The role of spatial and temporal radiation deposition in inertial fusion chambers: the case of HiPER¿

The first wall armour for the reactor chamber of HiPER will have to face short energy pulses of 5 to 20 MJ mostly in the form of x-rays and charged particles at a repetition rate of 5–10 Hz. Armour material and chamber dimensions have to be chosen to avoid/minimize damage to the chamber, ensuring the proper functioning of the facility during its planned lifetime. The maximum energy fluence that the armour can withstand without risk of failure, is determined by temporal and spatial deposition of the radiation energy inside the material. In this paper, simulations on the thermal effect of the radiation–armour interaction are carried out with an increasing definition of the temporal and spatial deposition of energy to prove their influence on the final results. These calculations will lead us to present the first values of the thermo-mechanical behaviour of the tungsten armour designed for the HiPER project under a shock ignition target of 48 MJ. The results will show that only the crossing of the plasticity limit in the first few micrometres might be a threat after thousands of shots for the survivability of the armour.

Control rod drop surveillance using two friction coefficients

In the case of large burnup, a control rod (CR) guide tube in the pressurized water reactor of a commercial nuclear power plant might bend. As a consequence, a CR drop experiment may indicate an event of a CR partially inserted and whether the CR should be deemed inoperable. Early prevention of such an event can be achieved by measuring two friction coefficients: the hydraulic coefficient and the sliding coefficient. The hydraulic coefficient hardly changes, so that the curvature of the guide tube can only be detected thanks to a variation of the sliding coefficient. A simple model for the CR drop is established and validated with CR drop experiments. If tmx denotes the instant of CR maximum velocity, a linear relationship between (tmx)_2 and the sliding coefficient is found.

Exploring polysilicon deposition conditions through a laboratory CVD prototype

Cost and energy consumption related to obtaining polysilicon impact significantly on the total photovoltaic module cost and its energy payback time. Process simplifications can be performed, leading to cost reductions. Nowadays, among several approaches currently pursued to produce the so called Solar Grade Silicon, the chemical route, named Siemens process, is the dominant one. At the Instituto de Energía Solar research on this topic is focused on the chemical route, in particular on the polysilicon deposition step by chemical vapor deposition (CVD) from Trichlorosilane through a laboratory prototype. Valuable information about the phenomena involved in the polysilicon deposition process and the operating conditions is obtained from our experiments. A particular feature of our system is the inclusion of a mass spectrometer. The present work comprises spectra characterization of the polysilicon deposition chemical reaction, temperature and inlet gas mixture composition influence on the deposition rate and analysis of polysilicon deposition conditions for the ?pop-corn' phenomenon to appear, based on experimental experience (Actas de la Special Issue: E-MRS 2012 Spring Meeting ? Symposium A

Electrophoretic Deposition of Transparent ZnO Thin Films from Highly Stabilized Colloidal Suspensions

The parameters that control the stability of ZnO-nanoparticles suspensions and their deposition by electrophoretic deposition were studied, so as to organize the assembly and compaction of nanoparticles. The addition of cationic polyelectrolyte - Polyethylenimine (PEI) - with different molecular weights was investigated, in order to study their effectiveness and the influence of the molecular weight of the organic chain on suspensions dispersion. It was found that PEI with the highest molecular weight provided better dispersion conditions. Cathodic EPD was performed under previously optimized suspensions conditions and over electropolished stainless steel substrates. Experimental results showed that the EPD process in these conditions allows obtaining dense transparent ZnO thin films. Deposition times and intensities were optimized by analyzing the resulting thin films characteristics. Finally, the deposits were characterized by FE-SEM, AFM, and different spectroscopic techniques.

Nitrogen deposition alters nitrogen cycling and reduces soil carbon content in low-productivity semiarid Mediterranean ecosystems.

Anthropogenic N deposition poses a threat to European Mediterranean ecosystems. We combined data from an extant N deposition gradient (4.3–7.3 kg N ha−1 yr−1) from semiarid areas of Spain and a field experiment in central Spain to evaluate N deposition effects on soil fertility, function and cyanobacteria community. Soil organic N did not increase along the extant gradient. Nitrogen fixation decreased along existing and experimental N deposition gradients, a result possibly related to compositional shifts in soil cyanobacteria community. Net ammonification and nitrification (which dominated N-mineralization) were reduced and increased, respectively, by N fertilization, suggesting alterations in the N cycle. Soil organic C content, C:N ratios and the activity of β-glucosidase decreased along the extant gradient in most locations. Our results suggest that semiarid soils in low-productivity sites are unable to store additional N inputs, and that are also unable to mitigate increasing C emissions when experiencing increased N deposition.

Toward a climate-dependent paradigm of ammonia emission & deposition.

Existing descriptions of bi-directional ammonia (NH3) land–atmosphere exchange incorporate temperature and moisture controls, and are beginning to be used in regional chemical transport models. However, such models have typically applied simpler emission factors to upscale the main NH3 emission terms. While this approach has successfully simulated the main spatial patterns on local to global scales, it fails to address the environment- and climate-dependence of emissions. To handle these issues, we outline the basis for a new modelling paradigm where both NH3 emissions and deposition are calculated online according to diurnal, seasonal and spatial differences in meteorology. We show how measurements reveal a strong, but complex pattern of climatic dependence, which is increasingly being characterized using ground-based NH3 monitoring and satellite observations, while advances in process-based modelling are illustrated for agricultural and natural sources, including a global application for seabird colonies. A future architecture for NH3 emission–deposition modelling is proposed that integrates the spatio-temporal interactions, and provides the necessary foundation to assess the consequences of climate change. Based on available measurements, a first empirical estimate suggests that 5°C warming would increase emissions by 42 per cent (28–67%). Together with increased anthropogenic activity, global NH3 emissions may increase from 65 (45–85) Tg N in 2008 to reach 132 (89–179) Tg by 2100.

Logic cells as basic structures to add/drop WDM information signals

Nowadays, in order to take advantage of fiber optic bandwidth, any optical communications system tends to be WDM. The way to extract a channel, characterized by a wavelength, from the optical fiber is to filter the specific wavelength. This gives the systems a low degree of freedom due to the fact of the static character of most of the employed devices. In this paper we will present a different way to extract channels from an optical fiber with WDM transmission. The employed method is based on an Optically Programmable Logic Cells (OPLC) previously published by us, for other applications as a chaotic generator or as basic element for optical computing. In this paper we will describe the configuration of the OPLC to be employed as a dropping device. It acts as a filter because it will extract the data carried by a concrete wavelength. It does depend, internally, on the wavelength. We will show how the intensity of the signal is able to select the chosen information from the line. It will be also demonstrated that a new idea of redundant information it is the way of selecting the concrete wavelength. As a matter of fact this idea is apparently the only way to use the OPLC as a dropping device. Moreover, based on these concepts, a similar way to route signals to different routes is reported. The basis is the use of photonic switching configurations, namely Batcher or Bayan structures, where the unit switching cells are the above indicated OPLCs.

Development of One Meter Long Double-Sided CeO2 Buffered Ni-5at.W Templates by Reel-to-Reel Chemical Solution Deposition Route

High performance long-length coated conductors fabricated using various techniques have attracted a lot of interest recently. In this work, a reel-to-reel design for depositing double-sided coatings on long-length flexible metallic tapes via a chemical solution method is proposed and realized. The major achievement of the design is to combine the dip coating and drying processes in order to overcome the technical difficulties of dealing with the wet films on both sides of the tape. We report the successful application of the design to fabricate a one-meter-long double side coated CeO2/Ni-5at%W template. The CeO2 films on both sides exhibit a dense, crack-free morphology, and a high fraction of cube texture on the surface. Homogeneity studies on global texture over the length also reveal that the average full width at half maximum values of the in-plane and out-of-plane orientation on the CeO2 layer are 7.2 ° and 5.8° with standard deviation of 0.26° and 0.34°, respectively, being indicative of the high quality epitaxial growth of the films prepared in the continuous manner. An all chemical solution derived YBCOLow-TFA/Ce0.9La0.1O2 /Gd2Zr2O7/CeO2 structure is obtained on a short sample, demonstrating the possibility of producing long-length texture templates for coated conductors by this low cost deposition route.

Microstructure and mechanical properties at high temperature of SiC-matrix by electrophoretic deposition and polymer infiltration and pyrolysis process

The EFDA-ITER programme for materials wants to develop new structural materials for future nuclear magnetic fusion reactors. In this context, special attention must be paid in the development of new composite materials that could support the hard working conditions of the nuclear fusion reactors: high temperature, high stresses, and high radiation.

An elicitor isolated from smut teliospores (Sporisorium scitamineum) enhances lignin deposition on the cell wall on both sclerenchyma and xylem in sugarcane leaves

Sugarcane leaf shows the classical arrangement of cells which defines a C4 species. Vascular bundles consist of xylem, phloem and fibres, surrounded by an outer layer of sclereids and an inner ring of stone cells associated with the phloem. Some sclereids located below and above the vascular bundles act as docking cells and connect the vascular bundle to the internal surfaces of upper and lower layers of the epidermis. A compact mass of sclereids occupies the total internal volume of the leaf edge. Neither docking cells nor the internal mass of sclereids in the edge were markedly coloured by acriflavin or phloroglucinol, indicating the absence of lignin in their cell walls. However, such staining indicated that fibres of the vascular bundle and the external layer of sclereids were strongly lignified. Incubation of leaf discs with an elicitor produced by the pathogen Sporisorium scitamineum increased the thickness of the lignified cell walls of sclereids as well as the mid and small xylem vessels, as a possible mechanical defense response to the potential entry of the pathogen.

Wettability, polarity and water absorption of Quercus ilex leaves: effect of leaf side and age

Plant trichomes play important protective functions and may have a major influence on leaf surface wettability. With the aim of gaining insight into trichome structure, composition and function in relation to water-plant surface interactions, we analyzed the adaxial and abaxial leaf surface of Quercus ilex L. (holm oak) as model. By measuring the leaf water potential 24 h after the deposition of water drops on to abaxial and adaxial surfaces, evidence for water penetration through the upper leaf side was gained in young and mature leaves. The structure and chemical composition of the abaxial (always present) and adaxial (occurring only in young leaves) trichomes were analyzed by various microscopic and analytical procedures. The adaxial surfaces were wettable and had a high degree of water drop adhesion in contrast to the highly unwettable and water repellent abaxial holm oak leaf sides. The surface free energy, polarity and solubility parameter decreased with leaf age, with generally higher values determined for the abaxial sides. All holm oak leaf trichomes were covered with a cuticle. The abaxial trichomes were composed of 8% soluble waxes, 49% cutin, and 43% polysaccharides. For the adaxial side, it is concluded that trichomes and the scars after trichome shedding contribute to water uptake, while the abaxial leaf side is highly hydrophobic due to its high degree of pubescence and different trichome structure, composition and density. Results are interpreted in terms of water-plant surface interactions, plant surface physical-chemistry, and plant ecophysiology.

The influence of gravity on the solidifcation of a drop

In this paper the influence of gravity on the solidification of a drop formed at the end of a rod is analyzed. Although similar studies (but ignoring gravity effects) already exist, a theoretical analysis including gravity effects allows one to improve the experimental procedure to measure on Earth relevant properties of crystals (mainly the receding contact angle <£,) which are of importance in shaped crystal growth processes. One of the main results here obtained are the shapes of the sohdified drops, which are strongly dependent on the value of <#>,. Therefore, fitting theoretical shapes to experimental ones is a wav to perform accurate measurements of <^.

Biogeochemical indicators of elevated nitrogen deposition in semiarid Mediterranean ecosystems

Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and biogeochemical indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found in the Iberian Peninsula (between 4.4 and 8.1 kg N ha(-1) year(-1)). We extended the ambient N deposition gradient by including experimental plots to which N had been added for 3 years at rates of 10, 20, and 50 kg N ha(-1) year(-1). Overall, N deposition (extant plus simulated) increased soil inorganic N availability and caused soil acidification. Nitrogen deposition increased phosphomonoesterase (PME) enzyme activity and PME/nitrate reductase (NR) ratio in both species, whereas the NR activity was reduced only in the moss. Responses of PME and NR activities were attributed to an induced N to phosphorus imbalance and to N saturation, respectively. When only considering the ambient N deposition, soil organic C and N contents were positively related to N deposition, a response driven by pine forests. The PME/NR ratios of the moss were better predictors of N deposition rates than PME or NR activities alone in shrublands, whereas no correlation between N deposition and the lichen physiology was observed. We conclude that integrative physiological measurements, such as PME/NR ratios, measured on sensitive species such as P. squarrosa, can provide useful data for national-scale biomonitoring programs, whereas soil acidification and soil C and N storage could be useful as additional corroborating ecosystem indicators of chronic N pollution.