Thermal Properties of Transparent Yb-Doped YAG Ceramics at Elevated Temperatures

International audienceThis work presents the thermal properties of ytterbium-doped yttrium aluminium garnet (Yb:YAG) transparent ceramics at elevated temperatures in dependence on the dopant concentration and on temperature. Transparent polycrystalline Yb:YAG ceramics were prepared by solid-state reaction of oxide powders sintered under high vacuum. The dopant amount varied from 0 to 20 at.% of Yb. Thermal diffusivity of the sintered samples was measured by the laser and xenon flash methods at temperatures ranging from room temperature to 900°C. Both the thermal diffusivity and thermal conductivity values decreased with increasing dopant content, and until 500°C a decrease was observed also with increasing temperature. When available, the measured values were compared to data published in literature, and were found to be in good agreement. Based on the measured values, empirical relations in the form of shifted power laws are proposed for the temperature dependence of thermal diffusivity

TORSCHE Scheduling Toolbox for Matlab User’s Guide (Release 0.4.0) TORSCHE Scheduling Toolbox for Matlab User’s Guide

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Spatio-temporal variation of air pollutants and the impact of anthropogenic effects on the photochemical buildup of ozone across Delhi-NCR

Continuous, real time measurements of gaseous and particulate air pollutants (surface ozone (O-3), NO, NO2, CO, PM2.5 and PM10) were carried out during October 2010 to December 2014 within a network of 8 air quality monitoring stations (AQMSs) located over 2000 km(2) across Delhi-NCR. The behavior of the pollutants' mixing ratios in the diverse microenvironments of an urban megacity was examined to comprehend their distribution on various temporal (daily, monthly, seasonal and annual) and spatial scales. Backward air mass trajectories and residence time (RT) analysis helped quantify the amount of photochemical O-3 buildup at the study site. Tagging of O-3 values with RT revealed significant positive correlations indicating that O-3 buildup begins when fresh air masses come into the polluted domain and is accumulated during 1-3 days, producing O-3 through photo-oxidation processes. Following this, less pronounced effects are observed due to saturated and aged air masses, showing reduced photochemistry. Maximum air mass stagnancy events were observed during winters, owing to a suppressed boundary layer with O-3 buildup occurring at the rate of 25.8 ppb day(-1) during this season. The study found out that large-scale anthropogenic emissions in the surrounding regions had the strongest influence on O-3 production within the study site, but long-range transport was a dominant likelihood, especially during the pre-monsoon season

Overview of the COMPASS results

COMPASS addressed several physical processes that may explain the behaviour of important phenomena. This paper presents results related to the main fields of COMPASS research obtained in the recent two years, including studies of turbulence, L–H transition, plasma material interaction, runaway electron, and disruption physics: • Tomographic reconstruction of the edge/SOL turbulence observed by a fast visible camera allowed to visualize turbulent structures without perturbing the plasma. • Dependence of the power threshold on the X-point height was studied and related role of radial electric field in the edge/SOL plasma was identified. • The effect of high-field-side error fields on the L–H transition was investigated in order to assess the influence of the central solenoid misalignment and the possibility to compensate these error fields by low-field-side coils. • Results of fast measurements of electron temperature during ELMs show the ELM peak values at the divertor are around 80% of the initial temperature at the pedestal. • Liquid metals were used for the first time as plasma facing material in ELMy H-mode in the tokamak divertor. Good power handling capability was observed for heat fluxes up to 12 MW m−2 and no direct droplet ejection was observed. • Partial detachment regime was achieved by impurity seeding in the divertor. The evolution of the heat flux footprint at the outer target was studied. • Runaway electrons were studied using new unique systems—impact calorimetry, carbon pellet injection technique, wide variety of magnetic perturbations. Radial feedback control was imposed on the beam. • Forces during plasma disruptions were monitored by a number of new diagnostics for vacuum vessel (VV) motion in order to contribute to the scaling laws of sideways disruption forces for ITER. • Current flows towards the divertor tiles, incl. possible short-circuiting through PFCs, were investigated during the VDE experiments. The results support ATEC model and improve understanding of disruption loads