Graded Germanium Doped CH_x Microshells Meeting the Specifications of the Megajoule Laser Cryogenic Target

For the CEA Laser "Mégajoule" (LMJ) facility, amorphous hydrogenated carbon (a-C:H or CH_x), is the nominal ablator for inertial confinement fusion (ICF) experiments. These capsules contain the fusible deuterium-tritium mixture in order to achieve ignition. Coatings are prepared by glow discharge polymerization (GDP) with trans-2-butene and hydrogen. They can be easily doped with germanium by adding tetramethylgermanium. The GDP technique is well known today and largely used in American and French laboratories. But the microshells for laser fusion targets have many stringent characteristics. Although the feasibility of the shells has been demonstrated, the goal is now to obtain graded germanium doped shells meeting all the specifications with a yield compatible with a production step.