The CEA (commissariat à l’énergie atomique et aux énergies alternatives) Laser Megajoule (LMJ) project builds up and develop s devices to guarantee target requirements from nanometric to millimetric scale. First of all, a Digital Holographic Microscopy (DHM ) technology is used to characterize the shape, the quality, the roughness and the geometrical defects (bumps) of target element. It captures holograms to rec nstruct a double image, one for the intensity and another for the phase. Using rotation axis, the defects counting for the whole microshell surface is possible with a very high speed. Using an images stitching and a 3D surface rebuilding software, map ping can be done in few minutes. Each bump can then be characterized on the map by i ts position, diameter and height. An AFM device is also used to scan target element s urface. This device was recently upgraded and is now able to measure a 10 μm high “d efect”. This improvement permits also the characterization of various tooled patterns like sinusoidal shapes.

Smooth and uniform solid D-T layers inside a spherical shell are needed to achieve ignition on the Laser Megajoule (LMJ) facility. The thermal environment around the capsule is the key to reach the low-mode D-T layer requirements. During the nineteenth Target Fabrication Meeting in Orlando, Florida (2010), an analytical model was presented to predict the low-mode time evolution of a D-T layer in a capsule caused by a thermal perturbation. The model showed that the dynamical response is ruled by the redistribution time constant. To check the validity of the model, experiments have been done with deuterium layers inside an integrating sphere. The use of an infrared laser to generate a volumetric heating of the deuterium allowed us to tune the conformation time constant. The experimental setup has also been modified to allow or cancel 300-K infrared radiation entering the integrating sphere, producing a local warming on the capsule. Using shadowgraphy techniques, we have been able to follow the dynamical behavior of the deuterium layer. Analyses conclude that the analytical model is right and can be used with confidence.

The cryogenic target assemblies (CTAs) designed for Laser Megajoule (LMJ) experiments have many functions and have to meet severe specifications imposed by implosion physics, the CTA thermal environment, and the CTA interfaces with the Megajoule laser cryogenic target positioner. Therefore, CTA fabrication uses many challenging materials and requires several technological studies. During the last 2 years, many developments have enabled better collection of comprehensive data on target constitutive materials and improvements in the fabrication of the CTA base, hohlraum, and aluminum turret.Studies have been carried out (a) to better characterize thermal properties of materials allowing optimization of the thermal simulation of the hohlraum, (b) to improve the CTA base fabrication process in order optimize thermal studies of the LMJ experimental filling station (EFS), and (c) to determine coatings on the polyimide membrane that may limit the 300 K thermal effect on the microshell and increase the deuterium-tritium fuel lifetime.CTAs have been produced to evaluate fabrication knowledge, to characterize CTAs, to study air tightness, and to study filling and D(2) ice layering on the EFS.An overview of the results that have been obtained during the past 2 years is presented in this paper.

Two major Inertial Confinement Fusion (ICF) projects are currently in progress. The US program at the National Ignition Facility (NIF), which has taken its first firing of a cryogenic target with DT fuel this year, mainly relies on cryogenic targets with capillary filled capsule [1]. For the French ICF experiments carried out on the Laser MegaJoule (LMJ), the nominal filling path of cryogenic target assemblies (CTAs) is permeation of DT fuel through the microshell 121 The CEA Valduc tritium facilities, where targets are filled, are thus original installations with specific designs and technologies.This paper deals with the description of the tritium facilities for the LMJ cryogenic targets (twelve gloveboxes are needed to deliver 6 CTAs at the same time). After a short presentation of the whole gloveboxes chain, the paper will focus on the heart of the plant: the filling and cooling station (IRCC: 4 gloveboxes). 3 out of 4 of these gloveboxes (LCCR, LCTC and LCPC) are at the moment under commissioning at the manufacturer's site. The last one (LCGC) has been delivered to CEA Valduc and is currently under testing with deuterium.A description of the IRCC design and specifications is given as well as the main results of the commissioning process.

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.

To characterize the shape, the quality, and the roughness of microshells, digital holographic microscopy technology is used because it offers an appropriate ability to these studies. It captures holograms to reconstruct a double image, one for the intensity and another one for the phase. Using rotation axis, bump counting for the complete microshell surface is possible with a very high speed. Using image stitching and three-dimensional surface re-building software, mapping can be done in a few minutes. Each bump can then be characterized on the map by its position, diameter, and height.

Low density foams (in this work, foam density refers to apparent density) are materials of interest for fusion experiments. Low density poly(4-methyl-1-pentene)(commercial name TPX) foams have been produced for 30 years. TPX foams have been shown to have densities as low as 3 mg.cm(-3), which is very close to air density (1.2 mg.cm(-3)). Around this density foams are very light and highly fragile. Their fabrication is thus a real technological challenge.However, shrinking always appears in ranges ranking from 25% to almost 200%. As a result, the apparent density of the final foam never matches the expected value given by the precursor solution concentration. Besides, even if the mold dimensions are precisely known, shrinkage is never linear, and foams have to be machined for precise density measurement.In our work we present a fabrication process for TPX foams and discuss machining and density measuring issues.Particularly, we have found that there are volume and weight limits for a determination of density within the range of 3% uncertainty. This raises the question whether density should rather be determined directly on millimeter-sized targets or should be performed on a bigger scale sample prepared from the same batch.

To carry out laser plasma experiments on CEA laser facilities, a R&D program was set up and is still under way to deliver complex targets. For a decade, specific developments are also dedicated to "Ligne d'Intégration Laser" (LIL) in France and Omega facilities (USA). To prepare the targets intended for the first experiments on the Laser "Mégajoule" (LMJ) facility, new developments are required, such as cocktail hohlraum fabrication, gas barrier coating and foam shells developments. For fusion experiments on LMJ, an important program is also under way to elaborate the Cryogenic Target Assembly (CTA), to fill and transport the CTA and to study the conformation process of the DT layer.

As part of the French Inertial Confinement Fusion program, Commissariat a l'Energie Atomique has developed cryogenic target assemblies (CTAs) for the Laser Migajoule (LMJ) and a program in two stages for the permeation filling of these CTAs: (a) the permeation filling studies with the Study Filling Station cryostats and (b) the design and manufacturing of the whole operational chain of CTA filling facilities. This paper deals with the description of both the cryogenic studying and the filling facilities for the LMJ targets.

The measurements of the solid DT layer, in terms of thickness and roughness, in the LAV geometry (i.e. in a hohlraum) are not trivial. The DT layer measurements will be done using a Matsukov-Cassegrain telescope placed 39 cm away from the target. This telescope will be used to acquire shadowgraphy images on equators, and interferometric measurements on pole areas using optical coherence tomography (OCT). Optical coherence tomography allows determining the DT layer thickness on a few points, in the polar regions of the target. By scanning around the poles, several points can be acquired in order to calculate the roughness and the local shape of the DT layer at the pole. Both techniques were demonstrated on a 175 pm thick microshell with a 100,um thick D-2 layer. A reconstruction algorithm was designed to give the whole shape of the DT layer from the partial data given by shadowgraphy and OCT A 3D spatial estimation of the DT layer can be obtained The algorithm efficiency was improved, with the use of 360 points on shadowgraphic image and 11 points on each pole. An estimation of the spatial DT layer shape was given on the first 90 longitudinal modes and on the first 5 equatorial modes.

The characterization of the solid DT layer, in terms of thickness and roughness, in the LMJ geometry (hohlraum) is not trivial. The DT layer measurements will be done using a Maksutov-Cassegrain telescope, 39 cm away from the target. This telescope will be used to acquire shadowgraphy images and spectralinterferometry measurements. Shadowgraphy imaging probes the DT layer geometry at the equator of the target. Spectral-interferometry gives the DT layer thickness on one spot on the shell, in the polar regions of the target. By scanning around the poles, severalpoints can be acquired to probe the roughness and the local shape of the DT layer at the poles. This paper presents the spectrainterferometry technique and explains how the DT layer thickness could be deduced from channelled spectra. First experimental results on a 125 mu m thick empty shell are also reported.

The "CEA cryogenic target fabrication project" includes materials and technological researches on the Cryogenic Target Assembly (CTA), the DT filling and cryogenic transport to the LMJ site, and the conformation of the DT solid layer. The Research program to deliver CTAs to LMJ in 2010 is described Some important experimental results have already been obtained and are presented.

A numerical model is presented in order to modelize the bright ring that appears in backlit optical shadow-graphy on a transparent hollow sphere with a solid deuterium-tritium layer inside. This novel model is based on computational calculations applied to the problem of the targets used in Inertial confinement fusion. The model takes into account the influences of the optical imaging system (numerical aperture, source divergence, camera resolution, etc.) and the effect of the capsule itself, diameter, thickness, and refractive index, and allows one to analyze the inner surface of a capsule in terms of thickness and roughness.

Laser targets specifications have stringent dimensional accuracy requirements on target components, especially on compositional levels of silicon and oxygen. A charge-coupled-device - based X-ray radiography instrument is used in target metrology where sample density precludes the use of optical techniques. In this work, we present a dopant model using an X-ray digital radiographic system. This model comes from an X-ray transmission method for dimension measurement. It links the transmitted X-ray energy to the gray level on the image through each point of the microshell. The complete X-ray radiography system has to be well known to use this method, that is to say the X-ray spectrum, the sensor response, the linearity of the sensor, and so on… The complete system is modelled with CIVA software. Experimental results on plastic samples agree with theoretical results. The method sensitivity is studied by comparing modelled images of microshell with varying parameters. The conclusion is that the X-ray digital radiographic system has a sensitivity enough to detect 4 % at. of oxygen and 0,5 % at. of silicon.