La fusión glaciar en el Pirineo: condicionantes ambientales y primeros resultados bianuales en el glaciar de Infiernos (Pirineo aragonés)

Data are presented about the environmental characters of the Infiernos glacier and of the regression suffered in the last century, as well as the meltwater flow values corresponding to two daily cycle of the Infierno glacier. These values were measured at the end of the summer of 1998 and 1999. There is a close relationship between these data and both thermic rythms. This fact suggests that meltwater flow should become a useful additional parameter to explain the environmental control of the drainage systems derived from the glacier fusion, as well as the serious glacier regression happened in the last decades, indicative of balances between the accumulation nival and the ablation clearly negative. The data are accompanied of measures of regression glacier among the summers of 1998 and 1999.Se presentan datos acerca de las características ambientales del Glaciar del Infierno y de la regresión sufrida en el Último siglo, así como los valores de los caudales de fusión de dos ciclos diarios en este glaciar, medidos a finales de dos veranos consecutivos (años 1998 y 1999). La relación entre este dato y los ritmos térmicos es muy estrecha, lo cual permite disponer de un dato más, de gran importancia, para explicar el control ambiental en los sistemas de drenaje de la fusión glaciar, así como la acusada regresión glaciar de las últimas décadas, indicativa de balances entre la acumulación nival y la ablación claramente negativos. Los datos se acompañan de medidas de retroceso glaciar entre los veranos de 1998 y 1999

Evolución reciente del glaciar del Infierno (Panticosa, Huesca)

Este artículo analiza la evolución del glaciar del pico Infierno desde un glaciar blanco hacia un glaciar cubierto y, tal vez, hacia un glaciar rocoso

Periglacial environments and frozen ground in the central Pyrenean high mountain area: Ground thermal regime and distribution of landforms and processes

Producción CientíficaThe periglacial belt is located in the highest parts of temperate mountains. The balance between mean air and ground temperatures and the presence of water determine the effectiveness of periglacial processes related to permafrost, the active layer or seasonally frozen ground (SFG). This study combines thermal and geomorphological data obtained in four Pyrenean massifs (Infierno‐Argualas, Posets, Maladeta and Monte Perdido) to improve knowledge on the occurrence and distribution of frozen ground. The methodology used is based on the study of landforms as frozen ground indicators, mapping processes, ground temperature analysis, basal temperature of snow, thermal mapping and geomatic surveys on rock glaciers and protalus lobes. In the Pyrenean high mountain areas the lower limit of frozen ground is at ~2,650m a.s.l., possible permafrost appears above 2,650m a.s.l. on north‐ and south‐facing slopes, and probable permafrost is dominant above 2,900m a.s.l. Unfrozen ground with cold‐associated geomorphological processes reach 2,900m a.s.l. and unfrozen and frozen ground distribution points to a patchy pattern throughout the periglacial belt. The most widespread frozen grounds are SFG. The thermal data, mean annual ground temperature, cold season temperatures, bottom temperature snow measurements, freeze/thaw cycles and distribution of landforms permit the establishment of a periglacial land system divided into three main belts: infraperiglacial, middle periglacial and supraperiglacial. The large number of processes and landforms that are involved and their altitudinal and spatial organization make up a complex environment that determines the geoecological dynamics of high mountain areas.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (projects CGL2015-68144-R / GL2017- 82216-R

Intrinsic evaluation of n/γ discrimination in organic plastic scintillators

Conference of 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013 ; Conference Code:102802International audienceThis paper is devoted to characterizing plastic scintillators with neutron/gamma (n/γ) discrimination abilities and understanding experimentally the photophysical processes down-stream. This experimental work is divided into two main studies, neutron sources irradiations and optical photoionization on a range of organic scintillators. The commercial liquid and plastic scintillators, respectively BC-501A from Bicron and EJ-200 from Eljen, are used as references in term of respectively extremely high [1] and poor n/γ discrimination efficiency, or more precisely Triplet-Triplet Annihilation rate probabilities after nuclear irradiations. We have characterized a range of organic plastic scintillators including one developped in our laboratory that shows good discrimination efficiency when compared to plastics that discriminate from litterature. For that purpose we use the well known charge comparison as a pulse shape discrimination (PSD) method. We have also studied raw wave forms acquired after neutron irradiation before any kind of treatment was applied and managed to separate two light components, prompt and delayed, thus two particle families. We have demonstrated that by exciting with a 70 femtoseconds pulsed LASER at the femtosecond up to 50 μJ at 260 nm, photoionization was achieved for a range of organic scintillators by observing a delayed light emission in the time decay fluorescence when the LASER energy deposited in the materials was increased. This work is ongoing at CEA in collaboration with the nuclear measurement industry Canberra and the Laboratoire de Chimie Physique from Orsay University

Temperature effect on the absorption spectrum of the hydrated electron paired with a lithium cation in deuterated water

International audienceThe absorption spectra of the hydrated electron in 1.0 to 4.0 M LiCl or LiClO4 deuterated water solutions were measured by pulse radiolysis techniques from room temperature to 300 °C at a constant pressure of 25 MPa. The results show that when the temperature is increased and the density is decreased, the absorption spectrum of the electron in the presence of a lithium cation is shifted to lower energies. Quantum classical molecular dynamics (QCMD) simulations of an excess electron in bulk water and in the presence of a lithium cation have been performed to compare with the experimental results. According to the QCMD simulations, the change in the shape of the spectrum is due to one of the three p-like excited states of the solvated electron destabilized by core repulsion. The study of s → p transition energies for the three p-excited states reveals that for temperatures higher than room temperature, there is a broadening of each individual s → p absorption band due to a less structured water solvation shell

Erratum to: ELYSE - A picosecond electron accelerator for pulse radiolysis research

Recent years have seen an increasing interest in the use of intense, short pulse electron beams for pulsed radiolysis research. Laser driven photo-cathodes inserted in radio frequency (RF) guns are ideal candidates to provide electron beams for time-resolved spectroscopic observation of very fast chemical reactions. These guns have been developed through accelerator R&D programmes in the field of high brightness sources for other applications (linear colliders, free electron lasers). The Physical Chemistry Laboratory at the University of Paris-Sud has created a Fast Kinetics Centre for experimental pulse radiolysis with picosecond time resolution. At the heart of this new facility is a compact 4-9 MeV electron accelerator. ELYSE, using RF gun technology. It has been designed and built by the Linear Accelerator Laboratory at the University of Paris-Sud. We will describe the construction and commissioning of ELYSE, the first machine of this type in Europe