Performance improvement of the multicell cavity prototype for proton Linac projects

The CEA-Saclay / IPN-Orsay collaboration allowed to manufacture a multicell superconducting RF cavity prototype for proton linac. Since the first experimental results [1], obtained in a vertical cryostat and the horizontal cryostat CryHoLab, the accelerating field Eacc has been recently increased up to 19 MV/m with a quality factor Q0 = 9.109 and a limitation by quench. However some improvements are still needed, in particular to suppress the field emission above 16 MV/m

Analyse des essais d'infiltration conduits sur le bassin de la Claduègne en Mai-Juin 2012. Contribution au WP3.4 du projet ANR FloodScale 2012-2015

In this report, we present the infiltration field campaign conducted in May-June 2015 in the 48 km2 Claduègne catchment (Ardèche, France). First we present the different measurement protocols using either simple ring infiltrometers (Beerkan method) or suction disk infiltrometers. Then the sampling strategy is presented. The theoretical aspects of infiltration equations and different methods used in infiltration tests analysis are described in details. In particular, the BEST (Beerkan Estimation of Soil Transfer) method is used in the analysis of single ring infiltration data and mini-disk infiltrometer with a -20 mm suction. This method is compared to the differential linear (DL) method, showing reasonable agreement, although systematic biases are evidenced. Multiple suction disk infiltrometers are analyzed using permanent regime equations. The single ring infiltration tests provide estimates of the retention curve and hydraulic conductivity curves. The infiltrometers provide information about the hydraulic conductivity close to saturation. We present the statistical analysis of the results, which show that the soils have generally high hydraulic conductivity, especially in forested soils. Dry bulk density is also much lower in natural soils than in cultivated soils. In situ measurements are compared with three representative pedo-transfer functions showing poor capability of the latter in reproducing observations. On the other hand, land use is found more discriminant in determining soil hydraulic properties. The statistical analysis on the samples allows defining two classes for dry bulk density with significantly different values gathering respectively natural and cultivated soils. In terms of saturated hydraulic conductivity, two land uses classes gathering forested fields and moors on the one hand, and pasture and cultivated land on the other hand can be distinguished. This allows proposing a first strategy of soil hydraulic properties spatialization in the Claduègne catchment, by combining the dry bulk density and hydraulic conductivity classes in three main families of soil hydraulic properties, depending on land use

Modélisation des transferts de chaleur, d'eau et des isotopes stables de l'eau (deutérieum et oxygène 18) dans la zone non-saturée. Description du modèle et premières validation sur des colonnes de sol nu

A model describing, for bare soils, coupled heat, water and stable isotope transfer within non-saturated soils is described. Model results are validated against available analytical solutions and data collected on drying soil columns in the laboratory. The model is shown to reproduce qualitatively well the time evolution of isotope concentration profiles, although errors on absolute values might be large, especially for deuterium concentration. Model results are sensitive to the specification of the kinetic fractionation factor at the soil surface, conditioning the surface isotope flux. Further laboratory experiments are required to properly quantify this factor.On présente un modèle décrivant, pour les sols nus, les transferts couplés de chaleur, d'eau et d'isotopes stables de l'eau dans les sols non-saturés. Les résultats du modèle sont validés par comparaison avec des solutions analytiques et des données collectées au laboratoire lors du séchage de colonnes de sol. On montre que le modèle reproduit qualitativement l'évolution temporelle des profils de concentrations en isotopes, bien que les erreurs sur les valeurs absolues soient parfois grandes, notamment pour les concentrations en deutérium. Les résultats du modèle sont sensibles à la spécification du facteur de fractionnement cinétique à la surface du sol, qui conditionne le flux d'isotopes en surface. De nouvelles expériences de laboratoire sont requises afin de pouvoir correctement quantifier ce facteur

SiSPAT-Isotope, un modèle couplé de transfert d`eau, de chaleur et d`isotopes stables de l`eau (HDO AND H218O) pour le sol nu. Partie I. Description du modèle et premières vérifications

International audienceStable water isotopes, namely deuterium and oxygen 18, are tracers of water movement within the soil-vegetation-atmosphere system. They provide useful information for a better understanding of evaporation and transpiration processes as well as water vapour transport within soils. To better evaluate those potentialities and to identify possible lack of knowledge, a coupled heat, water and stable isotope transport model, called SiSPAT-Isotope was developed for bare soil. This paper presents the theoretical basis of the model, revisiting existing formulations encountered in the literature. An emphasis was put on the formulation of the kinetic fractionation factor, conditioning the resistance to isotope transport between the soil surface and the atmosphere, for which no agreement exists in the literature. The paper also presents first validation tests, showing the consistency of the model by comparison with existing analytical solutions. Sensitivity tests showed that the isotope concentration was very sensitive to the formulation of the resistance to isotope transport between the soil surface and the atmosphere, especially under saturated soil conditions. Only a comparison with existing data sets and further laboratory and field experiments, can help decide which formulation has to be used and in which conditions. Finally, an example of simulation under non-steady state conditions is also presented and discussed.Les isotopes stables de l`eau, le deutérium et l`oxygène 18, sont des traceurs des mouvements de l`eau dans le système sol - végétation - atmosphère. Ils fournissent des information utiles pour mieux comprendre les processus d`évaporation et de transpiration, mais aussi de transfert en phase vapeur dans le sol. Afin de mieux évaluer ces potentialités et identifier les questions scientifiques non encore résolues en ce domaine, nous avons développé, pour sol nu, un modèle couplé de transport d`énergie, d`eau et d`isotopes stables de l`eau, appelé SiSpAT-Isotope. Cet article présente les bases théoriques du modèle et revisite les formulations existantes dans la littérature. On se focalise notamment sur la formulation du facteur de fractionnement cinétique, qui conditionne la résistance au transfert d`isotopes entre la surface du sol et l`atmosphère, pour lequel, il n`existe pas de consensus dans la littérature. L`article présente aussi des premiers tests de validation, par comparaison avec des solutions analytique, qui montrent la cohérence du modèle. Des tests de sensibilité ont montré que la concentration en isotopes était très sensible à ce fractionnement cinétique, notamment pour les sols saturés. Seule une comparaison avec des jeux de données et de nouvelles expérimentations de laboratoire ou de terrain permettront de définir les domaines d`applications des différentes formulations existantes. Enfin, on présente un exemple de simulation en conditions non stationnaires

Réponse hydrologique aux propriétés du sol dans un contexte de crues extrêmes

In September 2002 a flash flood killed 23 human lives and generated 1.2 billion Euros of damages in less than 24 hours over an area of 20000 km2 located in the south of France. The Gard river basin was hit by a storm that locally received more than 600 mm in one day. The Mesoscale Convective System firstly remained stationary for 14 hours then moved West, and finally interacted with a cold front moving. This storm triggered catastrophic flash floods on many upstream tributaries as well as the most important flood ever reported of the major rivers (Gard, Ceze and Vidourle). Postevent hydrological investigation using interviews of witnesses and river cross-sections surveys allowed estimation of specific peak discharges of 17 watersheds, the size of which ranged from 10 to 100 km2. It was noticeable that most of the estimations gave specific peak discharges of at least 5 m3.s−1.km2 whereas the 10 years return period discharge, in this region, is about 2 m3.s−1.km2for such catchment sizes. Below the 600 mm rain area, peak discharges even exceed 20 m3.s−1.km2, which was the most important value ever reported for watersheds of similar areas. The prediction of such extreme events remains an open question due to scarcity of observations and the unknown individual hydrological behavior of very small basins. The aggregation of small basins contributions along the river network remains also largely unknown. In order to study runoff generation on these small catchments, we implemented a physically based hydrological model developed under the numerical LIQUID platform on the Cévennes Vivarais region

Une méthode pour cartographier la conductivité hydraulique à saturation du sol de surface dans la région cévenole à l'aide d'essais d'infiltration réalisés avec différentes techniques

International audienceTopsoil field-saturated hydraulic conductivity, Kfs, is a parameter that controls the partition of rainfall between infiltration and runoff. It is a key parameter in most distributed hydrological models. However, there is a mismatch between the scale of local in situ measurements and the scale at which the parameter is required in models. Therefore it is necessary to design methods to regionally map this parameter at the model scale. The paper propose a method for mapping Kfs in the Cévennes-Vivarais region, south-east France, using more easily available GIS data: geology and land cover. The mapping is based on a data set gathering infiltration tests performed in the area or close to it for more than ten years. The data set is composed of infiltration tests performed using various techniques: Guelph permeameter, double ring and single ring infiltration tests, infiltrometers with multiple suctions. The different methods lead to different orders of magnitude for Kfs rendering the pooling of all the data challenging. Therefore, a method is first proposed to pool the data from the different infiltration methods, leading to a homogenized set of Kfs, based on an equivalent double ring/tension disk infiltration value. Statistical tests showed significant differences in distributions among different geologies and land covers. Thus those variables were retained as proxy for mapping Kfs at the regional scale. This map was compared to a map based on the Rawls and Brakensiek (RB) pedo-transfer function (Manus et al., 2009, Vannier et al., 2016), showing very different patterns between both maps. In addition, RB values did not fit observed values at the plot scale, highlighting that soil texture only is not a good predictor of Kfs

Réponse hydrologique à la variabilité des caractéristiques du sol dans un contexte Méditerranéen d'épisodes extrêmes

International audienceThe poster presents the sensitivity of the hydrological response with respect to rainfall variability and soil characteristics for the extreme event of september 2002 in the Gard

Study of thermal interaction between a 150 KW CW POWER coupler and a superconducting 704 MHZ elliptical cavity

The power coupler needed for β=0.65 SRF elliptical cavities dedicated to the driver of XADS (eXperimental Accelerator Driven System) should transmit a CW RF power of 150 kW to a 10 mA proton beam. The estimated average values of the RF losses in the coupler are 130 W (respectively 46 W) for the inner (respectively outer) conductor in SW mode. Due to such high values of RF losses, it is necessary to very carefully design and optimize the cooling circuits of the coupler in order to efficiently remove the generated heat and to reduce the thermal load to the cavity operating at T=2 K. An experiment simulating the thermal interaction between the power coupler and a 700 MHz SRF five cells cavity was performed in the CRYHOLAB test facility in order to determine the critical heat load that can be sustained by the cavity without degradation of RF performance. Experimental data are compared to numerical simulation results obtained with the Finite Element code COSMOS/M. These data allow us also to perform in-situ measurements of thermal parameters needed in the thermal model of the coupler (thermal conductivity, thermal contact resistance) and they were used to validate numerical simulations

Stratégie pour documenter l'hétérogénéité des propriétés des sols et impact sur les transferts d'eau de l'échelle du versant à celle du bassin versant

International audienceHeterogeneity in soil properties has been identified to impact water transfers at different scales from vertical column, hillslopes to watershed. Thus Distributed physically based hydrological models require distributed hydraulic characteristics to quantify these impacts. To characterize soil properties and their heterogeneity, a multi-scale sampling strategy was proposed based on distributed information including electromagnetic survey maps, topography and land use coverage. Each identified units are characterized by there hydraulic properties including in situ infiltration tests. This strategy was applied over the Ara Catchment (12km2) in northern Benin. It has been instrumented in the framework of the AMMA-Catch experimental network in West Africa, to better determine water resources and to investigate possible hydrological retro-action on monsoon cycle. From hydrological point of view, distributed soil hydraulic properties are supposed to impact water transfers and watershed dynamics all along the monsoon cycle. To document this heterogeneity, an electrical conductivity map and geological survey was used as starting points to identify the ground structures which align with the north-south direction with a dip angle of 20° east. A total of 20 pits have been opened to document the 0-2m horizons, and 2 more for the 0-5m horizons. 3 pits were digged within each geological structure areas at the surface. In each pit, the retention and hydraulic conductivity curves of each pedological horizon were characterized with three replicates. This database is used to document the variability of these properties and to produce soil hydraulic property maps. Using the variability information, we tested their impact with the Parflow-CLM 3D distributed model. It was run in an homogeneous configuration and compared with a data controlled heterogeneous configuration. The latest is prepared using a turning band algorithm to distribute soil hydraulic properties