[en] Smooth and uniform solid deuterium-tritium (DT) layers inside a spherical shell are needed in order to achieve ignition on the Laser Megajoule (LMJ) facility. The thermal environment around the capsule is the key to meeting the DT layer requirements. While keeping high mode roughness within the specifications at the shot temperature is now guaranteed by a rapid cooling technique, low mode roughness ('shape' of the layer) is still a complicated and demanding subject. A perfectly uniform temperature field around the capsule is needed. Final results of the constant thermal perturbation effects on the layer can be calculated, but the dynamic of reaction is not known. This paper presents a model that allows calculation of the low mode layer behavior depending on a change in the temperature field. This comes down to calculating a target lifetime for the low modes during a thermal transient state. (authors)

[en] In this paper we present and discuss recent experimental and theoretical advances concerning the redistribution process, the control of target temperature, and the effect of deuterium-tritium (D-T) aging on the optimum laser shot temperature at the Laser Megajoule (LMJ) facility. We introduce two analytical models to provide a better understanding of thermal target behavior. On one hand the first model describes the evolution of the D-T layer temperature, which cannot be recorded experimentally. On the other hand the second model highlights the necessity for the optimum laser shot temperature (i.e., 1.5 K below the triple point) to be adapted to the aging of the target. The analytical considerations are completed with experimental results obtained with D₂ taken as a reference system to investigate the properties of D-T in LMJ targets. (authors)

[en] We computed by a Monte Carlo method, derived from the solid on solid model, the evolution during thermal treatment of a polycrystalline thin film deposited on a substrate with no further deposition. Two types of substrates have been studied: a single crystalline substrate with no defects and a single crystalline substrate with defects. We obtain islands which are either flat (i.e., with a height which does not overcome a given value) or grow in height like narrow towers. The numerical results have been qualitatively compared with experimental data: the fragmentation after thermal treatment of an yttria stabilized zirconia thin film deposited on an Al₂O₃ substrate. A good agreement was found regarding the morphology of simulated and experimental nanoislands

[en] Sol-gel obtained yttria stabilized zirconia (YZS) nanocrystals have different morphologies when they grow on an α-alumina substrate after thermal treatment. When the substrate has planar defects, the nanocrystals grow in height and are narrow with a crystallographic orientation [111] in the vertical direction, while when the substrate is a perfect plane at the nanometric scale, the nanocrystals are rather extended over the substrate and do not grow in height, with a crystallographic orientation [100] in the vertical direction. We present here a Monte Carlo approach which computes the actions of the substrate on the nanocrystals during thermal treatment: one action is the change in crystallographic orientation depending on the presence of defects and the other is the action on the morphology of the nanocrystals. The equivalent of thermal treatment is obtained after applying the Metropolis algorithm with adequate expressions of the energy depending on the inter-plane spacings and surface diffusion. Our numerical approach is in good agreement with the experimental results on the orientations and morphologies of the YSZ nanocrystals growing on a α-alumina substrate with planar defects [R. Bachelet, A. Boulle, B. Soulestin, F. Rossignol, A. Dauger, R. Guinebretiere, Thin Solid Films 515 (2007) 7080].