Construction and Installation of the New CERN Proton Synchrotron Internal Beam Dumps

Source at https://inspirehep.net/literature/1961952.In the framework of the CERN Large Hadron Collider Injectors Upgrade (LIU) Project, the Proton Synchrotron (PS) has been equipped with two new movable Internal Dumps (PSID), each of them capable of absorbing particle beams of an energy of up to 100 kJ. These dumps replace the old Internal Dumps, which have been operated in the accelerator complex since their installation in 1975 until their decommissioning and removal from the machine during the second LHC Long Shut down (LS2). This contribution will address the construction and testing phases of the new PSIDs, including the assembly of the dump core, its actuation system and the respective shielding, mechanical running-in tests, metrology adjustments, Ultra-High Vacuum (UHV) and impedance acceptance tests. The described installation work was completed successfully, and the new generation Dumps are currently operational in the PS machine

Rapport de sondages et d'analyses, Le Kilian et les carrières anciennes de trachyte dans la Chaîne des Puys (Puy-de-Dôme)

En 2008, l'existence de carrières souterraines médiévales avait été mise en évidence dans la pente ouest du Bois de Manson qui domine la dépression du Cratère Kilian, au pied sud du puy de Dôme. En 2009-2010, des sondages et prospections ont été étendus à tout l'ensemble du Kilian de façon à préciser l'étendue et, si possible, la chronologie de son exploitation dans le passé. Ces travaux ont permis d'observer, dans le fond du cratère et sur son flanc interne ouest, des amoncellements de déblais d'un volume considérable, témoignant d'une extraction de roche à grande échelle durant le haut Moyen Âge et très probablement aussi à l'époque gallo-romaine. Une nouvelle carrière souterraine a été découverte dans la pente interne ouest du cratère. La base du remplissage de cette carrière a livré des charbons datés entre la fin du IV e siècle et le début du VI e siècle par le radiocarbone, tandis que le sommet du remplissage contenait des tessons de céramique datables, par leur typologie, de la fin du V e siècle au début du VIII e siècle. L'état actuel des investigations conduit à faire l'hypothèse que les gallo-romains ont exploité, au fond du cratère, un trachyte compact dont on ne trouve aujourd'hui que les déchets de taille, et dont les affleurements sont masqués par les déblais, tandis que les artisans du Moyen Âge ont recherché un trachyte plus tendre dans les pentes hautes du cratère. Le Kilian doit donc s'ajouter aux trois sources actuellement connues de trachyte d'oeuvre dans le passé, à savoir les volcans Sarcoui, Aumône (ou petit Suchet) et Cliersou. Dès cette découverte, en 2008, s'est posée la question de savoir quelle part éventuelle le trachyte du Kilian avait pu prendre dans la construction du temple de Mercure au sommet du puy de Dôme et dans l'agglomération gallo-romaine située au col de Ceyssat. Pour y répondre, une campagne d'analyses géochimiques et pétrographiques été engagée pour caractériser, aux fins de comparaison, non seulement les trachytes du Kilian et ceux des ruines gallo-romaines, mais, de plus, les trachytes du Cliersou, de l'Aumône et du Sarcoui. Ces analyses ont finalement montré qu'il est possible de faire une discrimination statistiquement significative entre les différents trachytes étudiés, à l'exception de ceux du couple Cliersou-Aumône dont les laves sont très peu différentes les unes des autres. Le résultat le plus remarquable est que tous les trachytes gallo-romains échantillonnés (dont 10 échantillons distincts au temple de Mercure et 10 au col de Ceyssat) se rattachent sans ambiguïté au Kilian. En toute rigueur, ces nouvelles données ne permettent pas d'exclure sans appel la possibilité d'utilisation à l'époque gallo-romaine, au temple de Mercure et au col de Ceyssat, de trachytes provenant d'autres sources que le Kilian (cas des chaperons de mur du col de Ceyssat, provenant du puy de Dôme). Cependant, il faut ajouter qu'un examen visuel des trachytes d'oeuvre dans ces deux sites, portant sur un nombre de moellons et d'éléments architecturaux bien supérieur au nombre de ceux qui ont été analysés, conduit à conclure que leur source est probablement commune. Cette conclusion est basée sur un faciès minéralogique particulier, observable à l'oeil nu ou à la loupe

Effect of solution saturation state and temperature on diopside dissolution

Steady-state dissolution rates of diopside are measured as a function of solution saturation state using a titanium flow-through reactor at pH 7.5 and temperature ranging from 125 to 175°C. Diopside dissolved stoichiometrically under all experimental conditions and rates were not dependent on sample history. At each temperature, rates continuously decreased by two orders of magnitude as equilibrium was approached and did not exhibit a dissolution plateau of constant rates at high degrees of undersaturation. The variation of diopside dissolution rates with solution saturation can be described equally well with a ion exchange model based on transition state theory or pit nucleation model based on crystal growth/dissolution theory from 125 to 175°C. At 175°C, both models over predict dissolution rates by two orders of magnitude indicating that a secondary phase precipitated in the experiments. The ion exchange model assumes the formation of a Si-rich, Mg-deficient precursor complex. Lack of dependence of rates on steady-state aqueous calcium concentration supports the formation of such a complex, which is formed by exchange of protons for magnesium ions at the surface. Fit to the experimental data yields [Formula: see text] where the Mg-H exchange coefficient, n = 1.39, the apparent activation energy, E(a )= 332 kJ mol(-1), and the apparent rate constant, k = 10(41.2 )mol diopside cm(-2 )s(-1). Fits to the data with the pit nucleation model suggest that diopside dissolution proceeds through retreat of steps developed by nucleation of pits created homogeneously at the mineral surface or at defect sites, where homogeneous nucleation occurs at lower degrees of saturation than defect-assisted nucleation. Rate expressions for each mechanism (i) were fit to [Formula: see text] where the step edge energy (α) for homogeneously nucleated pits were higher (275 to 65 mJ m(-2)) than the pits nucleated at defects (39 to 65 mJ m(-2)) and the activation energy associated with the temperature dependence of site density and the kinetic coefficient for homogeneously nucleated pits (E(b-homogeneous )= 2.59 × 10(-16 )mJ K(-1)) were lower than the pits nucleated at defects (E(b-defect assisted )= 8.44 × 10(-16 )mJ K(-1))

Circadian rhythms have significant effects on leaf-to-canopy scale gas exchange under field conditions

Background Molecular clocks drive oscillations in leaf photosynthesis, stomatal conductance, and other cell and leaf-level processes over ∼24 h under controlled laboratory conditions. The influence of such circadian regulation over whole-canopy fluxes remains uncertain; diurnal CO2 and H2O vapor flux dynamics in the field are currently interpreted as resulting almost exclusively from direct physiological responses to variations in light, temperature and other environmental factors. We tested whether circadian regulation would affect plant and canopy gas exchange at the Montpellier European Ecotron. Canopy and leaf-level fluxes were constantly monitored under field-like environmental conditions, and under constant environmental conditions (no variation in temperature, radiation, or other environmental cues). Results We show direct experimental evidence at canopy scales of the circadian regulation of daytime gas exchange: 20–79 % of the daily variation range in CO2 and H2O fluxes occurred under circadian entrainment in canopies of an annual herb (bean) and of a perennial shrub (cotton). We also observed that considering circadian regulation improved performance by 8–17 % in commonly used stomatal conductance models. Conclusions Our results show that circadian controls affect diurnal CO2 and H2O flux patterns in entire canopies in field-like conditions, and its consideration significantly improves model performance. Circadian controls act as a ‘memory’ of the past conditions experienced by the plant, which synchronizes metabolism across entire plant canopies

NanoSIMS mapping and LA-ICP-MS chemical and U-Th-Pb data in monazite from a xenolith enclosed in andesite (Central Slovakia Volcanic Field)

In this study, we use NanoSIMS element and isotope ratio mapping and LA-ICP-MS trace element measurements to elucidate the origins of monazites from a restitic xenolith enclosed in a 13.5±0.3Ma andesitic lava (Slovakia). The xenolith/lava interaction is mainly characterized by the growth of a plagioclase-bearing corona around the xenolith and magmatic garnet overgrowths on primary metamorphic garnets within the xenolith. NanoSIMS images (89Y, 139La, 208Pb, 232Th and 238U) and trace element analyses indicate that variations of HREE, Y and Eu contents in the monazite are correlated with the resorption and the following overgrowth of garnet and plagioclase in the xenolith. Three domains are distinguished in the monazite grains: the inherited Variscan core at ca. 310Ma (M1 domain) characterized by low Y and HREE contents and a weak negative Eu anomaly; the inner rim (M2 domain) crystallized during the growth of the plagioclase magmatic corona (large negative Eu anomaly) and the resorption of metamorphic garnet (high HREE and Y contents); and the external rim (M3 domain) crystallized during the growth of the plagioclase corona (large negative Eu anomaly) and during the crystallization of magmatic garnet (low Y, HREE contents) at ~13Ma, i.e. the age of the andesitic lava. The age and chemical zonation of the monazites attest to the preservation of primary monazite in the xenolith despite the interaction with the andesite lava. NanoSIMS imaging provides high-quality sub-µm scale images of the monazite that reveals chemical domains that were not distinguishable on WDS X-ray maps, especially for depleted elements such as U and Pb. Owing to its small size, the M2 domain could not be accurately dated by the LA-ICP-MS method. However, NanoSIMS isotopic maps reveal that the M2 domain has similar 208Pb/232Th isotope ratios to the M3 domain and thus similar ages. These results support the hypothesis that melt-assisted partial dissolution-precipitation in monazite efficiently records chemical and mineralogical changes during xenolith/lava interaction

NanoSIMS mapping and LA-ICP-MS chemical and U–Th–Pb data in monazite from a xenolith enclosed in andesite (Central Slovakia Volcanic Field)

International audienceIn this study, we use NanoSIMS element and isotope ratio mapping and LA-ICP-MS trace element measurements to elucidate the origins of monazites from a restitic xenolith enclosed in a 13.5 ± 0.3 Ma andesitic lava (Slovakia). The xenolith/lava interaction is mainly characterized by the growth of a plagioclase-bearing corona around the xenolith and magmatic garnet overgrowths on primary metamorphic garnets within the xenolith. NanoSIMS images (89Y, 139La, 208Pb, 232Th and 238U) and trace element analyses indicate that variations of HREE, Y and Eu contents in the monazite are correlated with the resorption and the following overgrowth of garnet and plagioclase in the xenolith. Three domains are distinguished in the monazite grains: the inherited Variscan core at ca. 310 Ma (M1 domain) characterized by low Y and HREE contents and a weak negative Eu anomaly; the inner rim (M2 domain) crystallized during the growth of the plagioclase magmatic corona (large negative Eu anomaly) and the resorption of metamorphic garnet (high HREE and Y contents); and the external rim (M3 domain) crystallized during the growth of the plagioclase corona (large negative Eu anomaly) and during the crystallization of magmatic garnet (low Y, HREE contents) at ~13 Ma, i.e. the age of the andesitic lava. The age and chemical zonation of the monazites attest to the preservation of primary monazite in the xenolith despite the interaction with the andesite lava. NanoSIMS imaging provides high-quality sub-µm scale images of the monazite that reveals chemical domains that were not distinguishable on WDS X-ray maps, especially for depleted elements such as U and Pb. Owing to its small size, the M2 domain could not be accurately dated by the LA-ICP-MS method. However, NanoSIMS isotopic maps reveal that the M2 domain has similar 208Pb/232Th isotope ratios to the M3 domain and thus similar ages. These results support the hypothesis that melt-assisted partial dissolution–precipitation in monazite efficiently records chemical and mineralogical changes during xenolith/lava interaction

Exploring the driving factors of the triple oxygen isotope composition of water at the soil/plant/atmosphere interface in climate chamber

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Lacustrine record of last millennia eruptions in Northern Chilean Patagonia (45–47°S)

Due to its tectonic setting, the Andean Southern Volcanism Zone (SSVZ) is characterized by frequent volcanic activity. Chilean Patagonia lake sediments represent powerful archives of historical and past eruptions since the deglaciation. The lacustrine tephra record is investigated in 10 Holocene sedimentary cores collected in five lakes located along a 45–47° transect through Northern Chilean Patagonia. All the tephras identified by visual observation and strong magnetic susceptibility signal have been characterized for the major chemical composition of their glass shards by microprobe analyses, bulk mineralogical content by x-ray diffraction analyses and grain-size distribution by laser diffraction. Special care has been given to the chronostratigraphical framework in order to determine the age interval for each tephra layer and further to correlate the lacustrine records. The sedimentary age models are based on 210Pb data and calibrated radiocarbon dates measured on macroremains or reservoir effect-corrected bulk sediment. To present a more complete tephrochronological record, 28 microtephras have been confirmed by their mineralogical signature. Our lacustrine tephra record is compared with the Holocene eruptions registered in both surface deposits and continental, lacustrine and peat bog, environments. The different lacustrine eruption records are discussed according to their origin, age and location (distance from volcanoes, wind direction and dispersion of eruption produced). Our data confirm that Chilean Ande SSVZ tephras are mainly derived from historical and past Hudson eruptions. However, the peculiar low-K2O signature of the glass shards observed in one tephra layer from the Northernmost lake, Lake Thompson, confirms an influence from some other SSVZ volcanoes with low-abundance magma type, such as Maca and Cay. Our tephrochronological data compliment the database for volcanic activity in Chile bringing new information essential for the running discussion on the temporal distribution of eruptions over the Holocene. © 2017, © The Author(s) 2017.CRHIAM/CONICYT/FONDAP/15130015 (Chilean project); FONDECYT no. 1140466 (Chilean project); FNRS proposal 1360 2007–2010; WBI 2007–2009; ULg CFRA 1060 2009–201

Exploring the driving factors of the triple oxygen isotope composition of water at the soil/plant/atmosphere interface in climate chamber

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Exploring the driving factors of the triple oxygen isotope composition of water at the soil/plant/atmosphere interface in climate chamber

International audienc