar ices are protected from stellar energetic UV photons. However, X-rays and energetic cosmic rays can penetrate inside these regions triggering chemical reactions, molecular dissociation and evaporation processes. We present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV Ni^13+) with ammonia-containing ices in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed inside a high vacuum chamber coupled to the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France.\textit{In-situ} analysis is performed by a Fourier transform infrared spectrometer (FTIR) at different fluences. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide due to heavy cosmic ray ion analogs are ~2x10^{-13}, 1.4x10^{-13} and 1.9x10^{-13} cm$^2$, respectively. In the presence of a typical heavy cosmic ray field, the estimated half life for the studied species is 2-3x10^6 years. The ice compaction (micropore collapse) due to heavy cosmic rays seems to be at least 3 orders of magnitude higher than the one promoted by (0.8 MeV) protons . In the case of the irradiated H2O:NH3:CO ice, the infrared spectrum at room temperature reveals five bands that were tentatively assigned to vibration modes of the zwitterionic glycine (+NH3CH2COO-).Comment: Accepted to be published in Astronomy and Astrophysics; Number of pages: 12; Number of Figures: 7; Number of Tables:

Estudio de la evolución de la red de comunicaciones de un operador logístico

Este proyecto surge a raíz de la aparición de nuevas posibilidades tecnológicas en el campo de las infraestructuras logísticas. El documento contiene una descripción actual de un operador logístico y realiza una propuesta de innovación tecnológica a partir de las debilidades detectadas. Se define que funciones tiene actualmente un operador y se coge como punto de partida uno en concreto. A partir de aquí se define primero la propuesta de red corporativa realizando el dimensionado de voz y datos para definir el esquema de red en la que se integran voz y datos. En el cuarto capítulo se propone un sistema de posicionamiento y control de flota que compone el operador con el objetivo de automatizar el proceso de entrega y trazar mediante aplicaciones de control y posicionamiento de la flota las rutas más rápidas y eficientes. En el quinto capítulo se definirá una solución de video vigilancia y centralización de alarmas que permitirá mecanizar y centralizar la seguridad de todas las sedes en la sede principal del operador. Posteriormente se realizará un plan de implantación en el tiempo de todas las innovaciones propuestas en el que se detallará los pasos realizados en la puesta en marcha de las propuestas del presente proyecto. En el capítulo siete se define un plan de explotación, mantenimiento y monitorización basados en los principios ITL de buenas prácticas. Se desarrollan los procesos y funciones necesarios para la gestión de la nueva infraestructura. En el octavo capítulo se ha detallado un plan de contingencia que servirá para amortiguar el impacto de las posibles fallidas tecnológicas en el desarrollo del negocio. Por último se realiza un análisis del impacto económico que tendrá este despliegue tecnológico en el operador y se sacan conclusiones

SPORT: A new sub-nanosecond time-resolved instrument to study swift heavy ion-beam induced luminescence - Application to luminescence degradation of a fast plastic scintillator

We developed a new sub-nanosecond time-resolved instrument to study the dynamics of UV-visible luminescence under high stopping power heavy ion irradiation. We applied our instrument, called SPORT, on a fast plastic scintillator (BC-400) irradiated with 27-MeV Ar ions having high mean electronic stopping power of 2.6 MeV/\mu m. As a consequence of increasing permanent radiation damages with increasing ion fluence, our investigations reveal a degradation of scintillation intensity together with, thanks to the time-resolved measurement, a decrease in the decay constant of the scintillator. This combination indicates that luminescence degradation processes by both dynamic and static quenching, the latter mechanism being predominant. Under such high density excitation, the scintillation deterioration of BC-400 is significantly enhanced compared to that observed in previous investigations, mainly performed using light ions. The observed non-linear behaviour implies that the dose at which luminescence starts deteriorating is not independent on particles' stopping power, thus illustrating that the radiation hardness of plastic scintillators can be strongly weakened under high excitation density in heavy ion environments.Comment: 5 figures, accepted in Nucl. Instrum. Methods

Ion-beam mixing induced by atomic and cluster bombardment in the electronic stopping-power regime

Single crystals of magnesium oxide containing nanoprecipitates of sodium were bombarded with swift ions (∼GeV-Pb, U) or cluster beams (∼20 MeV-C60) to study the phase change induced by electronic processes at high stopping power (≳10 keV/nm). The sodium precipitates and the defect creation were characterized by optical absorption and transmission electron microscopy. The ion or cluster bombardment leads to an evolution of the Na precipitate concentration but the size distribution remains unchanged. The decrease in Na metallic concentration is attributed to mixing effects at the interfaces between Na clusters and MgO. In addition, optical-absorption measurements show a broadening of the absorption band associated with electron plasma oscillations in Na clusters. This effect is due to a decrease of the electron mean free path, which could be induced by defect creation in the metal. All these results show an influence of high electronic stopping power in materials known to be very resistant to irradiation with weak ionizing projectiles. The dependence of these effects on electronic stopping power and on various solid-state parameters is discussed

LORCA (Murcia) (Partido Judicial). 1:34.000

Manuscrito firmado y rubricado por el autor. A plumilla en tinta negraOrientado con medio castilloRelieve representado por normale