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We have determined the thermal criterion for the Laser Megajoule cryogenic target that leads to a uniform layer of deuterium-tritium as specified for ignition. Thermal models were created, and computational fluid dynamics software was used to calculate this criterion in a spherical geometry as a function of capsule thermal conductivity. According to the values obtained, we have studied the possibility of removing anticonvection baffles in the cryogenic target. Results are presented in this paper and indicate that anticonvection baffles can be removed only if the gas density inside the cryogenic target is reduced and/or if the hydrogen content is reduced.

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 cap...

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...

The High Power laser Energy Research facility (HiPER) is a European project dedicated to demonstrating the feasibility of producing energy by laser-driven inertial confinement fusion. A first design of the fast ignition cryogenic target has been established. It is composed of a thin-walled microshell with an inserted gold cone and filled with deuterium-tritium (DT) fuel by means of a capillary (conically guided capsule). After assembly, targets must be tight at cryogenic temperatures (16 to 19.6 K).In order to evaluate the manufacturing feasibility of a single-shot target prototype, a program has been adapted from the Laser Megajoule (LMJ) cryogenic target fabrication know-how. Target component study for HiPER concerns a hollow gold cone (25-deg half-angle and ˜25-μm thickness), a thin polymeric microshell (2-mm diameter and 3- to 10-μm thickness), and a silica capillary (30-μm outer diameter).First gas-tight targets at 77 K have been produced (helium gas leak rate ˜1.4 × 10-11 Pa·m3/s). Major eff...

This paper presents a detailed assessment of the intermediate step design Laser Megajoule cryogenic target thermal behavior. Several simulations were carried out with a computational fluid dynamics code named FLUENT in order to better understand the effect of different parameters on this new design.

As part of the French Inertial Confinement Fusion program, Commissariat a l'Energie Atomique has developed cryogenic target assemblies (CTAs) for the Laser Megajoule (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.

As part of the French Inertial Confinement Fusion (ICF) experiments, cryogenic target assemblies (CTAs) for the Laser Megajoule (LMJ) program are manufactured and filled at CEA Valduc (Dijon) in tritium facilities. They will be moved at about 20 K into a transport cryostat for cryogenic targets, and will be driven from CEA/Valduc to CEA/CESTA (Bordeaux). This paper deals with the description of the tritium facilities for the LMJ cryogenic target. Twelve gloveboxes are needed to furnish 6 CTAs at the same time. These twelve gloveboxes make a relative independent set in the Valduc tritium building and house equipment to prepare the CTAs and the different vacuum vessels, to store and purify gas, to fill and cool the targets and transport them at cryogenic temperature.

Microcellular polymeric materials can be obtained by the polymerization of a high-internal-phase emulsion. These materials are good candidates as targets toward inertial confinement fusion. This application requires severe specifications, including a very low density and a small cell size. In this study, we examined the influence of parameters such as emulsification conditions, surfactant nature, and the presence of a porogen on the obtainment of those requirements. It was possible to obtain microcellular polymeric foams with apparent densities as low as 0.0126 g/cm3. However, it was difficult to obtain very low material density and still maintain a small average pore size. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2053–2063, 2005

The Megajoule Laser cryogenic system fills, transports and inserts on the Cryogenic Target Positioner (CTP) individual Cryogenic Target Assemblies (CTAs), which are manipulated at about 20K by several cryogenic grippers. This CTA has to meet severe specifications imposed by implosion physics, its own thermal environment, and to respect a lot of interfaces with the permeation cell of the filling station, the several cryogenic grippers, the Megajoule laser interaction chamber,... Therefore, the CTA definition is very complex, and induces a lot of challenging tasks for its fabrication. During the last year, many improvements have been achieved allowing the realization of the first CTA prototype at scale one.